Canadian Journal of Anesthesia, Vol 22, 154-163, Copyright © 1975 by Canadian Anesthesiologists' Society

Anaesthetic Management of Volume Controlled Unilateral Lung Lavage

¹ Departments of Anaesthesiology, Duke University Medical Center, Durham, N.C. 27710, U.S.A.
² Departments of Medicine, Physiology and Pharmacology, Duke University Medical Center, Durham, N.C. 27710, U.S.A.

Light general anaesthesia combined with marked muscle paralysis can be used as the procedure while unpleasant and terrifying is not painful nor surgically stimulating. In addition the airway is well anaesthetized topically. Paralysis permits maximal control over the patient and the maintenance of position of the Carlens tube, in a situation where movement or coughing might be dangerous. Paralysis also maximizes lung-thorax compliance, reduces O₂ consumption and permits lavage under light anaesthesia. The choice of maintenance anaesthetic appeared to be a negligible factor in the management of these patients. With the doses of ketamine employed, post-lavage CNS depression did not delay weaning and extubation. Dreaming, hallucinations and emergence delirium related to ketamine were not reported nor observed. The absence of these phenomena was probably related to the use of diazepam before and immediately after the lavage but prior to weaning from the respiratory support as suggested by Coppel, et al.¹¹ In our opinion either ketamine or halothane employed in these doses are suitable maintenance anaesthetics. The use of ketamine does avoid the controversial administration of two halothane anesthetics in close sequence. Of most importance, light anaesthesia with minimal cardiac and vasomotor depression facilitates maximal cardiovascular reactivity (as indicated by the maintenance of systemic pressure and tachycardia) in this setting of marked physical impediment to venous return which is imposed by the saline filled lung and vigorous ventilation of the contralateral lung.¹²

The lavage is conducted in the upper range of the vital capacity and the continuous assessment of Pao₂ is vital, to detect and to control the large fluctuations induced by the lavage and the consequent distribution of pulmonary blood flow.

Lavage in the upper portion of the vital capacity maximizes the liquid expiratory flow rate, as the lung-thorax recoil remained high.¹³ Blood flow to the lavaged side is minimized so that a higher arterial oxygen content and Pao₂ is achieved. The largest reduction of perfusion to the liquid filled lung is not obtained until lung filling has exceeded the FRC. In our experience this is best determined by: (1) prior knowledge of the FRC, so that the lung can be filled initially to this volume, (2) filling the lung until one can demonstrate a rise in Pao₂ coincident with each 500 ml tidal volume of saline, and (3) filling the lung until one can demonstrate a rise in airway pressure coincident with each 500 ml tidal volume of saline. Overfilling the lavaged lung would predictably reduce shunting or venous admixture even further; however, the danger of mechanical damage associated with overdistension precludes this maneuver. Prior knowledge of the total lung capacity and continuous monitoring of airway pressure in the lavaged lung at the time of no flow has been found useful in preventing overdistension.

Note:

Presented at the Canadian Anaesthetists' Society Meeting, St. John's, Newfoundland, June 1974.

Present address: Dept. Anaesthesia, Dalhousie University, Halifax, Nova Scotia.