Effect of therapeutic mild hypothermia initiated by cold fluids after cardiac arrest on haemostasis as measured by thrombelastography
© BioMed Central Ltd 2008
Published: 13 March 2008
Application of mild hypothermia (32–33°C) has been shown to improve neurological outcome in patients with cardiac arrest, and is therefore a class IIa recommendation in the treatment of those patients. However, hypothermia affects haemostasis, and even mild hypothermia has been found to be associated with bleeding and increased transfusion requirements in patients undergoing surgery . On the other hand, crystalloid hemodilution has been shown to enhance the coagulation onset . Currently, it is unknown in which way the induction of mild therapeutic hypothermia by a bolus infusion of cold crystalloids affects the coagulation system of patients with cardiac arrest.
This was a prospective pilot study in 18 patients with cardiac arrest and return of spontaneous circulation. Mild hypothermia was initiated by a bolus infusion of cold 0.9% saline fluid (4°C; 30 ml/kg/30 min) and maintained for 24 hours. At 0 hours (before hypothermia), 1 hour, 6 hours and 24 hours we assessed the prothrombin time, activated partial thromboplastin time (aPPT) and platelet count, and performed thrombelastography (ROTEM®) after in vitro addition of heparinase. Thrombelastography yields information on the cumulative effects of various blood compounds (for example, coagulation factors, haematocrit, platelets, leukocytes) involved in the coagulation process.
A total amount of 2,527 (± 527) ml of 0.9% saline fluid was given. Platelet counts dropped by 27% (P < 0.01) after 24 hours. The haematocrit significantly decreased after 1 hour (P < 0.05) due to hemodilution and returned thereafter to baseline values. The aPTT increased 2.7-fold after 1 hour (P < 0.01), mainly due to administration of heparins. All ROTEM® parameters did not significantly change in the time course. None of the patients developed bleeding complications during the observation period.
Despite significant changes in haematocrit, platelet count and APTT, thrombelastographic parameters were not altered during the course of mild hypothermia. Therapeutic hypothermia initiated by cold crystalloid fluids therefore has only minor overall effects on the coagulation system in patients with cardiac arrest.
This article is published under license to BioMed Central Ltd.