Small Doses Muscle Relaxant in General Anesthesia

Overview

This study will be held to assess the effect of minimal dose muscle relaxant on postoperative pulmonary function. The time to extubation in minutes will be the primary outcome as a clinical indicator of the return of muscle power. The extubation time will be defined as the time from injecting the muscle relaxant reversing agent given when regain the train of four (TOF) ratio to 0.9 till removal of endotracheal tube. Intraoperative surgical conditions will be assessed in the form of surgeon satisfaction and the need for more muscle relaxant boluses. Postoperative complications as desaturation (peripheral oxygen saturation (Spo2) less than 90%), the need for re-intubation or ventilation support will be recorded. Patient lung will be assessed using ultrasound-based lung aeration score. Also, the diaphragmatic and intercostal muscle function will be assessed in the early postoperative period. Immediate postoperative pulmonary function tests will be evaluated using simple spirometer. Patients will be followed up for 28 days for detection of pulmonary complications.

After arrival to the operating theater, a thoracic US examination will be done using LUS dynamic re-aeration score. Patients will be randomly allocated via sealed opaque envelopes into 2 groups of 30 patients each; control (C) group and minimal dose (Min) group. For general anesthesia; intubating dose of muscle relaxant will be injected according to the study group; in C group; atracurium 0.5 mg/kg while in min group 0.2 mg/kg will be injected. The trial for intubation will be assessed and recorded. Train-of-four (TOF) stimulation will be maintained less than 2 throughout the intraoperative period in the control group. While, in the min group, boluses of muscle relaxant will be given only upon complain of the surgeon and after a bolus dose of propofol 0.5 mg/kg. When required, 20% of the initial dose of muscle relaxant will be provided as a bolus to achieve this goal.