['This study investigated the incidence of hyperfibrinolysis upon emergency department (ED) admission in patients with out of hospital cardiac arrest (OHCA), and the association of the degree of hyperfibrinolysis with markers of hypoperfusion.', 'From 30 OHCA patients, cardiopulmonary resuscitation (CPR) time, pH, base excess (BE), and serum lactate were measured upon ED admission. A 20% decrease of rotational thromboelastometry maximum clot firmness (MCF) was defined as hyperfibrinolysis. Lysis parameters included maximum lysis (ML), lysis onset time (LOT) and lysis index at 30 and 45 min (LI30/LI45). The study was approved by the Human Subjects Committee.', 'Hyperfibrinolysis was present in 53% of patients. Patients with hyperfibrinolysis had longer median CPR times (36 (15-55) vs. 10 (7-18)min; P=0.001), a prolonged activated partial thromboplastin time (54 ± 16 vs. 38 ± 10s; P=0.006) and elevated D-dimers (6.1 ± 2.1 vs. 2.3 ± 2.0 μg/ml; P=0.02) when compared to patients without hyperfibrinolysis. Hypoperfusion markers, including pH (6.96 ± 0.11 vs. 7.17 ± 0.15; P<0.001), base excess (-20.01 ± 3.53 vs. -11.91 ± 6.44; P<0.001) and lactate (13.1 ± 3.7 vs. 8.0 ± 3.7 mmol/l) were more disturbed in patients with hyperfibrinolysis than in non-hyperfibrinolytic subjects, respectively. The LOT showed a good association with CPR time (r=-0.76; P=0.003) and lactate (r=-0.68; P=0.01), and was longer in survivors (3222 ± 34s) than in non-survivors (1,356 ± 833; P=0.044).'] Is hyperfibrinolysis in out of hospital cardiac arrest associated with markers of hypoperfusion?