ELECTROLYTES, CLOTTING IN BLOOD LOSS AND NORETHYNODREL 851 



The method of hemorrhage by cardiac puncture was standardized, and 

 changes in clotting characteristics, sérum pH and sérum ion concentrations were 

 investigated in expts. 1-3. Total blood volume was calculated from the équation 

 of Fernandez, Rettori and Mejia (1966): BV ml/100 g body weight = 9.94 — 

 0.12 B Wt. Cumulative percent blood loss was estimated for each blood sample. 

 In expt. 1, two successive blood samples, approximately 2.5 ml each, were removed 

 by cardiac puncture; blood losses estimated from the équation were 20 and 

 40 percent. In expt. 2, sample volumes were accurately recorded, but extracardiac 

 losses were not measured, so that the hemorrhage curve may be underestimated 

 by 1-2 percent at any point. In expt. 3 and subséquent experiments, extracardiac 

 blood losses, measured with cellulose sponges, were distributed equally over the 

 volumes taken by heart puncture. No correction was made for blood spécifie 

 gravity. 



In expt. 4, using 34 rats, 155 g average weight, the volumes removed in two 

 cardiac punctures were 1.98 ± 0.17 ml and 1.92 ± 0.19 ml. Extracardiac losses 

 averaged 6 percent of total blood volume, and estimated blood losses for the two 

 samples were 18.8 and 37.2 percent. The mean etherization time was 1 19 ± 28 secs. 

 The average time between the ventral incision and withdrawal of the first sample 

 was 14+13 secs; for the second sample, 94 + 55 secs. In expt. 7, 24 rats, 100 g 

 average weight, the volumes removed were 1.95 ± 0.16 and 1.03 ± 0.55 ml; 

 extracardiac losses were 6 percent; estimated blood losses for the two samples 

 were 25.2 and 39.4 percent. Etherization time was 118 + 28 secs; withdrawal 

 times were 27+18 secs for the first sample and 98 + 30 secs for the second 

 sample. 



AMg, the computed shift in sérum magnésium concentration between 20 and 

 40 percent hemorrhage was defined in expts. 4-5; the effects of Enovid injection 

 were examined in expts. 6-7. Female rats were used in ail experiments except 5. 



RESULTS 



Two successive blood samples were removed by cardiac puncture from 

 14 rats (Table 1). Sérum magnésium concentrations increased in the second blood 

 samples compared to the first. The elasticity of the clot (TEG a) increased, although 

 fibrinogen and platelets were relatively stable. In expt. 5 glass clotting time de- 

 creased 0.8 min between 21.4 and 38.4 percent hemorrhage. 



Two to five blood samples were removed from 6 rats, 129 g average weight 

 (expt. 2). Occasional samples were too small, so that pH could be determined but 

 not magnésium, or the blood clotted in the syringe so that volume could be noted 

 but not pH. Accordingly, curves of percent hemorrhage and sérum magnésium 

 concentrations were constructed from clustered pH values (Fig. 1). pH decreased 



