416 Capt. H. C. Bazett. Changes in Blood Pressure and 



all the Tables the calculations of blood volume are made neglecting this factor 

 of haemorrhage. 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 haemorrhage has been approximately allowed 

 for. The results obtained seemed to indicate that the changes in the 

 haemoglobin 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 haemoglobin changes following those in the blood 

 pressure. 



The results obtained are, briefly, that during the early stages of an opera- 

 tion the pulse rate, systolic, and pulse pressures are all raised, while the 

 diastolic pressure is also usually slightly raised, and at this time the- 

 haemoglobin percentage is slightly reduced, that is to say, the blood volume is 

 probably increased. In the later stages of an operation, or in the post- 

 operative stage, the blood-pressures all fall ; the pulse rate may remain fairly 

 fast, and with the fall of blood pressure there is a blood concentration. Thus 

 it is seen that in most cases the blood volume curve runs parallel with the 

 blood pressure, except that it usually lags about half an hour behind the 

 other curve, and when the circulation is sluggish, as in cases of shock, it may 

 lag an hour or more (compare Cases II and III). None the less, the two 

 curves usually show a marked similarity. The cases investigated, as a rule,^ 

 have shown very slight blood concentration, since nitrous oxide and oxygen 

 anaesthesia was used in all cases Jn which shock was feared, and with this 

 form of anaesthesia little or no shock was experienced. The pulse in even 

 desperate patients was often actually improved by the amputation of a 

 leg. Any ill effects following operation in these cases with nitrous oxide 

 seemed to be attributable to either loss of blood in the operation or exposure- 

 to cold. 



In one case (Case III) which was resplinted with no loss of blood, but 

 considerable exposure of both lower limbs, there was a considerable fall of 

 temperature, and this was the only case that showed real blood concentration 

 to any marked degree. This case was anaesthetised with pure chloroform. 



Since the curves always showed such a marked similarity, the diurnal 

 variations were investigated to determine if they showed a similar relation- 

 ship. One chart of these (Case IV) is included, and it will be seen that the- 

 relationship still holds good except for a brief half-hour after meals. Thesfr 

 diurnal variations cannot be discussed now ; I am indebted to Prof. Dreyer,. 

 who first drew my attention to these marked diurnal variations in the 

 haemoglobin percentage, for permission to mention this. He first worked out 

 these diurnal variations in the haemoglobin percentage, and I only mention 



