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Crit Care Med. 2011 Oct;39(10):2337-45. doi: 10.1097/CCM.0b013e318223b910.

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

Author information

1
Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA. jklee@jhmi.edu

Abstract

OBJECTIVE:

Knowledge remains limited regarding cerebral blood flow autoregulation after cardiac arrest and during postresuscitation 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-asphyxic cardiac arrest or sham surgery and recovered for 2 hrs with normothermia followed by 4 hrs 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 hrs postresuscitation. 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 postarrest animals compared to sham-operated controls during the 2-hr normothermic period after resuscitation. During the subsequent 4-hr recovery, hypothermia decreased laser-Doppler flux in both the sham surgery and postarrest groups. Autoregulation was intact during hypertension in all groups. With arterial hypotension, postarrest, hypothermic piglets had a significant decrease in the perfusion pressure lower limit of autoregulation compared to postarrest, 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 noninvasive near-infrared spectroscopy accurately identified the lower limit of autoregulation during normothermia and hypothermia in piglets resuscitated from arrest.

PMID:
21705904
PMCID:
PMC3178742
DOI:
10.1097/CCM.0b013e318223b910
[Indexed for MEDLINE]
Free PMC Article

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