Electroencephalogram spectral edge frequency,lower esophageal contractility,and autonomic responsiveness during general anesthesia

Both the electroencephalogram (EEG) spectral edge frequency (SEF) and lower esophageal contractility (LEC) indices have been reported to be useful indicators of anesthetic depth. We designed a prospective study to evaluate the relationship between changes in these two variables and objective measurements of physiologic responsiveness to surgical stress (i.e., changes in hemódynamic variables and plasma levels of norepinephrine, epinephrine, total catecholamines, and vasopressin). Eighty-nine consenting adult males undergoing radical prostatectomy procedures under a standardized general anesthetic technique were studied according to a randomized, single-blinded protocol. General anesthesia was induced with 30 µg/kg intravenous (IV) alfentanil, 2.5 mg/kg IV thiopental, and 0.1 mg/kg IV vecuronium, and subsequently maintained with 0.5 µg/kg/min alfentanil, nitrous oxide (N₂O) 67% in oxygen, and 0.8 µg/kg/min vecuronium. Following retropubic dissection, 81 patients (92%) manifested acute hypertensive responses, with mean arterial pressure increasing from 90±14 to 122±14 mm Hg (mean ± SD). This acute hypertensive response was treated with one of three different treatment modalities (20 to 60 µg/kg IV alfentanil, 0.5 to 2.0% inspired isoflurane, or 0.05 to 0.15 mg/kg IV trimethaphan) to return the mean arterial pressure to within 10% of the preincisional (baseline) value within 5 to 10 minutes. Although the mean arterial pressure, heart rate, and plasma levels of catecholamines and vasopressin significantly increased following the surgical stimulus, and decreased after adjunctive therapy, the EEG-SEF and LEC index (LECI) values did not significantly change during these study intervals. Furthermore, using a logistic regression analysis, we observed that preincision EEG-SEF and LECI values could not predict whether patients would manifest a hypertensive response. Therefore, the EEG-SEF and LECI were unreliable indicators of anesthetic depth.This study was supported in part by a grant from the Ambulatory Anesthesia Research Foundation, Los Altos, CA. (Dr White is a member of the Board of Directors.)The authors would like to thank Dan Kuni (Baxter Healthcare) for his assistance in obtaining the equipment used to perform the study; Vinod Kothapa, MD, for his valuable assistance with the anesthetic management of the study patients; Alex K. Mills, MD, for his assistance with the EEG interpretation; and Steven A. Bai, PhD, for his assistance with the plasma alfentanil analyses.     

Major Gynaecological Surgery in Patients with Severe Coronary Artery Disease — the Combined Approach

The gynaecologist today is likely to encounter elderly patients with severe coronary heart disease requiring major gynaecological surgery. The successful outcome in 2 such patients with compromised coronary circulation and impaired left ventricular function emphasized the importance of combined care with the cardiologist and the anaesthetist. The insertion of a Swan-Ganz catheter for close perioperative monitoring is vital. The intra-and postoperative problems are discussed.     

Phenelzine poisoning

A 46-year-old female with severe phenelzine poisoning was managed successfully by alpha blockade and fluid loading, with the aid of invasive haemodynamic monitoring. The pathophysiology was documented, showing elevated plasma and urinary catecholamines, cardiovascular abnormalities and a contracted blood volume. Most of these changes were reversed following treatment.     

Should we monitor alveolar and inspiratory concentrations of anesthetic and respiratory gases?

One essayist suggests that continuous monitoring of alveolar and inspiratory concentrations of anesthetic and respiratory gases has little or no positive effect on patient outcome and may even be detrimental to patients. Such monitoring, he says, tends to remove anesthesiologists from personal contact with their patients. He recommends careful monitoring of fresh gas concentrations leaving the anesthetic machine, careful monitoring of inspired gas in a circle absorption breathing system, and improved training of anesthesiologists to prevent human error. Another essayist suggests that continuous monitoring of alveolar and inspiratory concentrations of anesthetic and respiratory gases is cost-effective and relatively simple. He says that such monitoring, without being a source of legal problems for its users, improves the quality of patient care.     

Observer reliability in detecting surreptitious random occlusions of the monaural esophageal stethoscope

The esophageal stethoscope is used often during anesthesia to monitor ventilation and cardiac function. Deficiencies in observer vigilance may limit the effectiveness of this monitoring instrument. The aim of this study was to determine how long it took for an observer to detect a surreptitiously occluded monaural esophageal stethoscope in the setting of clinical anesthesia. During routine anesthesia, where an esophageal stethoscope was in use, a computer-guided device would artificially, silently, and at random time intervals, occlude the stethoscope tubing. Personnel using the stethoscope noted when they perceived the absence of stethoscope sounds. We studied 320 stethoscope occlusions in 32 patients. The time between stethoscope occlusion and detection was 34 ±59 seconds (mean ±SD). Eighty-seven percent of detections were made in less than 60 seconds. However, 13% of detections were delayed for more than 60 seconds, and 2.3% for more than 240 seconds. While anesthesia personnel using an esophageal stethoscope could detect most stethoscope occlusions, failure to appreciate such episodes occurred in a small but significant number of cases. This suggests that the esophageal stethoscope has some definite limitations as a continuous monitor and that other monitoring techniques, such as oximetry, capnography, and ventilator disconnect alarms, as well as visual/tactile inspection of the patient, should be used as well.     

Anaesthesia and the lipidoses: a review of patients treated by bone marrow transplantation

There are many potential problems associated with anaesthesia in patients with lipid storage diseases. This review covers an 8-year period (1983–1990) during which time 13 patients presented for procedures associated with bone marrow transplantation. The case notes of 12 patients who underwent a total of 48 general anaesthetics were reviewed. Pre-operative assessment revealed cardiorespiratory disease in six patients. Eighty per cent of the children were anaemic (haemoglobin < 95 g1^-1). Anaesthesia was tolerated well although tracheal intubation in two patients with Gaucher's disease was difficult and became progressively more difficult as they became older. Forty-five per cent of patients with Gaucher's disease were intubated with a tracheal tube smaller than predicted from the age of the child. Few complications were encountered but those which may be anticipated are discussed.     

The effect of diclofenac and nefopam on postoperative dental pain

Eighty-two outpatients who received general anaesthesia for surgical removal of maxillary or mandibular third molars were given either diclofenac 75 mg or nefopam 20 mg intramuscularly for postoperative pain control. They and the control group were also allowed oral paracetamol as required. The results showed that there was no significant pain relief from these single intramuscular injections.     

Propofol: clinical strategies for preventing the pain of injection

Eight modes of administration of propofol were assessed in order to minimise the pain of injection. An intravenous bolus injection in the antecubital fossa was the only approach that caused no pain. When administered intravenously in the dorsum of the hand the pain score and the number of patients who experienced pain was reduced significantly by mixing the agent with lignocaine when compared with a bolus injection. Slowing the speed of injection caused the greatest discomfort. An indirect biochemical mechanism for the pain is proposed.