RESUMO
BACKGROUND: Anticoagulation during cardiopulmonary bypass (CPB) is usually adapted to total body weight (TBW). This may be inaccurate in obese patients and lead to heparin overdose with a risk of bleeding. OBJECTIVES: To validate the efficacy and safety of an adjusted calculation model of heparin dosing based on ideal body weight (IBW) rather than TBW in obese CPB patients, with an expected target mean plasma heparin concentration of 4.5âIUâml after onset of CPB in the experimental group. DESIGN: Randomised controlled study. SETTING: University hospital. PATIENTS: Sixty obese patients (BMIâ≥â30âkgâm) scheduled for CPB were included from January to June 2016. INTERVENTIONS: Patients received a bolus dose of unfractionated heparin of either 300âIUâkg of TBW or 340âIUâkg of IBW before onset of CPB. Additional adjusted boluses were injected to maintain an activated clotting time (ACT) of at least 400âs. MAIN OUTCOME MEASURES: Plasma heparin concentration and ACT were measured at different time points. Total heparin doses and transfusion requirements were recorded. RESULTS: The target heparin concentration of 4.5âIUâml was reached in the IBW group at the onset of CPB and maintained at all time points during CPB. Heparin concentrations were significantly higher in the TBW group after the bolus (6.52â±â0.97 vs. 4.54â±â1.13âIUâml, Pâ<â0.001) and after cardioplegia (5.10â±â1.03 vs. 4.31â±â1.00âIUâml, Pâ=â0.02). Total heparin doses were significantly higher in the TBW group. Mean ACT was significantly lower in the IBW group but remained over 400âs during CPB. The correlation between heparin and ACT was poor. Peri-operative bleeding and transfusion requirements were comparable. No thrombotic event occurred in the CPB circuit. CONCLUSION: The current IBW-adjusted regimen of heparin administration may be used efficiently in obese CPB patients, thereby avoiding overdose which cannot be accurately assessed by ACT monitoring alone. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02675647.
Assuntos
Anticoagulantes/administração & dosagem , Ponte Cardiopulmonar/métodos , Heparina/administração & dosagem , Modelos Teóricos , Monitorização Intraoperatória/métodos , Obesidade/cirurgia , Idoso , Idoso de 80 Anos ou mais , Anticoagulantes/sangue , Feminino , Heparina/sangue , Humanos , Masculino , Pessoa de Meia-Idade , Obesidade/sangue , Obesidade/tratamento farmacológico , Estudos Prospectivos , Tempo de Coagulação do Sangue Total/métodosRESUMO
BACKGROUND: The 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. OBJECTIVES: The 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. DESIGN: Prospective comparative study. SETTING: University hospital. PATIENTS: Two groups of 50 patients (BMI≥ or <30âkgâm) were included in the study over a 9-month period in 2013. The study started on 27 February 2013. INTERVENTIONS: An unfractionated heparin (UFH) bolus of 300âIUâkg TBW was injected before initiation of CPB followed by additional doses (50 to 100âIUâkg) to maintain a target activated coagulation time (ACT) of at least 400âs. MAIN OUTCOME MEASURES: ACT and plasma heparin concentration were measured at different time points after initiation of, and weaning from CPB. RESULTS: Obese patients received higher initial and total doses of heparin (Pâ<â0.0001). Plasma heparin concentrations were significantly higher in obese patients at each time point (Pâ<â0.001) and reached very high values after the initial bolus (5.90 vs. 4.48âIUâml, Pâ<â0.0001). 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 (Pâ<â0.001). No significant differences in postoperative bleeding or global transfusion requirements were observed. CONCLUSION: The 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 340âIUâkg ideal body weight would achieve a heparin concentration of 4.5âIUâml, similar to that observed in nonobese patients. Further investigations are warranted to confirm this heparin regimen.