Effects of large volume-hemodilution perfusion on plasma volume, plasma proteins and plasma electrolytes in neonatal piglets.

Abstract

Two groups of 15 neonatal piglets underwent arteriovenous perfusion with the chest closed, at normothermia and without an oxygenator in the system until complete mixing of the blood and priming fluid was accomplished. The extracorporeal circuit was primed in one group with a warm (38 °C) buffered Ringer-lactate solution, and in the second group with an equally warm buffered solution of 2% Rheomacrodex in Ringer-lactate. The priming volumes of the perfused animals were individually tailored to result in a mixed (blood and priming solution) hematocrit of 22%. A control group of 15 piglets underwent the same surgical procedures but were not perfused. Large vessel hematocrit, plasma volume, the five major plasma protein components, plasma electrolytes and plasma osmolarity were measured before perfusion, immediately after and every 8 h for a period of 24 h. During perfusion, plasma volume, erythrocytes, and proteins were lost from the circulation. Plasma osmolarities showed larger fluctuations in the Rheomacrodex group than in the Ringer-lactate group. The neonatal pig is able to cope with large volume hemodilution resulting in a hematocrit of 22%. It shows a well-developed regulatory mechanism to counteract plasma volume and plasma protein losses; the replenishment of plasma volume and restoration of each major circulating plasma protein fraction, except γ-globulin, are accomplished in about 24 h. The restoration of plasma volume occurs faster than the restoration of plasma proteins, but when dextran is present the reverse is the case. Since the restoration of plasma volume, plasma proteins, and red blood cells do not show the same patterns, sequestration of whole blood is unlikely. 2% Rheomacrodex in Ringer-lactate appears to enhance protein restoration considerably.