Anesthesia and analgesia
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Anesthesia and analgesia · Sep 1989
The effects of airway impedance on work of breathing during halothane anesthesia.
Humidifiers and small diameter endotracheal tubes placed in the airway circuit increase the impedance to breathing. The effect of such impedances on the work of breathing and respiratory patterns was studied in eight healthy adult patients (60-80 kg) anesthetized with 1 and 2 MAC halothane in oxygen. A Cascade Humidifier and Portex Humid-Vent (dry and water saturated) were evaluated while patients breathed through an 8.0-mm endotracheal tube. ⋯ At 1 MAC the Cascade Humidifier and the wet Humid-Vent when used with the 8.0-mm tube increased the work of breathing to 86.8 ml and 76.8 ml, 77% and 70% above baseline levels of 48.1 ml, whereas the 6.0-mm tube without the humidifiers increased work 89% to 78.9 ml. Tidal volume and respiratory frequency were unchanged throughout the study, although inspiratory time was prolonged. Lightly to moderately anesthetized healthy adult patients are able to maintain minute ventilation despite the impedance associated with commonly used humidifiers by significantly increasing work of breathing.
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Anesthesia and analgesia · Sep 1989
Myocardial and cerebral drug concentrations and the mechanisms of death after fatal intravenous doses of lidocaine, bupivacaine, and ropivacaine in the sheep.
This paper reports the cardiovascular effects of intentionally toxic intravenous doses of lidocaine, bupivacaine, and ropivacaine and the mechanisms of death. Fatal doses of lidocaine, bupivacaine, and ropivacaine were established in sheep treated with successive daily dose increments of each drug. The mean fatal dose of lidocaine (+/- SD) was 1450 +/- 191 mg (30.8 +/- 5.8 mg/kg), that of bupivacaine was 156 +/- 31 mg (3.7 +/- 1.1 mg/kg), and that of ropivacaine was 325 +/- 108 mg (7.3 +/- 1.0 mg/kg); thus the ratio of fatal doses was approximately 9:1:2. ⋯ Three out of five animals given ropivacaine died in a manner resembling the fatal effects of lidocaine-treated animals, but unlike the lidocaine-treated animals, in all three sheep there were also periods of ventricular arrhythmias. The remaining two ropivacaine-treated sheep died as a result of the sudden onset of ventricular tachycardia/fibrillation. The mean percentages of the fatal dose found in the myocardium was 2.8 +/- 0.7 for lidocaine-treated animals, 3.3 +/- 0.9 for bupivacaine-treated animals, and 2.2 +/- 1.4 for ropivacaine-treated animals; the corresponding percentages in whole brain were, respectively, 0.71 +/- 0.01, 0.71 +/- 0.21, and 0.89 +/- 0.27.
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Anesthesia and analgesia · Sep 1989
Comparative StudyTime-courses of zones of differential sensory blockade during spinal anesthesia with hyperbaric tetracaine or bupivacaine.
The purposes of this study were twofold: to compare bupivacaine and tetracaine spinal anesthesia with regard to the zones of differential sensory blockade and to evaluate the time-courses of the widths of the zones of differential sensory blockade during spinal anesthesia. In 51 patients, the most rostral levels of sensory denervation to light touch, pinprick, and temperature discrimination were measured. There was no statistically significant difference in the height of sensory blockade in the 29 patients given bupivacaine and in the 22 patients given equipotent doses of tetracaine. ⋯ The width of the zones of differential blockade also remained unchanged within each group during onset, maintenance, and regression of anesthesia. Changes in, and absolute levels of, blood pressure and heart rate were similar with both bupivacaine and tetracaine throughout. We conclude that zones of differential sensory blockade are essentially the same with tetracaine and bupivacaine, that the widths of the zones of differential sensory blockade remain constant during onset, maintenance, and offset of spinal anesthesia, and that bupivacaine and tetracaine are associated with similar changes in heart rate and blood pressure during spinal anesthesia.
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Around World War I, American novelist Theodore Dreiser wrote several plays, one of which, "Laughing Gas," explores the odd experience of a physician undergoing surgery with nitrous oxide/oxygen anesthesia. The content of this play and its relationship to Dreiser's career are examined.