Fentanyl-induced
cough is a common phenomenon during
anesthesia induction.
Magnesium sulphate (MgSO4) is reported to have a powerful relaxation of airway smooth muscle. This study is to investigate the effects of prophylactic MgSO4 on the incidence and severity of
fentanyl-induced
cough. A total of 120 patients, scheduled for elective surgery under
general anesthesia, were randomly allocated into three groups (n = 40, each group) and injected with 50 ml
normal saline, 30 mg/kg and 50 mg/kg of MgSO4 (diluted with
normal saline into 50 ml) in groups I, II and III, respectively. One minute later all patients were injected with 5.0 μg/kg of
fentanyl within 5 s. The incidence and severity of
cough were recorded 30 s after
fentanyl injection. Hemodynamic parameters and plasma
magnesium concentration of the patients were also noted. Three patients dropped off the study due to obvious burning sense during injection of 50 mg/kg of MgSO4. Injection with 50 mg/kg of MgSO4 increased plasma
magnesium level at the end of its infusion, but the latter still remained within therapeutic range (2-4 mmol/L). The incidence of
cough in group I was much higher than those in groups II and III (45.0% vs. 15.0% and 8.1%, P < 0.05). Compared with the group I, both the groups II and III had lower incidence of moderate
cough (P < 0.05). There were no differences in the hemodynamic data at three timepoints among the three groups. In conclusion,
fentanyl-induced
cough may be suppressed effectively and safely by prophylactic 30 mg/kg of MgSO4 during
anesthetic induction.