Role of hemodilutional anemia and transfusion during cardiopulmonary bypass in renal injury after coronary revascularization: Implications on operative outcome.

Habib RH, Zacharias A, Schwann TA, et al. Crit Care Med 2005;33:1749-1756.

Reviewer: Michael H. Wall, MD
University of Texas Southwestern Medical Center at Dallas
Dallas, TX

Abstract: This retrospective review studied 1,760 patients undergoing isolated coronary artery bypass grafting using cardiopulmonary bypass between 1995-1996 and 2002-present. The pump was primed with plasmalyte and 250 mL of 20% mannitol. Cold blood cardioplegia and systemic normothermia (in 98% of cases) was used. Primary renal outcome variables were 1) %ΔCr, 2) %ΔCr clearance (calculated from Cockcroft-Gault equation), 3) renal injury (%ΔCr > 50%) and 4) acute renal failure (ARF) as defined by the Society of Thoracic Surgeons. In addition, mortality, length of hospital stay (LOS) and re-admission rates were evaluated. The independent variables were lowest hematocrit (Hct), cardiopulmonarybypasstime(TCPB)andintra-operativepackedredblood cell (PRBC) transfusion. The data was analyzed using multivariate and propensity analysis. Lowest Hct, TCPB and pre-CPB Cr were 22 ± 4.6%, 94 ± 35min and 1.01 ± 0.23 mg/dL. The overall %ΔCr was 24 ± 57%, ARI occurred in 285 (16%) patients and ARF occurred in 89 (5.1%) patients. Intra-operative PRBC transfusion was used in 21.9% of all patients.

The authors found that %ΔCr (p <0.001) and ARF (p <0.001) has a dose dependent association to lowest Hct (risk increases with Hct < 22-24%). Also, this risk was increased if the TCPB > 90min or pre-op Cr > 1.2 gm/dL. Furthermore, PRBC transfusion was associated with increased renal dysfunction ARI was significantly associated with increased mortality and LOS.

Comments: The excellent discussion section of this article, and the editorial by Spiess¹ should be required reading for all of us who give blood transfusions.

Briefly, this study is consistent with several other studies that have shown associations between lowest Hct's on-pump and increased mortal-ity, LOS and morbidity (including lung dysfunction, increased neurologic events, renal dysfunction and cardiac dysfunction). This study is the first that shows transfusion (probably given to prevent or treat a low Hct) actually is associated with worsening renal function. This presents a major daily clinical problem. Habib, et al and Spiess¹ thoroughly discuss theoretical reasons as to why transfusion may actually worsen outcomes (including problems with 2,3,DPG, increasing free iron, decreased tissue oxygenation following PRBC transfusion, abnormalities in RBC shape and deformability, inflammatory and immunosuppressant properties of PRBC's) .Habib,et al and Spiess¹ stress the importance of intra-operative blood conservation, modification/miniaturization of CPB circuits and the urgent need for large prospective randomized trials of transfusion in patients undergoing cardiac surgery. Until these trials are completed, we will continue to struggle with the frequent question: to transfuse or not to transfuse?

Reference

1. Spiess BD. Choose one: Damned if you do/damned if you don't! Crit Care Med 2005; 33:1871-4.

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Table of Contents:

• President's Message
• Call for Nominations


• Literature Reviews
  • Role of hemodilutional anemia and transfusion during cardiopulmonary bypass in renal injury after coronary revascularization: Implications on operative outcome.
  • Increased prothrombotic state lasting as long as one month after on-pump and off-pump coronary surgery.
  • Characterization of beta3-adrenoceptors in human internal mammary artery and putative involvement in coronary artery bypass management.
  • Aprotinin reduces bleeding and blood product use in patients treated with clopidogrel before coronary artery bypass grafting.
  • Secondary tricuspid regurgitation or dilatation: Which should be the criteria for surgical repair?
  • Stem cells in the dog heart are self-renewing, clonogenic, and multipotent and regenerate infarcted myocardium, improving cardiac function.
  • Overexpression of mitochondrial transcription factor A ameliorates mito­chondrial deficiencies and cardiac failure after myocardial infarction.
  • An essential role for mitochondrial aldehyde dehydrogenase in nitroglyc­erin bioactivation.


• Drug and Innovation Updates
  • Child-Pugh and MELD classifications and the mortality following cardiac surgery.
  • Anesthetic preconditioning and perioperative myocardial protection


• PRO/CON: Conscious Neuraxial Anesthesia is a Viable Alternative to General Anesthesia in Cardiac Surgery.
• Pro - Paul Kessler, MD
• Con - Peggy T. Y. Li, MBChB & Anthony M. H. Ho, MD, FRCPC, FCCP

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