Anesthesiology
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Cerebral metabolic and vascular effects of hypothermia (30 C) and deep pentobarbital anesthesia, separately and combined, were evaluated in 15 mongrel dogs. External cardiovascular support was not used, and mean arterial blood pressures remained greater than 60 torr. Normothermic deep pentobarbital anesthesia, characterized by an electroencephalographic (EEG) frequency of less than 1 Hz, was associated with 30% decreases in cerebral metabolic rates for oxygen (CMRO2) and glucose (CMRG) from lightly anesthetized control values. ⋯ No alteration in the oxygen-glucose or lactate-glucose index indicative of cerebral hypoxia occurred in any experimental group. This study indicates that barbiturates combined with hypothermia decrease cerebral metabolism to a greater extent than hypothermia or barbiturate alone. When cerebral hypometabolism is therapeutically necessary, barbiturates may be indicated as an adjunct to moderate hypothermia.
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Echocardiographic studies were made of 20 healthy patients scheduled for minor surgical procedures to determine whether this technique could be used routinely in the operating room and to evaluate the effects of halothane and enflurane on left ventricular performance. Thirteen minutes following induction of anesthesia with halothane in ten patients (mean end-tidal halothane concentration 0.93 per cent), mean arterial blood pressure, left ventricular (LV) diastolic dimension, LV fractional shortening, mean velocity of circumferential fiber shortening and systolic thickening of the posterior LV wall were significantly decreased. ⋯ Twelve minutes following induction of anesthesia with enflurane in ten patients (mean delivered enflurane concentration 2.4 per cent), mean arterial blood pressure and LV systolic and diastolic dimensions were decreased, while heart rate was increased significantly, indicating that enflurane caused vasodilatation and may have had some depressant effect on contractility. Echocardiography is a non-invasive, safe and relatively rapid method that can be used in the perioperative period to assess cardiac function and to evaluate the effects of pharmacologic agents on the heart.