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We conducted a placebo-controlled, randomized, and double-blinded study to evaluate the efficacy of manidipine given orally in attenuating the cardiovascular responses to laryngoscopy and tracheal intubation. Thirty normotensive patients (ASA physical status 1) undergoing elective surgery were allocated to one of three groups (n = 10 for each); placebo, 5 mg manidipine, and 10 mg manidipine groups. These tablets were orally administered 3 h before induction of anaesthesia. Anaesthesia was induced with thiopentone 5 mg.kg-1 iv, and tracheal intubation was facilitated with vecuronium 0.2 mg.kg-1. Laryngoscopy lasting 30 sec was attempted 2 min after induction of anaesthesia. Patients receiving placebo showed a significant increase in systolic and diastolic blood pressure associated with tracheal intubation. These increases following tracheal intubation were significantly reduced in patients receiving manidipine 10 mg compared with patients receiving placebo or manidipine 5 mg (P < 0.05). Oral administration of manidipine 10 mg before induction of anaesthesia is a simple and effective method for attenuating pressor response to laryngoscopy and tracheal intubation. We stressed that the potential beneficial effect of a reduced haemodynamic reaction to intubation might be obtained at the expense of hypotension later on.

Laryngoscopy and tracheal intubation often cause hypertension, tachycardia and arrhythmias, which may be exaggerated during rapid-sequence induction of anaesthesia. We have studied the efficacy of pindolol in attenuating the cardiovascular responses to laryngoscopy and intubation in patients receiving pindolol 2 micrograms kg-1 or 4 micrograms kg-1 3 min before induction of anaesthesia in a double-blind design. The data were compared with those in a control group receiving saline. Each group consisted of 10 patients undergoing elective surgery. Anaesthesia was induced with thiopentone 5 mg kg-1 i.v. and tracheal intubation was facilitated with vecuronium 0.2 mg kg-1. Patients receiving saline showed a significant increase in mean arterial pressure and heart rate associated with tracheal intubation. These increases after tracheal intubation were reduced in pindolol 4 micrograms kg-1 treated patients compared with those in the control group (P less than 0.05). Pindolol 2 micrograms kg-1 attenuated tachycardia in response to intubation but did not affect hypertension. These data suggest that a bolus injection of pindolol 4 micrograms kg-1 is a simple, practical and effective method for attenuating cardiovascular responses to laryngoscopy and tracheal intubation.