Cerebral blood flow and cerebrovascular autoregulation in a swine model of pediatric cardiac arrest and hypothermia*

Abstract

Objective Knowledge remains limited regarding cerebral blood flow autoregulation after cardiac arrest and during post-resuscitation hypothermia. We determined the relationship of cerebral blood flow to cerebral perfusion pressure in a swine model of pediatric hypoxic-asphyxic cardiac arrest during normothermia and hypothermia and tested novel measures of autoregulation derived from near-infrared spectroscopy. Design Prospective, balanced animal study. Setting Basic physiology laboratory at an academic institution. Subjects Eighty-four neonatal swine. Interventions Piglets underwent hypoxic-asphyhxic cardiac arrest or sham surgery and recovered for 2 hours with normothermia followed by 4 hours of either moderate hypothermia or normothermia. In half of the groups, blood pressure was slowly decreased through inflation of a balloon catheter in the inferior vena cava to identify the lower limit of cerebral autoregulation at 6 hours post-resuscitation. In the remaining groups, blood pressure was gradually increased by inflation of a balloon catheter in the aorta to determine the autoregulatory response to hypertension. Measures of autoregulation obtained from standard laser-Doppler flowmetry and indices derived from near-infrared spectroscopy were compared. Measurements and Main Results Laser-Doppler flux was lower in post-arrest animals compared to sham-operated controls during the 2-hour normothermic period after resuscitation. During the subsequent 4-hour recovery, hypothermia decreased laser-Doppler flux in both the sham surgery and post-arrest groups. Autoregulation was intact during hypertension in all groups. With arterial hypotension, post-arrest, hypothermic piglets had a significant decrease in the perfusion pressure lower limit of autoregulation compared to post-arrest, normothermic piglets. The near-infrared spectroscopy-derived measures of autoregulation accurately detected loss of autoregulation during hypotension. Conclusions In a pediatric model of cardiac arrest and resuscitation, delayed induction of hypothermia decreased cerebral perfusion and decreased the lower limit of autoregulation. Metrics derived from non-invasive near-infrared spectroscopy accurately identified the lower limit of autoregulation during normothermia and hypothermia in piglets resuscitated from arrest.

Additive Neuroprotection of a 20-HETE Inhibitor with Delayed Therapeutic Hypothermia after Hypoxia-Ischemia in Neonatal Piglets

“…Previous work demonstrated that cerebral blood flow fully recovers to pre-arrest levels in this model and HET0016 does not significantly affect this recovery of blood flow [23]. Although hypothermia does decrease cerebral blood flow in this model, it does not impair cerebrovascular autoregulation [31]. …”

A pilot study of cerebrovascular reactivity autoregulation after pediatric cardiac arrest

“…1–3 Some patients were enrolled in a therapeutic hypothermia trial. Hypothermia after cardiac arrest may acutely decrease the blood pressure limits of autoregulation, 2 although this shift may not be sustained with prolonged hypothermia or rewarming. 23 Finally, the effects of seizures were not examined.…”

Near-infrared spectroscopy during cardiopulmonary resuscitation and after restoration of spontaneous circulation

“…But the opposite may also happen as described by Putzer et al [54]. Cerebral autoregulation may be compromised early after ROSC and rSO 2 has been used in swine to determine the lower threshold for autoregulation during normothermia and hypothermia [55,56]. rSO 2 can be used as a guide to titrate the cerebral perfusion pressure above this threshold and consequently hinder secondary cerebral damage as a result of hypotensive ischemia.…”