Thoracic epidural clonidine attenuates haemodynamic responses induced by endobronchial intubation

Laryngoscopy and endobronchial intubation usually cause transient hypertension and tachycardia. We investigated whether thoracic epidurally injected 3 microg/kg clonidine attenuates cardiovascular responses to intubation compared with 2 microg/kg fentanyl and 1 mg/kg lidocaine. Epidural catheterization was performed at the T6-T7 or T7-T8 intervertebral space, and saline or clonidine in saline was injected 20 min before anaesthetic induction. Anaesthesia was induced using 5 mg/kg thiopental sodium and 0.1 mg/kg vecuronium. Laryngoscopy and endobronchial intubation were performed 2 min later. Mean blood pressure and heart rate were measured throughout anaesthetic induction. In the control group and the fentanyl group, mean blood pressure and heart rate 3 min after endobronchial intubation were elevated significantly compared with baseline. In the clonidine group, however, mean blood pressure and heart rate did not increase compared with baseline. The control group had higher mean blood pressure and heart rate than the clonidine group 3 min after endobronchial intubation. Thoracic epidural clonidine may attenuate the haemodynamic response to endobronchial intubation.