PULMONARY SHUNT DURING POSITIVE PRESSURE VENTILATION AND GENERAL ANESTHESIA.
WASHINGTON UNIV SEATTLE
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A series of patients who had general anesthesia for elective surgical procedures was studied. Intraarterial and right atrial catheters were placed preoperatively, control studies including cardiac-output were made, and the patients anesthetized with halothane. Cardiac-output and pulmonary shunt determinations were made under light and deep halothane anesthesia, and then the patients were maintained in a light plane of anesthesia with halothane, paralysed with auccinylcholine, and connected to the positive pressure breathing apparatus. Measurements of the cardiac-output and pulmonary shunt were made after the patient had been on 10, 15, 20, and 25 cm. H2O pressure, both with a zero and -2 cm. negative pressure, respectively. EACH PATIENTS WAS ALLOWED AT LEAST FIVE MINUTES ON EACH PRESSURE SETTING TO EQUILIBRATE HIS OUTPUT AND SHUNT. Results to date indicate that lower pressure settings are associated with a lower cardiac-output and increased shunt. Higher pressure, especially with the addition of negative pressure, brings the cardiac output to normal, but the amount of pulmonary shunting never returns to the low control levels. Author