Platelet dysfunction after Out of Hospital Cardiac Arrest. Results from POHCAR: A prospective observational, cohort study.

AIM: Coagulation and platelet function following out of hospital cardiac arrest (OHCA) at admission to a UK cardiology centre were investigated prospectively in this observational feasibility study, and compared to that of patients receiving percutaneous coronary intervention (PCI) for ST segment elevation myocardial infarction (STEMI). METHOD: Blood samples taken immediately at emergency department admission from patients after OHCA of probable cardiac origin were analysed using near-patient thromboelastometry and a platelet function analyser. Physiological parameters, demographic information, bleeding rates and 30-day survival were recorded, and compared to that of patients undergoing PCI for STEMI. RESULTS: Thirty patients were enrolled into each group. Platelet activation with thrombin receptor stimulation was reduced in OHCA patients compared to STEMI patients; mean TRAP AUC OHCA 79.3 (95% CI 63.7-94.9) vs STEMI 101.6 (95% CI 87.4-115.8), p = 0.03. The maximum clot firmness time was prolonged in the OHCA group compared to the STEMI group; 1718s (1545s-1906s) vs 1544s (1387s-1709s), p = 0.01. Other measures of clot formation and strength were comparable between groups. Hyperfibrinolysis (maximum lysis > = 15%) was common in both groups (57% in STEMI; 50% in OHCA) but did not increase 30-day bleeding risk. CONCLUSION: OHCA patients demonstrated reduced thrombin receptor function at hospital admission but overall clot formation dynamics comparable to STEMI patients, indicating no gross coagulopathy post OHCA in our cohort. Hyperfibrinolysis was common both post OHCA and after STEMI. The results of this small feasibility study cannot draw clinical conclusions but will inform power calculations for future studies.

Research protocol for platelets in out-of-hospital cardiac arrest: an observational, case-controlled, feasibility study to assess coagulation and platelet function abnormalities with ROTEM following out-of-hospital cardiac arrest (PoHCAR).

INTRODUCTION: Out-of-hospital cardiac arrest (OHCA) has an annual incidence of approximately 60 000 in the UK. Less than 10% of those who receive resuscitation survive to hospital discharge. For OHCA of a presumed cardiac cause, the optimal antiplatelet therapy is currently unknown. Previous studies indicate that a procoagulopathic state exists postcardiac arrest which may contribute to the formation of thrombi and contribute to poor outcomes. However, the administration of antiplatelet therapies needs to be balanced against the increased risk of bleeding that these individuals face. METHODS AND ANALYSIS: This observational feasibility study will recruit 30 individuals who achieve return of spontaneous circulation post-OHCA, are admitted to a single tertiary centre over a 6-month period and meet Utstein cohort criteria (witnessed cardiac arrest, VF or pulseless VT and cardiac cause of arrest likely). Rotational thromboelastometry and platelet function assessment will be performed on hospital arrival, postemergency percutaneous coronary intervention (PCI) and 12 hours, 24 hours and 48 hours post-PCI. As a comparator, 30 individuals presenting to our institution with ST-segment elevation myocardial infarction and undergoing primary PCI will have the same blood sampling performed. Plasma samples will be retained and batch tested on completion of the study for levels of protein C, protein S, thrombin-antithrombin complex, thrombin, antithrombin, plasminogen activator inhibitor-1, plasmin-antiplasmin complex, d-dimer, platelet factor-4, P selectin, E selectin and prothrombin fragments 1 and 2. 30-day follow-up for complications will be undertaken. ETHICS AND DISSEMINATION: This study has been approved by the Wales REC 7Research Ethics Committee. The results will be submitted to peer-reviewed medical journals and suitable national and international meetings. Results will be locally disseminated via our patient and public interest group. TRIAL REGISTRATION NUMBER: Pre-results; ISRCTN34122839.