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October 19, 2009
2:00 PM - 4:00 PM
Room Area N
CVP/PAD Ratio Predicts Length of ICU Stay after Cardiac Surgery
  **   Daniel Rubin, M.D., Avery Tung, M.D.
Anesthesia and Critical Care, University of Chicago, Chicago, Illinois
Introduction : Recent studies suggest that right ventricular (RV) failure is a risk factor for prolonged ICU stay in patients undergoing cardiac surgery.[1] Although RV function is difficult to measure, one possible assessment tool is the ratio of central venous pressure to pulmonary capillary wedge pressure (CVP/PCWP), which has been shown to predict outcomes after right ventricular infarction.[2] We hypothesized that, a related measure, an elevated CVP/PAD ratio, would predict a prolonged ICU course in patients undergoing cardiac surgery. To test our hypothesis, we prospectively examined patients undergoing complex cardiac surgery at a tertiary care medical center and compared the CVP/PAD ratio obtained preoperatively and postoperatively with ICU length of stay.

Methods: After informed consent and institutional review board approval, patients undergoing all types of cardiac surgery were prospectively enrolled. Measurements from the PA catheter were taken after induction and before incision, 10 minutes after full reversal of heparinization, and on the morning of postoperative day one (POD1). Patients were then followed daily until their discharge from the ICU. Data analysis was performed using Microsoft excel, with statistical significance taken at p<0.05.

Results: We enrolled 31 patients with an average of 66 ± 11 years. 19 were men and the average BMI was 28 ± 5.2 kg/m^2. Fifteen underwent CABG alone, 7 underwent CABG with a valve repair or replacement, 2 underwent robotic CABG, and 9 underwent valve replacement or repair including 2 tricuspid valve repairs. CVP/PAD ratios ranged from 0.08 to 1.13 and the average ICU stay for all patients was 3.1 ± 3.7days. All CVP/PAD ratios correlated positively with ICU length of stay with increasingly strong correlation on POD1.[table1] Conclusions: We found that CVP/PAD ratio correlated strongly with length of postoperative ICU stay. Our findings suggest that RV dysfunction, as measured by CVP/PAD ratio, likely plays a significant role in recovery from complex cardiac surgery. Possible mechanisms for this relationship include improved diuresis and/or a more rapid wean of inotropic support with better RV function. Further research is required to better quantitate right ventricular function and understand its relationship to postoperative outcome.

[1] Maslow AD, et al. Pre-cardiopulmonary Bypass Right Ventricular Function Is Associated with Poor Outcomes After Coronary Artery Bypass Grafting In Patients with Severe Left Ventricular Systolic Dysfunction. Anesth Analg 2002;95:1507-18

[2] Lopez-Sendon, J, et al. Sensitivity and Specificity of Hemodynamic Criteria in the Diagnosis of Acute Right Ventricular Infarction. Circulation 1981;64:515-25.

From Proceedings of the 2009 Annual Meeting of the American Society Anesthesiologists.
CVP/PAD correlation with ICU length of stay
Pre-op0.46 ± 0.180.32 (p<0.05)
Post-op0.56 ± 0.250.35 (p<0.05)
POD #10.55 ± 0.170.48 (p<0.005)