Large volume hemodilution perfusion in newborn pigs : its effect on plasma volume, plasma proteins, and plasma electrolytes

Le Gal, Yves Marcel (1973) Large volume hemodilution perfusion in newborn pigs : its effect on plasma volume, plasma proteins, and plasma electrolytes. Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

Simultaneous evaluations of plasma volume, plasma protein and plasma electrolyte changes in response to large volume hemodilution perfusion in newborn pigs were made. These data are needed for the application of the technique of extracorporeal circulation using large volume hemodilution in the neonate. -- Seven days old pigs were used in this study. Two groups of 15 animals underwent arteriovenous perfusion with the chest closed, at normothermia, and without an oxygenator in the system, perfusion was continued until complete mixing of the blood and priming fluid was accomplished. The extracorporeal circuit was primed in group I with a buffered Ringer-lactate solution, and in group II with a buffered solution of 2% Rheomacrodex in Ringer-lactate. Priming solutions were individually tailored to result in a (mixed blood and prime) hematocrit of 22%. The volume of the diluted blood in the circuit after perfusion, was identical to the volume of the priming fluid. A third group consisting of littermates of the above animals was subjected to the same surgical procedures but without perfusion. -- Hematocrit, plasma volume, total plasma proteins and electrophoretic patterns of proteins, osmolarity, and the major plasma electrolytes were measured immediately before and after perfusion, then every 8 hours over a period of 24 hours. Mean arterial blood pressure, heart rate and rectal temperature were monitored at the same time. -- In both groups the hematocrit values came very close to the desired target of 22%. The hematocrit in group I showed a further drop until 16 hours following perfusion, whereas, that of group II rose steadily. -- Immediately after perfusion the deficit in plasma volume was more pronounced in group I suggesting an internal loss from the intravascular space, since there was no corresponding reduction in body weight. The replenishment of plasma volumes followed an exponential curve and was faster in group I. The restoration of plasma proteins in both experimental groups was also exponential and was faster in group II. -- Osmotic equilibrium was reached at the end of perfusion. There was a steady rise in osmolarity during the following 24 hours. Sodium and chloride followed the osmolarity pattern. -- Newborn pigs can cope with a large volume hemodilution resulting in a hematocrit of 22%. Their ability to counteract plasma volume and plasma proteins losses is well developed so that restoration is accomplished in about 24 hours. The restoration of plasma volume occurs faster than the restoration of plasma proteins, but when Rheomacrodex is present the reverse is the case. -- The reappearance rate of proteins is about identical to the disappearance rate of Rheomacrodex. This substance binds water selectively, therefore it has a stabilizing effect on plasma volume shifts but not on plasma osmolarity. Two percent Rheomacrodex in Ringer-lactate enhances protein restoration considerably.

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