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SAFETY OF LOW DOSE HEPARINIZATION WITH HEPARIN-COATED BYPASS CIRCUITS FOR CORONARY ARTERY BYPASS SURGERY

Departments of Surgery and Anesthesia, University of Alberta Hospital, Edmonton, Alberta, T6G 2B7

INTRODUCTION

Cardiopulmonary bypass (CPB) involves the exposure of blood to non-biocompatible surfaces and the consequent activation of both the coagulation system and the inflammatory response mechanism.¹ Heparin-bonded circuits were developed with the aim of reducing heparin requirements and cytokine activation during CPB.² In this study, we determined the relationship between the administered dose of heparin and the level of heparin in the plasma with the consequences of the use of heparin-bonded circuits on transfusion requirements, TNF levels and patient outcome.

METHODS

After institutional approval and informed consent, 90 patients were prospectively and randomly assigned one of three Groups: Group I, CPB with standard heparinization (300 U.kg^-1, ACT > 480 sec) and CPB equipment (roller pump), Group II, a centrifugal pump plus a heparin-bonded CPB circuit plus standard dose heparin administered, Group III, equipment identical to Group II plus low-dose heparin (100 U.kg ^-1; ACT > 180 sec). Hematological and biochemical data were measured preoperatively, 5 minutes after cross-clamp release, 20 minutes after discontinuation of CPB, upon arrival in the ICU, and morning of the first post-operative day. One-way Anova compared continuous variables and Fisher's exact and chi-squared tests compared discrete variables between groups. A p-value 0.05 was considered significant.

RESULTS

82 patients were eligible for complete analysis. There was no significant difference between the three groups with respect to patient demographics. The mean heparin levels (U/ml) were 4.72 +/- 1.12, 4.93 +/- 1.23, and 1.55 +/- 0.86 in Groups I, II, and III respectively. TNFa levels were significantly elevated with respect to baseline values in Group I on postoperative Day 1, and in Group II immediately on arrival in the ICU. There were no differences between the Groups with respect to chest tube blood loss and blood and blood product transfusion requirements. There were also no differences between the groups with respect to intraoperative complications, inotrope, vasodilator, or 24-hour fluid requirements, intubation time, ICU length of stay or total hospital stay.

CONCLUSIONS

Heparin levels in the blood are closely related to the dose injected. The use of a centrifugal pump with a heparin-bonded CPB circuit allows the safe use of low-dose heparinization. However, this fact does not appear to confer any particular advantage with respect to blood transfusion requirements or TNF levels used in this study as an index of the inflammatory response.

REFERENCES

1 Ann Thorac Surg 1995; 60: 365–71[Abstract/Free Full Text]

2 J Thorac Cardiovasc Surg 1996; 112: 472–83[Abstract/Free Full Text]

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