Comparison of nicardipine, diltiazem and verapamil for controlling the cardiovascular responses to tracheal intubation

We have compared the efficacy of three calcium channel blockers,nicardipine, diltiazem and verapamil, in attenuating the cardiovascularresponses to laryngoscopy and intubation in 60 normotensive patients (ASAI) undergoing rapid sequence induction of anaesthesia with thiopentone andfentanyl. We also examined whether or not these blockers inhibitedcatecholamine release induced by intubation. The patients were allocated toone of four groups (n = 15 for each): saline (control), nicardipine 30micrograms kg-1, diltiazem 0.2 mg kg-1 or verapamil 0.1 mg kg-1. Verapamiland the three other drugs were administered 45 s and 60 s before the startof direct laryngoscopy, respectively, in a double-dummy design. Anaesthesiawas induced with thiopentone 4 mg kg-1 i.v. and fentanyl 2 micrograms kg-1i.v. Tracheal intubation was facilitated with vecuronium 0.2 mg kg-1.During anaesthesia, ventilation was assisted or controlled with 1%isoflurane and 50% nitrous oxide in oxygen. Laryngoscopy lasting 30 s wasattempted 2 min after administration of thiopentone and vecuronium.Patients receiving saline exhibited significant increases in systolic anddiastolic arterial pressures (AP), heart rate (HR) and plasmaconcentrations of catecholamines associated with tracheal intubation. Theincrease in AP was attenuated in patients treated with any calcium channelblocker. The greatest effect was elicited by verapamil, which attenuatedthe increase in HR, although nicardipine seemed to enhance tachycardia. Allthree drugs failed to suppress the increase in plasma catecholamineconcentrations in response to tracheal intubation. These findings suggestthat bolus injection of verapamil 0.1 mg kg-1 was a more effective methodof controlling hypertension and tachycardia associated with intubation thandiltiazem 0.2 mg kg-1 or nicardipine 30 micrograms kg-1, and that theseprophylactic effects were not caused by inhibition of the catecholamineresponse.