Effect of Pretreatment of Lignocaine Versus Midazolam in the Prevention of Etomidate Induced Myoclonus

INTRODUCTION:

General anaesthesia is loss of consciousness induced after administration of one or more general anaesthetic agent with overall aim of inducing sleep, amnesia, analgesia and skeletal muscles relaxation. Choosing an induction agent is a very vital step in commencing general anaesthesia1. Use of sedatives can prevent or minimize potentially harmful physiologic affects of airway manipulation that include increase in heart rate, BP, and raised intracranial pressure.

Etomidate, imidazole-derived, sedative-hypnotic agent, blocks neuroexcitation by its direct action on the gamma amino butyric acid (GABA) receptor complex1.Because of its many desirable properties like rapid onset of action, profound hypnosis, minimal histamine release, hemodynamic stability, minimal respiratory depression, and favorable cerebral effects, etomidate is considered as an ideal induction agent2. Concerns with etomidate include adrenal suppression and myoclonus3, 4.

30 to 60% of unpremedicated patients develop myoclonic movements after an induction dose (0.3 mg/kg) of etomidate1. Myoclonus is described as the involuntary contraction of some muscle fibers, leading to short observable movements of the body, more pronounced with the limbs5. In emergency scenarios, myoclonus can lead to increment in the chances of regurgitation and aspiration.

Various drugs like Lignocaine, Midazolam, Magnesium, Dezocine and dexmedetomidine have been used as pretreatment for reducing myoclonus after etomidate injection but the best drug for the purpose is yet to be discovered6, 7, 8, 9. Ideally a pretreatment drug should be short-acting, should affect respiration and hemodynamic minimally, and should not prolong the recovery period.