Anesthesiology
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Randomized Controlled Trial Comparative Study Clinical Trial
Treatment of hypotension after hyperbaric tetracaine spinal anesthesia. A randomized, double-blind, cross-over comparison of phenylephrine and epinephrine.
Despite many advantages, spinal anesthesia often is followed by undesirable decreases in blood pressure, for which the ideal treatment remains controversial. Because spinal anesthesia-induced sympathectomy and management with a pure alpha-adrenergic agonist can separately lead to bradycardia, the authors hypothesized that epinephrine, a mixed alpha- and beta-adrenergic agonist, would more effectively restore arterial blood pressure and cardiac output after spinal anesthesia than phenylephrine, a pure alpha-adrenergic agonist. ⋯ Epinephrine management of tetracaine spinal-induced hypotension increases heart rate and cardiac output and restores systolic arterial pressure but does not restore mean and diastolic blood pressure. Phenylephrine management of tetracaine spinal-induced hypotension decreases heart rate and cardiac output while restoring systolic, mean, and diastolic blood pressure.
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Randomized Controlled Trial Clinical Trial
Urine and plasma catecholamine and cortisol concentrations after myocardial revascularization. Modulation by continuous sedation. Multicenter Study of Perioperative Ischemia (McSPI) Research Group, and the Ischemia Research and Education Foundation (IREF).
Cardiopulmonary bypass is associated with substantial release of catecholamines and cortisol for 12 or more h. A technique was assessed that may mitigate the responses with continuous 12-h postoperative sedation using propofol. ⋯ Cardiopulmonary bypass graft surgery is associated with substantial increases in plasma and urine catecholamine and cortisol concentrations, which persist for 12 or more h. This hormonal response may be mitigated by a technique of intensive continuous 12-h postoperative sedation with propofol, which is associated with a decrease in tachycardia and hypertension and an increase in hypotension.
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Sweating, vasoconstriction, and shivering have been observed during general anesthesia. Among these, vasoconstriction is especially important because-once triggered-it minimizes further hypothermia. Surprisingly, the core-temperature plateau associated with vasoconstriction appears to preserve core temperature better in infants and children than adults. This observation suggests that vasoconstriction in anesthetized infants may be accompanied by hypermetabolism. Consistent with this theory, unanesthetized infants rely on nonshivering thermogenesis to double heat production when vasoconstriction alone is insufficient. Accordingly, the authors tested the hypothesis that intraoperative core hypothermia triggers nonshivering thermogenesis in infants. ⋯ Even at core temperatures approximately 2 degrees C below the vasoconstriction threshold, there was no evidence of nonshivering thermogenesis. This finding is surprising because all other major thermoregulatory responses have been detected during anesthesia. Infants and children thus appear similar to adults in being unable to increase metabolic rate in response to mild intraoperative hypothermia.
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Patients with mitral valve disease (MVD) are at greater risk for respiratory complications after cardiac surgery compared with patients with coronary artery disease (CAD). The authors hypothesized that ventilation-perfusion (VA/Q) inequality is more pronounced in patients with MVD before and after induction of anesthesia and during and after surgery when extracorporeal circulation (ECC) is used. ⋯ Qs/Qr is the main pathophysiologic mechanism of gas exchange impairment during cardiac surgery for MVD or CAD. Impairment of pulmonary gas exchange secondary to general anesthesia, cardiac surgery, and ECC are comparable for patients undergoing myocardial revascularization or mitral valve surgery.
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Recovery of the train-of-four (TOF) ratio to a value > 0.70 is synonymous with adequate return of neuromuscular function, but there is little information available concerning the subjective experience that accompanies residual neuromuscular block wherein the TOF ratio is in the range of 0.70 to 0.90. ⋯ All subjects had significant signs and symptoms of residual block at a TOF ratio of 0.70; none considered themselves remotely "street ready" at this time. The authors believe that satisfactory recovery of neuromuscular function after mivacurium-induced neuromuscular block requires return of the TOF ratio to a value > 0.90 and ideally to unity.