Wide Temperature Range Testing with ROTEM Coagulation Analyses

Abstract

Mild induced hypothermia is used for neuroprotection in patients successfully resuscitated after cardiac arrest. Temperature-dependent effects on rotational thromboelastometry (ROTEM(®)) assays with EXTEM(®), FIBTEM(®), or APTEM(®) in cardiac arrest patients have not previously been studied. Ten patients with out-of-hospital cardiac arrest who underwent induced hypothermia were studied during stable hypothermia at 33°C. ROTEM temperature effects on EXTEM, FIBTEM, and APTEM assays were studied at temperatures set between 30°C and 42°C. Citrated whole blood test tubes were incubated in temperature-adjusted heating blocks and then investigated at respective temperature in the temperature-adjusted ROTEM. The following variables were determined: clotting time (CT), clot formation time (CFT), α-angle, and maximum clot firmness (MCF). The results from hypo- and hyperthermia samples were compared with the samples incubated at 37°C using the Wilcoxon matched-pairs signed-rank test. A p-value of <0.05 was considered significant. CT-EXTEM(®) and CT-APTEM(®) were prolonged by hypothermia at 30°C (p<0.01 for both) and 33°C (p<0.05 for both). Hyperthermia at 42°C shortened CT-EXTEM (p<0.05) and CT-APTEM (p<0.01). CFT-EXTEM(®) and CFT-APTEM(®) were markedly prolonged by hypothermia at 30°C, 33°C, and 35°C (p<0.01 for all except CFT-EXTEM, 35°C [p<0.05]). The α-angle-EXTEM was markedly decreased at 30°C, 33°C, and 35°C (p<0.01) but increased at 40°C (p<0.05) and 42°C (p<0.01); α-angle-APTEM showed similar results. MCF was unchanged at different temperatures for all tests. ROTEM (EXTEM, FIBTEM, and APTEM assays) revealed a hypocoagulative response to in vitro-applied hypothermia in the blood of cardiac arrest patients reflected in the prolonged clot initiation and decreased clot propagation. Hyperthermia showed the opposite effects. Clot firmness was not affected by temperature.

Platelet Function During Hypothermia in Experimental Mock Circulation

“…This confirms previous findings stating that CPB‐induced clotting factor depletion and platelet dysfunction measured by ROTEM persisted after CPB and heparin neutralization . Others, however, stated that ROTEM revealed a hypocoagulative response to in vitro–applied hypothermia in blood reflected in the prolonged clot initiation and decreased clot propagation without affecting clot firmness . Changes of thromboelastometry parameters need to be interpreted with caution with respect to variations in hematocrit and platelet counts .…”

Adaptation of global hemostasis to therapeutic hypothermia in patients with out-of-hospital cardiac arrest: Thromboelastography study

“…TEG is a bedside test which allows assessment of the interaction between coagulation factors, platelets, fibrin and fibrinolysis. Routinely, TEG is performed at 37°C, nevertheless some studies were dedicated to test the influences of temperature on TEG measurements [27,28]. The results of the current TEG analysis under in vivo conditions demonstrated that application of MTH impaired both propagation of coagulation (a-angle), as well as K and MA, yet did not affect the R time.…”

“…As a standard feature, in most TEG studies blood tests were performed at 37°C, regardless of patient body temperature. This study examined whether the sample temperature had an impact on coagulation impairment during the TEG evaluation, similar studies has been performed for different patient groups with samples collected during MTH [27,31,35]. The MTH effects on coagulation tests from both in vivo (patient treatment) and in in vitro conditions (TEG) were analyzed.…”

Changes in coagulation during therapeutic hypothermia in cardiac arrest patients

“…11,15 Another previous thrombolastographic study on hypothermic cardiac arrest patients found the relevance of temperature adjustments to be low. 14 We chose to perform ROTEM ® analyses at 37 • C as recommended by the ROTEM ® manufacturer because this provided the most reproducible results.…”

“…9,10 Thromboelastometric studies with in vitro induced hypothermia on whole blood from healthy volunteers have shown an association between impairment of coagulation and decreasing temperatures. 11,12 Only a few studies have investigated the effect of hypothermia on coagulation in cardiac arrest patients, [13][14][15] and some of these indicated a prolonged clot initiation during hypothermia. 13 To the best of our knowledge, no previous studies have investigated coagulation in cardiac arrest patients both during hypothermia and subsequent normothermia.…”