Comparison of neuromuscular monitorings (TOF-Watch SX versus Philips NMT Module) in patients undergoing rhinoplasty or rhinoseptoplasty.

This investigation protocol seeks to compare the results obtained in clinical practice in curarised patients using two monitoring modules currently marketed (in line with EU standards): The results obtained simultaneously by the Philips Intellivue NMT module (Philips, The Netherlands) on a patient's hand will be compared with those obtained by the TOF-Watch SX (Organon, The Netherlands) fitted to their other hand stabilised in the SL TOF tube, an association which has demonstrated the adequacy of its results compared with mechanomyography, the established reference method. The investigation focusses on a cohort of 30 patients aged 18 to 80, classified ASA I or II and undergoing rhinoplasty or rhinoseptoplasty under general anaesthetic. . The patient's height, weight, age and sex are recorded in the protocol, as is their dominant hand (left or right) to define the population investigated. As premedication, the patient receives Alprazolam 0.5 mg an hour before they go to theatre. On arrival in theatre, the patient is conventionally monitored with a saturometer, an electrocardiogram with three or five derivations depending on their antecedents, and their blood pressure is measured non-invasively, scheduled in automatic mode with constant measurements at five-minute intervals. An intravenous drip (18G catheter) is inserted into their forearm or elbow, for intravenous perfusion of Plasmalyte 500 ml as the first perfusion. The module to monitor neuromuscular transmission using acceleromyography is connected (non-invasive and non-traumatic) to both hands as shown in the illustration. We observe the criteria for good clinical practice for pharmaco-dynamic investigations as proposed by Fuchs-Buder. The skin is cleaned with diethylether and two ECG skin electrodes are placed along the route of the ulnar nerve on each wrist. The arm on which the Philips Intellivue NMT module is placed is left free of any specific installation as recommended in its user manual, whilst the forearm on which the AMG TOF-Watch SX is placed is positioned in the SL TOF Tube and this is thus considered the reference curarisation monitoring module. The arms are then placed alongside the body in "spoon"-type arm supports with a thick layer of gel to protect nerve structures. Once all monitoring modules are in place, the patient is pre-oxygenated using pure oxygen, FiO2 100% at a rate of 8 l/min. The general anaesthetic is induced with continuous intravenous infusion of Remifentanyl 0.25 gamma/kg/min, and continuous infusion of Propofol 1% to obtain a theoretical plasma concentration of 3 to 4 gamma/cc (Diprifusor Cardinal Health, Basingstoke, UK) and Linisol 2% 1 mg/kg as an intravenous bolus. As soon as the patient loses consciousness, they are manually ventilated. Now, simultaneously with each NMT monitoring module, we can automatically investigate the supra-maximum stimulation threshold and 100% calibration of initial responses. The amperages determined by the two devices (+/- 50 mA) are recorded. Each ulnar nerve is stimulated simultaneously using a Train of Four (4 electric stimulations at 2 Hz, Train of Four, TOF) repeated at 15-second intervals. Four successive base value measurements for the TOF ratio (T4/T1 ratio) are recorded for each curarisation monitoring module, simultaneously, and their averages determine the reference values before curarisation. We calculate 90% of this base value to determine the neuromuscular blocking recovery threshold for each monitoring module using the following formula: Normalised TOF ratio 90% = sum of 4 TOF ratio × 9/40 with a result rounded up. With the baseline determined, the patient is curarised with administration of rocuronium 0.5 mg/kg. The theatre time is noted as the reference time (hh:mm:ss). Non-invasive automatic blood pressure measurement is suspended during the neuromuscular blocking induction phase so as not to limit the distribution of the Rocuronium in either of the two arms. So we expect to each a state of deep curarisation, with a TOF count of 0. Again, the exact time is recorded when the TOF count of 0 is reached using the TOF-Watch and when it is reached using the Philips NMT (onset duration). The patient is then conventionally intubated, eye protection is put in place, the tube is fitted and assisted ventilation in "Controlled volume" mode is begun, followed by the surgical equipment. Post-Tetanic-Count (PTC: automatic stimulation sequence including 50 Hz tetanic stimulation for 5 seconds adapted to monitor deep neuromuscular blocking) is then measured with each monitoring module at the same time (hours - minutes -seconds noted). After a free period of 3 minutes, TOF stimulation mode is launched every 15 seconds. Anaesthesia is maintained with continuous intravenous administration of Remifentanyl 0.15 gamma/kg/min and Propofol 1% in AIVOC mode with a target plasma concentration of 2 to 4 gamma/cc. Neither Magnesium, nor halogenated vapour, nor a further bolus of rocuronium is administered (to prevent potentialisation of neuromuscular blocking by these agents). We then continuously observe via the TOF spontaneous recovery of neuromuscular blocking with successive, simultaneous measurements (every 15 seconds) using the two curarisation monitoring modules. The investigation seeks to confirm (or otherwise) the similarity between the results obtained using each monitoring module.