Kinetics and characteristics of an acute phase response following cardiac arrest

Objective: Inflammation and hypoxia are frequently associated, but their interaction is poorly understood. In vitro studies have shown that hypoxia stimulates the genes of acute phase proteins (APP) and cytokines known to induce APP. We decided to determine kinetics and potential determinants of an acute phase response after cardiac arrest and to assess whether isolated moderate hypoxia can induce APP in humans in vivo. Design: Prospective, observational study in patients and human experiment, Setting: Tertiary care university hospital. Patients and participants: 22 patients after primarily successful cardiopulmonary resuscitation (CPR) and 7 healthy volunteers. Interventions: None in patients; exposure of volunteers to simulated altitude (460 torr/6 h). Results: Following CPR, type-1 APP (C-reactive protein, alpha(1)-acidglycoprotein, serum amyloid A) and type 2 APP (haptoglobin, alpha(1)-antitrypsin) increased consistently within 1-2 days and the 'negative' APP transferrin was downregulated. This APP response occurred irrespective of the cause of arrest, the estimated time of anoxia, clinical course or patient outcome and was not different in patients with and without infectious complications. Exposure of healthy volunteers to less severe but more prolonged hypoxia did not induce APP, although a time dependent increase of serum erythropoietin (EPO) was measurable under these conditions, indicating the activation of oxygen dependent gene expression. Conclusions: (i) A marked acute phase response occurs regularly after cardiac arrest, but within the complexity of this situation the severity of hypoxia is not a predominant determinant of this response. (ii) Despite in vitro evidence for similarities in the oxygen dependent regulation of APP and EPO production, the oxygen sensitivity of these proteins in vivo is different. (iii) Measurements of APP are not revealing regarding infectious complications in the early phase after CPR.