Anesthesiology
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Comparative Study
Pronounced, episodic oxygen desaturation in the postoperative period: its association with ventilatory pattern and analgesic regimen.
The respiratory effects of two postoperative analgesic regimens were compared in two groups of 16 patients each, recovering from general anesthesia and major surgery. One group received a pain-relieving dose of iv morphine (mean, 18.1 mg), with the same dose repeated as a continuous intravenous infusion over the subsequent 24 h. The other group received regional anesthesia using bupivacaine. ⋯ Central apnea, obstructive apnea, and paradoxic breathing occurred more frequently in patients in the morphine group (12, 10, and 10 patients, respectively) than patients in the regional anesthesia group (4, 3, and 5 patients, respectively). The interaction of sleep and morphine analgesia produced disturbances in ventilatory pattern, causing profound oxygen destruction. These results suggest that postoperative pain relief using regional anaesthesia has a greater margin of safety in terms of respiratory side effects than does the continuous administration of opiates.
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Thiopental was used in long-term infusion (3-4.5 mg . kg-1 . h-1 during 4-8 days) to protect the brain from injury following trauma. Thiopental plasma concentrations were measured during infusion (48 patients) and after infusion (14 patients) to determine the kinetics of the drug in continuous infusion. All mean values were mean +/- SD. ⋯ Phases of burst-suppression were observed on electroencephalographic traces for concentrations greater than 40 mg/l. The authors' results suggest that a continuous infusion at a dose of 4 mg . kg-1 . h-1 induces EEG changes consistent with a near-maximum reduction in cerebral metabolism. Because of the thiopental Michaelis-Menten kinetics at doses above 4 mg . kg-1 . h-1, the authors suggest that thiopental plasma concentrations be measured and/or the drug effect be measured with the EEG to prevent excessive thiopental overdosage, causing a prolonged recovery time.