Anesthesiology
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Preterm infants may become apneic during the immediate post-operative period. To define this risk, the authors studied prospectively the breathing patterns of 47 preterm infants less than 60 weeks postconception with pneumocardiograms before and after general inhalational anesthesia. Eighteen infants (37%) had prolonged apnea (greater than 15 s) postoperatively, and an additional seven infants (14%) had short apnea (6-15 s) postoperatively. ⋯ The first apneic event occurred within 2 h postoperatively in 13 of the infants (72%); the remaining five infants (28%) had their initial apneic episode as late as 12 h after operation. The postoperative time to the last prolonged apneic event was inversely related to the postconceptional age (P less than 0.01, r = -0.70) and extended up to 48 h postoperatively. The preoperative pneumocardiogram was not a reliable test for predicting postoperative apnea (sensitivity 56%, specificity 83%).(ABSTRACT TRUNCATED AT 250 WORDS)
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Randomized Controlled Trial Clinical Trial
Role of nitrous oxide and other factors in postoperative nausea and vomiting: a randomized and blinded prospective study.
Postoperative nausea and vomiting have been reported to be associated with the use of nitrous oxide. To further investigate this possibility, 780 patients undergoing anesthesia and surgery were randomly divided into four groups: group I: enflurane/nitrous oxide/oxygen; group II: enflurane/air/oxygen; group III: isoflurane/nitrous oxide/oxygen; and group IV: isoflurane/air/oxygen. The frequency of postoperative nausea and vomiting was ascertained in the recovery room and at 24-h follow-up by blinded observers. ⋯ Use of the 95% confidence interval allowed the authors to project a maximum potential increase in the frequency of postoperative nausea and vomiting associated with nitrous oxide to be 5.4% with enflurane and 9.7% with isoflurane in the immediate postoperative period. Female gender, younger age, and a previous history of postoperative nausea and vomiting, but not body mass index, were found to be associated with postoperative nausea and vomiting (P less than 0.05). It is concluded that there is no association between the use of nitrous oxide and the development of postoperative nausea and vomiting.
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Randomized Controlled Trial Clinical Trial
Dose-response curves for edrophonium, neostigmine, and pyridostigmine after pancuronium and d-tubocurarine.
To determine the potencies of neostigmine, pyridostigmine, and edrophonium in reversing pancuronium and d-tubocurarine blockade, dose-response curves were established for first twitch height recovery and train-of-four ratio. One hundred and twenty ASA physical status I or II patients scheduled for elective surgery received either 0.06 mg/kg pancuronium or 0.36 mg/kg d-tubocurarine during a thiopental-nitrous oxide-enflurane anesthetic. Train-of-four stimulation was applied every 12 s, and the force of contraction of the adductor pollicis muscle was recorded. ⋯ The ED50 for pyridostigmine and edrophonium obtained after d-tubocurarine was significantly larger (P less than 0.05) than that after pancuronium. The train-of-four dose-response curves were significantly flatter for edrophonium than for the other two agents, indicating a greater ability of edrophonium to antagonize fade at low doses. It is concluded that the potency of reversal agents may be different for different relaxants, and that potency ratios might depend upon the end-point chosen as full neuromuscular recovery.
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The effects of lidocaine on the fetal circulatory responses to asphyxia were evaluated in chronically instrumented pregnant sheep. Twenty-six preparations were studied. Animals were assigned to one of three groups. ⋯ Measurements included heart rate, blood pressure, arterial pH, and blood gases. Cardiac output and organ blood flow were determined using the radio-labelled microsphere technique. In general, arterial and tissue lidocaine concentrations in asphyxiated fetuses were higher than those in the nonasphyxiated ones, the differences being significant in the brain, heart, liver, and adrenal glands.(ABSTRACT TRUNCATED AT 250 WORDS)
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Intrathecally administered clonidine produces analgesia, but also produces hypotension. To assess the effects of epidural administration, the authors inserted lumbar epidural catheters in seven nonpregnant ewes, and injected, on separate days, clonidine (50-750 mcg), morphine (5-10 mg), and a clonidine-morphine combination (clonidine 150 mcg + morphine 5 mg). Clonidine produced dose-dependent antinociception and sedation, with the lowest maximally effective antinociceptive dose being 300 mcg. ⋯ Epidurally administered clonidine did not decrease blood pressure or heart rate or affect arterial blood gas tensions or spinal cord histology. These data suggest that epidurally administered clonidine produces analgesia by a local, alpha 2-adrenergic mechanism. In sheep, epidurally administered clonidine does not produce hypotension.