Objective:
Reliable early prognostication of neurologic recovery in comatose cardiac arrest (CA) survivors remains a major clinical challenge. We hypothesized that continuous somatosensory evoked potentials (SSEP) in the immediate post-CA period could enable early quantification of cortical recovery.
Methods:
Pigs were instrumented for hemodynamic and SSEP monitoring. For SSEP, stimulation was applied to the right median nerve and electrodes in the brachial plexus and scalp acquired recordings. The primary cortical signal was the N20. Animals were then subjected to ventricular fibrillation CA that was left untreated for up to 4 minutes and followed by advanced cardiac life support until return of spontaneous circulation (ROSC). SSEP monitoring started before CA and continued after ROSC until SSEPs were unchanged for 60 minutes.
Results:
Six experiments were performed. In all animals, peripheral, subcortical, and cortical SSEPs were acquired prior to CA, demonstrating morphology similar to that of humans. Cortical potentials completely disappeared during CA. Average arrest duration was 6.9 ± 3.0 min. After ROSC, the N20 signal returned but with variable recovery rate and amplitude. The final N20 amplitude inversely trended with total duration of arrest (Figure 1). The N20 amplitude recovery over time took a logarithmic shape and ranged from 5 to 180 minutes to reach maximum (Figure 2).
Conclusions:
Continuous SSEP monitoring allows for quantification of cortical recovery within hours of short duration CA in a porcine model. The maximum N20 amplitude and rate of increase may be useful tools for quantifying recovery of cortical function in comatose cardiac arrest survivors.
The capacity of neurological pupil index to predict absence of somatosensory evoked potentials after cardiac arrest – a study protocol
