THE EFFECT OF HYPOTHERMIA ON PLATELETS AND 

 WHITE CELLS IN DOGS 



TULIO J. VILLALOBOS, EDWARD ADELSON and PHILIP RILEY 

 (With technical assistance of Harold Glaucke) 



In a previous report from this laboratory, results of hematologic studies in nine 

 hypothermic dogs cooled below 20° C. were presented. These results showed a rise 

 in red cell count, hemoglobin concentration and hematocrit ; a marked drop in white 

 cell count ; and nearly complete disappearance of platelets. On rewarming these 

 changes all returned to normal. A number of studies have been carried out to learn 

 the mechanism of these alterations. In the present paper, we will summarize these 

 studies — especially as they concern the platelets and white cells. 



The platelets and white cells, which nearly completely disappear during hypo- 

 thermia, return within a period of minutes during the early phase of rewarming. 

 The first question which presented itself was whether these returned platelets and 

 white cells are newly formed, or are simply the old platelets and white cells return- 

 ing to the circulation after a period of sequestration. 



To study this question, we applied to animals a technique described by Desai 

 et al. in humans. By this technique we injected 2 millicures of P^" into a normal 

 dog. One week later we withdrew 500 cc. of blood from a vein of this animal. The 

 blood was obtained in plastic bags with sequestrene as anticoagulant. Simultane- 

 ously, a second dog which had not received P^^- was phlebotomized, and immedi- 

 ately thereafter the second dog received a transfusion of the 500 cc. of whole blood 

 obtained from the radioactive donor dog. This whole blood contained many radio- 

 active substances, among which were radioactive platelets. One-half hour after the 

 infusion, an aliquot of blood was drawn from the recipient animal, the platelets 

 separated, washed and counted. There were Z.7 (10"'') counts per second per 

 platelet. The animal was then subjected to hypothermia, his platelets nearly dis- 

 appeared, and the animal was then rewarmed. With the return of his platelets, the 

 radioactivity of aliquots of his platelets also returned. This radioactivity was deter- 

 mined to be 3.0 (10"^) counts per second per platelet. In other words, 81 per cent 

 of the tagged platelets, which had been infused early in the morning prior to 

 hypothermia, were still present in the afternoon after hypothermia. The slight drop 

 in platelets could easily be explained by the normal life span of the platelet. The 

 fact that 81 per cent of the transfused radioactive platelets were still present showed 

 clearly that the drop in platelets due to hypothermia is a result of sequestration of 

 platelets, not of destruction of platelets. The return of the platelet count toward 

 normal after hypothermia is not due to the production of new platelets, but to the 

 return of the sequestered platelets to the circulation. Figure 1 summarizes these 

 findings. 



The next question which presented itself is: where does the sequestration occur? 

 Table I shows that the sequestration does not occur in the capillaries of the body, 

 at least not in the capillaries of the tongue. Here the results of platelet counts in 

 the aorta are compared with those found in the capillary blood in the tongue. It 



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