Arrhythmogenic effect of hypercapnia in ducks anesthetized with halothane

Objective-To determine effects of hypercapnia on arrhythmias in ducks anest hetized with halothane. Animals-12 ducks, 6 to 8 months old, weighing 1.1 to 1.6 kg Procedures-Each duck was anesthetized with a 1.5% mixture of halothane in o xygen, and anesthetic depth was stabilized during a 20-minute period. We ad ded CO2 to the inspired oxygen to produce CO2 partial pressures of 40, 60, and 80 mm Hg in the inspired gas mixture. The coa partial pressure was incr eased in a stepwise manner. When arrhythmias were not evident during inhala tion of the gas mixture at a specific CO2 partial pressure, the CO2 partial pressure was maintained for 10 minutes before a sample was collected for b lood gas analysis. When arrhythmias were detected, a sample for blood gas a nalysis was collected after the CO2 partial pressure was maintained for at least 2 minutes, and CO2 inhalation then was terminated. Results-During the stabilization period, Paco(2) (mean +/- SD) was 33 +/- 5 mm Hg,and arrhythmias were not detected. in 6 ducks, arrhythmias such as u nifocal and multifocal premature ventricular contractions developed during inhalation of CO2. Mean Paco(2) at which arrhythmias developed was 67 +/- 1 2 mm Hg. In 5 of 6 ducks with arrhythmias, the arrhythmias disappeared afte r CO2 inhalation was terminated. Conclusion and Clinical Relevance-Analysis of data from this study indicate d that hypercapnia can lead to arrhythmias in ducks during halothane-induce d anesthesia. Thus, ventilatory support to maintain normocapnia is importan t for managing ducks anesthetized with halothane.