• Emmanuel Haas, François Fischer, François Levy, Su-Emmanuelle Degirmenci, Lelia Grunebaum, Michel Kindo, Olivier Collange, Paul-Michel Mertes, and Annick Steib.
• From the Department of Anaesthesiology (EH, FF, FL, SD, OC, PMM, AS); Department of Haematology (LG); and Department of Cardiovascular Surgery, Strasbourg University Hospital, France (MK).
• Eur J Anaesthesiol. 2016 Jun 1; 33 (6): 408-16.

BackgroundThe heparin regimen providing anticoagulation during cardiopulmonary bypass (CPB) is usually adapted to total body weight (TBW), but may be inaccurate in obese patients in whom TBW exceeds their ideal body weight.ObjectivesThe objective is to compare the effects of heparin injection based on TBW on haemostatic parameters between obese and nonobese patients during cardiac surgery and to calculate the optimal heparin regimen.DesignProspective comparative study.SettingUniversity hospital.PatientsTwo groups of 50 patients (BMI≥ or <30 kg m) were included in the study over a 9-month period in 2013. The study started on 27 February 2013.InterventionsAn unfractionated heparin (UFH) bolus of 300 IU kg TBW was injected before initiation of CPB followed by additional doses (50 to 100 IU kg) to maintain a target activated coagulation time (ACT) of at least 400 s.Main Outcome MeasuresACT and plasma heparin concentration were measured at different time points after initiation of, and weaning from CPB.ResultsObese patients received higher initial and total doses of heparin (P < 0.0001). Plasma heparin concentrations were significantly higher in obese patients at each time point (P < 0.001) and reached very high values after the initial bolus (5.90 vs. 4.48 IU ml, P < 0.0001). The relationship between plasma heparin concentration and ACT after the initial bolus was not linear and followed an asymptotic regression curve. Haemoglobin concentration decreased intraoperatively to a greater extent in the obese group (P < 0.001). No significant differences in postoperative bleeding or global transfusion requirements were observed.ConclusionThe standard heparin regimen based on TBW in obese patients during CPB results in excessive plasma heparin concentrations and a significant intraoperative decrease in haemoglobin concentration. ACT monitoring was not accurate in identifying this excess dosage. An initial bolus of 340 IU kg ideal body weight would achieve a heparin concentration of 4.5 IU ml, similar to that observed in nonobese patients. Further investigations are warranted to confirm this heparin regimen.

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