Awareness with recall after general anesthesia is an infrequent, but well described, phenomenon that may result in posttraumatic stress disorder. There are no recent data on the incidence of this complication in the United States. We, therefore, undertook a prospective study to determine the incidence of awareness with recall during general anesthesia in the United States. This is a prospective, nonrandomized descriptive cohort study that was conducted at seven academic medical centers in the United States. Patients scheduled for surgery under general anesthesia were interviewed in the postoperative recovery room and at least a week after anesthesia and surgery by using a structured interview. Data from 19,575 patients are presented. A total of 25 awareness cases were identified (0.13% incidence). These occurred at a rate of 1-2 cases per 1000 patients at each site. Awareness was associated with increased ASA physical status (odds ratio, 2.41; 95% confidence interval, 1.04-5.60 for ASA status III-V compared with ASA status I-II). Age and sex did not influence the incidence of awareness. There were 46 additional cases (0.24%) of possible awareness and 1183 cases (6.04%) of possible intraoperative dreaming. The incidence of awareness during general anesthesia with recall in the United States is comparable to that described in other countries. Assuming that approximately 20 million anesthetics are administered in the United States annually, we can expect approximately 26,000 cases to occur each year.

The incidence of awareness during anesthesia: a multicenter United States study.

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(99)11010-9.pdf

Awareness during anaesthesia: a prospective case study

Development and Clinical Application of Electroencephalographic Bispectrum Monitoring Jay Johansen;Peter Sebel; Anesthesiology

http://www.angelfire.com/hi5/anaesthesia/articles/BIS.pdf

Development and Clinical Application of Electroencephalographic Bispectrum Monitoring

IN homeothermic species, a thermoregulatory system coordinates defenses against cold and heat to maintain internal body temperature within a narrow range, thus optimizing normal physiologic and metabolic function. The combination of anesthetic-induced thermoregulatory impairment and exposure to a cool environment makes most unwarmed surgical patients hypothermic. Although shivering is but one consequence of perioperative hypothermia, and rarely the most serious, it occurs frequently (i.e., 40–60% after volatile anesthetics), and it remains poorly understood. While coldinduced thermoregulatory shivering remains an obvious etiology, the phenomenon has also been attributed to numerous other causes. Our first goal is to review the organization of the thermoregulatory system, and particularly the physiology of postanesthetic shivering. We then discuss the pharmacology of thermoregulation and review the putative mechanisms and sites of action of various antishivering drugs.

/pdf/perioperative-shivering-physiology-and-pharmacology-2je650rbp3.pdf

Perioperative shivering: physiology and pharmacology.

Propofol is an intravenous sedative hypnotic agent which rapidly and reliably causes loss of consciousness. It is also associated with a quick and 'smooth' recovery, which distinguishes it from many of the more traditional anaesthetic regimens. Like other intravenous agents, propofol is both a cardiovascular and a respiratory depressant; however, the risk of these effects can be lessened by appropriate dosage adjustment or patient management. Anaphylaxis with propofol is rare. Propofol anaesthesia in day case surgery is consistently associated with a quicker early recovery than other intravenous agents and the more traditional anaesthetic regimens. Savings in time to discharge were more variable compared with these regimens, although propofol was commonly associated with less post-operative nausea and vomiting in this period. In the future, the relative benefits of propofol compared with the newer volatile agents (desflurane and sevoflurane) and propofol/volatile agent combinations need to be examined in this clinical setting. There is now clinical experience with propofol in major surgical procedures including cardiac and neurosurgery. Propofol has also been investigated as a sedative accompanying regional or local anaesthesia for diagnostic and therapeutic procedures, and in other clinical settings (ophthalmic surgery, cardioversion and electroconvulsive therapy). The unique antiemetic, antiepileptic and antipruritic effects of propofol may further broaden its appeal. As a result of its favourable recovery profile, propofol holds a central place in day case surgery anaesthesia. Accumulating clinical experience in cardiac and neurosurgery suggests that the full potential of propofol has yet to be realised.

Propofol. An update of its use in anaesthesia and conscious sedation.

Summary

One thousand patients who were anaesthetised between February and April 1990 at University Hospital, Nottingham were interviewed between 20 and 36 hours after their operation. Patients under 16 years of age, those who had undergone obstetric or intracranial surgery, those who were unable to communicate and patients who were discharged from hospital before the postoperative visit were not interviewed. A standard set of questions was used to determine the incidences of recall of events and dreams during the operation. These incidences were 0.2% and 0.9% respectively, considerably lower than reported in previous comparable studies.

https://associationofanaesthetists-publications.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2044.1991.tb11677.x

Incidence of awareness with recall during general anaesthesia.

The incidence and amount of migration of epidural catheters was investigated in a prospective randomised study of 153 women who required analgesia in labour. Inward or outward migration occurred in 36% of patients. Inward migration by 1-3 cm occurred in 21 (13.7%) patients and outward migration by 1 cm or more occurred in 34 (22.2%); three (2%) catheters migrated out through the skin. There were significant positive correlations between outward migration and weight, body mass index, and depth of the epidural space. There was no relationship between migration and height, age, intervertebral space used or duration of catheterisation. Problems with epidural block were no more likely in patients in whom migration of 1 cm or more occurred compared with those in whom migration was limited to a maximum of +/- 0.5 cm. However, the pattern of problems was different. All cases of failed epidural block occurred in patients whose epidural catheter migrated outward by 2.5 cm or more. Unilateral blockade was not more likely if migration of 1 cm or more occurred.

Factors influencing epidural catheter migration.

The aims of this randomised double-blind study were to investigate whether 25 micrograms of fentanyl administered prophylactically by the epidural route would influence the incidence of shivering in parturients who underwent elective Caesarean section under epidural analgesia and whether it would affect the axillary and calf temperatures. There was a 50% reduction (p less than 0.05) in the overall incidence of shivering in patients who received fentanyl and there was some evidence to suggest that low-dose epidural fentanyl might reduce shivering by an influence on thermoregulation.

The effect of prophylactic fentanyl on shivering in elective caesarean section under epidural analgesia.

trace, measured through the distal lumen of the catheter, had become damped. Considerable resistance was encountered when attempts were made to flush this lumen and the other two proximal lumens of the catheter. It was apparent on close examination that the locking nut on the catheter positioning sleeve had been overtightened and was compressing the catheter, with the result that the lumina had become partially occluded. The quality of the pressure trace improved and the resistance to injection decreased when the nut was loosened. It was not clear whether this is a problem with the particular introducer and positioning sheath we used (Peter Von Berg Medizintechnik Cat. No. EKV-8-K-JS) or a more general problem, but it is obvious that care needs to be exercised since the signs are similar to those which would be caused by partial occlusion of the lumina of the catheter by blood clot and might lead to premature and unnecessary removal of the catheter. We suspect that problems with previous similar catheters in this unit may have been due to the same cause.

W. H. D. Liu

Papers

Incidence of awareness with recall during general anaesthesia.

Factors influencing epidural catheter migration.

The effect of prophylactic fentanyl on shivering in elective caesarean section under epidural analgesia.

Drug usage by anaesthetists.