Effect of Electrical Vagus Nerve Stimulation on Cerebral Blood Flow and Neurological Outcome in Asphyxial Cardiac Arrest Model of Rats

BackgroundVagus nerve stimulation (VNS) during post-resuscitation may increase recovery of cerebral blood flow (CBF) and reduce neurological injury.ObjectiveThis study was designed to investigate the effect of electrical VNS on neurological outcomes following cardiac arrest (CA).MethodsMale Sprague-Dawley rats (n=48) were subjected to the asphyxial CA model and blindly allocated to the VN isolation (CA+VN isolation) or VNS group (CA+VNS group). Cardiopulmonary resuscitation was initiated 450s after pulseless electrical arrest, and the left cervical vagus nerve was electrically stimulated (0.05mA, 1Hz) for 3h in the CA+VNS group. The neurological deficit score (NDS) and overall performance category (OPC) were assessed at 24h after resuscitation, and histological injury of the hippocampus was evaluated. Independent experiments were performed to evaluate the effect of VNS on global cortical CBF after resuscitation using laser speckle Doppler imaging through a thinned skull window from pre-arrest to 6h after resuscitation.ResultsThe baseline characteristics were not significantly different between the two groups. The NDS was significantly higher, and the OPC was substantially lower in the CA+VNS group (p=0.022 and p=0.049, respectively) supported by decrease in histological injury of the hippocampal CA1 region. CBF in the early period of post-return of spontaneous circulation (ROSC) was significantly higher in the CA+VNS group (p<0.05 at post-ROSC 2h and 4h), and 4-hydroxynonenal was significantly lower in the CA+VNS group (p=0.026).ConclusionsVNS improved cerebral perfusion and neurological outcomes at 24h after ROSC in an asphyxial CA model of rats.