Impact of Hematocrit Value after Coronary Artery Surgery on Perioperative Myocardial Infarction Rate

Introduction

The optimal hematocrit (HCT) value after coronary artery bypass graft (CABG) surgery is not known. A wide range of transfusion practice after CABG operations exists [1] despite general guidelines for perioperative transfusion of blood and blood products, published by the National Institutes of Health consensus conference on perioperative transfusion of red cells [2], the American College of Physicians [3], and the Canadian Medical Association [4]. It has been speculated that anemia might increase the risk of myocardial ischemia after CABG, but several studies failed to find an association between anemia and morbidity following CABG [5]. Thus, no safe HCT range or “best” HCT value after CABG has been established. The risk for myocardial ischemic events is highest during the immediate perioperative period [6]. A recent study by Spiess et al. [7] assessed the relation between HCT value at the time of entry into the intensive care unit (ICU) and perioperative myocardial infarction rate. They found that perioperative MI rate was significantly lower in patients entering the ICU with a HCT ≤ 24 %, and suggested that HCT values ≤ 24 % protect against perioperative MI [7]. However, their definition of perioperative MI was solely based on ECG changes (Minnesota Code criteria); cardiac enzyme release was not considered [7]. As ECG changes alone may not be sufficient for perioperative MI determination [8], we sought to include cardiac enzyme release in our definition of perioperative MI as suggested by Braunwald et al. [9].

References

• 1 Stover E P, Siegel L C, Parks R. et al . Variability in transfusion practice for coronary artery bypass surgery persists despite national consensus guidelines: a 24-institution study. Institutions of the Multicenter Study of Perioperative Ischemia Research Group.  Anesthesiology. 1998;  882 327-333
• 2 American College of Physicians . Practice strategies for elective red blood cell transfusion.  Ann Intern Med. 1992;  116 403-406
• 3 Consensus conference . Perioperative red blood cell transfusion.  JAMA. 1988;  260 2700-2703
• 4 Expert Working Group . Guidelines for red blood cell and plasma transfusions for adults and children.  Can Med Assoc J. 1997;  15 (Suppl 1) S1-S24
• 5 Cohen E, Neustein S M, Silvay G. Profound anemia following cardiac surgery. Profound anemia following cardiac surgery.  J Cardiothorac Vase Anesth. 1993;  7 (6) 721-723
• 6 Smith R C, Leung J M, Mangano D T. Postoperative myocardial ischemia in patients undergoing coronary artery bypass graft surgery. S.P.I. Research Group.  Anesthesiology. 1991;  74 (3) 464-473
• 7 Spiess B D, Ley C, Body S C. et al . Hematocrit value on intensive care unit entry influences the frequency of Q-wave myocardial infarction after coronary artery bypass grafting. The Institutions of the Multicenter Study of Perioperative Ischemia (McSPI) Research Group.  J Thorac Cardiovasc Surg. 1998;  1163 460-467
• 8 Myocardial infarction redefined - a consensus document of The Joint European Society of Cardiology/American College of Cardiology Committee for the redefinition of myocardial infarction. J Am Coll Cardiol Sep/2000 36 3 959-969
• 9 Antman E M. Medical management of the patient undergoing cardiac surgery. Braunwald E Heart Disease. Philadelphia: WB Saunders and Co 1997 5: 1715-1740
• 10 Doak G J, Hall R l. Does hemoglobin concentration affect perioperative myocardial lactate flux in patients undergoing coronary artery bypass surgery?.  Anesth Analg. 1995;  80 (5) 910-916
• 11 Mathru M, Kleinman B, Blakeman B, Sullivan H, Kumar P, Dries D J. Myocardial metabolism and adaptation during extreme hemodilution in humans after coronary revascularization.  Crit Care Med. 1992;  20 (10) 1420-1425
• 12 Kirn Y D, Katz N M, Ng L, Nancherla A, Ahmed S W, Wallace R B. Effects of hypothermia and hemodilution on oxygen metabolism and hemodynamics in patients recovering from coronary artery bypass operations.  J Thorac Cardiovasc Surg. 1989;  971 (1) 36-42
• 13 Reimers R C, Sutera S P, Joist J H. Potentiation by red blood cells of shear-induced platelet aggregation: relative importance of chemical and physical mechanisms.  Blood 1984. Dec ;  64 (6) 1200-1206
• 14 Radomski M W, Moncada S. The biological and pharmacological role of nitric oxide in platelet function.  Adv Exp Med Biol. 1993;  344 251-264
• 15 Nollert G, Sperling J, Sakamoto T, Jaeger B R, Jonas R A. Higher hematocrit improves liver blood flow and metabolism during cardiopulmonary bypass in piglets.  Thorac Cardiovasc Surg. 2001;  49 (4) 226-230
• 16 Hsu C Y, Bates D W, Kuperman G J, Curhan G C. Relationship between hematocrit and renal function in men and women.  Kidney Int. 2001;  59 (2) 725-731
• 17 Kazmi W H, Kausz A T, Khan S, Abichandani R, Ruthazer R, Obrador G T, Pereira B J. Anemia: an early complication of chronic renal insufficiency.  Am J Kidney Dis. 2001;  38 (4) 803-812
• 18 Dittrich S, Priesemann M, Fischer T. et al . Hemorheology and renal function during cardiopulmonary bypass in infants.  Cardiol Young. 2001;  11 (5) 491-497
• 19 Benoit M O, Paris M, Silleran J, Fiemeyer A, Moatti N. Cardiac troponin I: its contribution to the diagnosis of perioperative myocardial infarction and various complications of cardiac surgery.  Grit Care Med. 2001;  29 10. 1880-1886
• 20 Wu W C, Rathore S S, Wang Y, Radford M J, Krumholz H M. Blood transfusion in elderly patients with acute myocardial infarction.  N Engl J Med. 2001;  345 (17) 1230-1236