EXTRAVASCULAR FLUID UPTAKE DURING CARDIOPULMONARY BYPASS IN HYPERTENSIVE DOGS

We investigated the effects of increases in central venous pressure (C VP) and carotid baroreceptor-induced vasodilation on the rate of extra vascular fluid uptake during cardiopulmonary bypass in normotensive an d Goldblatt hypertensive dogs. Carotid sinus baroreceptors were select ively perfused to control the level of vasodilation. Central venous pr essure was controlled by changing the height of the venous outflow can nula. Extravascular fluid uptake was determined from the rate of chang e in reservoir volume. After 3 hours of bypass, total fluid accumulati on was 56.11 +/- 14.16 mL/kg in normotensive dogs, significantly less than in hypertensive dogs (110.90 +/- 23.20 mL/kg) (p < 0.05). Raising CVP from 1 to 5 mm Hg increased the rate of extravascular fluid uptak e in both normotensive (from 0.05 +/- 0.25 to 0.85 +/- 0.22 mL.kg(-1). min(-1); p < 0.05) and hypertensive dogs (from 0.68 +/- 0.28 to 2.57 /- 0.46 mL.kg(-1).min(-1); p CVP, baroreceptor-induced vasodilation in creased the rate of extravascular fluid uptake in normotensive (from 0 .25 +/- .15 to 0.81 +/- .22 mL.kg(-1).min(-1)) and84 +/- .12 to 1.72 /- .32 mL kg-l min-l; p < 0.05). Hypertensive dogs were more sensitive to changes in CVP and to baroreceptor-induced vasodilation. The resul ts of this study imply that elevations in CVP or the use of vasodilato rs may lead to increased extravascular fluid uptake during bypass; thi s effect may be exacerbated in the hypertensive state.