Serum inflammatory markers after postcardiac arrest resuscitation: Surrogate markers of efficacy, therapeutic targets, or innocent bystanders*:

Single administration of soluble epoxide hydrolase inhibitor suppresses neuroinflammation and improves neuronal damage after cardiac arrest in mice

Cardiac arrest (CA) causes ischemia-reperfusion injury in the whole body among victims. Especially in the brain, inflammation and neuronal cell death can lead to irreversible dysfunction. Our goal was to determine whether a single administration of soluble epoxide hydrolase inhibitor (AS2586144-CL) has a neuroprotective effect and decreases the inflammatory response after CA and cardiopulmonary resuscitation (CPR). Global cerebral ischemia was induced in male C57BL/6 mice with 8min of CA. Thirty minutes after recovery of spontaneous circulation, the mice were randomly assigned to three groups and administered AS2586144-CL: 1mg/kg (n=25), 10mg/kg (n=25), or 0mg/kg (vehicle, n=25). At 6 and 7 days after CA/CPR, behavioral tests were conducted and brains were removed for histological evaluation. Analysis of histological damage 7 days after CA/CPR revealed that 10mg/kg of AS2586144-CL protected neurons, and suppressed cytokine production and microglial migration into the hippocampus. Two hours after CA/CPR, 10mg/kg of AS2586144-CL suppressed serum tumor necrosis factor-α and hippocampal nuclear factor κB expression. Our data show that 10mg/kg of AS2586144-CL administered following CA/CPR suppresses inflammation and decreases neuronal damage.

Predictive value of interleukin-6 in post-cardiac arrest patients treated with targeted temperature management at 33 °C or 36 °C

AIM

Post-cardiac arrest syndrome (PCAS) is characterized by systemic inflammation, however data on the prognostic value of inflammatory markers is sparse. We sought to investigate the importance of systemic inflammation, assessed by interleukin-6 (IL-6) in comatose survivors of out-of-hospital cardiac arrest.

METHODS

A total of 682 patients enrolled in the Target Temperature Management (TTM) trial, surviving >24h with available IL-6 data were included. IL-6 was measured on days 1, 2 and 3 after return of spontaneous circulation. Severity of PCAS was assessed daily by the Sequential Organ Failure Assessment score. Survival status was recorded at 30 days.

RESULTS

High levels of IL-6 at day 1-3 (all p<0.0001) were independently associated with severity of PCAS with no interaction of target temperature (all p=NS). IL-6 levels did not differ between temperature groups (p(interaction)=0.99). IL-6 levels at day 2 (p<0.0001) and day 3 (p<0.0001) were associated with crude mortality. Adjusted Cox proportional-hazards analysis showed that a two-fold increase of IL-6 levels at day 2 (HR=1.15 (95% CI: 1.07-1.23), p=0.0002) and day 3 (HR=1.18 (95% CI: 1.09-1.27), p<0.0001) were associated with mortality. IL-6 levels at day 3 had the highest discriminative value in predicting mortality (AUC=0.66). IL-6 did not significantly improve 30-day mortality prediction compared to traditional prognostic factors (p=0.08).

CONCLUSIONS

In patients surviving >24h following cardiac arrest, IL-6 levels were significantly elevated and associated with severity of PCAS with no significant influence of target temperature. High IL-6 levels were associated with increased mortality. Measuring levels of IL-6 did not provide incremental prognostic value.

Complement inhibition as a proposed neuroprotective strategy following cardiac arrest

Out-of-hospital cardiac arrest (OHCA) is a devastating disease process with neurological injury accounting for a disproportionate amount of the morbidity and mortality following return of spontaneous circulation. A dearth of effective treatment strategies exists for global cerebral ischemia-reperfusion (GCI/R) injury following successful resuscitation from OHCA. Emerging preclinical as well as recent human clinical evidence suggests that activation of the complement cascade plays a critical role in the pathogenesis of GCI/R injury following OHCA. In addition, it is well established that complement inhibition improves outcome in both global and focal models of brain ischemia. Due to the profound impact of GCI/R injury following OHCA, and the relative lack of effective neuroprotective strategies for this pathologic process, complement inhibition provides an exciting opportunity to augment existing treatments to improve patient outcomes. To this end, this paper will explore the pathophysiology of complement-mediated GCI/R injury following OHCA.