Anesthesiology
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Clinical Trial Controlled Clinical Trial
Heat flow and distribution during epidural anesthesia.
Core hypothermia after induction of epidural anesthesia results from both an internal core-to-peripheral redistribution of body heat and a net loss of heat to the environment. However, the relative contributions of each mechanism remain unknown. The authors thus evaluated regional body heat content and the extent to which core hypothermia after induction of anesthesia resulted from altered heat balance and internal heat redistribution. ⋯ Core hypothermia during the 1st hour after induction of epidural anesthesia resulted largely from redistribution of body heat from the core thermal compartment to the distal legs. Even after 3 h of anesthesia, redistribution remained the major cause of core hypothermia. Despite the greater fractional contribution of redistribution during epidural anesthesia, core temperature decreased only half as much as during general anesthesia because metabolic rate was maintained and the arms remained vasoconstricted.
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Comparative Study
One-day hypothermic preservation of isolated hearts with halothane improves cardiac function better than low calcium.
Halothane exerts a potent negative inotropic effect on the heart and mimics many of the cardiac effects of lowered extracellular CaCl2. Reduced slow inward Ca2+ current and sarcoplasmic reticular effects on intracellular Ca2+ are likely involved. The authors reported previously that halothane protects against hypoxic and ischemia reperfusion injury in isolated hearts. The aim of this isolated heart study was to compare protective effects of halothane and low CaCl2 (0.5 mM) administered during 1 day of hypothermic perfusion on return of normothermic perfusion. ⋯ Halothane administered during hypothermia restores left ventricular pressure, cardiac efficiency, basal coronary flow, and flow responses better than low CaCl2. Although halothane and low CaCl2 both reduce intracellular Ca2+, contractile force, and metabolic demand, the better protective effect of halothane is not likely simply due to a reduction in contractile function and metabolic rate before or initially after hypothermia because these were reduced much more by low CaCl2 than by halothane.
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Clinical Trial
Pharmacokinetics of computer-controlled alfentanil administration in children undergoing cardiac surgery.
Cardiopulmonary bypass (CPB) induces changes in the pharmacokinetics of drugs. The purpose of this study was to model the pharmacokinetics of alfentanil in children undergoing cardiac surgery to provide accurate dosage titration intraoperatively as well as in the postoperative period. ⋯ The population pharmacokinetics of alfentanil in children undergoing cardiac surgery were well described by both a simple weight-proportional, three-compartment model and a weight-proportional, CPB-adjusted three-compartment model. Cross-validation estimated an expected median inaccuracy of approximately 18-20% with the estimated models in identical experimental circumstances. The flexible CPB-adjusted pharmacokinetic model could be used for modeling any drug with linear pharmacokinetics given in the context of CPB.
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Comparative Study
Evaluation of a double-lumen multiorifice catheter for resuscitation of swine from lethal venous air embolism.
A double-lumen multiorifice catheter has been developed to potentially enhance accurate electrocardiographic central venous localization and resuscitation from a massive venous air embolism (VAE). This double-lumen multiorifice catheter was compared to a Bunegin-Albin multiorifice catheter for flow characteristics, air aspiration efficiency, and efficacy in resuscitating swine from a lethal VAE. ⋯ Multiorifice catheters are effective in resuscitating swine from a lethal VAE. The double-lumen multiorifice catheter evaluated aspirated a larger percentage of the VAE but was not statistically more effective than the Bunegin-Albin catheter in resuscitating the animals. Based on these findings of improved flow rate and efficiency in air aspiration, further investigation of this double-lumen multiorifice catheter is warranted.