Effects of cyanide and doxapram during hypothermia

The ventilatory responses, blood gases and acid-base status to intravenous injections of KCN and doxapram hydrochloride were studied in anesthetized dogs during normothermia and at two levels of hypothermia. In the normothermic animal, KCN evoked significant elevations of minute and alveolar ventilations. For the mildly hypothermic (32-33 degrees C) dog, minute and alveolar ventilations were proportionally greater than for normothermia. Bolus infusions of KCN to deeply hypothermic dogs (28-29 degrees C) elicited larger and nearly similar increases of minute and alveolar ventilations as compared, respectively, with normothermia and mild hypothermia. Compared to their controls, injections of doxapram during normothermia, mild and deep hypothermia augmented VE 43.3%, 63.6% and 31.5%, respectively. With doxapram there was a feeble increase in alveolar ventilation. These results demonstrate that the peripheral (arterial) chemoreceptors preserve the capacity to respond to stimuli given acutely while lowering core temperature and in some circumstances this capacity is even enhanced as compared to normothermia.