Cor Vasa 2009, 51(9):567-571 | DOI: 10.33678/cor.2009.140

Heparin resistance and its incidence in patients undergoing on-pump surgery

Vladimír Brzek^1,*, Vladimír Lonský², Stanislav Jiška³, Jaroslav Kubíček¹, Martin Volt¹, Dana Nováková¹, Pavla Valentová¹, Jaroslava Bímová¹

¹ Kardiochirurgická klinika, Fakultní nemocnice Hradec Králové a Lékařská fakulta Univerzity Karlovy, Hradec Králové

² Kardiochirurgická klinika, Fakultní nemocnice Olomouc a Lékařská fakulta Univerzity Palackého, Olomouc

³ Chirurgická klinika, Fakultní nemocnice Hradec Králové a Lékařská fakulta Univerzity Karlovy, Hradec Králové, Česká republika

Aim: To determine the real incidence of heparin resistance in patients scheduled for a cardiac surgical procedure. To determine whether there is an association between preoperative treatment with heparin and the incidence of heparin resistance. Also, to establish whether there is an association between platelet count, patients' age, and heparin resistance.

Patients and methods: A total of 624 patients scheduled for on-pump surgery were included into a prospective study over a period of three years. Preoperative and intraoperative activated clotting time (ACT) values were recorded. Additionally, four factors referred to in the relevant literature as potential causes of developing heparin resistance were monitored in all patients: age 65 years, preoperative platelet count ≥ 300 × 109/l, preoperative administration of various types of heparin, antithrombin concentration ≤ 60%, and a combination of all. Patients were considered heparin-resistant if a heparin dose ≥ 5 mg/kg had not produced an anticoagulation response with ACT ≥ 480 s. Our data were evaluated using the test of agreement of relative frequency and the χ2 test.

Results: In our group, heparin resistance was detected in 203 of the 624 patients (32.5%). The incidence of heparin resistance differed significantly from the anticipated 22%. Among the 624 patients, 363 (58.2%) were older than 65 years. The hypothesis of age-dependence ≥ 65 years is rejected (p = 0.0391) or is of bordeline statistical significance. Regarding preoperative platelet count higher than 300 × 109/l, the hypothesis of independence was tested as opposed to the hypothesis of dependence. The hypothesis of independence was rejected (p = 0.000027). Before surgery, heparin was administered to 181 patients (29%). The hypothesis of dependence was tested as opposed to the alternative hypothesis of independence. The independence hypothesis was rejected (p < 0.001). Regarding preoperative antithrombin levels ≤ 60%, the hypothesis of independence was tested as opposed to the alternative hypothesis of independence. The hypothesis of independence of heparin resistance on antithrombin levels ≤ 60% was rejected (p < 0.001).

Conclusion: Results of our study have confirmed an incidence of heparin resistance significantly higher than anticipated. Furthermore, our results have confirmed the incidence of heparin resistance to depend significantly on the tested risk factors, except for patients' age, which was of bordeline statistical significance.

Keywords: Heparin resistance; Heparin; Antithrombin; ACT; Extracorporeal circulation; Platelets

Published: September 1, 2009  Show citation