Intravenous Magnesium Sulphate Infusion As First Line Therapy In The Control Of Spasms And Muscular Rigidity In Childhood Tetanus

Introduction: Tetanus remains an important cause of mortality in the developing world. Conventional therapy with heavy sedation, paralysis and artificial ventilation, even in the best centres is associated with unacceptably high mortality due to the disease and complications of the therapy itself. Magnesium therapy has the advantage of controlling spasms and sympathetic over activity without sedation. This simplifies nursing care and minimizes the need for ventilatory support. Magnesium sulphate has been used in the primary therapy of tetanus in adult patients. There are also case reports of its use as primary therapy in the treatment of childhood tetanus.

Aims and Objectives: To study the efficacy of intravenous magnesium sulphate infusion as primary therapy in the control of spasms and muscular rigidity in the treatment of children with tetanus.

Methods: Consecutive patients admitted to the PICU with a clinical diagnosis of tetanus were enrolled after taking informed consent. Patients with renal dysfunction ie serum creatinine >1mg/dL or urine output <1mg/kg/hour were excluded. All patients received injection tetanus toxoid and intramuscular anti-tetanus immunoglobulin. All patients received intravenous metronidazole for the antibiotic treatment of tetanus. Additional antibiotics were administered if indicated eg. in patients with otitis media or wound infection. Wound toilet was done where necessary.

Intravenous magnesium sulphate was started with a loading dose of 100 mg/kg given over 30 minutes followed by an infusion at the rate of 40mg/kg/hour. The dose was titrated to control spasms and provide control of muscle rigidity by increasing the infusion rate by 5 mg/kg every 6 hours to a maximum rate of 100 mg/kg/hour or lower if the knee jerk could not be elicited.

Serum magnesium was monitored daily initially till a stable dose was attained and later twice a week. Since magnesium sulphate is known to cause both hypocalcemia and hypercalciuria, serum calcium and urinary calcium/creatinine were also monitored daily initially and later twice weekly. Patients with hypocalcemia received intravenous 10% calcium gluconate 8 hourly in addition to oral calcium supplements. Patients with hypercalciuria also received oral potassium citrate for prevention of nephrocalcinosis.

Tracheostomy was done if indicated. Mechanical ventilation was also started if indicated. Ryle’s tube feeds were started as soon as patient was spasm-free for 24 hours. Additional sedation with diazepam and/or paralysis with pancuronium was done if spasms were not controlled with magnesium sulphate alone.

Patients were monitored for complications of the disease such as autonomic dysfunction, secondary infections related to interventions such as tracheostomy, ventilation and urinary catheterization. Patient were also be monitored for complications of magnesium therapy such as depression of deep tendon reflexes, altered sensorium, hypocalcemia and hypercalciuria. Magnesium sulphate infusion rate was tapered and stopped over 7-10 days once the patient has been spasm-free for 7-10 days  in those with mild to moderate tetanus (Ablett score 1 or 2) and 2 weeks in those with severe tetanus (Ablett score 3a or 3b).

Results: Seventeen of 27 patients had severe tetanus (Ablett score 3 and 4). The portal of entry of tetanus spores was injury in 14 patients, chronic otitis media in nine patients and unknown in four patients. Ten of 27 patients required more than 80mg/kg/hour for control of spasms. All patients developed hypercalciuria and hypocalcemia. Eight of 27 patients required mechanical ventilation and additional sedation/paralysis. Ventilator associated pneumonia developed in four of eight patients ventilated. There were five deaths (mortality 18.5%), all in patients with severe tetanus and all occurring in the first week of admission.

Conclusions: Intravenous magnesium sulphate is a cheap and effective drug in the management of post-neonatal tetanus. It decreases the need for ventilatory support. Mortality was 18.5% which is lower than the 35-40 % described in other centres in India.