Bradycardia following negative pressure suction of subgaleal drain during craniotomy closure

We report bradycardia (50 beats/min) in a patient, following application of negative pressure (50 mmHg) suction to the subgaleal drain, after an uneventful clipping of an anterior communicating artery aneurysm. This episode recurred even with application of a lesser negative pressure of 23 mmHg. It was noted that the time lag between application of suction pressure and the occurrence of bradycardia increased, from 10 sec in the former to 50 sec in the later instance. None of these episodes were associated with changes of blood pressure. Moreover, there was a temporal association between the intensity of negative pressure applied and the time of occurrence of bradycardia. This phenomenon is possibly due to intracranial hypotension causing reverse brain herniation that bears a relationship with the intensity of negative pressure applied. We recommend that negative pressure suction is avoided during skin suture and applied gradually, after the closure.