Comparison Of Deep Versus Moderate Neuromuscular Blockade on Intra-Operative Blood Loss During Spinal Surgery

Comparison Of Deep Versus Moderate Neuromuscular Blockade on Intra-Operative Blood Loss During Spinal Surgery

Comparison Of Deep Versus Moderate Neuromuscular Blockade on Intra-Operative Blood Loss During Spinal Surgery, Randomized Double Blinded Clinical Trial

Spine surgery is usually performed using a posterior approach with the patient in the prone position, but on the other hand this position causes venous engorgement in the back and increases bleeding with the risk of interruption of surgery and increases the need for blood transfusion. The prone position also produces undesirable haemodynamic changes resulting from compression of large vessels and decreased venous return to the heart. Deep neuromuscular blockade has been shown to improve surgical conditions compared with moderate neuromuscular blockade in various surgical procedures specially different laparoscopic procedures to optimize surgical field conditions. In spine surgery, although many other factors such as the body habitus of the patient and the surgical equipment are important, an improvement in surgical field conditions can be achieved through reducing muscle tension in the back, and also reducing intra-abdominal and thoracic pressure. This goal may be attainable by using deep neuromuscular blockade. Better operating conditions offer the surgeon easier access to the surgical field with less damage. However, the effect of deep neuromuscular blockade on surgical bleeding in spinal surgery in the prone position has been yet under evaluation. The investigators hypothesise that deep, compared with moderate, neuromuscular blockade would cause less surgical bleeding in spinal surgery in the prone position. The investigators aim to evaluate the effects and superiority of deep neuromuscular blockade on surgical bleeding in patients undergoing posterior lumbar interbody fusion surgery in the prone position.

After applying standard monitoring of pulse oximetry, ECG, noninvasive blood pressure, general anesthesia will be induced with fentanyl 1 µg/kg and propofol 2-3 mg/kg and Rocuronium 0.6 mg/kg will be administered for muscle relaxation after loss of consciousness, under the guidance of neuromuscular blockade monitoring. Tracheal intubation will be performed at a train-of-four count of 0. After that end-tidal carbon dioxide and temperature will be continuously monitored during the procedure. Mechanical ventilation will be instituted with o2:air of 4 L/min, tidal volume of 6-8 ml/kg and respiratory rate appropriate to achieving end-tidal carbon dioxide of 30-35 mmHg. no positive end-expiratory pressure; and inspiratory/expiratory ratio 1: 2. The patient's position will then be changed from supine to prone. Ephedrine 4 mg (if mean arterial pressure < 60 mmHg and heart rate < 40 bpm), or atropine 0.5 to 1.0 mg (if heart rate < 40 bpm) are used to prevent hypotension or bradycardia

Neuromuscular blockade monitoring will be established and continuously monitored after induction using the Train Of Four (TOF) at the adductor pollicis muscle on the opposite hand and wrist to radial artery cannulation. Two surface electrocardiography electrodes will be placed on cleaned skin overlying the ulnar nerve, with one electrode positioned on the ulnar side of the flexor carpi radialis tendon and the other positioned 3cm proximal to the first. The transducer is then positioned with the flat side against the thumb. Supramaximal stimuli will be applied after autonomic calibration of acceleromyograph after an initial tetanic stimulus. After confirming a train-of-four ratio of 95 to 105%, neuromuscular blockade monitoring will start. The train-of-four mode of supramaximal stimulation (0.2 ms duration, frequency 2 Hz, two s duration) will be applied at 15 s intervals, which last until the end of anaesthesia.

Volume of surgical bleeding will be recorded before surgical field lavage, and again at the end of surgery, by measuring the total volume of blood collected in the suction bottle minus the lavage fluid volume used for wound irrigation.

The score for the surgeon's satisfaction (lowest, 1; highest, 5) with the surgical conditions will be assessed at the end of surgery. Extremely poor (Score 1) indicated that the surgeon is unable to work because of an inability to obtain a visible field due to inadequate muscle relaxation; poor (Score 2) indicated that there is a visible field, but the surgeon is severely hampered by inadequate muscle relaxation; acceptable (Score 3) indicated that there is a wide visible field and acceptable muscle relaxation; good (Score 4) indicated a wide working field with adequate muscle relaxation; excellent (Score 5) indicated a wide visible working field without any muscle rigidity.

Inclusion Criteria: Age 18- 65 years. American Society of Anesthesiologists physical status classification (ASA) I - III Patients scheduled for posterior lumbar interbody fusion (2-level or 3-level). Exclusion Criteria: Urgent or emergency case or re-operation. History of pre-operative anticoagulant medication or an indication for peri-operative anticoagulant medication. ASA classification more than III. Age less than 16 years. Reduced left and right ventricular function (ejection fraction <40%). Previous respiratory disease or a diagnosed neuromuscular disorder. Pre-operative dysrhythmia. Allergy to neuromuscular blocking agents. Family history of malignant hyperthermia. Decreased renal function (serum creatinine level more than twice the normal range, urine output <0.5 ml kg/h, glomerular filtration ratio <60 ml/ h).

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