Heparin dose adjustment required to maintain goal-activated partial thromboplastin time during therapeutic...

The impact of therapeutic hypothermia (TH) on unfractionated heparin (UFH) management is essentially unknown. The aim of this study was to evaluate the effect of TH on UFH dosing and activated partial thromboplastin (aPTT) response.

Consecutive patients treated from 2005 to 2011 who received intravenous UFH via a dosing nomogram during TH were included. First, heparin doses and aPTT responses were compared between 2 core temperature groups, less than or equal to 33°C and greater than 35°C. Next, the first aPTT, drawn at 6 hours for temperature less than or equal to 33°C, was assessed. Lastly, a linear model was developed to predict the mean aPTT, based on temperatures and heparin doses.

Of the 156 TH patients, 68 were included. At temperatures less than or equal to 33°C, 76.3% of all aPTT levels and 81.0% of the first aPTTs were above goal range, respectively. Using a linear model, an UFH dose of 12 U/kg per hour predicts an aPTT of 134 seconds at less than or equal to 33°C.

Using guideline-recommended heparin dosing without dose adjustment for temperature changes produced excessive aPTT during the cooling phase for TH patients. Reduction in the UFH dose of 43% to 54% may be required during TH. We recommend frequent aPTT monitoring during the cooling and rewarming phases to attain a desired aPTT range.