Continuous time-domain analysis of cerebrovascular autoregulation using near-infrared spectroscopy

Ken M. Brady, Jennifer K. Lee, Kathleen K. Kibler, Piotr Smielewski, Marek Czosnyka, R. Blaine Easley, Raymond C. Koehler, Donald H. Shaffner

Research output: Contribution to journalArticlepeer-review

199 Scopus citations


BACKGROUND AND PURPOSE - Assessment of autoregulation in the time domain is a promising monitoring method for actively optimizating cerebral perfusion pressure (CPP) in critically ill patients. The ability to detect loss of autoregulatory vasoreactivity to spontaneous fluctuations in CPP was tested with a new time-domain method that used near-infrared spectroscopic measurements of tissue oxyhemoglobin saturation in an infant animal model. METHODS - Piglets were made progressively hypotensive over 4 to 5 hours by inflation of a balloon catheter in the inferior vena cava, and the breakpoint of autoregulation was determined using laser-Doppler flowmetry. The cerebral oximetry index (COx) was determined as a moving linear correlation coefficient between CPP and INVOS cerebral oximeter waveforms during 300-second periods. A laser-Doppler derived time-domain analysis of spontaneous autoregulation with the same parameters (LDx) was also determined. RESULTS - An increase in the correlation coefficient between cerebral oximetry values and dynamic CPP fluctuations, indicative of a pressure-passive relationship, occurred when CPP was below the steady state autoregulatory breakpoint. This COx had 92% sensitivity (73% to 99%) and 63% specificity (48% to 76%) for detecting loss of autoregulation attributable to hypotension when COx was above a threshold of 0.36. The area under the receiver-operator characteristics curve for the COx was 0.89. COx correlated with LDx when values were sorted and averaged according to the CPP at which they were obtained (r=0.67). CONCLUSIONS - The COx is sensitive for loss of autoregulation attributable to hypotension and is a promising monitoring tool for determining optimal CPP for patients with acute brain injury.

Original languageEnglish (US)
Pages (from-to)2818-2825
Number of pages8
Issue number10
StatePublished - Oct 2007


  • Autoregulation
  • Cerebral blood flow
  • Hypotension
  • Neonate
  • Oxygenation
  • Piglet

ASJC Scopus subject areas

  • Clinical Neurology
  • Cardiology and Cardiovascular Medicine
  • Advanced and Specialized Nursing


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