Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Crit Care Med. 2011 Oct;39(10):2337-45. doi: 10.1097/CCM.0b013e318223b910.
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.
Prospective, balanced animal study.
Basic physiology laboratory at an academic institution.
Eighty-four neonatal swine.
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.
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.
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.
心脏骤停后和复温期间，脑血流自动调节的知识仍然有限。我们在正常体温和低温的新生缺氧性窒息性心脏骤停猪模型中，确定了脑血流与脑灌注压之间的关系，并测试了来自近红外光谱的自动调节新指标。
前瞻性、平衡动物研究。
学术机构的基础生理学实验室。
84 头新生猪。
仔猪经历缺氧性窒息性心脏骤停或假手术，并在正常体温下恢复 2 小时，然后进行 4 小时中度低温或正常体温。在一半的组中，通过充气下腔静脉中的气球导管缓慢降低血压，以确定复苏后 6 小时脑自动调节的下限。在其余组中，通过充气主动脉中的气球导管逐渐增加血压，以确定高血压的自动调节反应。比较从标准激光多普勒流量测量获得的自动调节测量值和从近红外光谱获得的指数。
与复苏后 2 小时正常体温期间的假手术对照相比，心脏骤停后动物的激光多普勒通量较低。在随后的 4 小时恢复期间，低温在假手术和心脏骤停组中均降低了激光多普勒通量。所有组的自动调节在高血压期间均完好。在动脉低血压时，与心脏骤停后正常体温的仔猪相比，心脏骤停后低温的仔猪自动调节下限的灌注压显著降低。自动调节的近红外光谱衍生指标准确地检测到低血压期间自动调节的丧失。
在儿科心脏骤停和复苏模型中，延迟诱导低温会降低脑灌注并降低自动调节下限。来自非侵入性近红外光谱的指标准确地识别了复苏后心脏骤停仔猪正常体温和低温期间的自动调节下限。
