Hydroxyethyl starch or gelatin impairs, but Ringer's acetate enhances, coagulation capacity dose dependently after cardiac surgery

Introduction

All colloid solutions have negative effects on blood coagulation, but these effects are dependent on the dose and type of fluid administered [1, 2]. Since cardiopulmonary bypass increases the risk of postoperative bleeding, we examined to what extent various doses of rapidly degradable hydroxyethyl starch (HES) or gelatin, in comparison with Ringer's acetate, impaired whole blood coagulation after cardiac surgery.

Methods

Forty-five patients received three relatively rapid boluses (each 7 ml/kg) of either 6% HES (130/0.4) (n = 15), 4% gelatin (n = 15), or Ringer's acetate (n = 15) in a randomized, blinded fashion after elective on-pump cardiac surgery to maintain optimal intravascular volume. The study solution was continued as an infusion (7 ml/kg) for the following 12 hours. The total cumulative dose of the study solution was 28 ml/kg. If signs of hypovolemia were observed, Ringer's acetate was given. Blood coagulation was assessed by thromboelastometry (ROTEM).

Results

Clot formation time was prolonged, and the alpha-angle as well as maximum clot firmness (MCF) decreased similarly after infusion of 7 ml/kg both colloid solutions (P < 0.05). These ROTEM parameters, indicative of delayed clot formation and impaired clot strength, still deteriorated after the cumulative doses of 14 ml/kg and 21 ml/kg colloids (P < 0.05). In contrast, after infusion of 14 ml/kg and 21 ml/kg Ringer's acetate MCF increased slightly but significantly. Some signs of disturbed coagulation were seen in the gelatin group on the first postoperative morning: MCF and the α angle were still decreased in comparison with the Ringer group (P < 0.05). Signs of excessive fibrinolysis were not observed. Chest tube output was comparable between all groups. No clinical thromboses were observed.

Conclusion

HES (130/0.4) 7 ml/kg or gelatin impaired clot formation and firmness shortly after cardiac surgery. This effect became more pronounced as the dose increased. Ringer's acetate increased blood coagulation capacity slightly.