Abstract
In the current studies of the development of shock during surgical procedures, alterations in the rhythmical variations in the caliber of the small peripheral blood vessels of the fingers and toes have been noticed after spinal anesthesia and anesthetization of the stellate ganglion.
It is well known that spinal anesthesia may occasion a fall in blood pressure especially in the presence of moderate hemorrhage or trauma. 1 , 2 , 3 , 4 It is also known that peripheral blood vessels dilate when denervated of their sympathetic supply. 5 These two phenomena, fall in pressure and dilatation of the vessels, are related. What is still unknown is how those other small peripheral blood vessels with their sympathetic supply still intact participate in this result. If the blood pressure and the pulse rate were to remain constant, then, on the assumption that the cardiac output also remains constant, it may be assumed that, as one large set of vessels dilates, another contracts.
Method. The pneumoplethysmograph of Turner, 6 as modified by Neumann 7 was used to record the variations in volume of fingers and toes simultaneously. Normally, waves are inscribed representing constantily occurring changes in volume. These include the pulse waves, synchronous with the cardiac beat, and alpha waves 8 which occur 5 to 7 times per minute and vary in size up to 10 times that of the pulse waves.
Twelve patients free from hypertension and from peripheral vascular diseases, ranging in age from 24 to 54 years were studied. In 9, records were made during and after intrathecal injection of procaine hydrochloride or monocaine formate (150 mg). Sensory anesthesia as determined by testing sensory dermatomes reached the level of the umbilicus (T 12).
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