Unconsciousness is a fundamental component of general anesthesia (GA), but anesthesiologists have no reliable ways to be certain that a patient is unconscious. To develop EEG signatures that track loss and recovery of consciousness under GA, we recorded high-density EEGs in humans during gradual induction of and emergence from unconsciousness with propofol. The subjects executed an auditory task at 4-s intervals consisting of interleaved verbal and click stimuli to identify loss and recovery of consciousness. During induction, subjects lost responsiveness to the less salient clicks before losing responsiveness to the more salient verbal stimuli; during emergence they recovered responsiveness to the verbal stimuli before recovering responsiveness to the clicks. The median frequency and bandwidth of the frontal EEG power tracked the probability of response to the verbal stimuli during the transitions in consciousness. Loss of consciousness was marked simultaneously by an increase in low-frequency EEG power (<1 Hz), the loss of spatially coherent occipital alpha oscillations (8–12 Hz), and the appearance of spatially coherent frontal alpha oscillations. These dynamics reversed with recovery of consciousness. The low-frequency phase modulated alpha amplitude in two distinct patterns. During profound unconsciousness, alpha amplitudes were maximal at low-frequency peaks, whereas during the transition into and out of unconsciousness, alpha amplitudes were maximal at low-frequency nadirs. This latter phase–amplitude relationship predicted recovery of consciousness. Our results provide insights into the mechanisms of propofol-induced unconsciousness, establish EEG signatures of this brain state that track transitions in consciousness precisely, and suggest strategies for monitoring the brain activity of patients receiving GA.

http://www.pnas.org/content/pnas/110/12/E1142.full.pdf

Electroencephalogram signatures of loss and recovery of consciousness from propofol

The purpose of this guideline is to present evidence-based and consensus-based recommendations for the prevention and treatment of postoperative delirium. The cornerstones of the guideline are the preoperative identification and handling of patients at risk, adequate intraoperative care, postoperative detection of delirium and management of delirious patients. The scope of this guideline is not to cover ICU delirium. Considering that many medical disciplines are involved in the treatment of surgical patients, a team-based approach should be implemented into daily practice. This guideline is aimed to promote knowledge and education in the preoperative, intraoperative and postoperative setting not only among anaesthesiologists but also among all other healthcare professionals involved in the care of surgical patients.

European Society of Anaesthesiology evidence-based and consensus-based guideline on postoperative delirium

Disclosure Information: Disclosures for the members of t Geriatrics Society Postoperative Delirium Panel are listed in Support: Supported by a grant from the John A Hartford Fou to the Geriatrics-for-Specialists Initiative of the American Geri (grant 2009-0079). This article is a supplement to the American Geriatrics Soci Practice Guidelines for Postoperative Delirium in Older Adu at the American College of Surgeons 100 Annual Clinic San Francisco, CA, October 2014.

Postoperative Delirium in Older Adults: Best Practice Statement from the American Geriatrics Society

Fast-track hip and knee arthroplasty.

For patients undergoing coronary-artery bypass grafting (CABG), adverse neurologic outcomes, including stroke and cognitive decline, are major concerns. Even mild cognitive deficits before surgery may be a marker for cerebrovascular disease and increased risk.

Cognitive and neurologic outcomes after coronary-artery bypass surgery.

Postoperative delirium (PD) is a common but serious problem after major surgery with a multifactorial pathogenesis including age, pain, opioid use, sleep disturbances and the surgical stress response. These factors have been minimised by the “fast-track methodology” previously demonstrated to enhance recovery and reduce morbidity. Clinical symptoms of PD were routinely collected three times daily from preoperatively until discharge in a well-defined enhanced recovery program after colonic surgery in 247 consecutive patients. Total median length of hospital stay was 3 days. Seven patients (2.8 %) developed clinical signs of PD most within the first 72 postoperative hours and only 1 patient with PD extending to 120 h postoperatively. Only 1 PD patient required treatment with serenase. PD patients were older (83 vs. 73 years) and had longer median stay (6 vs. 3 days). No difference in development of PD between open and laparoscopic operation could be demonstrated. Among the 7 patients with PD, 3 of these patients had later surgical complications. One patient had a subsequent strangulated small intestine, another an anastomotic leakage complicated by a bleeding gastric ulcer and death on day 12 and 1 with fever, abdominal pain and suspected but disproven anastomotic leakage (stay 21, 12 and 22 days, respectively). The remaining 4 PD patients stayed 4, 4, 5 and 6 days with an uncomplicated course. These data support that an enhanced postoperative recovery program may decrease the risk and duration of PD after colonic surgery.

Delirium in fast-track colonic surgery

Delirium in the fast-track surgery setting

Background Major surgery is followed by pronounced sleep disturbances after traditional perioperative care potentially leading to prolonged recovery. The aim was to evaluate the rapid eye movement (REM) sleep duration and sleep architecture before and after fast-track hip and knee replacement with length of stay (LOS) Methods Ten subjects (≥60 yr) receiving spinal anaesthesia and multimodal opioid-sparing postoperative analgesia for total hip or knee arthroplasty were included. Ambulatory polysomnography was performed one night before operation at home, continuously during hospitalization, and on the fourth postoperative night at home. Sleep staging was performed according to the American Academy of Sleep Medicine manual. Opioid use, pain, and inflammatory response (C-reactive protein) were also evaluated. Results The mean LOS was 1.5 (1–2) days. The mean REM sleep time decreased from a mean of 18.2 (9.5–23.5)% of total sleep time to 1.2 (0–5.8)% on the first postoperative night ( P =0.002); awake time increased from 19.1 (3.7–44.4)% to 44.3 (12.2–70.6)% ( P =0.009); and sleep architecture on the first postoperative night was more disturbed than before operation. Sleep architecture normalized on the fourth postoperative night. There was no association between opioid use, pain scores, and inflammatory response with a disturbed sleep pattern. Conclusions Despite ultra-short LOS and provision of spinal anaesthesia with multimodal opioid-sparing analgesia, REM sleep was almost eliminated on the first postoperative night after fast-track orthopaedic surgery but returned to pre-admission levels when at home on the fourth postoperative night.

Sleep Disturbances After Fast-Track Hip and Knee Arthroplasty

1392 December 2012 We read with interest the recent article by Flink et al.1 in which the authors evaluated the frequency of postoperative delirium (POD) in 106 elderly patients aged 65 yr or older after elective knee replacement. The screening for POD was thorough and well-conducted with recognized screening tools, with an incidence of 25% on days 2–3 postoperatively. The pathophysiologic mechanisms are multiple, including anemia, electrolyte disturbances, infection, pain, and benzodiazepine and opioid use.2 Patients with obstructive sleep apnea are at an increased risk of postoperative complications in general, and this is especially true when combined with opioid-based analgesia in the postoperative period.2,3 It is therefore unfortunate that this otherwise well-conducted study did not include data on pain, opioid use, and other sedatives, because this may worsen the adverse effects of obstructive sleep apnea. In addition, there was little specific information on the anesthetic technique per se. The incidence of POD of 25% seems high in an elective, nondemented surgical population. Our group recently found no cases of POD in a similar population of patients undergoing knee and hip replacement.4 However, our patients received multimodal optimized care with reduced opioid use and only moderate postoperative pain, combined with short length of stay (mean 2.6 days). We believe that future studies evaluating the complex cognitive outcome of POD with multiple pathophysiologic mechanisms should include an optimized multimodal enhanced recovery program (the fast-track methodology)3–5 to provide a better understanding of POD and preventive techniques.

Postoperative obstructive sleep apnea and delirium

Variability in heart rate response (HRR) can be used as a measure for autonomic nervous system function, which may influence sleep disturbances and the recovery phase after major surgery. The aim of this study was to evaluate autonomic function by assessment of HRR during sleep arousals in the postoperative period after fast-track hip and knee arthroplasty. Determination of autonomic function was gained from polysomnographic evaluation of 10 patients > 60 years undergoing either hip or knee arthroplasty (mean age 69.9 years) evaluating HRR during the different sleep phases. Sleep monitoring took place in the patients’ home preoperatively, during hospitalization on the first postoperative night, and on the fourth postoperative night at home. HRR was reduced (P < 0.01) during arousal from non-REM stage 2 sleep on the first postoperative night, and was still reduced on the fourth postoperative night compared to preoperative level (P = 0.01). HRR during arousal from REM sleep was not different between the preoperative and fourth postoperative night (P = 0.92), while this could not be determined on the first postoperative night where REM sleep disappeared. The reduced HRR during sleep arousal after major arthroplasty surgery in elderly patients may reflect a functional change in sympathetic nervous system potentially relevant for postoperative sleep changes, fatigue and cognitive function.

Lene Krenk

Papers

Delirium in fast-track colonic surgery

Delirium in the fast-track surgery setting

Sleep Disturbances After Fast-Track Hip and Knee Arthroplasty

Postoperative obstructive sleep apnea and delirium

Heart rate response during sleep in elderly patients after fast-track hip and knee arthroplasty