Purpose of the study

Neuron-specific enolase (NSE) and protein S100 are robust predictors of neurological outcome after cardiac arrest. However, the role of both biomarkers in the context of target temperature management (TTM) after cardiac arrest has not been fully studied. Here, we aimed to study serum levels of NSE and protein S100 in a porcine model of cardiac arrest and TTM at 34ºC or 37ºC.

Methods

Sixteen female Landrace x Large-White pigs underwent a 5 min cardiac arrest by ventricular fibrillation (CAxVF) followed by advanced life support until return of spontaneous circulation (ROSC). Animals presenting ROSC were randomized to TTM at 34ºC (n=8) or 37ºC (n=8) for 30h. 37-38ºC is considered normal core temperature in pigs. Serum samples from arterial blood were collected to determine NSE and S100ß levels, at 24h and 30h after ROSC. NSE was quantified by electrochemiluminescence immunoassay and S100ß by ELISA. At 30h, brains were obtained by craniotomy and fixed in formaldehyde for histological analysis. Hematoxylin-eosin stains of six specific regions were selected and assessed for morphological ischaemic alterations.

Results

Seven animals per group were resuscitated after 11.14  5.2 minutes in TTM 34ºC and 13.4  9.6 minutes in TTM 37ºC. Animals underwent similar administration of adrenaline and number of defibrillations. Time to ROSC was similar in both groups. Table 1 shows that NSE and S100 concentrations were not statistically different between TTM groups, either at 24 or 30 hours after ROSC. Histological analyses showed similar neuronal death in both groups at 30 hours. 

	               TTM 34ºC (n=7)	 TTM 37ºC (n=7)	
NSE 24h	1.71  0.7±6 ng/mL	1.86  0.69 ng/mL	p=0.72
NSE 30h	1   0.58 ng/mL	0.71  0.76 ng/mL	p=0.44
S100 24h	0.13  0.024 µg/L	0.14  0.023 µg/L	p=0.66
S100 30h	0.13  0.027 µg/L	0.11  0.031 µg/L	p=0.13

Table 1: Mean and standard deviation concentrations of NSE and S100.

Conclusions

In a porcine model of CAxVF and TTM, NSE and S100 peak concentrations were lower than reported in humans. However, levels of NSE and S100 were not significantly affected by TTM at 34ºC compared with 37ºC.

2 - Neuron-specific enolase and protein S100ß are not affected by different target temperature management protocols in a clinically relevant model