The early effect on the arterial hematocrit reading of major acute arterial hemorrhage and of crystalloid infusion has been studied in splenectomized dogs. Within 30 minutes of completion of hemorrhage of 25% of estimated blood volume, the arterial hematocrit reading had decreased 15% from base line and remained at that level for the ensuing five hours. This rapid rate of transcapillary refill was comparable whether the hemorrhage was external or "intraperitoneal." The infusion of 0.9% sodium chloride solution in a volume equal to 75% of estimated blood volume over two hours resulted in a decrease in hematocrit reading during the infusion exceeding the decrease to be anticipated if the entire infused solution were equally distributed throughout the extracellular space. This apparent delayed dispersal of crystalloid from the intravascular to the interstitial space was not modified by prior hemorrhage.
Cowen SZ, White EJ, Donovan AJ. Alterations in Arterial Hematocrit ReadingEffect of Major Acute Hemorrhage and of Crystalloid Infusion in the Dog. Arch Surg. 1973;107(1):56-61. doi:10.1001/archsurg.1973.01350190044012