Experimental investigation of the cardiovascular and respiratory effects of increasing concentrations of isoflurane in the dog.

The cardiovascular and respiratory effects of the new inhalational anaesthetic agent isoflurane were investigated in dogs. Anaesthesia was induced with thiopentone after premedication with acepromazine. Isoflurane was administered with nitrous oxide and oxygen by spontaneous ventilation after base line values had been determined. Arterial blood pressure decreased as the concentration of administered isoflurane increased. Isoflurane produced a profound and dose related respiratory depression as measured by the increase in end tidal carbon dioxide levels. Isoflurane administration did not produce any visible muscle twitching.