A prospective randomized study examining the impact of intravenous versus inhalational anesthesia on postoperative cognitive decline and delirium.

The present prospective randomized study was designed to investigate whether the development of Post Operative Cognitive Decline (POCD) is related to anesthesia type in older adults. All patients were screened for delirium and mental status, received baseline neuropsychological assessment, and evaluation of activities of daily living (ADLs). Follow-up assessments were performed at 3-6 months and 12-18 months. Patients were randomized to receive either inhalation anesthesia (ISO) with isoflurane or total intravenous anesthesia (TIVA) with propofol for maintenance anesthesia. ISO (n = 99) and TIVA (n = 100) groups were similar in demographics, preoperative cognition, and incidence of post-operative delirium. Groups did not differ in terms of mean change in memory or executive function from baseline to follow-up. Pre-surgical cognitive function is the only variable predictive of the development of POCD. Anesthetic type was not predictive of POCD. However, ADLs were predictive of post-operative delirium development. Overall, this pilot study represents a prospective, randomized study demonstrating that when examining ISO versus TIVA for maintenance of general anesthesia, there is no significant difference in cognition between anesthetic types. There is also no difference in the occurrence of postoperative delirium. Postoperative cognitive decline was best predicted by lower baseline cognition and functional status.

Isomeric Carborane Neuromuscular Blocking Agents.

We synthesized a family of neuromuscular blocking agents (NMB) based on decamethonium, but containing a carborane cluster in the methylene chain between the two quaternary ammonium groups. The carborane cluster isomers o-NMB, m-NMB, and p-NMB were tested in animals for neuromuscular block and compared with agents used clinically: rocuronium and decamethonium. All three isomers caused reversible muscle weakness in mice as determined by grip strength and inverted screen tests, with a potency rank of p-NMB > rocuronium > decamethonium > m-NMB > o-NMB. The mechanism of action of the compounds was determined by using the in vitro rat phrenic nerve hemi-diaphragm preparation and electrophysiologic measurements in cells. Neostigmine reversed hemi-diaphragm weakness caused by the three isomers and rocuronium, but not succinylcholine. In electrophysiologic recordings of currents through acetylcholine receptor channels, the carborane compounds did not activate channel activity but did inhibit channel activation by acetylcholine. These results demonstrate that the carborane neuromuscular blocking agents are non-depolarizers in contrast to the depolarizing action of the parent compound.

Intermediate-Acting Nondepolarizing Neuromuscular Blocking Agents and Risk of Postoperative 30-Day Morbidity and Mortality, and Long-term Survival.

BACKGROUND: Nondepolarizing neuromuscular blocking drugs (NNMBDs) are commonly used as an adjunct to general anesthesia. Residual blockade is common, but its potential adverse effects are incompletely known. This study was designed to assess the association between NNMBD use with or without neostigmine reversal and postoperative morbidity and mortality. METHODS: This is a retrospective observational study of 11,355 adult patients undergoing general anesthesia for noncardiac surgery at 5 Veterans Health Administration (VA) hospitals. Of those, 8984 received NNMBDs, and 7047 received reversal with neostigmine. The primary outcome was a composite of respiratory complications (failure to wean from the ventilator, reintubation, or pneumonia), which was "yes" if a patient had any of the 3 component events and "no" if they had none. Secondary outcomes were nonrespiratory complications, 30-day and long-term all-cause mortality. We adjusted for differences in patient risk using propensity matched (PM) followed by assessment of the association of interest by logistic regression between the matched pairs as our primary analysis and multivariable logistic regression (MLR) as a sensitivity analysis. RESULTS: Our primary aim was to assess the adverse outcomes in the patients who had received NNMBDs with and without neostigmine. Administration of an NNMBD without neostigmine reversal compared with NNMBD with neostigmine reversal was associated with increased odds of respiratory complications (PM odds ratio [OR], 1.75 [95% confidence interval [CI], 1.23-2.50]; MLR OR, 1.71 [CI, 1.24-2.37]) and a marginal increase in 30-day mortality (PM OR, 1.83 [CI, 0.99-3.37]; MLR OR, 1.78 [CI, 1.02-3.13]). However, there were no statistically significant associations with nonrespiratory complications or long-term mortality. Patients who were administered an NNMBD followed by neostigmine had no differences in outcomes compared with patients who had general anesthesia without an NNMBD. CONCLUSIONS: The use of NNMBDs without neostigmine reversal was associated with increased odds of our composite respiratory outcome compared with patients reversed with neostigmine. Based on these data, we conclude that reversal of NNMBDs should become a standard practice if extubation is planned.

Use of Sugammadex in Patients With Obesity: A Pooled Analysis.

A growing proportion of patients undergoing surgical procedures are obese, providing anesthesiologists with numerous challenges for patient management. The current pooled analysis evaluated recovery times following sugammadex reversal of neuromuscular blockade by body mass index (BMI) in general, and in particular, in patients with BMIs ≥30 kg/m (defined as obese) and <30 kg/m (defined as non-obese). Data were pooled from 27 trials evaluating recommended sugammadex doses for reversal of moderate [reappearance of the second twitch of the train-of-four (TOF); sugammadex 2 mg/kg] or deep (1-2 post-tetanic counts or 15 minutes after rocuronium; sugammadex 4 mg/kg) rocuronium- or vecuronium-induced neuromuscular blockade. All doses of sugammadex were administered based on actual body weight. The recovery time from sugammadex administration to a TOF ratio ≥0.9 was the primary efficacy variable in all individual studies and in the pooled analysis. This analysis comprised a total of 1418 adult patients treated with sugammadex; 267 (18.8%) of these patients had a BMI ≥30 kg/m. The average time to recovery of the TOF ratio to 0.9 was 1.9 minutes for rocuronium-induced blockade and 3.0 minutes for vecuronium-induced blockade. No clinically relevant correlation was observed between BMI and recovery time. The recommended sugammadex doses based on actual body weight provide rapid recovery from neuromuscular blockade in both obese and non-obese patients; no dose adjustments are required in the obese patient.

Effect of positive end-expiratory pressure on blood loss during retropubic and robot-assisted laparoscopic radical prostatectomy.

OBJECTIVES: To study the effect of end-expiratory pressure used during anesthesia on blood loss during radical prostatectomy. METHODS: We evaluated 247 patients who underwent either radical retropubic prostatectomy or robot-assisted laparoscopic prostatectomy at a single institution from 2008 to 2013 by one of four surgeons. Patient characteristics were compared using t-tests, rank sum or χ(2) -tests as appropriate. The association between positive end-expiratory pressure and estimated blood loss was tested using linear regression. RESULTS: Patients were classified into high (≥4 cmH2 O) and low (≤1 cmH2 O) positive-end expiratory pressure groups. Estimated blood loss in radical retropubic prostatectomy was higher in the high positive end-expiratory pressure group (1000 mL vs 800 mL, P = 0.042). Estimated blood loss in robot-assisted laparoscopic prostatectomy was lower in the high positive end-expiratory pressure group (150 mL vs 250 mL, P = 0.015). After adjusting for other factors known to influence blood loss, a 5-cmH2 O increase in positive end-expiratory pressure was associated with a 34.9% increase in estimated blood loss (P = 0.030) for radical retropubic prostatectomy, and a 33.0% decrease for robot-assisted laparoscopic prostatectomy (P = 0.038). CONCLUSIONS: In radical retropubic prostatectomy, high positive end-expiratory pressure was associated with higher estimated blood loss, and the benefits of positive end-expiratory pressure should be weighed against the risk of increased estimated blood loss. In robot-assisted laparoscopic prostatectomy, high positive end-expiratory pressure was associated with lower estimated blood loss, and might have more than just pulmonary benefits.

Depressive Symptoms and Risk of Postoperative Delirium.

OBJECTIVE: Previous studies have shown that elevated depressive symptoms are associated with increased risk of postoperative delirium. However, to our knowledge no previous studies have examined whether different components of depression are differentially predictive of postoperative delirium. METHODS: One thousand twenty patients were screened for postoperative delirium using the Confusion Assessment Method and through retrospective chart review. Patients underwent cognitive, psychosocial, and medical assessments preoperatively. Depression was assessed using the Geriatric Depression Scale-Short Form. RESULTS: Thirty-eight patients developed delirium (3.7%). Using a factor structure previously validated among geriatric medical patients, the authors examined three components of depression as predictors of postoperative delirium: negative affect, cognitive distress, and behavioral inactivity. In multivariate analyses controlling for age, education, comorbidities, and cognitive function, the authors found that greater behavioral inactivity was associated with increased risk of delirium (OR: 1.95 [1.11, 3.42]), whereas negative affect (OR: 0.65 [0.31, 1.36]) and cognitive distress (OR: 0.95 [0.63, 1.43]) were not. CONCLUSION: Different components of depression are differentially predictive of postoperative delirium among adults undergoing noncardiac surgery.

Association between Intraoperative Hypotension and Hypertension and 30-day Postoperative Mortality in Noncardiac Surgery.

BACKGROUND: Although deviations in intraoperative blood pressure are assumed to be associated with postoperative mortality, critical blood pressure thresholds remain undefined. Therefore, the authors estimated the intraoperative thresholds of systolic blood pressure (SBP), mean blood pressure (MAP), and diastolic blood pressure (DBP) associated with increased risk-adjusted 30-day mortality. METHODS: This retrospective cohort study combined intraoperative blood pressure data from six Veterans Affairs medical centers with 30-day outcomes to determine the risk-adjusted associations between intraoperative blood pressure and 30-day mortality. Deviations in blood pressure were assessed using three methods: (1) population thresholds (individual patient sum of area under threshold [AUT] or area over threshold 2 SDs from the mean of the population intraoperative blood pressure values), (2). absolute thresholds, and (3) percent change from baseline blood pressure. RESULTS: Thirty-day mortality was associated with (1) population threshold: systolic AUT (odds ratio, 3.3; 95% CI, 2.2 to 4.8), mean AUT (2.8; 1.9 to 4.3), and diastolic AUT (2.4; 1.6 to 3.8). Approximate conversions of AUT into its separate components of pressure and time were SBP < 67 mmHg for more than 8.2 min, MAP < 49 mmHg for more than 3.9 min, DBP < 33 mmHg for more than 4.4 min. (2) Absolute threshold: SBP < 70 mmHg for more than or equal to 5 min (odds ratio, 2.9; 95% CI, 1.7 to 4.9), MAP < 49 mmHg for more than or equal to 5 min (2.4; 1.3 to 4.6), and DBP < 30 mmHg for more than or equal to 5 min (3.2; 1.8 to 5.5). (3) Percent change: MAP decreases to more than 50% from baseline for more than or equal to 5 min (2.7; 1.5 to 5.0). Intraoperative hypertension was not associated with 30-day mortality with any of these techniques. CONCLUSION: Intraoperative hypotension, but not hypertension, is associated with increased 30-day operative mortality.

A pilot study evaluating presurgery neuroanatomical biomarkers for postoperative cognitive decline after total knee arthroplasty in older adults.

BACKGROUND: Total knee arthroplasty improves quality of life but is associated with postoperative cognitive dysfunction in older adults. This prospective longitudinal pilot study with a parallel control group tested the hypotheses that (1) nondemented adults would exhibit primary memory and executive difficulties after total knee arthroplasty, and (2) reduced preoperative hippocampus/entorhinal volume would predict postoperative memory change, whereas preoperative leukoaraiosis and lacunae volumes would predict postoperative executive dysfunction. METHODS: Surgery (n = 40) and age-education-matched controls with osteoarthritis (n = 15) completed pre- and postoperative (3 weeks, 3 months, and 1 yr) memory and cognitive testing. Hypothesized brain regions of interest were measured in patients completing preoperative magnetic resonance scans (surgery, n = 31; control, n = 12). Analyses used reliable change methods to identify the frequency of cognitive change at each time point. RESULTS: The incidence of postoperative memory difficulties was shown with delay test indices (i.e., story memory test: 3 weeks = 17%, 3 months = 25%, 1 yr = 9%). Postoperative executive difficulty with measures of inhibitory function (i.e., Stroop Color Word: 3 weeks = 21%, 3 months = 22%, 1 yr = 9%). Hierarchical regression analysis assessing the predictive interaction of group (surgery, control) and preoperative neuroanatomical structures on decline showed that greater preoperative volumes of leukoaraiosis/lacunae were significantly contributed to postoperative executive (inhibitory) declines. CONCLUSIONS: This pilot study suggests that executive and memory declines occur in nondemented adults undergoing orthopedic surgery. Severity of preoperative cerebrovascular disease may be relevant for understanding executive decline, in particular.

Does depth of anesthesia monitoring improve postoperative outcomes?

PURPOSE OF REVIEW: Devices using the electroencephalogram to estimate anesthetic depth have been available since 1996. Despite the use of these monitors for over a decade, there is little agreement among clinicians about the need for or value of depth of anesthesia monitoring. Since the majority of the studies evaluating the impact of depth of anesthesia monitoring on postoperative outcomes have utilized the bispectral index (BIS Covidian), this manuscript will focus on studies with this device. This review will evaluate the evidence that BIS monitoring can improve long-term outcomes. RECENT FINDINGS: BIS-guided anesthesia can reduce the incidence of awareness with recall in high-risk patients, but a recent study found that anesthetic management directed by an end-tidal anesthetic-agent concentration protocol is equally effective, and probably less expensive. Deep anesthesia (BIS < 45) during the intraoperative period is associated with increased postoperative mortality, but this relationship may be an epiphenomenon rather than causal. SUMMARY: There is growing concern that anesthetic management and even specific anesthetic agents may worsen outcomes in high-risk patients. There is, however, no conclusive evidence that depth of anesthesia monitors can improve outcomes and no evidenced-based reasons for anesthesia providers to change their current practice.

Postoperative cognitive disorders.

PURPOSE OF REVIEW: The elderly are the fastest growing segment of the population and undergo 25-30% of all surgical procedures. Postoperative cognitive problems are common in older patients following major surgery. The socioeconomic implications of these cognitive disorders are profound; cognitive decline is associated with a loss of independence, a reduction in the quality of life, and death. This review will focus on the two most common cognitive problems following surgery: postoperative delirium and postoperative cognitive dysfunction (POCD). RECENT FINDINGS: For years, preoperative geriatric consultation/screening was the only intervention proven to decrease postoperative delirium. There are, however, several recent publications indicating that preoperative and postoperative pharmacological and medical (hydration, oxygenation) management can reduce postoperative delirium. Spinal anesthesia with minimal propofol sedation has been shown to decrease the incidence of postoperative delirium in hip-fracture patients. Likewise, dexmedetomidine sedation in mechanically ventilated patients in the ICU is associated with less postoperative delirium and shorter ventilator times. Preoperative levels of education and brain function (cognitive reserve) may predict patients at risk for postoperative cognitive problems. Reduced white matter integrity is reported to place patients at a higher risk for both postoperative delirium and POCD. SUMMARY: The etiology of postoperative cognitive problems is unknown, but there is emerging evidence that decreased preoperative cognitive function contributes to the development of postoperative delirium and POCD. There is growing concern that inhalation anesthetics may be neurotoxic to the aging brain, but there are no human data evaluating this hypothesis to date. Randomized controlled trials evaluating interventions to improve long-term cognitive outcomes in elderly patients are urgently needed.

Efficacy, safety, and pharmacokinetics of sugammadex for the reversal of rocuronium-induced neuromuscular blockade in elderly patients.

BACKGROUND: The management of elderly patients can be challenging for anesthesiologists for many reasons, including altered pharmacokinetics and dynamics. This study compared the efficacy, safety, and pharmacokinetics of sugammadex for moderate rocuronium-induced neuromuscular blockade reversal in adult (aged 18-64 yr) versus elderly adult (aged 65 yr or older) patients. METHODS: This phase 3a, multicenter, parallel-group, comparative, open-label study enrolled 162 patients aged 18 yr and older, American Society of Anesthesiologists class 1-3, scheduled for surgery with general anesthesia and requiring neuromuscular blockade. After anesthesia induction, patients received rocuronium, 0.6 mg/kg, before tracheal intubation, with maintenance doses of 0.15 mg/kg as required. At the end of surgery, patients received sugammadex, 2.0 mg/kg, at reappearance of the second twitch of the train-of-four (TOF) for reversal. The primary efficacy variable was time from sugammadex administration to recovery of the TOF ratio to 0.9 or greater. Pharmacokinetics and safety were also evaluated. RESULTS: Overall, 150 patients were treated and had at least one postbaseline efficacy assessment; 48 were aged 18-64 yr (adult), 62 were aged 65-74 yr (elderly), and 40 were aged 75 yr or older (old-elderly). The geometric mean time (95% confidence interval) from sugammadex administration to recovery of the TOF ratio to 0.9 increased with age, from 2.3 (2.0-2.6) min (adults) to 2.9 (2.7-3.2) min (elderly/old-elderly groups combined). Recovery of the TOF ratio to 0.9 was estimated to be 0.7 min faster in adults compared with patients aged 65 yr or older (P = 0.022). Sugammadex was well tolerated by all patients. CONCLUSION: Sugammadex facilitates rapid reversal from moderate rocuronium-induced neuromuscular blockade in adults of all ages.

Executive function and depression as independent risk factors for postoperative delirium.

BACKGROUND: Postoperative delirium has been associated with greater complications, medical cost, and increased mortality during hospitalization. Recent evidence suggests that preoperative executive dysfunction and depression may predict postoperative delirium; however, the combined effect of these risk factors remains unknown. This study examined the association among preoperative executive function, depressive symptoms, and established clinical predictors of postoperative delirium among 998 consecutive patients undergoing major noncardiac surgery. METHODS: A total of 998 patients were screened for postoperative delirium (n = 998) using the Confusion Assessment Method as well as through retrospective chart review. Patients underwent cognitive, psychosocial, and medical assessments preoperatively. Executive function was assessed using the Concept Shifting Task, Letter-Digit Coding, and a modified Stroop Color Word Interference Test. Depression was assessed by the Beck Depression Inventory. RESULTS: Preoperative executive dysfunction (P = 0.007) and greater levels of depressive symptoms (P = 0.049) were associated with a greater incidence of postoperative delirium, independent of other risk factors. Secondary analyses of cognitive performance demonstrated that the Stroop Color Word Interference Test, the executive task with the greatest complexity in this battery, was more strongly associated with postoperative delirium than simpler tests of executive function. Furthermore, patients exhibiting both executive dysfunction and clinically significant levels of depression were at greatest risk for developing delirium postoperatively. CONCLUSIONS: Preoperative executive dysfunction and depressive symptoms are predictive of postoperative delirium among noncardiac surgical patients. Executive tasks with greater complexity are more strongly associated with postoperative delirium relative to tests of basic sequencing.

Measures of executive function and depression identify patients at risk for postoperative delirium.

BACKGROUND: Postoperative delirium is associated with increased morbidity and mortality. Preexisting cognitive impairment and depression have been frequently cited as important risk factors for this complication. This prospective cohort study was designed to determine whether individuals who perform poorly on preoperative cognitive tests and/or exhibited depressive symptoms would be at high risk for the development of postoperative delirium. METHODS: One hundred nondemented patients, aged 50 yr and older, scheduled to undergo major, elective noncardiac surgery completed a preoperative test battery that included measures of global cognition, executive function, and symptoms of depression. Known preoperative risk factors for delirium were collected and examined with the results of the preoperative test battery to determine the independent predictors of delirium. RESULTS: The overall incidence of delirium was 16% and was associated with increased hospital duration of stay (P < 0.05) and an increased incidence of postoperative complications (P < 0.01). Delirious subjects did not differ from their nondelirious cohorts with regard to their preoperative global cognitive function, preexisting medical comorbidities, age, anesthetic management, or history of alcohol use. Preoperative executive scores (P < 0.001) and depression (P < 0.001), as measured by the Trail Making B test and Geriatric Depression Scale-Short Form, respectively, were found to be independent predictors of postoperative delirium. CONCLUSIONS: Low preoperative executive scores and depressive symptoms independently predict postoperative delirium in older individuals. A rapid, simple test combination including tests of executive function and depression could improve physicians' ability to recognize patients who might benefit from a perioperative intervention strategy to prevent postoperative delirium.

An efficient screening tool for preoperative depression: the Geriatric Depression Scale-Short Form.

BACKGROUND: Depression is highly prevalent in patients before surgery, and it has been widely shown to have a serious impact on their postoperative outcomes. It would therefore be desirable for physicians to obtain a quick, simple screen to evaluate depression to consider treatment of symptomatology and potentially optimize postoperative outcomes. METHODS: In this study, we investigated the prevalence of depression in a presurgical inpatient sample undergoing major, noncardiac surgery. In addition, we sought to establish the Geriatric Depression Scale-Short Form (GDS-SF) as a valid screening tool for depression by examining its relationship to the Beck Depression inventory (BDI) by age and gender. RESULTS: In our sample of 1043 presurgical candidates, prevalence of depression as established by the BDI was significantly higher than rates consistently found in healthy community samples. Depression was more common in women than in men (P = 0.02), and depression rates were lower in elders relative to middle-aged and younger groups (P = 0.003 and 0.003, respectively). In addition, we found that there was a high correlation between the BDI and the GDS-SF within each of the age groups. CONCLUSIONS: These data further support the need for depression screens in presurgical populations and establish the validity of the GDS-SF as a valid quick assessment alternative available to physicians.

Type and severity of cognitive decline in older adults after noncardiac surgery.

BACKGROUND: The authors investigated type and severity of cognitive decline in older adults immediately and 3 months after noncardiac surgery. Changes in instrumental activities of daily living were examined relative to type of cognitive decline. METHODS: Of the initial 417 older adults enrolled in the study, 337 surgery patients and 60 controls completed baseline, discharge, and/or 3-month postoperative cognitive and instrumental activities of daily living measures. Reliable change methods were used to examine three types of cognitive decline: memory, executive function, and combined executive function/memory. SD cutoffs were used to grade severity of change as mild, moderate or severe. RESULTS: At discharge, 186 (56%) patients experienced cognitive decline, with an equal distribution in type and severity. At 3 months after surgery, 231 patients (75.1%) experienced no cognitive decline, 42 (13.6%) showed only memory decline, 26 (8.4%) showed only executive function decline, and 9 (2.9%) showed decline in both executive and memory domains. Of those with cognitive decline, 36 (46.8%) had mild, 25 (32.5%) had moderate, and 16 (20.8%) had severe decline. The combined group had more severe impairment. Executive function or combined (memory and executive) deficits involved greater levels of functional (i.e., instrumental activities of daily living) impairment. The combined group was less educated than the unimpaired and memory groups. CONCLUSION: Postsurgical cognitive presentation varies with time of testing. At 3 months after surgery, more older adults experienced memory decline, but only those with executive or combined cognitive decline had functional limitations. The findings have relevance for patients and caregivers. Future research should examine how perioperative factors influence neuronal systems.

Predictors of cognitive dysfunction after major noncardiac surgery.

BACKGROUND: The authors designed a prospective longitudinal study to investigate the hypothesis that advancing age is a risk factor for postoperative cognitive dysfunction (POCD) after major noncardiac surgery and the impact of POCD on mortality in the first year after surgery. METHODS: One thousand sixty-four patients aged 18 yr or older completed neuropsychological tests before surgery, at hospital discharge, and 3 months after surgery. Patients were categorized as young (18-39 yr), middle-aged (40-59 yr), or elderly (60 yr or older). At 1 yr after surgery, patients were contacted to determine their survival status. RESULTS: At hospital discharge, POCD was present in 117 (36.6%) young, 112 (30.4%) middle-aged, and 138 (41.4%) elderly patients. There was a significant difference between all age groups and the age-matched control subjects (P < 0.001). At 3 months after surgery, POCD was present in 16 (5.7%) young, 19 (5.6%) middle-aged, and 39 (12.7%) elderly patients. At this time point, the prevalence of cognitive dysfunction was similar between age-matched controls and young and middle-aged patients but significantly higher in elderly patients compared to elderly control subjects (P < 0.001). The independent risk factors for POCD at 3 months after surgery were increasing age, lower educational level, a history of previous cerebral vascular accident with no residual impairment, and POCD at hospital discharge. Patients with POCD at hospital discharge were more likely to die in the first 3 months after surgery (P = 0.02). Likewise, patients who had POCD at both hospital discharge and 3 months after surgery were more likely to die in the first year after surgery (P = 0.02). CONCLUSIONS: Cognitive dysfunction is common in adult patients of all ages at hospital discharge after major noncardiac surgery, but only the elderly (aged 60 yr or older) are at significant risk for long-term cognitive problems. Patients with POCD are at an increased risk of death in the first year after surgery.

The effect of intravenous indigo carmine on near-infrared cerebral oximetry.

The effects of IV-administered dyes on pulse oximetry have been well described. However, the effects on near-infrared cerebral oximetry have not been well documented. We report a series of four patients undergoing radical prostatectomy who were monitored with cerebral oximetry during surgery. After the administration of indigo carmine, intraoperative desaturations were observed for an extended period. Because clinical use of near-infrared cerebral oximetry is increasing, anesthesiologists should be aware of this issue.

Processed EEG and patient outcome.

The era of research evaluating clinical outcomes associated with processed electroencephalogram (EEG) monitoring began with the first randomized trial of bispectral index monitoring (BIS) performed as part of the clearance process for approving routine clinical use of the BIS monitor by the United States Food and Drug Administration. Subsequent to this initial investigation, numerous other clinical investigations have demonstrated that the use of processed EEG monitors as an additional method of patient assessment and an aid to anaesthetic dosing can decrease anaesthetic usage and hasten recovery times. Because of the presumed association between anaesthetic effect and EEG changes, it is not surprising that the additional research has focused on the impact of processed EEG monitoring on postoperative outcomes and perioperative safety especially the prevention of intraoperative awareness.