PRE-TREATMENT WITH MAGNESIUM SULPHATE BEFORE NON-DEPOLARIZING MUSCLE RELAXANTS: EFFECT ON SPEED ON ONSET, INDUCTION AND RECOVERY

Background: Magnesium sulphate is used during anaesthesia for its antihypertensive/ antiarrhythmic properties and attenuating the response to endotrachial intubation and as an anticonvulsant for women with eclampsia. At the motor nerve terminal, MgSO 4 inhibits acetylcholine release. Thus, it enhances the effect of neuromuscular blocking agents. Aims & Objectives: To determine the effect of magnesium sulphate pre-treatment on the onset, duration and recovery of nondepolarizing muscle relaxant and to quantify the haemodynamic effects of administration of MgSO4 on the arterial blood pressure. Materials and Methods: One year old prospective, randomized, double blinded, controlled clinical study was conducted on randomly selected 45 patients of either sex, aged between 18-55 years, of grade I or II of American Society of Anaesthesiologists, undergoing elective surgery at a Medical College of eastern Uttar Pradesh. Patients were divided into three groups according to the doses of MgSO4 used for pre-treatment. Statistical evaluation was done by using student’s ‘t’ test for paired data. Results: The Mean Arterial Blood Pressure response to laryngoscopy, tracheal intubation, was almost abolished in Group A (p<0.05) followed by Group B (p<0.05) and maximum pressure response occurred in Group C where MgSO4 was not used (p<0.05). The speed of onset of neuromuscular block was accelerated by pre-treatment with MgSO4 before non-depolarizing muscle relaxants. The mean onset time was 144.3 ± 12.08 seconds (p<0.001) in Group A, 192.66 ± 19.81 second (p<0.001) in Group B and 286.33 ± 34.20 seconds in Group C. The clinical duration was prolonged in MgSO4 group as compared with control group. Mean value was 52.4 ± 8.97 minutes (p<0.001), 44.86 ± 6.59 minutes (p<0.01), and 34.2±8.05 minutes respectively in Group A, B and C. Pre-treatment with MgSO4 before non-depolarizing muscle relaxant, accelerated speed of onset of neuromuscular block, necessary for intubation of trachea. MgSO4, in the presence of non-depolarizing muscle relaxant, intensified and prolonged the neuromuscular blockade and recovery.