Effect of Electrical Vagus Nerve Stimulation on Cerebral Blood Flow and Neurological Outcome in Asphyxial Cardiac Arrest
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ORIGINAL ARTICLE
Effect of Electrical Vagus Nerve Stimulation on Cerebral Blood Flow and Neurological Outcome in Asphyxial Cardiac Arrest Model of Rats Byunghyun Kim†, Inwon Park†, Jae Hyuk Lee*, Seonghye Kim, Min Ji Lee and You Hwan Jo © 2018 Springer Science+Business Media, LLC, part of Springer Nature and Neurocritical Care Society
Abstract Background: Vagus nerve stimulation (VNS) during post-resuscitation may increase recovery of cerebral blood flow (CBF) and reduce neurological injury. Objective: This study was designed to investigate the effect of electrical VNS on neurological outcomes following cardiac arrest (CA). Methods: Male 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 450 s after pulseless electrical arrest, and the left cervical vagus nerve was electrically stimulated (0.05 mA, 1 Hz) for 3 h in the CA + VNS group. The neurological deficit score (NDS) and overall performance category (OPC) were assessed at 24 h 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 6 h after resuscitation. Results: The 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 60 mmHg on room air and no decrease in mean arterial pressure for 5 min after disconnecting the mechanical ventilator. After disconnection, the intravascular catheters were removed, and the groin wound was closed. The endotracheal tube was then removed, and the rats were returned to the cage for a 24-h period of observation. The sham group (n = 5) received the same procedure except for CA and vagus nerve stimulation. Study of the Effect of VNS on Global Cortical Cerebral Blood Flow
Separate experiments were performed to assess CBF via the experimental procedure described above. After ROSC, rats were randomized into the CA + VN isolation group (n = 7) or the CA + VNS group (n = 7). CBF was identified using Doppler laser speckle contrast imager for 6 h. After 6 h of observation, rats were euthanized via exsanguination through the femoral artery catheter, and the cerebral cortex was harvested for the assessment of oxidative stress. To assess changes in baseline CBF after the onset of anesthesia, the sham control group (n = 3) without CA was observed for 6 h. Measurements Neurological Outcomes
Neurological outcomes were assessed at 24 h after ROSC with the neurological deficit scale (NDS) with a validated
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