P N Beaupre | PubMed Health

PubMed1988

Does anesthetic technique make a difference? Augmentation of systolic blood pressure during carotid endarterectomy: effects of phenylephrine versus light anesthesia and of isoflurane versus halothane on the incidence of myocardial ischemia.

Whether anesthetic technique affected the incidence of myocardial ischemia in 60 patients undergoing carotid endarterectomy was investigated. The patients were randomly assigned to receive halothane or isoflurane (with nitrous oxide) either at a low concentration alone or at a higher concentration with phenylephrine added to support blood pressure. Blood pressure was maintained within 20% of each patient's average ward systolic pressure. Seven leads of electrocardiograms (ECG) and echocardiograms were analyzed for segmental wall motion. The echocardiograms were analyzed using standard formulae for end-systolic meridional wall stress (SWS) and rate-corrected velocity of fiber shortening (Vcfc). Because of the nature of these calculations, only echocardiograms with normal regional wall motion could be accurately analyzed. The patients had postoperative ECG and creatinine phosphokinase (CPK) isoenzyme determinations and regularly scheduled clinical examinations to detect perioperative myocardial infarction and neurologic deficits. Although blood pressures were similar, the patients who received a higher concentration of anesthetic plus phenylephrine had a higher wall stress, regardless of the choice of anesthetic agent. All four techniques allowed provision of the same stump pressures (the marker surgeons used for adequacy of collateral carotid flow). No difference could be found in wall stress or incidence of myocardial ischemia between isoflurane and halothane. The patients who received phenylephrine had a threefold greater incidence of myocardial ischemia than did the patients who had light anesthesia to maintain similar systolic blood pressures and stump pressures. The groups were demographically and hemodynamically similar; in particular, the heart rates were not different.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗

PubMed1987

Narcotics decrease heart rate during inhalational anesthesia.

We determined the heart rate (HR) response to enflurane, halothane, and isoflurane and the effects of narcotics on this response in 81 healthy patients scheduled for elective surgery. Patients were randomly assigned to one of six treatment groups: one of the three anesthetics (approximately 0.9 MAC) in 60% nitrous oxide, and either 0.15 mg/kg of intramuscular morphine 30-60 min before induction or 1 microgram/kg of IV fentanyl 10 min after skin incision. All patients received diazepam, 10 mg orally, 60-90 min before anesthesia, a rapid sequence intravenous induction, and mechanically controlled ventilation. During inhalational anesthesia and the first 10 min of surgery, no significant change in HR occurred in any group (compared to the preinduction HR), although patients given morphine premedication tended to have a decreased HR and those not given morphine premedication tended to have an increased HR. These trends partially account for significant differences that emerged between groups after induction of anesthesia. Patients given morphine premedication and halothane had lower HR (64 +/- 3 SEM) than patients given isoflurane (80 +/- 3) or enflurane (84 +/- 3) and no morphine premedication. Patients anesthetized with enflurane and morphine premedication had lower HR (71 +/- 3) than patients given enflurane without morphine premedication. Administration of fentanyl 10 min after incision (these patients had received no morphine) significantly decreased HR in the presence of any of the vapors. We conclude that inhalational anesthetics used in the clinical setting we employed do not significantly increase heart rate, and that prior administration of morphine or concurrent administration of fentanyl may significantly decrease HR.

Adult↗