Failure of phenylephrine to prolong isobaric bupivacaine spinal anesthesia in elderly patients.

Abstract

The effects of phenylephrine on the duration of spinal anesthesia produced by plain bupivacaine were investigated in a double-blind study of 100 elderly patients. Each patient received a basic solution of 3 ml 0.5% plain bupivacaine to which was added either 1 ml physiologic saline, 0.2 ml (1 mg) 0.5% phenylephrine plus 0.8 ml normal saline, 0.4 ml phenylephrine plus 0.6 ml normal saline, 0.6 ml phenylephrine plus 0.4 ml normal saline, or 0.8 ml phenylephrine plus 0.2 ml normal saline. The duration of sensory block (measured by two- and four-segment regression times and times to regression to T12 and L2 dermatomes) was not statistically prolonged by addition of phenylephrine. It is concluded that, in an attempt to prolong plain bupivacaine spinal anesthesia, the addition of phenylephrine does not appear to be advantageous for routine clinical practice.