Erythrocyte and plasma circulation times in haemorrhagic shock

A method has been developed in which the simultaneous administration of 51Cr‐labelled red bloodcells and 125I‐labelled albumin in the dog has been used to compare the flow rates and transit times of erythrocytes and of plasma in three circulatory beds–the hindlimb, the kidney, and the small intestine. Blood‐flow rates calculated from either isotope agreed well and were significantly greater than simultaneous direct measurements and electromagnetic flowmeter readings. This difference was due to in complete recovery of the isotope from the venous cannula, recovery ranging from 23 to 96 per cent. When the isotope‐flow results were corrected for these losses they did not differ significantly from direct measurements though they were still greater than the electromagnetic flowmeter readings. The mean transit time for erythrocytes was, on average, 6–8 per cent shorter than that for plasma. There was no significant difference in this percentage for the three vascular beds studied or between a control period and haemorrhagic shock. Thus, in this shock preparation red‐cell ‘sludging’ cannot have been extensive. The rationale for the use of low‐molecular‐weight dextran as a specific ‘antisludging’ agent in shock is, therefore, not supported.