Jared Doan, BS

Study 1 Overview (Chang et al)

Objective: To assess the incidence of postoperative delirium (POD) following propofol- vs sevoflurane-based anesthesia in geriatric spine surgery patients.

Design: Retrospective, single-blinded observational study of propofol- and sevoflurane-based anesthesia cohorts.

Setting and participants: Patients eligible for this study were aged 65 years or older admitted to the SMG-SNU Boramae Medical Center (Seoul, South Korea). All patients underwent general anesthesia either via intravenous propofol or inhalational sevoflurane for spine surgery between January 2015 and December 2019. Patients were retrospectively identified via electronic medical records. Patient exclusion criteria included preoperative delirium, history of dementia, psychiatric disease, alcoholism, hepatic or renal dysfunction, postoperative mechanical ventilation dependence, other surgery within the recent 6 months, maintenance of intraoperative anesthesia with combined anesthetics, or incomplete medical record.

Main outcome measures: The primary outcome was the incidence of POD after administration of propofol- and sevoflurane-based anesthesia during hospitalization. Patients were screened for POD regularly by attending nurses using the Nursing Delirium Screening Scale (disorientation, inappropriate behavior, inappropriate communication, hallucination, and psychomotor retardation) during the entirety of the patient’s hospital stay; if 1 or more screening criteria were met, a psychiatrist was consulted for the proper diagnosis and management of delirium. A psychiatric diagnosis was required for a case to be counted toward the incidence of POD in this study. Secondary outcomes included postoperative 30-day complications (angina, myocardial infarction, transient ischemic attack/stroke, pneumonia, deep vein thrombosis, pulmonary embolism, acute kidney injury, or infection) and length of postoperative hospital stay.

Main results: POD occurred in 29 patients (10.3%) out of the total cohort of 281. POD was more common in the sevoflurane group than in the propofol group (15.7% vs 5.0%; P = .003). Using multivariable logistic regression, inhalational sevoflurane was associated with an increased risk of POD as compared to propofol-based anesthesia (odds ratio [OR], 4.120; 95% CI, 1.549-10.954; P = .005). There was no association between choice of anesthetic and postoperative 30-day complications or the length of postoperative hospital stay. Both older age (OR, 1.242; 95% CI, 1.130-1.366; P < .001) and higher pain score at postoperative day 1 (OR, 1.338; 95% CI, 1.056-1.696; P = .016) were associated with increased risk of POD.

Conclusion: Propofol-based anesthesia was associated with a lower incidence of and risk for POD than sevoflurane-based anesthesia in older patients undergoing spine surgery.

Study 2 Overview (Mei et al)

Objective: To determine the incidence and duration of POD in older patients after total knee/hip replacement (TKR/THR) under intravenous propofol or inhalational sevoflurane general anesthesia.

Design: Randomized clinical trial of propofol and sevoflurane groups.

Setting and participants: This study was conducted at the Shanghai Tenth People’s Hospital and involved 209 participants enrolled between June 2016 and November 2019. All participants were 60 years of age or older, scheduled for TKR/THR surgery under general anesthesia, American Society of Anesthesiologists (ASA) class I to III, and assessed to be of normal cognitive function preoperatively via a Mini-Mental State Examination. Participant exclusion criteria included preexisting delirium as assessed by the Confusion Assessment Method (CAM), prior diagnosed neurological diseases (eg, Parkinson’s disease), prior diagnosed mental disorders (eg, schizophrenia), or impaired vision or hearing that would influence cognitive assessments. All participants were randomly assigned to either sevoflurane or propofol anesthesia for their surgery via a computer-generated list. Of these, 103 received inhalational sevoflurane and 106 received intravenous propofol. All participants received standardized postoperative care.

Main outcome measures: All participants were interviewed by investigators, who were blinded to the anesthesia regimen, twice daily on postoperative days 1, 2, and 3 using CAM and a CAM-based scoring system (CAM-S) to assess delirium severity. The CAM encapsulated 4 criteria: acute onset and fluctuating course, agitation, disorganized thinking, and altered level of consciousness. To diagnose delirium, both the first and second criteria must be met, in addition to either the third or fourth criterion. The averages of the scores across the 3 postoperative days indicated delirium severity, while the incidence and duration of delirium was assessed by the presence of delirium as determined by CAM on any postoperative day.

Main results: All eligible participants (N = 209; mean [SD] age 71.2 [6.7] years; 29.2% male) were included in the final analysis. The incidence of POD was not statistically different between the propofol and sevoflurane groups (33.0% vs 23.3%; P = .119, Chi-square test). It was estimated that 316 participants in each arm of the study were needed to detect statistical differences. The number of days of POD per person were higher with propofol anesthesia as compared to sevoflurane (0.5 [0.8] vs 0.3 [0.5]; P =  .049, Student’s t-test).

Conclusion: This underpowered study showed a 9.7% difference in the incidence of POD between older adults who received propofol (33.0%) and sevoflurane (23.3%) after THR/TKR. Further studies with a larger sample size are needed to compare general anesthetics and their role in POD.

Commentary

Delirium is characterized by an acute state of confusion with fluctuating mental status, inattention, disorganized thinking, and altered level of consciousness. It is often caused by medications and/or their related adverse effects, infections, electrolyte imbalances, and other clinical etiologies. Delirium often manifests in post-surgical settings, disproportionately affecting older patients and leading to increased risk of morbidity, mortality, hospital length of stay, and health care costs.¹ Intraoperative risk factors for POD are determined by the degree of operative stress (eg, lower-risk surgeries put the patient at reduced risk for POD as compared to higher-risk surgeries) and are additive to preexisting patient-specific risk factors, such as older age and functional impairment.¹ Because operative stress is associated with risk for POD, limiting operative stress in controlled ways, such as through the choice of anesthetic agent administered, may be a pragmatic way to manage operative risks and optimize outcomes, especially when serving a surgically vulnerable population.

In Study 1, Chang et al sought to assess whether 2 commonly utilized general anesthetics, propofol and sevoflurane, in older patients undergoing spine surgery differentially affected the incidence of POD. In this retrospective, single-blinded observational study of 281 geriatric patients, the researchers found that sevoflurane was associated with a higher risk of POD as compared to propofol. However, these anesthetics were not associated with surgical outcomes such as postoperative 30-day complications or the length of postoperative hospital stay. While these findings added new knowledge to this field of research, several limitations should be kept in mind when interpreting this study’s results. For instance, the sample size was relatively small, with all cases selected from a single center utilizing a retrospective analysis. In addition, although a standardized nursing screening tool was used as a method for delirium detection, hypoactive delirium or less symptomatic delirium may have been missed, which in turn would lead to an underestimation of POD incidence. The latter is a common limitation in delirium research.

In Study 2, Mei et al similarly explored the effects of general anesthetics on POD in older surgical patients. Specifically, using a randomized clinical trial design, the investigators compared propofol with sevoflurane in older patients who underwent TKR/THR, and their roles in POD severity and duration. Although the incidence of POD was higher in those who received propofol compared to sevoflurane, this trial was underpowered and the results did not reach statistical significance. In addition, while the duration of POD was slightly longer in the propofol group compared to the sevoflurane group (0.5 vs 0.3 days), it was unclear if this finding was clinically significant. Similar to many research studies in POD, limitations of Study 2 included a small sample size of 209 patients, with all participants enrolled from a single center. On the other hand, this study illustrated the feasibility of a method that allowed reproducible prospective assessment of POD time course using CAM and CAM-S.

Applications for Clinical Practice and System Implementation

The delineation of risk factors that contribute to delirium after surgery in older patients is key to mitigating risks for POD and improving clinical outcomes. An important step towards a better understanding of these modifiable risk factors is to clearly quantify intraoperative risk of POD attributable to specific anesthetics. While preclinical studies have shown differential neurotoxicity effects of propofol and sevoflurane, their impact on clinically important neurologic outcomes such as delirium and cognitive decline remains poorly understood. Although Studies 1 and 2 both provided head-to-head comparisons of propofol and sevoflurane as risk factors for POD in high-operative-stress surgeries in older patients, the results were inconsistent. That being said, this small incremental increase in knowledge was not unexpected in the course of discovery around a clinically complex research question. Importantly, these studies provided evidence regarding the methodological approaches that could be taken to further this line of research.

The mediating factors of the differences on neurologic outcomes between anesthetic agents are likely pharmacological, biological, and methodological. Pharmacologically, the differences between target receptors, such as GABAA (propofol, etomidate) or NMDA (ketamine), could be a defining feature in the difference in incidence of POD. Additionally, secondary actions of anesthetic agents on glycine, nicotinic, and acetylcholine receptors could play a role as well. Biologically, genes such as CYP2E1, CYP2B6, CYP2C9, GSTP1, UGT1A9, SULT1A1, and NQO1 have all been identified as genetic factors in the metabolism of anesthetics, and variations in such genes could result in different responses to anesthetics.² Methodologically, routes of anesthetic administration (eg, inhalation vs intravenous), preexisting anatomical structures, or confounding medical conditions (eg, lower respiratory volume due to older age) may influence POD incidence, duration, or severity. Moreover, methodological differences between Studies 1 and 2, such as surgeries performed (spinal vs TKR/THR), patient populations (South Korean vs Chinese), and the diagnosis and monitoring of delirium (retrospective screening and diagnosis vs prospective CAM/CAM-S) may impact delirium outcomes. Thus, these factors should be considered in the design of future clinical trials undertaken to investigate the effects of anesthetics on POD.

Given the high prevalence of delirium and its associated adverse outcomes in the immediate postoperative period in older patients, further research is warranted to determine how anesthetics affect POD in order to optimize perioperative care and mitigate risks in this vulnerable population. Moreover, parallel investigations into how anesthetics differentially impact the development of transient or longer-term cognitive impairment after a surgical procedure (ie, postoperative cognitive dysfunction) in older adults are urgently needed in order to improve their cognitive health.

Practice Points

• Intravenous propofol and inhalational sevoflurane may be differentially associated with incidence, duration, and severity of POD in geriatric surgical patients.
• Further larger-scale studies are warranted to clarify the role of anesthetic choice in POD in order to optimize surgical outcomes in older patients.

–Jared Doan, BS, and Fred Ko, MD
Icahn School of Medicine at Mount Sinai

Study 1 Overview (Chang et al)

Objective: To assess the incidence of postoperative delirium (POD) following propofol- vs sevoflurane-based anesthesia in geriatric spine surgery patients.

Design: Retrospective, single-blinded observational study of propofol- and sevoflurane-based anesthesia cohorts.

Setting and participants: Patients eligible for this study were aged 65 years or older admitted to the SMG-SNU Boramae Medical Center (Seoul, South Korea). All patients underwent general anesthesia either via intravenous propofol or inhalational sevoflurane for spine surgery between January 2015 and December 2019. Patients were retrospectively identified via electronic medical records. Patient exclusion criteria included preoperative delirium, history of dementia, psychiatric disease, alcoholism, hepatic or renal dysfunction, postoperative mechanical ventilation dependence, other surgery within the recent 6 months, maintenance of intraoperative anesthesia with combined anesthetics, or incomplete medical record.

Main outcome measures: The primary outcome was the incidence of POD after administration of propofol- and sevoflurane-based anesthesia during hospitalization. Patients were screened for POD regularly by attending nurses using the Nursing Delirium Screening Scale (disorientation, inappropriate behavior, inappropriate communication, hallucination, and psychomotor retardation) during the entirety of the patient’s hospital stay; if 1 or more screening criteria were met, a psychiatrist was consulted for the proper diagnosis and management of delirium. A psychiatric diagnosis was required for a case to be counted toward the incidence of POD in this study. Secondary outcomes included postoperative 30-day complications (angina, myocardial infarction, transient ischemic attack/stroke, pneumonia, deep vein thrombosis, pulmonary embolism, acute kidney injury, or infection) and length of postoperative hospital stay.

Main results: POD occurred in 29 patients (10.3%) out of the total cohort of 281. POD was more common in the sevoflurane group than in the propofol group (15.7% vs 5.0%; P = .003). Using multivariable logistic regression, inhalational sevoflurane was associated with an increased risk of POD as compared to propofol-based anesthesia (odds ratio [OR], 4.120; 95% CI, 1.549-10.954; P = .005). There was no association between choice of anesthetic and postoperative 30-day complications or the length of postoperative hospital stay. Both older age (OR, 1.242; 95% CI, 1.130-1.366; P < .001) and higher pain score at postoperative day 1 (OR, 1.338; 95% CI, 1.056-1.696; P = .016) were associated with increased risk of POD.

Conclusion: Propofol-based anesthesia was associated with a lower incidence of and risk for POD than sevoflurane-based anesthesia in older patients undergoing spine surgery.

Study 2 Overview (Mei et al)

Objective: To determine the incidence and duration of POD in older patients after total knee/hip replacement (TKR/THR) under intravenous propofol or inhalational sevoflurane general anesthesia.

Design: Randomized clinical trial of propofol and sevoflurane groups.

Setting and participants: This study was conducted at the Shanghai Tenth People’s Hospital and involved 209 participants enrolled between June 2016 and November 2019. All participants were 60 years of age or older, scheduled for TKR/THR surgery under general anesthesia, American Society of Anesthesiologists (ASA) class I to III, and assessed to be of normal cognitive function preoperatively via a Mini-Mental State Examination. Participant exclusion criteria included preexisting delirium as assessed by the Confusion Assessment Method (CAM), prior diagnosed neurological diseases (eg, Parkinson’s disease), prior diagnosed mental disorders (eg, schizophrenia), or impaired vision or hearing that would influence cognitive assessments. All participants were randomly assigned to either sevoflurane or propofol anesthesia for their surgery via a computer-generated list. Of these, 103 received inhalational sevoflurane and 106 received intravenous propofol. All participants received standardized postoperative care.

Main outcome measures: All participants were interviewed by investigators, who were blinded to the anesthesia regimen, twice daily on postoperative days 1, 2, and 3 using CAM and a CAM-based scoring system (CAM-S) to assess delirium severity. The CAM encapsulated 4 criteria: acute onset and fluctuating course, agitation, disorganized thinking, and altered level of consciousness. To diagnose delirium, both the first and second criteria must be met, in addition to either the third or fourth criterion. The averages of the scores across the 3 postoperative days indicated delirium severity, while the incidence and duration of delirium was assessed by the presence of delirium as determined by CAM on any postoperative day.

Main results: All eligible participants (N = 209; mean [SD] age 71.2 [6.7] years; 29.2% male) were included in the final analysis. The incidence of POD was not statistically different between the propofol and sevoflurane groups (33.0% vs 23.3%; P = .119, Chi-square test). It was estimated that 316 participants in each arm of the study were needed to detect statistical differences. The number of days of POD per person were higher with propofol anesthesia as compared to sevoflurane (0.5 [0.8] vs 0.3 [0.5]; P =  .049, Student’s t-test).

Conclusion: This underpowered study showed a 9.7% difference in the incidence of POD between older adults who received propofol (33.0%) and sevoflurane (23.3%) after THR/TKR. Further studies with a larger sample size are needed to compare general anesthetics and their role in POD.

Commentary

Delirium is characterized by an acute state of confusion with fluctuating mental status, inattention, disorganized thinking, and altered level of consciousness. It is often caused by medications and/or their related adverse effects, infections, electrolyte imbalances, and other clinical etiologies. Delirium often manifests in post-surgical settings, disproportionately affecting older patients and leading to increased risk of morbidity, mortality, hospital length of stay, and health care costs.¹ Intraoperative risk factors for POD are determined by the degree of operative stress (eg, lower-risk surgeries put the patient at reduced risk for POD as compared to higher-risk surgeries) and are additive to preexisting patient-specific risk factors, such as older age and functional impairment.¹ Because operative stress is associated with risk for POD, limiting operative stress in controlled ways, such as through the choice of anesthetic agent administered, may be a pragmatic way to manage operative risks and optimize outcomes, especially when serving a surgically vulnerable population.

In Study 1, Chang et al sought to assess whether 2 commonly utilized general anesthetics, propofol and sevoflurane, in older patients undergoing spine surgery differentially affected the incidence of POD. In this retrospective, single-blinded observational study of 281 geriatric patients, the researchers found that sevoflurane was associated with a higher risk of POD as compared to propofol. However, these anesthetics were not associated with surgical outcomes such as postoperative 30-day complications or the length of postoperative hospital stay. While these findings added new knowledge to this field of research, several limitations should be kept in mind when interpreting this study’s results. For instance, the sample size was relatively small, with all cases selected from a single center utilizing a retrospective analysis. In addition, although a standardized nursing screening tool was used as a method for delirium detection, hypoactive delirium or less symptomatic delirium may have been missed, which in turn would lead to an underestimation of POD incidence. The latter is a common limitation in delirium research.

In Study 2, Mei et al similarly explored the effects of general anesthetics on POD in older surgical patients. Specifically, using a randomized clinical trial design, the investigators compared propofol with sevoflurane in older patients who underwent TKR/THR, and their roles in POD severity and duration. Although the incidence of POD was higher in those who received propofol compared to sevoflurane, this trial was underpowered and the results did not reach statistical significance. In addition, while the duration of POD was slightly longer in the propofol group compared to the sevoflurane group (0.5 vs 0.3 days), it was unclear if this finding was clinically significant. Similar to many research studies in POD, limitations of Study 2 included a small sample size of 209 patients, with all participants enrolled from a single center. On the other hand, this study illustrated the feasibility of a method that allowed reproducible prospective assessment of POD time course using CAM and CAM-S.

Applications for Clinical Practice and System Implementation

The delineation of risk factors that contribute to delirium after surgery in older patients is key to mitigating risks for POD and improving clinical outcomes. An important step towards a better understanding of these modifiable risk factors is to clearly quantify intraoperative risk of POD attributable to specific anesthetics. While preclinical studies have shown differential neurotoxicity effects of propofol and sevoflurane, their impact on clinically important neurologic outcomes such as delirium and cognitive decline remains poorly understood. Although Studies 1 and 2 both provided head-to-head comparisons of propofol and sevoflurane as risk factors for POD in high-operative-stress surgeries in older patients, the results were inconsistent. That being said, this small incremental increase in knowledge was not unexpected in the course of discovery around a clinically complex research question. Importantly, these studies provided evidence regarding the methodological approaches that could be taken to further this line of research.

The mediating factors of the differences on neurologic outcomes between anesthetic agents are likely pharmacological, biological, and methodological. Pharmacologically, the differences between target receptors, such as GABAA (propofol, etomidate) or NMDA (ketamine), could be a defining feature in the difference in incidence of POD. Additionally, secondary actions of anesthetic agents on glycine, nicotinic, and acetylcholine receptors could play a role as well. Biologically, genes such as CYP2E1, CYP2B6, CYP2C9, GSTP1, UGT1A9, SULT1A1, and NQO1 have all been identified as genetic factors in the metabolism of anesthetics, and variations in such genes could result in different responses to anesthetics.² Methodologically, routes of anesthetic administration (eg, inhalation vs intravenous), preexisting anatomical structures, or confounding medical conditions (eg, lower respiratory volume due to older age) may influence POD incidence, duration, or severity. Moreover, methodological differences between Studies 1 and 2, such as surgeries performed (spinal vs TKR/THR), patient populations (South Korean vs Chinese), and the diagnosis and monitoring of delirium (retrospective screening and diagnosis vs prospective CAM/CAM-S) may impact delirium outcomes. Thus, these factors should be considered in the design of future clinical trials undertaken to investigate the effects of anesthetics on POD.

Given the high prevalence of delirium and its associated adverse outcomes in the immediate postoperative period in older patients, further research is warranted to determine how anesthetics affect POD in order to optimize perioperative care and mitigate risks in this vulnerable population. Moreover, parallel investigations into how anesthetics differentially impact the development of transient or longer-term cognitive impairment after a surgical procedure (ie, postoperative cognitive dysfunction) in older adults are urgently needed in order to improve their cognitive health.

Practice Points

• Intravenous propofol and inhalational sevoflurane may be differentially associated with incidence, duration, and severity of POD in geriatric surgical patients.
• Further larger-scale studies are warranted to clarify the role of anesthetic choice in POD in order to optimize surgical outcomes in older patients.

–Jared Doan, BS, and Fred Ko, MD
Icahn School of Medicine at Mount Sinai

Study 1 Overview (Chang et al)

Objective: To assess the incidence of postoperative delirium (POD) following propofol- vs sevoflurane-based anesthesia in geriatric spine surgery patients.

Design: Retrospective, single-blinded observational study of propofol- and sevoflurane-based anesthesia cohorts.

Setting and participants: Patients eligible for this study were aged 65 years or older admitted to the SMG-SNU Boramae Medical Center (Seoul, South Korea). All patients underwent general anesthesia either via intravenous propofol or inhalational sevoflurane for spine surgery between January 2015 and December 2019. Patients were retrospectively identified via electronic medical records. Patient exclusion criteria included preoperative delirium, history of dementia, psychiatric disease, alcoholism, hepatic or renal dysfunction, postoperative mechanical ventilation dependence, other surgery within the recent 6 months, maintenance of intraoperative anesthesia with combined anesthetics, or incomplete medical record.

Main outcome measures: The primary outcome was the incidence of POD after administration of propofol- and sevoflurane-based anesthesia during hospitalization. Patients were screened for POD regularly by attending nurses using the Nursing Delirium Screening Scale (disorientation, inappropriate behavior, inappropriate communication, hallucination, and psychomotor retardation) during the entirety of the patient’s hospital stay; if 1 or more screening criteria were met, a psychiatrist was consulted for the proper diagnosis and management of delirium. A psychiatric diagnosis was required for a case to be counted toward the incidence of POD in this study. Secondary outcomes included postoperative 30-day complications (angina, myocardial infarction, transient ischemic attack/stroke, pneumonia, deep vein thrombosis, pulmonary embolism, acute kidney injury, or infection) and length of postoperative hospital stay.

Main results: POD occurred in 29 patients (10.3%) out of the total cohort of 281. POD was more common in the sevoflurane group than in the propofol group (15.7% vs 5.0%; P = .003). Using multivariable logistic regression, inhalational sevoflurane was associated with an increased risk of POD as compared to propofol-based anesthesia (odds ratio [OR], 4.120; 95% CI, 1.549-10.954; P = .005). There was no association between choice of anesthetic and postoperative 30-day complications or the length of postoperative hospital stay. Both older age (OR, 1.242; 95% CI, 1.130-1.366; P < .001) and higher pain score at postoperative day 1 (OR, 1.338; 95% CI, 1.056-1.696; P = .016) were associated with increased risk of POD.

Conclusion: Propofol-based anesthesia was associated with a lower incidence of and risk for POD than sevoflurane-based anesthesia in older patients undergoing spine surgery.

Study 2 Overview (Mei et al)

Objective: To determine the incidence and duration of POD in older patients after total knee/hip replacement (TKR/THR) under intravenous propofol or inhalational sevoflurane general anesthesia.

Design: Randomized clinical trial of propofol and sevoflurane groups.

Setting and participants: This study was conducted at the Shanghai Tenth People’s Hospital and involved 209 participants enrolled between June 2016 and November 2019. All participants were 60 years of age or older, scheduled for TKR/THR surgery under general anesthesia, American Society of Anesthesiologists (ASA) class I to III, and assessed to be of normal cognitive function preoperatively via a Mini-Mental State Examination. Participant exclusion criteria included preexisting delirium as assessed by the Confusion Assessment Method (CAM), prior diagnosed neurological diseases (eg, Parkinson’s disease), prior diagnosed mental disorders (eg, schizophrenia), or impaired vision or hearing that would influence cognitive assessments. All participants were randomly assigned to either sevoflurane or propofol anesthesia for their surgery via a computer-generated list. Of these, 103 received inhalational sevoflurane and 106 received intravenous propofol. All participants received standardized postoperative care.

Main outcome measures: All participants were interviewed by investigators, who were blinded to the anesthesia regimen, twice daily on postoperative days 1, 2, and 3 using CAM and a CAM-based scoring system (CAM-S) to assess delirium severity. The CAM encapsulated 4 criteria: acute onset and fluctuating course, agitation, disorganized thinking, and altered level of consciousness. To diagnose delirium, both the first and second criteria must be met, in addition to either the third or fourth criterion. The averages of the scores across the 3 postoperative days indicated delirium severity, while the incidence and duration of delirium was assessed by the presence of delirium as determined by CAM on any postoperative day.

Main results: All eligible participants (N = 209; mean [SD] age 71.2 [6.7] years; 29.2% male) were included in the final analysis. The incidence of POD was not statistically different between the propofol and sevoflurane groups (33.0% vs 23.3%; P = .119, Chi-square test). It was estimated that 316 participants in each arm of the study were needed to detect statistical differences. The number of days of POD per person were higher with propofol anesthesia as compared to sevoflurane (0.5 [0.8] vs 0.3 [0.5]; P =  .049, Student’s t-test).

Conclusion: This underpowered study showed a 9.7% difference in the incidence of POD between older adults who received propofol (33.0%) and sevoflurane (23.3%) after THR/TKR. Further studies with a larger sample size are needed to compare general anesthetics and their role in POD.

Commentary

Delirium is characterized by an acute state of confusion with fluctuating mental status, inattention, disorganized thinking, and altered level of consciousness. It is often caused by medications and/or their related adverse effects, infections, electrolyte imbalances, and other clinical etiologies. Delirium often manifests in post-surgical settings, disproportionately affecting older patients and leading to increased risk of morbidity, mortality, hospital length of stay, and health care costs.¹ Intraoperative risk factors for POD are determined by the degree of operative stress (eg, lower-risk surgeries put the patient at reduced risk for POD as compared to higher-risk surgeries) and are additive to preexisting patient-specific risk factors, such as older age and functional impairment.¹ Because operative stress is associated with risk for POD, limiting operative stress in controlled ways, such as through the choice of anesthetic agent administered, may be a pragmatic way to manage operative risks and optimize outcomes, especially when serving a surgically vulnerable population.

In Study 1, Chang et al sought to assess whether 2 commonly utilized general anesthetics, propofol and sevoflurane, in older patients undergoing spine surgery differentially affected the incidence of POD. In this retrospective, single-blinded observational study of 281 geriatric patients, the researchers found that sevoflurane was associated with a higher risk of POD as compared to propofol. However, these anesthetics were not associated with surgical outcomes such as postoperative 30-day complications or the length of postoperative hospital stay. While these findings added new knowledge to this field of research, several limitations should be kept in mind when interpreting this study’s results. For instance, the sample size was relatively small, with all cases selected from a single center utilizing a retrospective analysis. In addition, although a standardized nursing screening tool was used as a method for delirium detection, hypoactive delirium or less symptomatic delirium may have been missed, which in turn would lead to an underestimation of POD incidence. The latter is a common limitation in delirium research.

In Study 2, Mei et al similarly explored the effects of general anesthetics on POD in older surgical patients. Specifically, using a randomized clinical trial design, the investigators compared propofol with sevoflurane in older patients who underwent TKR/THR, and their roles in POD severity and duration. Although the incidence of POD was higher in those who received propofol compared to sevoflurane, this trial was underpowered and the results did not reach statistical significance. In addition, while the duration of POD was slightly longer in the propofol group compared to the sevoflurane group (0.5 vs 0.3 days), it was unclear if this finding was clinically significant. Similar to many research studies in POD, limitations of Study 2 included a small sample size of 209 patients, with all participants enrolled from a single center. On the other hand, this study illustrated the feasibility of a method that allowed reproducible prospective assessment of POD time course using CAM and CAM-S.

Applications for Clinical Practice and System Implementation

The delineation of risk factors that contribute to delirium after surgery in older patients is key to mitigating risks for POD and improving clinical outcomes. An important step towards a better understanding of these modifiable risk factors is to clearly quantify intraoperative risk of POD attributable to specific anesthetics. While preclinical studies have shown differential neurotoxicity effects of propofol and sevoflurane, their impact on clinically important neurologic outcomes such as delirium and cognitive decline remains poorly understood. Although Studies 1 and 2 both provided head-to-head comparisons of propofol and sevoflurane as risk factors for POD in high-operative-stress surgeries in older patients, the results were inconsistent. That being said, this small incremental increase in knowledge was not unexpected in the course of discovery around a clinically complex research question. Importantly, these studies provided evidence regarding the methodological approaches that could be taken to further this line of research.

The mediating factors of the differences on neurologic outcomes between anesthetic agents are likely pharmacological, biological, and methodological. Pharmacologically, the differences between target receptors, such as GABAA (propofol, etomidate) or NMDA (ketamine), could be a defining feature in the difference in incidence of POD. Additionally, secondary actions of anesthetic agents on glycine, nicotinic, and acetylcholine receptors could play a role as well. Biologically, genes such as CYP2E1, CYP2B6, CYP2C9, GSTP1, UGT1A9, SULT1A1, and NQO1 have all been identified as genetic factors in the metabolism of anesthetics, and variations in such genes could result in different responses to anesthetics.² Methodologically, routes of anesthetic administration (eg, inhalation vs intravenous), preexisting anatomical structures, or confounding medical conditions (eg, lower respiratory volume due to older age) may influence POD incidence, duration, or severity. Moreover, methodological differences between Studies 1 and 2, such as surgeries performed (spinal vs TKR/THR), patient populations (South Korean vs Chinese), and the diagnosis and monitoring of delirium (retrospective screening and diagnosis vs prospective CAM/CAM-S) may impact delirium outcomes. Thus, these factors should be considered in the design of future clinical trials undertaken to investigate the effects of anesthetics on POD.

Given the high prevalence of delirium and its associated adverse outcomes in the immediate postoperative period in older patients, further research is warranted to determine how anesthetics affect POD in order to optimize perioperative care and mitigate risks in this vulnerable population. Moreover, parallel investigations into how anesthetics differentially impact the development of transient or longer-term cognitive impairment after a surgical procedure (ie, postoperative cognitive dysfunction) in older adults are urgently needed in order to improve their cognitive health.

Practice Points

• Intravenous propofol and inhalational sevoflurane may be differentially associated with incidence, duration, and severity of POD in geriatric surgical patients.
• Further larger-scale studies are warranted to clarify the role of anesthetic choice in POD in order to optimize surgical outcomes in older patients.

–Jared Doan, BS, and Fred Ko, MD
Icahn School of Medicine at Mount Sinai

Study 1 Overview (Oberhaus et al)

Objective: To compare the 3-Minute Diagnostic Confusion Assessment Method (3D-CAM) to the long-form Confusion Assessment Method (CAM) in detecting postoperative delirium.

Design: Prospective concurrent comparison of 3D-CAM and CAM evaluations in a cohort of postoperative geriatric patients.

Setting and participants: Eligible participants were patients aged 60 years or older undergoing major elective surgery at Barnes Jewish Hospital (St. Louis, Missouri) who were enrolled in ongoing clinical trials (PODCAST, ENGAGES, SATISFY-SOS) between 2015 and 2018. Surgeries were at least 2 hours in length and required general anesthesia, planned extubation, and a minimum 2-day hospital stay. Investigators were extensively trained in administering 3D-CAM and CAM instruments. Participants were evaluated 2 hours after the end of anesthesia care on the day of surgery, then daily until follow-up was completed per clinical trial protocol or until the participant was determined by CAM to be nondelirious for 3 consecutive days. For each evaluation, both 3D-CAM and CAM assessors approached the participant together, but the evaluation was conducted such that the 3D-CAM assessor was masked to the additional questions ascertained by the long-form CAM assessment. The 3D-CAM or CAM assessor independently scored their respective assessments blinded to the results of the other assessor.

Main outcome measures: Participants were concurrently evaluated for postoperative delirium by both 3D-CAM and long-form CAM assessments. Comparisons between 3D-CAM and CAM scores were made using Cohen κ with repeated measures, generalized linear mixed-effects model, and Bland-Altman analysis.

Main results: Sixteen raters performed 471 concurrent 3D-CAM and CAM assessments in 299 participants (mean [SD] age, 69 [6.5] years). Of these participants, 152 (50.8%) were men, 263 (88.0%) were White, and 211 (70.6%) underwent noncardiac surgery. Both instruments showed good intraclass correlation (0.98 for 3D-CAM, 0.84 for CAM) with good overall agreement (Cohen κ = 0.71; 95% CI, 0.58-0.83). The mixed-effects model indicated a significant disagreement between the 3D-CAM and CAM assessments (estimated difference in fixed effect, –0.68; 95% CI, –1.32 to –0.05; P = .04). The Bland-Altman analysis showed that the probability of a delirium diagnosis with the 3D-CAM was more than twice that with the CAM (probability ratio, 2.78; 95% CI, 2.44-3.23).

Conclusion: The high degree of agreement between 3D-CAM and long-form CAM assessments suggests that the former may be a pragmatic and easy-to-administer clinical tool to screen for postoperative delirium in vulnerable older surgical patients.

Study 2 Overview (Shenkin et al)

Objective: To assess the accuracy of the 4 ‘A’s Test (4AT) for delirium detection in the medical inpatient setting and to compare the 4AT to the CAM.

Design: Prospective randomized diagnostic test accuracy study.

Setting and participants: This study was conducted in emergency departments and acute medical wards at 3 UK sites (Edinburgh, Bradford, and Sheffield) and enrolled acute medical patients aged 70 years or older without acute life-threatening illnesses and/or coma. Assessors administering the delirium evaluation were nurses or graduate clinical research associates who underwent systematic training in delirium and delirium assessment. Additional training was provided to those administering the CAM but not to those administering the 4AT as the latter is designed to be administered without special training. First, all participants underwent a reference standard delirium assessment using Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) (DSM-IV) criteria to derive a final definitive diagnosis of delirium via expert consensus (1 psychiatrist and 2 geriatricians). Then, the participants were randomized to either the 4AT or the comparator CAM group using computer-generated pseudo-random numbers, stratified by study site, with block allocation. All assessments were performed by pairs of independent assessors blinded to the results of the other assessment.

Main outcome measures: All participants were evaluated by the reference standard (DSM-IV criteria for delirium) and by either 4AT or CAM instruments for delirium. The accuracy of the 4AT instrument was evaluated by comparing its positive and negative predictive values, sensitivity, and specificity to the reference standard and analyzed via the area under the receiver operating characteristic curve. The diagnostic accuracy of 4AT, compared to the CAM, was evaluated by comparing positive and negative predictive values, sensitivity, and specificity using Fisher’s exact test. The overall performance of 4AT and CAM was summarized using Youden’s Index and the diagnostic odds ratio of sensitivity to specificity.

Results: All 843 individuals enrolled in the study were randomized and 785 were included in the analysis (23 withdrew, 3 lost contact, 32 indeterminate diagnosis, 2 missing outcome). Of the participants analyzed, the mean age was 81.4 [6.4] years, and 12.1% (95/785) had delirium by reference standard assessment, 14.3% (56/392) by 4AT, and 4.7% (18/384) by CAM. The 4AT group had an area under the receiver operating characteristic curve of 0.90 (95% CI, 0.84-0.96), a sensitivity of 76% (95% CI, 61%-87%), and a specificity of 94% (95% CI, 92%-97%). In comparison, the CAM group had a sensitivity of 40% (95% CI, 26%-57%) and a specificity of 100% (95% CI, 98%-100%).

Conclusions: The 4AT is a pragmatic screening test for delirium in a medical space that does not require special training to administer. The use of this instrument may help to improve delirium detection as a part of routine clinical care in hospitalized older adults.

Delirium is an acute confusional state marked by fluctuating mental status, inattention, disorganized thinking, and altered level of consciousness. It is exceedingly common in older patients in both surgical and medical settings and is associated with increased morbidity, mortality, hospital length of stay, institutionalization, and health care costs. Delirium is frequently underdiagnosed in the hospitalized setting, perhaps due to a combination of its waxing and waning nature and a lack of pragmatic and easily implementable screening tools that can be readily administered by clinicians and nonclinicians alike.¹ While the CAM is a well-validated instrument to diagnose delirium, it requires specific training in the rating of each of the cardinal features ascertained through a brief cognitive assessment and takes 5 to 10 minutes to complete. Taken together, given the high patient load for clinicians in the hospital setting, the validation and application of brief delirium screening instruments that can be reliably administered by nonphysicians and nonclinicians may enhance delirium detection in vulnerable patients and consequently improve their outcomes.

In Study 1, Oberhaus et al approach the challenge of underdiagnosing delirium in the postoperative setting by investigating whether the widely accepted long-form CAM and an abbreviated 3-minute version, the 3D-CAM, provide similar delirium detection in older surgical patients. The authors found that both instruments were reliable tests individually (high interrater reliability) and had good overall agreement. However, the 3D-CAM was more likely to yield a positive diagnosis of delirium compared to the long-form CAM, consistent with its purpose as a screening tool with a high sensitivity. It is important to emphasize that the 3D-CAM takes less time to administer, but also requires less extensive training and clinical knowledge than the long-form CAM. Therefore, this instrument meets the prerequisite of a brief screening test that can be rapidly administered by nonclinicians, and if affirmative, followed by a more extensive confirmatory test performed by a clinician. Limitations of this study include a lack of a reference standard structured interview conducted by a physician-rater to better determine the true diagnostic accuracy of both 3D-CAM and CAM assessments, and the use of convenience sampling at a single center, which reduces the generalizability of its findings.

In a similar vein, Shenkin et al in Study 2 attempt to evaluate the utility of the 4AT instrument in diagnosing delirium in older medical inpatients by testing the diagnostic accuracy of the 4AT against a reference standard (ie, DSM-IV–based evaluation by physicians) as well as comparing it to CAM. The 4AT takes less time (~2 minutes) and requires less knowledge and training to administer as compared to the CAM. The study showed that the abbreviated 4AT, compared to CAM, had a higher sensitivity (76% vs 40%) and lower specificity (94% vs 100%) in delirium detection. Thus, akin to the application of 3D-CAM in the postoperative setting, 4AT possesses key characteristics of a brief delirium screening test for older patients in the acute medical setting. In contrast to the Oberhaus et al study, a major strength of this study was the utilization of a reference standard that was validated by expert consensus. This allowed the 4AT and CAM assessments to be compared to a more objective standard, thereby directly testing their diagnostic performance in detecting delirium.

Application for Clinical Practice and System Implementation

The findings from both Study 1 and 2 suggest that using an abbreviated delirium instrument in both surgical and acute medical settings may provide a pragmatic and sensitive method to detect delirium in older patients. The brevity of administration of 3D-CAM (~3 minutes) and 4AT (~2 minutes), combined with their higher sensitivity for detecting delirium compared to CAM, make these instruments potentially effective rapid screening tests for delirium in hospitalized older patients. Importantly, the utilization of such instruments might be a feasible way to mitigate the issue of underdiagnosing delirium in the hospital.

Several additional aspects of these abbreviated delirium instruments increase their suitability for clinical application. Specifically, the 3D-CAM and 4AT require less extensive training and clinical knowledge to both administer and interpret the results than the CAM.² For instance, a multistage, multiday training for CAM is a key factor in maintaining its diagnostic accuracy.^3,4 In contrast, the 3D-CAM requires only a 1- to 2-hour training session, and the 4AT can be administered by a nonclinician without the need for instrument-specific training. Thus, implementation of these instruments can be particularly pragmatic in clinical settings in which the staff involved in delirium screening cannot undergo the substantial training required to administer CAM. Moreover, these abbreviated tests enable nonphysician care team members to assume the role of delirium screener in the hospital. Taken together, the adoption of these abbreviated instruments may facilitate brief screenings of delirium in older patients by caregivers who see them most often—nurses and certified nursing assistants—thereby improving early detection and prevention of delirium-related complications in the hospital.

The feasibility of using abbreviated delirium screening instruments in the hospital setting raises a system implementation question—if these instruments are designed to be administered by those with limited to no training, could nonclinicians, such as hospital volunteers, effectively take on delirium screening roles in the hospital? If volunteers are able to take on this role, the integration of hospital volunteers into the clinical team can greatly expand the capacity for delirium screening in the hospital setting. Further research is warranted to validate the diagnostic accuracy of 3D-CAM and 4AT by nonclinician administrators in order to more broadly adopt this approach to delirium screening.

Practice Points

• Abbreviated delirium screening tools such as 3D-CAM and 4AT may be pragmatic instruments to improve delirium detection in surgical and hospitalized older patients, respectively.
• Further studies are warranted to validate the diagnostic accuracy of 3D-CAM and 4AT by nonclinician administrators in order to more broadly adopt this approach to delirium screening.

Jared Doan, BS, and Fred Ko, MD
Geriatrics and Palliative Medicine, Icahn School of Medicine at Mount Sinai

Study 1 Overview (Oberhaus et al)

Objective: To compare the 3-Minute Diagnostic Confusion Assessment Method (3D-CAM) to the long-form Confusion Assessment Method (CAM) in detecting postoperative delirium.

Design: Prospective concurrent comparison of 3D-CAM and CAM evaluations in a cohort of postoperative geriatric patients.

Setting and participants: Eligible participants were patients aged 60 years or older undergoing major elective surgery at Barnes Jewish Hospital (St. Louis, Missouri) who were enrolled in ongoing clinical trials (PODCAST, ENGAGES, SATISFY-SOS) between 2015 and 2018. Surgeries were at least 2 hours in length and required general anesthesia, planned extubation, and a minimum 2-day hospital stay. Investigators were extensively trained in administering 3D-CAM and CAM instruments. Participants were evaluated 2 hours after the end of anesthesia care on the day of surgery, then daily until follow-up was completed per clinical trial protocol or until the participant was determined by CAM to be nondelirious for 3 consecutive days. For each evaluation, both 3D-CAM and CAM assessors approached the participant together, but the evaluation was conducted such that the 3D-CAM assessor was masked to the additional questions ascertained by the long-form CAM assessment. The 3D-CAM or CAM assessor independently scored their respective assessments blinded to the results of the other assessor.

Main outcome measures: Participants were concurrently evaluated for postoperative delirium by both 3D-CAM and long-form CAM assessments. Comparisons between 3D-CAM and CAM scores were made using Cohen κ with repeated measures, generalized linear mixed-effects model, and Bland-Altman analysis.

Main results: Sixteen raters performed 471 concurrent 3D-CAM and CAM assessments in 299 participants (mean [SD] age, 69 [6.5] years). Of these participants, 152 (50.8%) were men, 263 (88.0%) were White, and 211 (70.6%) underwent noncardiac surgery. Both instruments showed good intraclass correlation (0.98 for 3D-CAM, 0.84 for CAM) with good overall agreement (Cohen κ = 0.71; 95% CI, 0.58-0.83). The mixed-effects model indicated a significant disagreement between the 3D-CAM and CAM assessments (estimated difference in fixed effect, –0.68; 95% CI, –1.32 to –0.05; P = .04). The Bland-Altman analysis showed that the probability of a delirium diagnosis with the 3D-CAM was more than twice that with the CAM (probability ratio, 2.78; 95% CI, 2.44-3.23).

Conclusion: The high degree of agreement between 3D-CAM and long-form CAM assessments suggests that the former may be a pragmatic and easy-to-administer clinical tool to screen for postoperative delirium in vulnerable older surgical patients.

Study 2 Overview (Shenkin et al)

Objective: To assess the accuracy of the 4 ‘A’s Test (4AT) for delirium detection in the medical inpatient setting and to compare the 4AT to the CAM.

Design: Prospective randomized diagnostic test accuracy study.

Setting and participants: This study was conducted in emergency departments and acute medical wards at 3 UK sites (Edinburgh, Bradford, and Sheffield) and enrolled acute medical patients aged 70 years or older without acute life-threatening illnesses and/or coma. Assessors administering the delirium evaluation were nurses or graduate clinical research associates who underwent systematic training in delirium and delirium assessment. Additional training was provided to those administering the CAM but not to those administering the 4AT as the latter is designed to be administered without special training. First, all participants underwent a reference standard delirium assessment using Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) (DSM-IV) criteria to derive a final definitive diagnosis of delirium via expert consensus (1 psychiatrist and 2 geriatricians). Then, the participants were randomized to either the 4AT or the comparator CAM group using computer-generated pseudo-random numbers, stratified by study site, with block allocation. All assessments were performed by pairs of independent assessors blinded to the results of the other assessment.

Main outcome measures: All participants were evaluated by the reference standard (DSM-IV criteria for delirium) and by either 4AT or CAM instruments for delirium. The accuracy of the 4AT instrument was evaluated by comparing its positive and negative predictive values, sensitivity, and specificity to the reference standard and analyzed via the area under the receiver operating characteristic curve. The diagnostic accuracy of 4AT, compared to the CAM, was evaluated by comparing positive and negative predictive values, sensitivity, and specificity using Fisher’s exact test. The overall performance of 4AT and CAM was summarized using Youden’s Index and the diagnostic odds ratio of sensitivity to specificity.

Results: All 843 individuals enrolled in the study were randomized and 785 were included in the analysis (23 withdrew, 3 lost contact, 32 indeterminate diagnosis, 2 missing outcome). Of the participants analyzed, the mean age was 81.4 [6.4] years, and 12.1% (95/785) had delirium by reference standard assessment, 14.3% (56/392) by 4AT, and 4.7% (18/384) by CAM. The 4AT group had an area under the receiver operating characteristic curve of 0.90 (95% CI, 0.84-0.96), a sensitivity of 76% (95% CI, 61%-87%), and a specificity of 94% (95% CI, 92%-97%). In comparison, the CAM group had a sensitivity of 40% (95% CI, 26%-57%) and a specificity of 100% (95% CI, 98%-100%).

Conclusions: The 4AT is a pragmatic screening test for delirium in a medical space that does not require special training to administer. The use of this instrument may help to improve delirium detection as a part of routine clinical care in hospitalized older adults.

Delirium is an acute confusional state marked by fluctuating mental status, inattention, disorganized thinking, and altered level of consciousness. It is exceedingly common in older patients in both surgical and medical settings and is associated with increased morbidity, mortality, hospital length of stay, institutionalization, and health care costs. Delirium is frequently underdiagnosed in the hospitalized setting, perhaps due to a combination of its waxing and waning nature and a lack of pragmatic and easily implementable screening tools that can be readily administered by clinicians and nonclinicians alike.¹ While the CAM is a well-validated instrument to diagnose delirium, it requires specific training in the rating of each of the cardinal features ascertained through a brief cognitive assessment and takes 5 to 10 minutes to complete. Taken together, given the high patient load for clinicians in the hospital setting, the validation and application of brief delirium screening instruments that can be reliably administered by nonphysicians and nonclinicians may enhance delirium detection in vulnerable patients and consequently improve their outcomes.

In Study 1, Oberhaus et al approach the challenge of underdiagnosing delirium in the postoperative setting by investigating whether the widely accepted long-form CAM and an abbreviated 3-minute version, the 3D-CAM, provide similar delirium detection in older surgical patients. The authors found that both instruments were reliable tests individually (high interrater reliability) and had good overall agreement. However, the 3D-CAM was more likely to yield a positive diagnosis of delirium compared to the long-form CAM, consistent with its purpose as a screening tool with a high sensitivity. It is important to emphasize that the 3D-CAM takes less time to administer, but also requires less extensive training and clinical knowledge than the long-form CAM. Therefore, this instrument meets the prerequisite of a brief screening test that can be rapidly administered by nonclinicians, and if affirmative, followed by a more extensive confirmatory test performed by a clinician. Limitations of this study include a lack of a reference standard structured interview conducted by a physician-rater to better determine the true diagnostic accuracy of both 3D-CAM and CAM assessments, and the use of convenience sampling at a single center, which reduces the generalizability of its findings.

In a similar vein, Shenkin et al in Study 2 attempt to evaluate the utility of the 4AT instrument in diagnosing delirium in older medical inpatients by testing the diagnostic accuracy of the 4AT against a reference standard (ie, DSM-IV–based evaluation by physicians) as well as comparing it to CAM. The 4AT takes less time (~2 minutes) and requires less knowledge and training to administer as compared to the CAM. The study showed that the abbreviated 4AT, compared to CAM, had a higher sensitivity (76% vs 40%) and lower specificity (94% vs 100%) in delirium detection. Thus, akin to the application of 3D-CAM in the postoperative setting, 4AT possesses key characteristics of a brief delirium screening test for older patients in the acute medical setting. In contrast to the Oberhaus et al study, a major strength of this study was the utilization of a reference standard that was validated by expert consensus. This allowed the 4AT and CAM assessments to be compared to a more objective standard, thereby directly testing their diagnostic performance in detecting delirium.

Application for Clinical Practice and System Implementation

The findings from both Study 1 and 2 suggest that using an abbreviated delirium instrument in both surgical and acute medical settings may provide a pragmatic and sensitive method to detect delirium in older patients. The brevity of administration of 3D-CAM (~3 minutes) and 4AT (~2 minutes), combined with their higher sensitivity for detecting delirium compared to CAM, make these instruments potentially effective rapid screening tests for delirium in hospitalized older patients. Importantly, the utilization of such instruments might be a feasible way to mitigate the issue of underdiagnosing delirium in the hospital.

Several additional aspects of these abbreviated delirium instruments increase their suitability for clinical application. Specifically, the 3D-CAM and 4AT require less extensive training and clinical knowledge to both administer and interpret the results than the CAM.² For instance, a multistage, multiday training for CAM is a key factor in maintaining its diagnostic accuracy.^3,4 In contrast, the 3D-CAM requires only a 1- to 2-hour training session, and the 4AT can be administered by a nonclinician without the need for instrument-specific training. Thus, implementation of these instruments can be particularly pragmatic in clinical settings in which the staff involved in delirium screening cannot undergo the substantial training required to administer CAM. Moreover, these abbreviated tests enable nonphysician care team members to assume the role of delirium screener in the hospital. Taken together, the adoption of these abbreviated instruments may facilitate brief screenings of delirium in older patients by caregivers who see them most often—nurses and certified nursing assistants—thereby improving early detection and prevention of delirium-related complications in the hospital.

The feasibility of using abbreviated delirium screening instruments in the hospital setting raises a system implementation question—if these instruments are designed to be administered by those with limited to no training, could nonclinicians, such as hospital volunteers, effectively take on delirium screening roles in the hospital? If volunteers are able to take on this role, the integration of hospital volunteers into the clinical team can greatly expand the capacity for delirium screening in the hospital setting. Further research is warranted to validate the diagnostic accuracy of 3D-CAM and 4AT by nonclinician administrators in order to more broadly adopt this approach to delirium screening.

Practice Points

• Abbreviated delirium screening tools such as 3D-CAM and 4AT may be pragmatic instruments to improve delirium detection in surgical and hospitalized older patients, respectively.
• Further studies are warranted to validate the diagnostic accuracy of 3D-CAM and 4AT by nonclinician administrators in order to more broadly adopt this approach to delirium screening.

Jared Doan, BS, and Fred Ko, MD
Geriatrics and Palliative Medicine, Icahn School of Medicine at Mount Sinai

Study 1 Overview (Oberhaus et al)

Objective: To compare the 3-Minute Diagnostic Confusion Assessment Method (3D-CAM) to the long-form Confusion Assessment Method (CAM) in detecting postoperative delirium.

Design: Prospective concurrent comparison of 3D-CAM and CAM evaluations in a cohort of postoperative geriatric patients.

Setting and participants: Eligible participants were patients aged 60 years or older undergoing major elective surgery at Barnes Jewish Hospital (St. Louis, Missouri) who were enrolled in ongoing clinical trials (PODCAST, ENGAGES, SATISFY-SOS) between 2015 and 2018. Surgeries were at least 2 hours in length and required general anesthesia, planned extubation, and a minimum 2-day hospital stay. Investigators were extensively trained in administering 3D-CAM and CAM instruments. Participants were evaluated 2 hours after the end of anesthesia care on the day of surgery, then daily until follow-up was completed per clinical trial protocol or until the participant was determined by CAM to be nondelirious for 3 consecutive days. For each evaluation, both 3D-CAM and CAM assessors approached the participant together, but the evaluation was conducted such that the 3D-CAM assessor was masked to the additional questions ascertained by the long-form CAM assessment. The 3D-CAM or CAM assessor independently scored their respective assessments blinded to the results of the other assessor.

Main outcome measures: Participants were concurrently evaluated for postoperative delirium by both 3D-CAM and long-form CAM assessments. Comparisons between 3D-CAM and CAM scores were made using Cohen κ with repeated measures, generalized linear mixed-effects model, and Bland-Altman analysis.

Main results: Sixteen raters performed 471 concurrent 3D-CAM and CAM assessments in 299 participants (mean [SD] age, 69 [6.5] years). Of these participants, 152 (50.8%) were men, 263 (88.0%) were White, and 211 (70.6%) underwent noncardiac surgery. Both instruments showed good intraclass correlation (0.98 for 3D-CAM, 0.84 for CAM) with good overall agreement (Cohen κ = 0.71; 95% CI, 0.58-0.83). The mixed-effects model indicated a significant disagreement between the 3D-CAM and CAM assessments (estimated difference in fixed effect, –0.68; 95% CI, –1.32 to –0.05; P = .04). The Bland-Altman analysis showed that the probability of a delirium diagnosis with the 3D-CAM was more than twice that with the CAM (probability ratio, 2.78; 95% CI, 2.44-3.23).

Conclusion: The high degree of agreement between 3D-CAM and long-form CAM assessments suggests that the former may be a pragmatic and easy-to-administer clinical tool to screen for postoperative delirium in vulnerable older surgical patients.

Study 2 Overview (Shenkin et al)

Objective: To assess the accuracy of the 4 ‘A’s Test (4AT) for delirium detection in the medical inpatient setting and to compare the 4AT to the CAM.

Design: Prospective randomized diagnostic test accuracy study.

Setting and participants: This study was conducted in emergency departments and acute medical wards at 3 UK sites (Edinburgh, Bradford, and Sheffield) and enrolled acute medical patients aged 70 years or older without acute life-threatening illnesses and/or coma. Assessors administering the delirium evaluation were nurses or graduate clinical research associates who underwent systematic training in delirium and delirium assessment. Additional training was provided to those administering the CAM but not to those administering the 4AT as the latter is designed to be administered without special training. First, all participants underwent a reference standard delirium assessment using Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) (DSM-IV) criteria to derive a final definitive diagnosis of delirium via expert consensus (1 psychiatrist and 2 geriatricians). Then, the participants were randomized to either the 4AT or the comparator CAM group using computer-generated pseudo-random numbers, stratified by study site, with block allocation. All assessments were performed by pairs of independent assessors blinded to the results of the other assessment.

Main outcome measures: All participants were evaluated by the reference standard (DSM-IV criteria for delirium) and by either 4AT or CAM instruments for delirium. The accuracy of the 4AT instrument was evaluated by comparing its positive and negative predictive values, sensitivity, and specificity to the reference standard and analyzed via the area under the receiver operating characteristic curve. The diagnostic accuracy of 4AT, compared to the CAM, was evaluated by comparing positive and negative predictive values, sensitivity, and specificity using Fisher’s exact test. The overall performance of 4AT and CAM was summarized using Youden’s Index and the diagnostic odds ratio of sensitivity to specificity.

Results: All 843 individuals enrolled in the study were randomized and 785 were included in the analysis (23 withdrew, 3 lost contact, 32 indeterminate diagnosis, 2 missing outcome). Of the participants analyzed, the mean age was 81.4 [6.4] years, and 12.1% (95/785) had delirium by reference standard assessment, 14.3% (56/392) by 4AT, and 4.7% (18/384) by CAM. The 4AT group had an area under the receiver operating characteristic curve of 0.90 (95% CI, 0.84-0.96), a sensitivity of 76% (95% CI, 61%-87%), and a specificity of 94% (95% CI, 92%-97%). In comparison, the CAM group had a sensitivity of 40% (95% CI, 26%-57%) and a specificity of 100% (95% CI, 98%-100%).

Conclusions: The 4AT is a pragmatic screening test for delirium in a medical space that does not require special training to administer. The use of this instrument may help to improve delirium detection as a part of routine clinical care in hospitalized older adults.

Delirium is an acute confusional state marked by fluctuating mental status, inattention, disorganized thinking, and altered level of consciousness. It is exceedingly common in older patients in both surgical and medical settings and is associated with increased morbidity, mortality, hospital length of stay, institutionalization, and health care costs. Delirium is frequently underdiagnosed in the hospitalized setting, perhaps due to a combination of its waxing and waning nature and a lack of pragmatic and easily implementable screening tools that can be readily administered by clinicians and nonclinicians alike.¹ While the CAM is a well-validated instrument to diagnose delirium, it requires specific training in the rating of each of the cardinal features ascertained through a brief cognitive assessment and takes 5 to 10 minutes to complete. Taken together, given the high patient load for clinicians in the hospital setting, the validation and application of brief delirium screening instruments that can be reliably administered by nonphysicians and nonclinicians may enhance delirium detection in vulnerable patients and consequently improve their outcomes.

In Study 1, Oberhaus et al approach the challenge of underdiagnosing delirium in the postoperative setting by investigating whether the widely accepted long-form CAM and an abbreviated 3-minute version, the 3D-CAM, provide similar delirium detection in older surgical patients. The authors found that both instruments were reliable tests individually (high interrater reliability) and had good overall agreement. However, the 3D-CAM was more likely to yield a positive diagnosis of delirium compared to the long-form CAM, consistent with its purpose as a screening tool with a high sensitivity. It is important to emphasize that the 3D-CAM takes less time to administer, but also requires less extensive training and clinical knowledge than the long-form CAM. Therefore, this instrument meets the prerequisite of a brief screening test that can be rapidly administered by nonclinicians, and if affirmative, followed by a more extensive confirmatory test performed by a clinician. Limitations of this study include a lack of a reference standard structured interview conducted by a physician-rater to better determine the true diagnostic accuracy of both 3D-CAM and CAM assessments, and the use of convenience sampling at a single center, which reduces the generalizability of its findings.

In a similar vein, Shenkin et al in Study 2 attempt to evaluate the utility of the 4AT instrument in diagnosing delirium in older medical inpatients by testing the diagnostic accuracy of the 4AT against a reference standard (ie, DSM-IV–based evaluation by physicians) as well as comparing it to CAM. The 4AT takes less time (~2 minutes) and requires less knowledge and training to administer as compared to the CAM. The study showed that the abbreviated 4AT, compared to CAM, had a higher sensitivity (76% vs 40%) and lower specificity (94% vs 100%) in delirium detection. Thus, akin to the application of 3D-CAM in the postoperative setting, 4AT possesses key characteristics of a brief delirium screening test for older patients in the acute medical setting. In contrast to the Oberhaus et al study, a major strength of this study was the utilization of a reference standard that was validated by expert consensus. This allowed the 4AT and CAM assessments to be compared to a more objective standard, thereby directly testing their diagnostic performance in detecting delirium.

Application for Clinical Practice and System Implementation

The findings from both Study 1 and 2 suggest that using an abbreviated delirium instrument in both surgical and acute medical settings may provide a pragmatic and sensitive method to detect delirium in older patients. The brevity of administration of 3D-CAM (~3 minutes) and 4AT (~2 minutes), combined with their higher sensitivity for detecting delirium compared to CAM, make these instruments potentially effective rapid screening tests for delirium in hospitalized older patients. Importantly, the utilization of such instruments might be a feasible way to mitigate the issue of underdiagnosing delirium in the hospital.

Several additional aspects of these abbreviated delirium instruments increase their suitability for clinical application. Specifically, the 3D-CAM and 4AT require less extensive training and clinical knowledge to both administer and interpret the results than the CAM.² For instance, a multistage, multiday training for CAM is a key factor in maintaining its diagnostic accuracy.^3,4 In contrast, the 3D-CAM requires only a 1- to 2-hour training session, and the 4AT can be administered by a nonclinician without the need for instrument-specific training. Thus, implementation of these instruments can be particularly pragmatic in clinical settings in which the staff involved in delirium screening cannot undergo the substantial training required to administer CAM. Moreover, these abbreviated tests enable nonphysician care team members to assume the role of delirium screener in the hospital. Taken together, the adoption of these abbreviated instruments may facilitate brief screenings of delirium in older patients by caregivers who see them most often—nurses and certified nursing assistants—thereby improving early detection and prevention of delirium-related complications in the hospital.

The feasibility of using abbreviated delirium screening instruments in the hospital setting raises a system implementation question—if these instruments are designed to be administered by those with limited to no training, could nonclinicians, such as hospital volunteers, effectively take on delirium screening roles in the hospital? If volunteers are able to take on this role, the integration of hospital volunteers into the clinical team can greatly expand the capacity for delirium screening in the hospital setting. Further research is warranted to validate the diagnostic accuracy of 3D-CAM and 4AT by nonclinician administrators in order to more broadly adopt this approach to delirium screening.

Practice Points

• Abbreviated delirium screening tools such as 3D-CAM and 4AT may be pragmatic instruments to improve delirium detection in surgical and hospitalized older patients, respectively.
• Further studies are warranted to validate the diagnostic accuracy of 3D-CAM and 4AT by nonclinician administrators in order to more broadly adopt this approach to delirium screening.

Jared Doan, BS, and Fred Ko, MD
Geriatrics and Palliative Medicine, Icahn School of Medicine at Mount Sinai