Spinal anesthesia: practical applications.

The recent widespread popularity of spinal anesthesia can be traced to two events. One is the appreciation that, when used for operations below the level of the umbilicus, anesthetically induced physiologic trespass is less with spinal than with general anesthesia. The other is the recognition that modest hypotension with peripheral vasodilation, that may be seen with spinal anesthesia or intravenous infusion of nitroprusside, is, unlike hypotension associated with hypovolemia, unaccompanied by physiologically significant changes in peripheral distribution of cardiac output or changes in the balance between tissue oxygen supply and demand in the myocardium or elsewhere. Spinal anesthesia also has special advantages specific to urinary tract surgery in the geriatric patient.