Proceedings

The Role of Colloid Osmotic Pressure in Post Bypass Pulmonary Dysfunction

Veterans Administration Medical Center and University of Arkansas for Medical Sciences, Little Rock, AR 72206

^* Correspondence to: F. Elvis Wright, B.S., C.C.P., Surgical Service (112), VA Medical Center, 300 E. Roosevelt Road, Little Rock, AR 72206.

Abstract

Determination of colloid osmotic pressure (COP), arterial blood gases (ABG) and weight were made in 25 consecutive patients undergoing cardiopulmonary bypass (CPB) with hemodilution. COP measurements were made prior to CPB, at 30 minute intervals during perfusion, and at 6, 12, 24 and 48 hours following CPB. Arterial blood gases were measured at 6, 12, 24 and 48 hours post-operatively. COP decreased abruptly with the initiation of bypass from 25.4 ± 3.4 mmHg to 16.8 ± 4.6 mmHg (p < 0.05) and remained at this level throughout the duration of bypass. All COPs returned to baseline levels, 23.6 ± 4.1 mmHg, 48 hours after surgery. Maximum decrease in COP was compared to the increase in calculated alveolar-arterial O₂ gradient at 6, 12, 24 and 48 hours post-operative, and no significant correlation could be found. Similarly, the decrease in COP did not correlate with the weight gain present at 24 and 48 hours. COP is significantly altered by CPB and undoubtedly results in changes in fluid compartment dynamics. However, changes in COP do not seem to play a role in ventilatory problems following CPB in the routine patient.