Therapeutic hypothermia (TH) is recommended for unconscious victims of cardiac arrest in an effort to improve neurologic outcomes. We decrease the temperature to 33 degrees Celsius (C) for 24 hour. Purpose of the present study was to find out requirement of heparin in patients undergone for therapeutic hypothermia and to study spectrum of changes related to that.
This was a retrospective chart review study in which patients who received IV heparin during implementing the TH protocol were enrolled. Demographics and other clinical data ere collected. Timings of heparin institution, heparin dose (adjusted for body weight) aPTT and body temperature were noted at baseline, twice during hypothermia, during rewarming phase and during stable condition.
The mean age was 63.5 ± 16.5; mean BMI 31.6 ± 10.3 and mean APACHE II score 26.6 ± 6.6. Indications for heparin were acute MI, atrial fibrillation, pulmonary embolism and LV thrombus. Heparin was started at a rate of 10.1 ± 1.6 Units/kg/hr. All patients experienced initial elevations in PTT to greater than 2.5X baseline at this dose when temperature < 35.5C. Analysis of variance (ANOVA) of aPTT during baseline, therapeutic hypothermia and rewarming phase showed significant change (34.1, 141.4, 88.9, 48.2; p = 0.029). Same way ANOVA of dose of heparin also showed significant difference during TH (2 set of values) and during rewarming phase respectively (13.04, 8.7, 8.1 U/kg/hr; p = 0.014). This was suggestive of reduction in dose by almost 50% Change in aPTT between baseline aPTT and aPTT during hypothermia was in linear relationship with temperature during hypothermia by linear regression (Coefficient = 18.76442, p = 0.033, 95% CI = 1.8–35.7) Two of our patients had significant bleeding.
If IV heparin is required during TH then a reduction in the starting rate is recommended in order to avoid over anticoagulation. Based on this data, the recommended heparin rate should be 50% of the usual starting dose, or 5 Units/kg/hr.
Dose reduction in Heparin during hypothermia is necessary. Further studies are needed to validate these results.
Bhavinkumar Dalal, No Financial Disclosure Information; No Product/Research Disclosure Information