Autoregulation of renal blood flow during ether, halothane and methoxyflurane anesthesia in dogs

The effects of ether, halothane and methoxyflurane (0.5-1.5 MAC) on renal blood flow and its autoregulation were studied in 24 dogs. The left renal artery was perfused with the animals' own blood by a constant pressure perfusion system. The perfusion pressure ranged from 60 to 200 mmHg. Renal blood flow at the perfusion pressure of 100 mmHg was changed neither by ether nor by halothane, while it was decreased dose-dependently by methoxyflurane. At equipotent anesthetic concentrations the autoregulation of renal blood flow was only slightly impaired by ether, but significantly by halothane and methoxyflurane. Adenosine (100 mug/min) or calcium chloride (10 mg/min) which was infused directly into the renal artery resulted in a restoration of autoregulation impaired by MAC-1 of each anesthetic when perfusion pressure was raised stepwise from 100 to 200 mmHg, but no restoration was observed at low perfusion pressure below 100 mmHg. The results indicate that methoxyflurane exerts a direct constrictive effect on the renal vasculature. Adenosine and calcium may play a significant role on the response of the renal vasculature to raised perfusion pressure.