title: Heparin pretreatment does not alter heparin requirements during cardiopulmonary bypass.
abstract: Heparin infusion may cause heparin resistance and may affect monitoring by measurement of the activated coagulation time (ACT), making the assessment of anticoagulation difficult, with the risk of over- or undertreatment, especially during cardiac surgery. We studied two groups of patients undergoing cardiopulmonary bypass (CPB): patients on heparin infusions (group H) and heparin-naive controls (group C). All patients received heparin 300 IU kg(-1) before CPB and a further dose of 5000 IU if the ACT 5 min after commencing bypass was less than 400 s. Measurements of ACT, heparin concentration, antithrombin-3, thrombin-antithrombin complex, prothrombin fragment F(1+2) and D-dimers were made before and 5 and 20 min after start of CPB. A second dose of heparin was given to eight out of 18 patients in group C and 10 out of 24 in group H. Antithrombin-3 in group H was significantly less than in group C at 5 min [59 (14) vs 52 (9)%, P<0.05]. ACT was significantly lower in group H than group C at 20 min [387 (64) vs 431 (67) s, P<0.05]. Despite ACTs of less than 400 s in both groups, no coagulation was seen, suggesting that 300 IU kg(-1) heparin is a safe dose for anticoagulation in CPB even after heparin therapy.
authors.affiliation: Nuffield Department of Anaesthetics, John Radcliffe Hospital, Headley Way, Oxford, UK.
authors.forename: S C
authors.initials: SC
authors.lastname: Nicholson
authors.forename: D M
authors.initials: DM
authors.lastname: Keeling
authors.forename: M E
authors.initials: ME
authors.lastname: Sinclair
authors.forename: R D
authors.initials: RD
authors.lastname: Evans
mesh_terms: D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage*; D000991:Antithrombins / Q000378:metabolism; D001777:Blood Coagulation / Q000187:drug effects; D002315:Cardiopulmonary Bypass; D004334:Drug Administration Schedule; D004351:Drug Resistance; D006493:Heparin / Q000008:administration & dosage*; D006801:Humans; D007430:Intraoperative Care; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D011300:Preoperative Care / Q000379:methods*; D014914:Whole Blood Coagulation Time
chemical_list: D000925:Anticoagulants; D000991:Antithrombins; D006493:Heparin