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A study to determine the adsorption potential of a hydroxyapatite preparation for removal of heparin from circulating blood / by David K. Hurd.

by Hurd, David K.

Cardiopulmonary bypass -- Adverse effects

Blood -- Circulation, Artificial

Anticoagulants (Medicine)

Biocompatible Materials

56 leaves : ill. ; 28 cm.

Advisor: Dr. Charles Tritt

Committee members: Dr. Ronald Gerrits, Dr. Larry Fennigkoh

Introduction -- Problem statement -- Hypotheses -- Background -- Methods and materials -- Results -- Discussion -- Conclusions -- References -- Appendix 1) Data Collection Sheets from the 11 Experimental Trials 2) Additional Heparin Concentration Graph 3) Additional ACT Value Graph 4) Isotherm Calculations 5) Polynomial Regression Analysis 6) Schematic Representation of Adsorption Column.

The purpose of this study was to assess the heparin removal potential of hydroxyapatite as a possible alternative to protamine. For almost 30 years, protamine has been used as a reversal agent for heparin (7). In a recent study, it was reported that almost 2% of heart surgery patients have some degree of protamine sensitivity (13). The same study also reported that 0.1% of heart surgery patients died as a result of a protamine reaction (13). Many alternatives to protamine have been investigated with varied degrees of success (12).

This study used hydroxyapatite in a mock bypass circuit to adsorb (neutralize) heparin. Adsorption beds were created with various amounts of hydroxyapatite, in order to assess their adsorption potential. Since hydroxyapatite is a natural component of bone, it is anticipated that the allergic reactions seen with protamine administration could be reduced or avoided.

A previous investigation at The Wales College of Medicine by Wassell and Embrey (24) found that heparin and serum bovine albumin competed for the same binding sites on the hydroxyapatite crystals. The groundwork of Wassell and Embrey was the motivation for this study. It was hypothesized that hydroxyapatite's natural binding properties with negatively charged elements would bind heparin and remove it from blood.

The study consisted of 11 experimental trials in which the hematocrit, plasma volume, blood volume and amount of adsorbent were varied. Parameters such as temperature, line pressure, pH, and flow were monitored to assure consistency between trials. The average decrease seen in the activated clotting time (ACT) was 336.3 seconds. Heparin concentration decrease for the eleven trials averaged 2.83 ug/ml. These decreased values for ACT and heparin concentration show hydroxyapatite's effectiveness as a neutralizing agent. Evaluation of hemolysis of test samples compared favorably to the baseline protamine sample and pH values change at most 0.11 pH units between the beginning and end of the trials.

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