Background
Magnesium is (NMDA) receptor antagonist used as an adjuvant for postoperative analgesia. There are several studies comparing the efficacy of the different routes of administration of magnesium. We aimed to study the effects of adding magnesium to IT fentanyl on peri-operative analgesic requirements after elective pediatric cardiac surgery.
Methods
This prospective double controlled randomized study (closed envelop method) included eighty pediatric patients subjected to elective open cardiac surgery. They were randomly allocated into four equal groups (20 patients each): (A) (i.v. fentanyl), (B) (ITF) (received IT 1 μg/kg of fentanyl), (C)   (received IT 1 μg/kg of fentanyl citrate and 0.5 mg/kg magnesium sulfate), and (D)   (received IT 1 μg/kg of fentanyl citrate, and 1 mg/kg magnesium sulphate). The perioperative anesthetic management was standardized.
Results
The results of this study demonstrated that the analgesic profile tended to be better with ITF, ITF-Mg 0.5 mg/kg and ITF-Mg 1 mg/kg groups than the control group. Also, intraoperative fentanyl used in ITF-Mg (1 mg) was statistically less as compared with ITF and ITF-Mg (0.5 mg) groups. Time to extubation (h) was surprisingly, shorter in ITF-Mg (1 mg) as compared with ITF and control groups. Also, postoperative intravenous fentanyl consumption μg/kg/24 h was more in control group as compared with other groups.
Conclusion
In conclusion, the use of intrathecal fentanyl-magnesium (1 mg/kg) in pediatric patients subjected to open cardiac surgery reduced intra and postoperative analgesic consumption, prolonged the time to first analgesic requirement and allowed early tracheal extubation when compared with intravenous fentanyl, intrathecal fentanyl or intrathecal fentanyl-magnesium (0.5 mg/kg).