The effect of dilution and prolonged injection time on fentanyl‐induced coughing*

This study was designed to evaluate the effect of diluting fentanyl 50 microg x ml(-1) to 25 or 10 microg x ml(-1) with 0.9% saline and prolonged injection time on fentanyl-induced cough. Two hundred patients requiring general anaesthesia were randomly allocated into four groups: 50 microg x ml(-1) (Group I), 25 microg x ml(-1) (Group II), 10 microg x ml(-1) (Group III) or 10 microg x ml(-1) combined with prolonged injection (Group IV). Fentanyl 3 microg x kg(-1) was administered within 5 s in Groups I, II, and III, or over 30 s in Group IV. Occurrence of cough was significantly reduced in Group IV (2% vs 32%, 16% and 12% in Groups I, II and III, respectively, p < 0.05). There were no statistically significant differences in the severity of coughing between the four groups (p > 0.05). We conclude that dilution of fentanyl to 10 microg x ml(-1) with 0.9% saline combined with a prolonged injection time eliminates fentanyl-induced cough.