Cremasteric reflex test as an objective indicator of spinal anaesthesia.

We studied 100 men who were scheduled for urological surgery (Group 1) and another 50 men for orthopaedic surgery (Group 2). We attempted to anaesthetise both sides of the lower body in Group 1 and to anaesthetise one leg in Group 2 by injecting 0.3% hyperbaric dibucaine intrathecally. The presence or absence of the cremasteric reflex and loss of sensation to pinprick higher than the first lumbar dermatome were examined by two researchers who were blind to each other's results. In Group 1, both the reflex and the pinprick sensation were always absent bilaterally 5 min after intrathecal injection. In Group 2, in 23 of 50 patients the reflex had become absent bilaterally; in all these patients, bilateral sensory loss was detected. In the remaining 27 patients, both the reflex and the pinprick sensation were absent on the operation side, whereas both were present on the nonoperation side. Sensitivity, specificity and positive or negative predictive value for the cremasteric reflex were all 100%. Disappearance of the cremasteric reflex is a simple objective indicator of spinal anaesthesia at the first lumbar dermatome. This test may be useful in patients who cannot give reliable answers to conventional tests, such as the pinprick test.