Anesthesiology
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Letter Biography Historical Article
An American dentist pioneered anesthesia in Spain.
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Multicenter Study Clinical Trial
Prediction of malignant hyperthermia susceptibility in low-risk subjects. An epidemiologic investigation of caffeine halothane contracture responses. The North American Malignant Hyperthermia Registry.
The most commonly used laboratory test for predicting malignant hyperthermia susceptibility is the caffeine halothane contracture test. However, the specificity and sensitivity of proposed North American diagnostic guidelines for this test have never been evaluated in a large, human study population. Therefore, the authors conducted a multiinstitutional, prospective study of skeletal muscle contracture responses in a subject population at low risk for malignant hyperthermia susceptibility to help determine the specificity of the proposed guidelines. ⋯ Third, the percentages of subjects with 1 or more fascicles exceeding the proposed threshold for both halothane and caffeine were as follows: 9.5% for 3% halothane and 2 mM caffeine, 2.0% for 3% halothane and 7% maximal increase in tension at 2 mM caffeine, and 11.0% for 1% halothane and 2 mM caffeine. Fourth, center-to-center differences were the major source of variation in the rate that subjects exceeded proposed thresholds. These data demonstrate that proposed diagnostic guidelines must be modified to improve specificity estimates before adoption by diagnostic centers.(ABSTRACT TRUNCATED AT 400 WORDS)
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Randomized Controlled Trial Clinical Trial
Accelographic train-of-four at near-threshold currents.
The authors evaluated train-of-four (TOF) fade, as quantified by accelography, in response to neurostimulation at currents ranging from 10 to 60 mA. This was done to determine the range of currents over which measurements of fade remain consistent. In 31 patients (ASA Physical Status 1,2, and 3), anesthesia was induced with fentanyl, midazolam, and thiopental and was maintained with isoflurane and 66% nitrous oxide in oxygen. ⋯ This inconsistency was eliminated by testing at greater than or equal to 10 mA above threshold. TOF ratios obtained at 10 mA above T4 threshold correlated highly with those at 60 mA (Spearman r value = 0.94). The authors conclude that the TOF ratio is consistent over a wide range of stimulating currents and that testing with submaximal currents can be performed reliably at greater than or equal to 10 mA above the T4 threshold.(ABSTRACT TRUNCATED AT 250 WORDS)
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Opioids are known to affect the MAC of inhalational anesthetics. We have determined the interaction between fentanyl and desflurane, following a bolus injection of fentanyl at induction in 134 adult patients. Five groups of patients were studied. ⋯ Recovery was faster in patients who received desflurane than in those who received isoflurane. The authors conclude that the MAC of desflurane is significantly reduced 25 min following a single dose of 3 micrograms/kg of fentanyl and that increasing the fentanyl dose to 6 micrograms/kg produces little further decrease in MAC. Desflurane is also associated with faster recovery from anesthesia than is isoflurane.
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The increased metabolic and respiratory demand during naloxone recovery from opioid-based anesthesia could be related to the return of thermoregulation in hypothermic patients and thus be avoided by preventing intraoperative hypothermia. In this study, we measured O2 uptake (VO2) during naloxone-induced recovery in two groups of patients to determine the effect of intraoperative heat loss on postoperative VO2 changes. In seven patients, intraoperative hypothermia was prevented (normothermic group), whereas hypothermia was allowed to develop in seven other patients (hypothermic group). ⋯ VO2 was integrated throughout the recovery period to calculate recovery energy expenditure. Recovery energy expenditure and intraoperative heat loss were highly correlated (r = 0.88; P less than 0.01). This study demonstrates that the metabolic and respiratory stresses associated with naloxone-induced recovery from opioid-based anesthesia depend on the intraoperative heat loss and can therefore be reduced by preventing intraoperative hypothermia.