Erythrocyte and plasma circulation times in haemorrhagic shock

Abstract

SUMMARYA method has been developed in which the simultaneous administration of 51Cr-labelled red bloodcells and 1251-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 incomplete 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.CIRCULATORY shock is a state in which the circulation fails to meet the nutritional needs of the body at rest (Guyton and Crowell, 1964). The absolute reduction in blood-flow in shock may be accompanied by disruption of the orderly passage of erythrocytes through the capillaries, as seen by direct observation of the microcirculation using the techniques of Chambers and Zweifach (1944). Aggregation and slowing of the red cells, plasma skimming, and arteriovenous shunting have been observed in these circumstances . The present paper is concerned with the first of these microcirculatory effects-the slowing of the flow of erythrocytes relative to plasma which is often described as 'sludging'. Low-molecular-weight dextran (L.M.W.D.) therapy is designed to correct this process (Bergentz, Gelin, Rudenstam, and Zederfeldt, 1961).The evidence of in vivo microscopy is qualitative and is obtained in artificial situations, as with the rat's meso-appendix spread on a microscope stage. T o provide a quantitative measure of any relative slowing of the red cells their transit times from artery to vein have been compared with those for plasma. In health the circulation time for erythrocytes is 10-15 per cent shorter than that for plasma (Rowlands, Groom, and Thomas, 1963)~ the difference * Present address: Leicester Royal Infirmary. being attributed to axial streaming of cells in the smaller blood-vessels. If the changes seen on microscopy are occurring on a physiologically important scale, then in shock the mean transit time should be longer for erythrocytes than for plasma. METHODSThe measurements were made in 14 anaesthetized mongrel dogs weighing from 15 to 32 kg. (mean, 21.6 kg.). Transit times for red cells and plasma were compared before and after the production of haemorrhagic shock. The...