Lidocaine prolongs the safe duration of circulatory arrest during deep hypothermia in dogs

Purpose To test the hypothesis that lidocaine prolongs the safe period of circulatory arrest during deep hypothermia. Methods Sixteen dogs were subjected to cooling, first surface cooling to 30°C and then core cooling to 20°C rectal temperature). The circulation was then stopped for 90 min. In the lidocaine group, 4 mg·kg −1 lidocaine was injected into the oxygenator two minutes before circulatory arrest and 2 mg·kg −1 at the beginning of reperfusion and rewarming. The control group received equivalent volumes of normal saline. Post-operatively, using a neurological deficit scoring system (maximum deficit score — 100; minimum — zero indicating that no scored deficit could be detected). Neurological function was evaluated hourly for six hours and then daily for one week. the pharmacokinetic parameters were calculated using one compartment model. Results On the seventh day, the neurological deficit score and overall performance were better in the lidocaine (0.83 ± 2.04) than in the control group (8.33 ± 4.08 P < 0.05). During the experiment, the base excess values were also better in the lidocaine than in the control group (at 30 min reperfusion: −4.24 ± 1.30 vs −8.20 ± 2.82 P < 0.01, at 60 min reperfusion was −3.34 ± 1.87 vs −7.52 ± 2.40 ( P < 0.01). On the eighth day the extent of pathological changes were milder in the lidocaine group than that in the control group. The elimination half life of lidocaine was 40.44 ± 7.99 during hypothermia and 2.01 ± 4.56 during rewarming. Conclusions In dogs lidocaine prolongs the safe duration of circulatory arrest during hypothermia.