Response to hypercapnia under ketamine anaesthesia

The respiratory response to hypercapnia in dogs anaesthetized with ketamine was increased. This respiratory stimulation was most probably due to a direct effect of the drug on the medullary respiratory neurones. This effect was not modified by preanaesthetic medication pentobarbitone 5 mg/kg or morphine 0.1 mg/kg. Catecholamine response to hypercapnia was essentially the same as that reported by hypercapnic dogs anaesthetized with thiopentone.