Thromboelastography in term neonates: an alternative approach to evaluating coagulopathy.

OBJECTIVE: To develop normative ranges for citrate-modified and heparinase-modified thromboelastography (TEG) in term neonates. DESIGN: Prospective observational study. SETTING: An outborn neonatal and cardiac intensive care unit in a free-standing academic children's hospital. PATIENTS: Thirty term neonates were enrolled as control subjects. Seventeen infants with clinically documented bleeding requiring blood transfusion were enrolled in the comparison group. MAIN OUTCOME MEASURES: Citrate-modified and heparinase-modified TEG parameters were calculated from blood specimens drawn via peripheral arterial stick or arterial line. RESULTS: TEG in neonates differs from older children and adults; clotting time (R) and clot kinetics (K) values are generally lower while fibrinolysis or rate of clot breakdown (LY30) and coagulation index (CI) are often higher in neonates. TEG values in term neonates calculated as median (Q1-Q3) are as follows: R 4.150 (3.200-6.200), K 1.550 (1.200-1.800), α angle (α) 70.100 (66.000-72.900), maximum amplitude (MA) 61.850 (59.400-66.000), LY30 1.050 (0.100-1.600) and CI 1.950 (0.100 to 2.900). Cut points selected for optimal predictive value for bleeding using receiver operating curve analyses were R>6.3 (sensitivity 82.4%, specificity 80%); K>2.5 (sensitivity 82.4%, specificity 96.7%); α<59 (sensitivity 82.4%, specificity 96.7%); MA<57 (sensitivity 82.4%, specificity 86.7%); CI<-0.15 (sensitivity 88.2%, specificity 83.3%). CONCLUSIONS: The reference ranges and cut points for citrate-modified and heparinase-modified TEG can be used to diagnose and evaluate coagulopathy in term neonates.

Effect of temperature on thromboelastography and implications for clinical use in newborns undergoing therapeutic hypothermia.

BACKGROUND: Encephalopathic neonates undergoing therapeutic hypothermia have increased risk for coagulopathy secondary to perinatal asphyxia and effects of cooling on the coagulation enzyme cascade. Thromboelastography (TEG) allows for a comprehensive assessment of coagulation that can be regulated for temperature. TEG has not been previously evaluated in newborns undergoing hypothermia treatment. METHODS: Encephalopathic neonates treated with systemic hypothermia were enrolled in this prospective observational study. Daily blood specimens were collected for standard coagulation tests and platelet counts during hypothermia and after rewarming. Concurrent TEG assays were performed at 33.5 and 37.0 °C for comparison. RESULTS: A total of 48 paired TEGs from 24 subjects were performed. Forty percent of the subjects were males, the mean (± SD) birth weight was 3.2 ± 0.7 kg, and the mean gestational age was 38.4 ± 1.4 wk. TEG results differed significantly between assays performed at 37.0 vs. 33.5 °C, indicating more impaired coagulation at 33.5 °C. TEG parameters clot kinetics, angle, maximum amplitude (MA), and coagulation index were significantly associated with clinical bleeding (P < 0.05). These remained significant (except for MA) after controlling for transfusion therapy. CONCLUSION: TEG results are affected by temperature, consistent with the known association of hypothermia with coagulopathy. Several TEG parameters are predictive of clinical bleeding in newborns undergoing hypothermia. Selected cutpoints to predict bleeding risk are temperature dependent.