Remifentanil sometimes elicits cough during induction of anesthesia, as with the use of other fentanyl congeners. We designed this study to investigate the incidence of remifentanil-induced cough (RIC) in children and to evaluate the effect of injection speed on RIC.

One hundred twenty ASA physical status I-II patients, aged 3-12 yr, undergoing general anesthesia were enrolled in the study. Patients were randomly assigned to one of the three groups. Patients in Group R30 received remifentanil 1.5 µg/kg at a constant rate over 30 s. Patients in Group R45 received remifentanil 1.5 µg/kg over 45 s, and patients in Group R60 received remifentanil 1.5 µg/kg over 60 s, respectively. Episodes of cough were recorded and graded as mild (1-2), moderate (3-4), or severe (5 or more). Mean arterial pressure (MAP), heart rate (HR), and SpO₂ were recorded on arrival in the operating room (baseline) and 1 min after remifentanil infusion.

The incidence of RIC was 33.3% in Group R30 (13 of 39 patients), 17.9% in Group R45 (7 of 39 patients), and 5.0% in Group R60 (2 of 40 patients). Patients in Group R60 had a significantly lower incidence of RIC than those in Group R30 (P = 0.001). The MAP, HR, and SpO₂ values were not significantly different between groups.

When intravenous remifentanil 1.5 µg/kg was administered in pediatric patients, the incidence of RIC decreased from 33 to 5% by increasing the injection time from 30 to 60 s. Remifentanil should be administered slowly over 60 s in children to suppress cough during anesthesia induction.