Effects of patient age, pH of cerebrospinal fluid, and vasopressors on onset and duration of spinal anesthesia.

Two hundred twenty-two spinal anesthesias were administered with 10 mg. of tetracaine and 1 ml. of 10 percent dextrose to investigate the effects of vasopressors, patients age, and pH of cerebrospinal fluid on the onset and duration of spinal anesthesia. Neither the differences in overall age, cerebrospinal fluid pH, nor the addition of vasopressors had any significant effect on onset. Duration, however, was significantly prolonged by the addition of vasopressors, 53 percent prolongation by 0.2 mg. of epinephrine and 72 percent prolongation by 2 mg. of phenylephrine.