Anticoagulation and pediatric extracorporeal membrane oxygenation: impact of activated clotting time and heparin dose on survival.

BACKGROUND: Anticoagulation during pediatric extracorporeal membrane oxygenation (ECMO) is accomplished by titrating heparin administration to maintain an activated clotting time (ACT) of between 180 and 220 seconds. We hypothesized that an ACT of 180 to 220 seconds results in inadequate anticoagulation during pediatric ECMO and that increased heparin levels will lead to increased survival.
METHODS: A retrospective review was conducted of 604 consecutive pediatric ECMO patients at a single institution between 1980 and 2001. Multiple logistic regressions were used to assess the impact on survival of ACT, heparin, age, weight, diagnosis, and previous surgery.
RESULTS: There were 349 survivors (57.8%), and 255 (42.2%) nonsurvivors. Mean hours on ECMO were 182 +/- 134 (range, 3 to 957 hours), mean ACT was 227 +/- 50 seconds (range, 158 to 620 seconds), and the mean hourly heparin dose was 45 +/- 21 U/kg (range, 6 to 134 U/kg). Regression analysis indicated that increased heparin administration was predictive of survival (p < 0.0001), independent of all other variables. The ACT was not a predictor of survival (p = 0.096). Although previous surgery was independently associated with an increased likelihood of ECMO death (p < 0.001), increased heparin administration again exerted a survival advantage (p = 0.012).
CONCLUSIONS: Adherence to the recommended ACT of 180 to 220 seconds in pediatric ECMO patients may result in inadequate anticoagulation. Survival is improved by increased heparin administration independent of the ACT. The ACT may be too insensitive to maintain adequate long-term systematic anticoagulation, and other methods, such as heparin levels or functional parameters such as anti-Factor Xa activity or thrombin generation, should be investigated.