Based on reports of fatal venous air embolism (VAE) occurring during lumbar laminectomy and spinal fusion in prone patients positioned with the abdomen hanging freely, it has been recommended that monitoring for VAE should be used for such cases and that a multiorificed central venous catheter should be inserted for aspiration of VAE. The present study was designed to examine aspiration of VAE when prone dogs positioned with the abdomen hanging freely were given a fatal VAE via a femoral vein. Twenty-one dogs were anesthetized with halothane and nitrous oxide in oxygen and positioned with the abdomen ventral and hanging freely, the head fixed in a stereotaxic frame, the upper extremities resting on a surface approximately 10 cm below the level of the stereotaxic frame, and the lower extremities on a surface below the level of the upper extremities (to ensure that VAE entering the inferior vena cava would ascend toward the heart). In the control group (n = 7), a central catheter was placed but was not used to aspirate VAE. In a second group (n = 7), a Cook Bunegin-Albin multiorificed catheter was inserted; and in a third group (n = 7), an American Edwards 7F Swan-Ganz catheter was inserted. Dogs were then given a predetermined lethal dose of air (5 mL/kg) over 30 s via the femoral vein. In groups 2 and 3, attempts to aspirate VAE were begun with the first decrease in expired C02. The amounts of gas retrieved (expressed as a percent of the injected air) and the incidence of successful resuscitation were compared. Significantly greater percentages of injected venous air were retrieved with the Bunegin-Albin catheter (47% ± 20% [mean ± SD]) than with the Swan-Ganz catheter (8% ± 6%). However, the success rate of resuscitation was identical whether attempts to aspirate VAE were performed with Bunegin-Albin or Swan-Ganz catheters or no attempt was made to aspirate VAE (1 of 7 survivors in all three groups). It is concluded that in prone dogs positioned with the abdomen hanging freely, central catheters located near the junction of the right atrium and superior vena cava may be ineffective for retrieval of VAE reaching the heart via the inferior vena cava and do not increase the success rate of resuscitation.
Address correspondence to Dr. Artru, Department of Anesthesiology, RN-10, University of Washington School of Medicine, Seattle, WA 98195.
© 1992 International Anesthesia Research Society