New Method of Fast-Track Weaning of Post-Open Heart Patient Using the Siemens Servo 300A in PRVC with Automode

Introduction: Pressure Regulated Volume Control (PRVC) in conjunction with Automode is a ventilation application available on the Servo 300a. PRVC is a time cycled, pressure limited, control mode that will deliver a preset target volume by automatically varying the inspiratory pressure control level according to the mechanical properties of the lung/thorax. Automode is an adjunct to PRVC that allows the ventilator to switch back and forth between a machine established rate and a patient established spontaneous rate (Support). The application of this ventilator strategy may be beneficial in effectively and efficiently liberating patients from the ventilator. The following case summary highlights the benefits of this application in a postoperative cardiac surgery patient.

Case Summary: After having a Ross procedure in the usual fashion under standard general anesthesia, a 55-year-old male with a history of aortic insufficiency and stenosis was placed on the Servo 300a in the PRVC mode with the Automode on. Ventilator settings were as follows; f:10, Vt:900cc, FiO2:.70, PEEP:5cwp. Our extubation criteria were; spontaneous RR < 25bpm, spontaneous Vt >300cc, FiO2 <.50, PEEP <6cwp, Pressure Support <13cwp, and ETCO2 within 15 mm Hg of baseline. An initial ABG was drawn after 20 minutes and correlated with the ETCO2 and SaO2 monitors. Appropriate changes were made at this time, adjusting rate and FiO2 to achieve normal blood gas parameters. After spontaneous respirations were noted, the Automode/Support adjunct was utilized. The patient?s lung mechanics were evaluated and hemodynamic stability was verified with the RN. The FVC was > 10ml/kg of IBW and MIP was > -20cwp. The set Vt was reset to 300cc. After 30 minutes, an ABG was drawn and found to be acceptable. The patient was then extubated without difficulty.

Results: A November 1998 publication from the Cardiology Roundtable presented a FACT BRIEF titled ?National Benchmark Information Regarding Post-Open Heart Ventilation Weaning?. The identified benchmark was 6-8 hours with outliers defined as ventilator time greater than 12 hours for comparable hospitals to our own. Our facility benchmark, based on 587 cases in fiscal year 2000, reflected a mean of 8.4, a median of 7, and a mode of 5 hours respectively. As the table below reflects, this patient was well below both benchmark targets.

In conclusion, and for this patient, PRVC in conjunction with Automode was an effective tool, capable of utilizing less therapist time while still effectively and quickly liberating patients from the ventilator. Further, more controlled studies are warranted to evaluate the long-term effectiveness of this promising approach to weaning ventilated post-operative open-heart patients.

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