BACKGROUND: This study examined the cardiovascular responses to double-lumen endobronchial intubation during rapid sequence induction of anesthesia, and compared the effect of remifentanil and alfentanil in a randomized, double-blind, placebo-controlled study in three groups of 20 elderly patients each. METHODS: Anesthesia was induced with intravenous thiopental (4-6 mg/kg) immediately followed by either remifentanil 2 microgram/kg, alfentanil 30microgram/kg, or saline (placebo) given over 30 sec. Succinylcholine 1.5 mg/kg was given for neuromuscular block. The laryngoscopy and intubation were performed 60 sec later. RESULTS: The intubation significantly increased systolic arterial pressure (SAP) and heart rate (HR) in all groups. The maximum pressure changes in the remifentanil and alfentanil groups (36 +/- 26 and 33 +/- 30 mmHg, respectively) were significantly lower than the 83 +/- 35 mmHg in the control group. The maximum HR in the remifentanil (77 +/- 13 bpm) and alfentanil (80 +/- 13 bpm) groups was lower when compared to controls (93 +/- 11 bpm). The norepinephrine and epinephrine concentrations increased after intubation in the control group but remained unaltered in both the alfentanil and remifentanil groups. There were no significant differences between the remifentanil and alfentanil groups in HR, SAP or catecholamines at any time. Five patients in the remifentanil group and three in the alfentanil group received ephedrine for hypotension. CONCLUSIONS: Endobronchial intubation elicited a significant pressor response, and that both remifentanil and alfentanil similarly attenuated the pressor response. However, the incidence of hypotension confirms that both drugs should be used with caution in elderly patients.