In shock the blood pressure picture is low but the pulse pressure drops to abnormally low figures. It seems to me that the blood pressure instrument has its greatest value in surgery in the warning it gives to the operating surgeon in cases of impending shock.
It is well known that the first effect of ether, the commonly used anesthetic, is to raise the blood pressure and quicken the pulse rate. The whole blood pressure picture is at first elevated (Fig. 54). Soon the whole pressure falls slightly but continues at a higher level than normal. The diastolic pressure drops back nearly to normal and the increased pulse pressure is due almost entirely to the slight rise in the systolic pressure. Now the whole duty of the anesthetist is to administer the ether so that this ratio of systolic and diastolic is maintained throughout the operation. Warning comes to him of impending shock before it comes to any one in the neighborhood (Fig. 55). Any sudden change in the pressure is a signal for increased watchfulness. Should the pressure all at once drop he can immediately notify the surgeon and institute measures to resuscitate the patient.
Fig. 54.—Blood pressure record from a normal reaction to ether. Note that the systolic and diastolic rise and fall together. At the end of the anesthetization the pulse pressure is practically the same as at the beginning. Compare this with the record in Fig. 55, where the operation had to be discontinued on account of the onset of shock.
Fig. 55.—Beginning of operative shock. Chart showing the method of recording blood pressure during operation. Note that the pulse and respiration show no remarkable changes, but the blood pressure steadily fell, the systolic more than the diastolic so that the pulse pressure was gradually reaching the danger point. Further work on this case was stopped following the warning given by the blood pressure. The patient was returned to the ward and a week later anesthesia was again given, the operation was completed, and the patient had a satisfactory convalescence.
A method which is widely used is as follows: The anesthetist wraps the cuff of one of the dial instruments around the patient's arm, and arranges the dial so that it can easily be seen by him at all times. This does not in any way interfere with the work of the surgeon. Over the brachial artery below the cuff is the bell of a binaural stethoscope held in place by the strap attachment now on the market. The tubes of the stethoscope are long enough to reach conveniently to the ear pieces. A watch is pinned to the sheet of the table. He has a chart, as illustrated (Fig. 56) on a board and makes a dot in every space for five minute intervals. By joining the lines a curve is obtained which tells at a glance what the circulation is doing. I feel sure that more attention and care exercised on the part of the anesthetist would be the means of conserving many lives lost from shock following operation.