Effect of neuroleptanaesthesia on VA/Q distribution and pulmonary shunt

The authors studied changes in the ventilation-perfusion ratio and pulmonary shunt in the course of pulmonary surgery in relation to their presurgery values. The study was conducted at the Jordanovac University Department for Thoracal Surgery in Zagreb, examining 35 patients in whom, owing to pulmonary carcinoma, thoracotomy and pulmonary resection were performed. Relevant data were obtained concerning hypoxemia, its incidence, and its intensity in the patients examined. The results obtained have shown that in the presurgery period all the patients had an elevation of pulmonary shunt and an increased ratio of ventilation and blood flow, leading to mild hypoxemia. During the operation, the fall of the pulmonary shunt amounted to 8%; it was smaller after the ligature (bronchi, artery, and vein of the respective lung or its part) than at the end of the surgery (P < 0.001), whereas the ventilation-perfusion ratio fell more markedly after ligature (P < 0.001) than at the end of the operation. The authors conclude that, by knowing the ventilation-perfusion ratio and pulmonary shunt in the presurgical period, it is not possible to predict the changes of these parameters in the course of surgery. This is of special importance, because hypoxemia, occurring as a result of changes in the ventilation-perfusion ratio and pulmonary shunt, seriously endangers the patient's fate during surgery.