title: Influence of temperature on thromboelastometry and platelet aggregation in cardiac arrest patients undergoing targeted temperature management.
abstract: BACKGROUND
  Coagulation can be visualised using whole blood coagulation analyses such as thromboelastometry and platelet aggregation tests; however, the role of temperature in the analyses is ambiguous. The aim was to examine whether temperature influences the whole blood coagulation tests.
  
  
  METHODS
  We included 40 patients treated with targeted temperature management (33 ± 1 °C) after out-of-hospital cardiac arrest. The blood samples were obtained on hypothermia and normothermia. Each blood sample was analysed simultaneously at 33 °C and 37 °C by thromboelastography (ROTEM®) employing the assays EXTEM®, INTEM®, FIBTEM® and HEPTEM®, and by Multiplate®Analyzer, using COLtest®, ADPtest®, ASPItest® and TRAPtest® as agonists. Data on antithrombotic drugs were collected systematically from medical records, and data were analysed using repeated measurement analysis of variance (ANOVA).
  
  
  RESULTS
  The ROTEM® analyses showed increased clotting time, lower maximum velocity and increased time to maximum velocity (all p values <0.02) when performed at 33 °C compared with 37 °C, irrespective of the patients being hypothermic (median 33.1 °C) or normothermic (median 37.5 °C). However, EXTEM® time to maximum velocity showed no difference between the analyses performed at 33 °C and 37 °C when the patients were hypothermic (p = 0.83). No differences were found in maximum clot firmness (all p values >0.09) analysed at 33 °C and 37 °C, independent of the body temperature. In the hypothermic blood sample, no difference was found when using the COLtest®, ASPItest® or TRAPtest® to compare platelet aggregation analysed at 33 °C and 37 °C (all p values >0.19), but platelet aggregation was significantly higher using the ADPtest® (p < 0.001) when analysed at 33 °C. In the normothermic blood sample, the TRAPtest® showed no difference (p = 0.73) when performed at 33 °C; however, significantly lower aggregation was found using the COLtest® and ASPItest® (all p values <0.001), while a higher aggregation at 33 °C was found using the ADPtest® (p = 0.003).
  
  
  CONCLUSIONS
  ROTEM® analyses seemed not to be dependent on body temperature but showed a slower initiation of coagulation when analysed at 33 °C compared with 37 °C. The Multiplate®Analyzer results were dependent on the temperature used in the analyses and the body temperature. In whole blood coagulation tests, the temperature used in the analyses should be kept at 37 °C irrespective of the patient's body temperature being 33 °C or 37 °C.
authors.affiliation: Research Centre for Emergency Medicine, Aarhus University Hospital, Nørrebrogade 44, Building 30, 8000, Aarhus C, Denmark. anni.jeppesen@clin.au.dk.|Department of Anaesthesiology and Intensive Care Medicine, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark. anni.jeppesen@clin.au.dk.
authors.forename: Anni Nørgaard
authors.initials: AN
authors.lastname: Jeppesen
authors.affiliation: Research Centre for Emergency Medicine, Aarhus University Hospital, Nørrebrogade 44, Building 30, 8000, Aarhus C, Denmark.|Department of Anaesthesiology and Intensive Care Medicine, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark.
authors.forename: Hans
authors.initials: H
authors.lastname: Kirkegaard
authors.affiliation: Department of Anaesthesiology and Intensive Care Medicine, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark.
authors.forename: Susanne
authors.initials: S
authors.lastname: Ilkjær
authors.affiliation: Center for Haemophilia and Thrombosis, Department of Clinical Biochemistry, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark.
authors.forename: Anne Mette
authors.initials: AM
authors.lastname: Hvas
mesh_terms: D000328:Adult; D000368:Aged; D001777:Blood Coagulation / Q000502:physiology; D019468:Disease Management; D005260:Female; D006801:Humans; D007036:Hypothermia, Induced / Q000379:methods* / Q000639:trends; D008297:Male; D008875:Middle Aged; D058687:Out-of-Hospital Cardiac Arrest / Q000628:therapy*; D010974:Platelet Aggregation / Q000502:physiology*; D013696:Temperature; D013916:Thrombelastography / Q000379:methods*
keywords: Coagulation; Haemostasis; Heart arrest; Hypothermia; Platelet function test; Thromboelastometry