Central venous pressure after coronary artery bypass surgery: does it predict postoperative mortality or renal failure?

Abstract

Objective: Although hemodynamic monitoring is often performed after coronary artery bypass grafting (CABG), the role of monitoring postoperative central venous pressure (CVP) measurement as a predictor of clinical outcomes is unknown. As such, this study tests the hypothesis that postoperative CVP is predictive of operative mortality or renal failure.

Methods: This is an observational cohort study of detailed clinical data from 2390 randomly selected patients undergoing high-risk CABG or CABG/valve at 55 hospitals participating in the Society of Thoracic Surgeons' National Cardiac Surgery Database 2004-2005. Eligible patients underwent elective/urgent CABG with an ejection fraction less than 40% or elective/urgent CABG at 65 years or older with diabetes or a glomerular filtration rate less than 60 mL/min per 1.73 m2. The exposure of interest is CVP monitoring in the intensive care unit after adult cardiac surgery. The primary outcome measure was correlation between postoperative CVP and inhospital/30-day mortality and renal failure, assessed as a continuous variable, both unadjusted and after adjusting for important clinical factors using logistic regression modeling.

Results: Mean age was 72 years, 54% of patients had diabetes mellitus, 49% were urgent procedures, and mean cardiopulmonary bypass time was 105 minutes. Patients' CVP 6 hours postoperation was strongly associated with inhospital and 30-day mortality: odds ratio (OR) of 1.5 (95% confidence interval [CI], 1.23-1.87) for every 5-mm Hg increase in CVP; P<.0001. This association remained significant after risk adjustment: adjusted OR of 1.44 (95% CI, 1.10-1.89); P<.01. A model adjusting for cardiac index also revealed increased incidence of mortality or renal failure: adjusted OR of 1.5 (95% CI, 1.28-1.86) for every 5-mm Hg increase in CVP; P<.0001.

Conclusions: Patients' CVP at 6 hours after CABG surgery was highly predictive of operative mortality or renal failure, independent of cardiac index and other important clinical variables. Future studies will need to assess whether interventions guided by postoperative CVP can improve patient outcomes.

Keywords: Cardiac index; Central venous pressure; Coronary artery bypass; Hemodynamic monitoring; Perioperative care; Surgery.

Figure 1

Relationship between central venous pressure (CVP) at 6 hours and predicted probability of death through 30 days or in-hospital. Solid dark blue line represents point estimates and light blue shaded area represents 95% confidence interval.

Figure 2

Relationship between central venous pressure (CVP) and predicted probability of death according to cardiac index (CI) ≥ 2 or < 2 L/min/m² at 6 hours. The shapes of the curves are approximately the same indicating that the relationship between CVP and mortality is independent of cardiac index. Solid dark blue line represents point estimates and light blue shaded area represents 95% confidence interval.