Canadian Journal of Anesthesia, Vol 27, 485-490, Copyright © 1980 by Canadian Anesthesiologists' Society

Continuous Ketamine Infusion for One-Lung Anaesthesia

¹ Department of Anesthesiology, The Mount Sinai Medical Center of the City of New York, One Gustave L. Levy Place, New York, N.Y. 10029, U.S.A.

The mechanism which normally affects distribution of blood flow through unventilated areas of the lung is hypoxic pulmonary vasoconstriction; this acts to divert the blood to well ventilated alveoli, resulting in a better ratio of ventilation to perfusion.

Several reports have focused attention on the reduction or abolition of this reflex in the unventilated lung by most of the volatile anaesthetic agents used in clinical practice. This response was not abolished by the intravenous anaesthetic agents.

One hundred and ten patients undergoing elective pulmonary resection were studied to evaluate the effect of a continuous infusion of ketamine during one-lung anaesthesia, by observing the changes in Pa_oo2 as a reflection of shunt. Ketamine was chosen as the intravenous agent for its positive inotropic and chronotropic action. Additionally, by providing both analgesia and hypnosis, we were able to admininster inspired oxygen concentrations of 50-100 per cent without concern that the patient might have recall for events during operation.

We have demonstrated that in all cases a Pa_oo2 in excess of 9.31 kPa (70 torr) was achieved with ketamine and Fi_oo2 1.0 as well as an increase in shunt fraction from 25.9 per cent (Fi_oo2 0.5) to 36.0 per cent (Fi_oo2 1.0).

We feel that ketamine provides a satisfactory alternative to the volatile agents for one-lung anaesthesia in patients where relative hypoxaemia might be unacceptable during operation.