Anesthesiology
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Randomized Controlled Trial Clinical Trial
Oxygen uptake after major abdominal surgery: effect of clonidine.
To examine the effect of an alpha-2 agonist, clonidine, on oxygen uptake and on the incidence of postoperative shivering, 28 patients presenting for major abdominal surgery were randomly assigned in a double-blind manner to one of two groups. Intraoperatively, 14 patients received 5 micrograms.kg-1 clonidine infused over 3 h (clonidine group), and 14 patients received placebo (placebo group). Oxygen uptake was measured continuously over the first 3 postoperative hours with a mass spectrometer system. ⋯ There were no differences among groups in the incidence of shivering and in the rate of increase of esophageal temperature. By contrast, oxygen uptake was lower in the clonidine group (P = 4 x 10(-4)). This contrasting pattern may be secondary to a reduction in the intensity of mean muscular tremor in the clonidine group.
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Malpractice claims filed against anesthesiologists for care involving obstetric (OB) anesthesia (n = 190) were taken from the American Society of Anesthesiologists' Closed Claims Database and compared to claims not involving OB cases (n = 1351). The most common complications in the OB claims were (percentage of all OB claims): maternal death (22%), newborn brain damage (20%), and headache (12%). In contrast, the most common complications in the nonobstetric (non-OB) group were (percentage of all non-OB claims): death (39%), nerve damage (16%), and brain damage (13%). ⋯ Claims involving general anesthesia were more frequently associated with severe injuries and resulted in higher payments than did claims involving regional anesthesia. Payments were made in a similar proportion of OB and non-OB claims (53 and 59%, respectively). For cases in which payments were made, the median payment for OB claims was significantly greater ($203,000) than for non-OB claims ($85,000; P less than or equal to 0.05).
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Central body temperature, which usually is well controlled, typically decreases more than 1 degree C during the 1st h of general anesthesia. This hypothermia has been attributed partially to an anesthetic-induced peripheral vasodilation, which increases cutaneous heat loss to the environment. Based on the specific heat of humans, heat loss would have to increase more than 70 W for 1 h (in a 70-kg person) to explain hypothermia after induction of general anesthesia. ⋯ Isoflurane anesthesia decreased mean arterial blood pressure approximately 20%. Average skin-surface temperature increased over 15 min to 0.5 degree C above control. Heat loss from the trunk, head, arms, and legs decreased slightly, whereas loss from the hands and feet (10.5% of the body surface area) doubled (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)
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Randomized Controlled Trial Comparative Study Clinical Trial
Clinical efficacy of oral-transdermal clonidine combinations during the perioperative period.
In an attempt to maintain stable levels of an alpha 2-adrenergic agonist throughout the perioperative period, two different oral-transdermal clonidine dosage regimens were administered according to a randomized, double-blind, placebo-controlled study in patients undergoing abdominal surgery. We determined the clinical efficacy of a high- and a low-dose clonidine regimen on sedation, hemodynamic parameters, anesthesia, and analgesia. The low-dose clonidine group of patients (n = 14) received a 7-cm2 clonidine transdermal patch (Catapres-TTS #2), which was supplemented with oral doses of clonidine approximately 3 micrograms.kg-1 on the evening prior to surgery and on the morning of surgery. ⋯ Isoflurane was added when the blood pressure exceeded 110% of the patient's prestudy value. For pain relief postoperatively, the patients received morphine, 1-2-mg iv boluses, via a patient-controlled analgesia pump. The low-dose clonidine patient group had mean plasma clonidine concentrations that varied from 1.47 ng.ml-1 (preoperative) to 1.32 ng.ml-1 (postoperative day 2).(ABSTRACT TRUNCATED AT 250 WORDS)
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In seeking a means to reverse local anesthetic block of peripheral nerve, we examined the actions of veratridine (VTD), an agent known to antagonize competitively the binding of local anesthetics to Na channels. The actions of VTD, a steroidal alkaloid "activator" of voltage-gated Na channels, were studied in the rabbit vagus nerve by two methods. In one, the effects of VTD on compound action potentials (APc) propagating through a "veratrinized" segment (11-mm) of nerve were measured by extracellular recording. ⋯ Repetitive stimulation, particularly of C-fibers, produced a cumulative VTD-induced depolarization (VID) that was sustained over several seconds and during which the C-fiber APc was selectively reduced. We propose that this local, use-dependent VID provides the means to inhibit impulses propagating through the veratrinized region. The preferential effect of VTD on C-fibers suggests its possibilities as a relatively selective agent for block of impulse trains in nociceptive afferents.