Hypothermia and hyperthermia decrease the anticoagulant potency of low molecular weight heparin measured with thrombelastgraphy

Abstract

Zusammenfassung. Grundlagen: Das antikoagulatorische Potential von niedrig molekularem Heparin (Low Molecular Weight Heparin -LMWH) ist ausreichend nachgewiesen. Ziel unserer Studie war es, den Einfluss von Hypo-und Hyperthermie auf die LMWH-Antikoagulation abzuschätzen.Methodik: Es wurde Blut von 10 gesunden Freiwilligen vor und nach subkutaner Gabe von 5000 I.E. LMWH (Dalteparin) untersucht. Citrat-Blut, mit und ohne Heparinase, welches vor und während des Messvorganges in verschiedene Temperaturniveaus gebracht wurde, wurde mit dem Thomboelastographen untersucht.Ergebnisse: Vor der Verabreichung des LMWH war die Reaktionszeit r (18 ± 5,4 mm bei 37°C) im Normalbereich. Die Reaktionszeit verlängerte sich bei 37° Celsius nach LMWH-Gabe auf 35 mm. Bei hypothermen (28 mm bei 33°C und 33 mm bei 35°C) und hyperthermen Bedingungen (21 mm bei 38°C, 20 mm bei 41°C) war die Reaktionszeit verringert. Ähnliche Ergebnisse zeigen sich auch bei der Clot Formation Time, die bei 37°C noch 24 mm aufweist und bei 33°C und 35°C 19 bzw. 22 mm misst. Bei 38°C ist die Clot Formation Time mit 21 ebenfalls kürzer wie auch bei 41°C mit 20 mm (P < 0,05).Schlussfolgerungen: Die Ergebnisse zeigen eine signifikante Reduktion des mittels TEG gemessenen antikoagulatorischen Effekts. Diese Ergebnisse könnten für den klinischen Alltag von großer Bedeutung sein.Schlüsselwörter: Blut, Antikoagulanzien, Low Molecular Weight Heparin, Thrombelastographie, Temperatureffekt.Summary. Background: It is a fact that anticoagulant potency of low molecular weight heparin (LMWH) is well established under normothermic conditions. The aim of our study was to evaluate the effect of hypo-and hyperthermia on LMWH anticoagulation as measured by thrombelastography.Methods: Blood from 10 healthy volunteers was investigated before and after subcutaneous administration of 5000 IE of LMWH (dalteparin). Thrombelastography was performed with recalcified citrated whole blood with and without heparinase incubation at different test temperatures.Results: Mean ± SD reaction time was within the normal range before LMWH administration (18 ± 5.4 mm at 37°C). LMWH prolonged reaction time to 35 mm at 37°C, but non-normothermic test temperatures significantly decreased reaction time to 28 mm at 33°C, to 33 mm at 35°C, to 21 mm at 38°C, and to 20 mm at 41°C. Similarly, clot formation time was decreased from 24 mm at 37°C to 19 mm at 33°C, to 22 mm at 35°C, to 21 mm at 38°C, and to 20 mm at 41°C (P < 0.05).Conclusions: These results show that both hypo-and hyperthermic conditions significantly decreased the anticoagulant potency of LMWH when assessed by TEG ® analysis. These findings may be of clinical relevance in non-normothermic patients.

Thromboelastographic Study of Psychophysiological Stress

“…Measurement temperature was mostly set at 37°C but can be adjusted which is useful to study coagulation under hyper- and hypothermia. 41 In addition, modified TEG methods allow the evaluation of specific coagulation functions using the blood treated with different coagulation activators (eg, celite, kaolin, tissue factor, and thrombin) or anticoagulants (eg, heparin). For TEG, tissue factor and kaolin mixed with phospholipids and buffered stabilizer are supplemented with blood in most applications.…”

“…Temperature itself may also affect these biochemical processes. 41 For example, it is expected that the speed at which a series of enzymatic reactions occur in the coagulation cascade would vary with temperature. 70 In addition, as another way to assess the temperature effects for a long period of time, seasonal changes in blood coagulation and fibrinolysis have been investigated indicating a greater tendency to clot in circulatory system in cold weather with a mean temperature <20°C than in warm weather (>20°C) due to the activated coagulation system.…”

Thromboelastographic study of biomaterials

“…73 Measurement temperature was mostly set at 37 C, but can be adjusted, which is useful to study coagulation under hyper-and hypothermia where a temperature range from 28 to 41 C has been controlled. 74,75 In addition, modified TEG methods allow the evaluation of specific coagulation functions. For example, heparinase-modified TEG has been conducted to investigate the heparinlike anticoagulant effects.…”