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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The bispectral index (BIS), a value derived from the electroencephalograph (EEG), has been proposed as a measure of anesthetic effect. To establish its utility for this purpose, it is important to determine the relation among BIS, measured drug concentration, and increasing levels of sedation. This study was designed to evaluate this relation for four commonly used anesthetic drugs: propofol, midazolam, isoflurane, and alfentanil. ⋯ The BIS both correlated well with the level of responsiveness and provided an excellent prediction of the loss of consciousness. These results imply that BIS may be a valuable monitor of the level of sedation and loss of consciousness for propofol, midazolam, and isoflurane.
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Septic shock leads to increased splanchnic blood flow (Qspl) and oxygen consumption (VO2spl). The increased Qspl, however may not match the splanchnic oxygen demand, resulting in hepatic dysfunction. This concept of ongoing tissue hypoxia that can be relieved by increasing splanchnic oxygen delivery (DO2spl), however, was challenged because most of the elevated VO2spl was attributed to increased hepatic glucose production (HGP) resulting from increased substrate delivery. Therefore the authors tested the hypothesis that a dobutamine-induced increase in Qspl and DO2spl leads to increased VO2spl associated with accelerated HGP in patients with septic shock. ⋯ In the patients with septic shock in whom blood pressure had been stabilized with volume resuscitation and norepinephrine, no delivery-dependency of VO2spl could be detected. Oxygen consumption was not related to the accelerated HGP either, and thus the concept that HGP dominates VO2spl must be questioned in well-resuscitated patients with septic shock.