The Science Journal of the American Association for Respiratory Care

2003 OPEN FORUM Abstracts

SAFETY AND EFFICACY OF MMV/ATC FOR THE WEANING OF POST-OPERATIVE OPEN-HEART PATIENTS: A PILOT STUDY.

Angela Lutz, RRT; Daniel Ray, MD; Kenneth Miller, MEd, RRT; Kenton Clay, RRT;
Bryn Surgeoner, RRT; Karen Meloy, RRT; Thomas Wasser, PhD. Lehigh Valley Hospital, Allentown, PA 18105.

Introduction:
 Early extubation of patients undergoing elective coronary artery bypass surgery is a trend in surgical practice. Mandatory Minute Ventilation (MMV) is a mode of ventilation that guarantees set minute ventilation but allows an automatic transition from mechanical support to spontaneous breathing. Automatic Tube Compensation (ATC) is a mode extension that provides compensation for the flow-dependent endotracheal tube resistance during both inspiration and expiration.

Objective: 
To evaluate the safety and efficacy of a computer-driven MMV/ATC (Drager Medical, Telford, PA) as a weaning method in the post-operative open-heart patient. 

Methods:  The study was a prospective trial performed in a 12-bed Open Heart Unit (OHU) of a 600-bed tertiary referral community hospital. Stable, uncomplicated post-operative patients were randomized to either MMV/ATC or an established OHU weaning protocol that includes therapist- driven spontaneous breathing trials. The two groups were compared for weaning intolerance as well as length of ventilatory support, OHU length of stay (LOS), and hospital LOS. 

RESULTS: 
Between 3/1/02 and 5/1/02, 49 of 75 eligible patients were randomized. There were no differences between groups for age, pre-operative severity score, pump time, cross-clamp time, transfusion requirement, fluid administration, or total operative time (p>0.05). Patients in the MMV group had higher doses of narcotics and benzodiazepine intra-operatively (p=0.014). One of 25 patients in the MMV group failed weaning due to hemodynamic instability. No patients in the control group failed weaning process. However, 4/24 patients in the control group and 8/25 in the MMV group (p=0.252) failed to be liberated at the end of the trial primarily due to persistent sedation. There was no difference between groups for OHU LOS or hospital LOS. 

CONCLUSION: In this small pilot study, MMV was well tolerated as a weaning method in post-operative cardiac patients. Its impact on the post-operative course of cardiac patients needs to be further studied and will likely be determined by a joint strategy incorporating pre-operative patient assessment, intra-operative technique, and anesthesia practices.  This study was supported by the Dexter F. and Dorothy H. Baker Fund, the Dorothy Rider Pool Trust. 

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