PROFOUND MUSCLE RELAXATION DOES NOT DISTURB PRESSURE SUPPORT VENTILATION .

1. PROFOUND MUSCLE RELAXATION DOES NOT DISTURB PRESSURE SUPPORT VENTILATION. Mulier J.P.1, Blacoe D. , Dillemans B.2, 1. Dep of Anaesthesiology, Sint JAN Brugge-Oostende, Bruges, Belgium, 2. Dep of General Surgery Sint JAN Brugge-Oostende, Bruges, Belgium Contact Email: jan.mulier@azbrugge.be More info: www.publicationslist.com/jan.mulier Background and Goal of Study: • Pressure support ventilation (PSV) during anesthesia is used in non paralyzed patients at a low morfine dose. • Aim of this study is to verify at what relaxation level PSV remains possible. Results: • No backup mode started in any patient meaning that no patient stops triggering the ventilator. • The respiratory frequency varied in some patients but was not significant different at the 4 levels of muscle relaxation. • Graph1: Example of one patient: from no muscle relaxation to deep muscle relaxation with high dose esmeron infusion. Conclusion: • We can only conclude that for unknown reason PSV is possible during deep muscle relaxation. Materials and Methods: • Ten patients needing muscle relaxation were included with approval of the hospital ethical committee. • They were first ventilated without muscle relaxants through a laryngeal mask after an induction dose of 2.5 mg/kg Propofol and 10 ug of Sufentanil. Sevoflurane inhalation was given at 1 Mac for maintenance. • The patients were pressure support ventilated with a General Electric Aestiva S/5 with a trigger sensitivity = 0.4 L/min. The support pressure was adapted to keep end tidal CO2 between 35 and 45 mmHg. • A rocuronium infusion was given at 500 mg/h till TOF and PTC were 0. The backup ventilation mode was set to start after 30 seconds of no ventilation. No additional Sufentanil was given during the measurement. • At a TOF of 4/4, 1/4, 0 and PTC > 5 and < 5 the ventilation frequency was measured and the state of the backup mode. • Further mechanical ventilation was given as clinical required. Discussion: • The support level is set to the same level as in pressure controlled ventilation allowing normal ventilation. • No patient stopped triggering the ventilator. The exact mechanism is unclear. PTC measured zero at the thumb does not mean a totally relaxed diaphragm. • Auto triggering of the ventilator or triggering by the cardiac interference is not totally excluded by this study. If it happens it would create a high frequency and would not stop when high dose of morfine is given. PGA New York 11-15 December 2009