Observations on changes in the blood pressure and blood volume following operations in man. (Preliminary communication.)

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 Riva Rocci apparatus being used. The auscultatory method recommended by Oliver was used to determine the two levels. The hæmoglobin was estimated also, as far as possible, at the same time. The actual level of the hæmoglobin value was read by Haldane’s method, while the changes in any patient were determined by comparison of the different samples in a Du Borscq colourimeter. For this purpose suspensions 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 hæmolysed 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 hæmoglobin percentage. During and after operations this will be only relatively true, since hæmorrhage occurs. The amount of blood lost may, however, be roughly estimated by the loss of hæmoglobin 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 hæmoglobin 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 hæmoglobin 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 all the Tables the calculations of blood volume are made neglecting this factor of hæmorrhage. At the bottom of the Tables the estimated blood lost is given, and in the last column of the Tables corrected values for the blood volume are given in which the hæmorrhage has been approximately allowed for. The results obtained seemed to indicate that the changes in the hæmoglobin percentage of capillary blood do demonstrate the changes seen in the blood volume, provided that the lag due to a slow circulation and partial stasis is allowed for, the hæmoglobin changes following those in the blood pressure.