Cerebrovascular autoregulation after rewarming from hypothermia in a neonatal swine model of asphyxic brain injury

After hypoxic brain injury, maintaining blood pressure within the limits of cerebral blood flow autoregulation is critical to preventing secondary brain injury. Little is known about the effects of prolonged hypothermia or rewarming on autoregulation after cardiac arrest. We hypothesized that rewarming would shift the lower limit of autoregulation (LLA), that this shift would be detected by indices derived from near-infrared spectroscopy (NIRS), and that rewarming would impair autoregulation during hypertension. Anesthetized neonatal swine underwent sham surgery or hypoxic-asphyxic cardiac arrest, followed by 2 h of normothermia and 20 h of hypothermia, with or without rewarming. Piglets were further divided into cohorts for cortical laser-Doppler flow (LDF) measurements during induced hypotension or hypertension. We also tested whether indices derived from NIRS could identify the LDF-derived LLA. The LLA did not differ significantly among groups with sham surgery and hypothermia (29 ± 8 mmHg), sham surgery and rewarming (34 ± 7 mmHg), arrest and hypothermia (29 ± 10 mmHg), and arrest and rewarming (38 ± 11 mmHg). The LLA was not affected by arrest ( P = 0.60), temperature ( P = 0.08), or interaction between arrest and temperature ( P = 0.73). The NIRS-derived indices detected the LLA accurately, with the area under the receiver-operator characteristic curves of 0.81–0.96 among groups. In groups subjected to arrest and hypothermia, with or without rewarming, the slope of LDF relative to cerebral perfusion pressure during hypertension was not significantly different from zero ( P > 0.10). In conclusion, rewarming did not shift the LLA during hypotension or affect autoregulation during hypertension after asphyxic cardiac arrest. The NIRS-derived autoregulation indices identified the LLA accurately.

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Abstract 273: Noninvasive Mitochondrial Modulation: Neuroprotection in a Translational Model of Cardiac Arrest and Resuscitation

Circulation ◽

10.1161/circ.140.suppl_2.273 ◽

2019 ◽

Vol 140 (Suppl_2) ◽

Author(s):

Joseph M Wider ◽

Erin Gruley ◽

Jennifer Mathieu ◽

Emma Murphy ◽

Rachel Mount ◽

...

Keyword(s):

Cardiac Arrest ◽

Brain Injury ◽

Near Infrared ◽

Small Animal ◽

Spontaneous Circulation ◽

Infrared Light ◽

Swine Model ◽

Treatment Groups ◽

The Brain ◽

Neuroprotective Therapies

Background: Mitochondrial dysfunction contributes to cardiac arrest induced brain injury and has been a target for neuroprotective therapies. An emerging concept suggests that hyperactivation of neuronal mitochondria following resuscitation results in hyperpolarization of the mitochondrial membrane during reperfusion, which drives generation of excess reactive oxygen species. Previous studies from our group demonstrated that limiting mitochondrial hyperactivity by non-invasively modulating mitochondrial function with specific near infrared light (NIR) wavelengths can reduce brain injury in small animal models of global and focal ischemia. Hypothesis: Inhibitory wavelengths of NIR will reduce neuronal injury and improve neurocognitive outcome in a clinically relevant swine model of cardiac arrest. Methods: Twenty-eight male and female adult swine were enrolled (3 groups: Sham, CA/CPR, and CA/CPR + NIR). Cardiac arrest (8 minutes) was induced with a ventricular pacing wire and followed by manual CPR with defibrillation and epinephrine every 30 seconds until return of spontaneous circulation (ROSC), 2 of the 20 swine that underwent CA did not achieve ROSC and were not enrolled. Treatment groups were randomized prior to arrest and blinded to the CPR team. Treatment was applied at onset of ROSC by irradiating the scalp with 750 nm and 950 nm LEDs (5W) for 2 hours. Results: Sham-operated animals all survived (8/8), whereas 22% of untreated animals subjected to cardiac arrest died within 45 min of ROSC (CA/CPR, n= 7/9). All swine treated with NIR survived the duration of the study (CA/CPR + NIR, n=9/9). Four days following cardiac arrest, neurological deficit score was improved in the NIR treatment group (50 ± 21 CA/CPR vs. 0.8 ± 0.8 CA/CPR + NIR, p < 0.05). Additionally, neuronal death in the CA1/CA3 regions of the hippocampus, assessed by counting surviving neurons with stereology, was attenuated by treatment with NIR (17917 ± 5534 neurons/mm 3 CA/CPR vs. 44655 ± 5637 neurons/mm 3 CA/CPR + NIR, p < 0.05). All data is reported as mean ± SEM. Conclusions: These data provide evidence that noninvasive modulation of mitochondria, achieved by transcranial irradiation of the brain with NIR, mitigates post-cardiac arrest brain injury.

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