4,15 



Observations on Changes in the Blood Pressure and Blood Volume 

 following Operations in Man. {P7'eliminary Communication.) 

 By Captain H. C. Bazett, M.C, E.A.M.C. 



(Communicated by Prof. W. M. Bayliss, F.R.S. Received October 8, 1918.) 



The cases here investigated were wounded men undergoing operations, and 

 repeated examinations were usually made. Most of the cases showed only 

 slight symptoms of shock. 



Methods. — The systolic and diastolic blood pressures were measured before, 

 during, and after operations, a Eiva Rocci apparatus being used. The 

 auscultatory method recommended by Oliver was used to determine the two 

 levels. The haemoglobin was estimated also, as far as possible, at the same 

 time. The actual level of the haemoglobin value was read by Haldane's 

 method, while the changes in any patient were determined by comparison of 

 the different samples in a Da Borscq colourimeter. For this purpose suspen- 

 sions of the corpuscles in a dilution of 1 in 200 in saline were used, the 

 volume chosen being 10 c.c, and these samples were heemolysed with saponin 

 before being read in the colourimeter. For this method I am indebted to 

 Prof. Dreyer, and it has proved more accurate than any other. The blood 

 has been taken always from either the ear or the finger. In estimating 

 the blood volume changes from these readings, it has been assumed that the 

 blood volume varies inversely as the haemoglobin percentage. During and 

 after operations this will be only relatively true, since haemorrhage occurs. 

 The amount of blood lost may, however, be roughly estimated by the loss of 

 haemoglobin in the first 24 hours after operation. In cases of slight shock, 

 equilibrium will probably have been reached in this time. That this is true 

 is indicated by the results obtained and put forward in Case I. In this 

 patient a fair amount of blood was lost during the process of decompression 

 for a fractured skull, and nearly all the blood lost was washed into buckets 

 by a stream of saline running over the wound. The saline in these buckets 

 was collected after the operation and the haemoglobin content was determined 

 by reading the contents in the Du Borscq colourimeter against a sample of the 

 patient's own blood, taken before operation. In this way it was calculated 

 that he lost 782 c.c. of blood. By the determination of the change in the 

 haemoglobin value in 24 hours, it was estimated that he lost 17'7 per cent, of 

 his blood volume, and this was reckoned (taking Dreyer's formula for blood 

 volume) to correspond to a loss of 760 c.c. The agreement was therefore 

 remarkable, and it is probable that the methods are moderately accurate. In 



VOL. XC. — B. 2 L 



