Algorithm of Muscle Function Tests to Detect Residual Neuromuscular Blockade.

Development of an Algorithm Using Clinical Tests to Avoid Post-operative Residual Neuromuscular Block

Technical University of Munich, University Hospital Muenster, University Hospital Schleswig-Holstein, Johannes Gutenberg University Mainz

Objective neuromuscular monitoring is the gold standard to detect postoperative residual curarization (PORC). Many anesthesiologist just use qualitative neuromuscular monitoring or unreliable, clinical tests. Goal of this study is to develop an algorithm of muscle function tests to identify PORC

Background: Quantitative neuromuscular monitoring is the gold standard to detect postoperative residual curarization (PORC). Many anesthesiologists, however, use insensitive, qualitative neuromuscular monitoring or unreliable, clinical tests. Goal of this multicentre, prospective, double-blinded, assessor controlled study is to develop an algorithm of muscle function tests to identify PORC. Methods: After extubation a blinded anesthetist performs eight clinical tests in 165 patients. Test results are correlated to calibrated electromyography train-of-four (TOF) ratio and to a postoperatively applied uncalibrated acceleromyography. A classification and regression tree (CART) is calculated developing the algorithm to identify PORC. This is validated against uncalibrated acceleromyography and tactile judgement of TOF fading in separate 100 patients.

During anaesthesia calibrated neuromuscular function is monitored using evoked EMG of the adductor pollicis muscle (immobilised forearm) with a NMT module by a non-blinded investigator. During surgery, the (blinded) attending anaesthesiologist administers maintenance doses of atracurium according to clinical needs, i.e. without knowing the TOFR. After surgery patients' trachea is extubated according to clinical judgement. Immediately after extubation blinded anaesthesiologist tests the patient. The postoperative evaluation of neuromuscular function consists of eight clinical tests applied in a random order. Thereafter, an uncalibrated acceleromyography (50 mA, 2 Hz) is started on the contralateral arm and TOF ratio is measured. During the validation part of the developed algorithm the anaesthesiologist additionally had to judge tactile fading of the adductor pollicis. If a patient had any clinical signs of neuromuscular dysfunction, reversal with neostigmine is administered.

Immediately after extubation the blinded anaesthesiologist (care provider), who performs anesthesia, tests the patient in the operating room. The blinded anaesthesiologist is unable to see the data on the EMG monitor and the movement of the adductor pollicis muscle.

Neuromuscular function was monitored, using evoked electromyography of the adductor pollicis muscle with a neuromuscular transmission module by a non-blinded investigator.

Immediately after extubation the blinded anaesthesiologist tested with an uncalibrated acceleromyography on the contralateral arm.

Measurement of postoperative residual curarisation with clinical muscle function test: time able to open the eyes appearence of diplopic images time able to stick out the tongue spatula pressure test time able to lift the head time able to lift the arm strength of the patient pressing the investigator's hand ability to swallow 20 ml of water

Contralateral to the electromyography arm an uncalibrated acceleremyography measures objectively postoperative residual curarisation by examination of the train of four ratio.

Contralateral to the electromyography arm qualitative tactile judgement of the train of four stimulation was measured by acceleremyography to scale postoperative residual curarisation.

Inclusion Criteria: The patients were scheduled for elective low risk surgical procedures: laparoscopic abdominal procedures orthopedic minor visceral surgery Exclusion Criteria: participation in another study body mass index over 30 history of neuromuscular diseases gastro-esophageal reflux disease.

6Klinik für Anästhesiologie und Operative Intensivmedizin, Universitätsklinikum Schleswig-Holstein, Campus Kiel,

Klinik und Poliklinik für Anästhesiologie und operative Intensivmedizin, Universitätsklinikum Münster

Klinik für Anaesthesiologie und operative Intensivmedizin, Klinikum am Steinenberg, Steinenbergstr. 31, 72764 Reutlingen, Germany

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