Small Doses Muscle Relaxant in General Anesthesia (relaxant)

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.

Patients will be randomly allocated via sealed opaque envelopes into 2 groups of 30 patients each; control (C) group and minimal dose (M) group

Basal US assessment and its repetition in the recovery room, will be done by an anesthetist who is not involved in randomization or anesthetic technique except, after ending the surgery and after dressing, he will be responsible for reversal agent injection and the extubation with recording the extubation time

Intubating dose of muscle relaxant will be atracurium 0.5 mg/kg Maintenance doses of muscle relaxant will be given throughout the intraoperative period to maintain the Train-of-four values continuously less than 2

Intubating dose of muscle relaxant will be 0.2 mg/kg will be injected 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.

Intubating dose of muscle relaxant will be atracurium 0.5 mg/kg Maintenance doses of muscle relaxant will be given throughout the intraoperative period to maintain the Train-of-four values continuously less than 2

atracurium boluses of muscle relaxant 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

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

blouse of muscle relaxant given only upon complain of the surgeon and after a bolus dose of propofol 0.5 mg/kg

Given intraoperatively only upon complain of the surgeon and after a bolus dose of propofol 0.5 mg/kg

a bolus dose of propofol 0.5 mg/kg given in the M group, upon complain of the surgeon and before boluses of muscle relaxant

0= normal aeration (horizontal A-lines or ≤ 2 B-lines); 1 = moderate loss of aeration (multiple B-lines, either regularly spaced (7 mm apart), or irregularly spaced and even coalescent but only visible in a limited area of the intercostal space); 2 = loss of aeration (multiple coalescent B-lines, in prevalent areas of the intercostal spaces and observed in one or several intercostal spaces); 3 = complete loss of aeration (lung consolidation, with or without air bronchograms)

Inclusion Criteria: adult patients aged from 20 to 50 years old scheduled for non-cardiothoracic surgery under general anesthesia in supine position after informed consent Exclusion Criteria: American Society of Anesthesiologists (ASA) score more than 3 suspected full stomach or who will undergo intervention expected to necessitate profound muscle relaxation or dressing interferes with ultrasound (US) probe positioning Lung parenchymatous disease renal disease hepatic disease neuromuscular disease electrolytes imbalanc on medication interfere with muscle contraction with known allergy to any drug used in the study