Anesthesiology
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Comparative Study
Toxicity and resuscitation in lidocaine- or bupivacaine-infused cats.
Controversy persists surrounding the relative safety of bupivacaine compared with lidocaine especially with regard to its cardiovascular toxicity and the ability to resuscitate following such occurrences. The margin of safety between seizure onset and cardiovascular collapse was compared in lightly anesthetized and ventilated cats given an equipotent infusion of either lidocaine or bupivacaine (N = 10 for each group). The infusion rates were 4 mg X kg-1 X min-1 bupivacaine or 16 mg X kg-1 X min-1 lidocaine. ⋯ Despite very high plasma local anesthetic concentrations, all lidocaine-infused animals were quickly resuscitated (4.4 +/- 3.0 min; mean +/- SD). The resuscitation time for the bupivacaine group (5.4 +/- 2.4 min) was similar. Two cats in the bupivacaine group could not be brought to resuscitation criterion, a difference, however, that was not statistically significant.
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The emergency management of respiratory arrest can be a difficult problem. The authors hypothesized that tracheal insufflation of O2 (TRIO) at low flows could provide adequate oxygenation and sufficient CO2 elimination to sustain life until more definitive (but more difficult to implement) measures could be applied. Therefore, 10 anesthetized, paralyzed dogs (15.9-48.2 kg), initially ventilated with conventional mechanical ventilation (CMV) using room air, were studied. ⋯ These studies were stopped at between 4 and 5 h, with no dogs showing any signs of cardiovascular or other decompensation. Results in which catheter position was studied indicated that as long as the catheter tip was at or past the carina, gas transport was similar to that observed when the catheter tip was 1 cm proximal to the carina. The authors conclude that TRIO at low flow rates can produce sufficient gas exchange to support life for prolonged periods in apneic dogs.