Noninvasive autoregulation monitoring with and without intracranial pressure in the naïve piglet brain

Ken M. Brady, Jennifer O. Mytar, Kathleen K. Kibler, Charles W. Hogue, Jennifer Lee-Summers, Marek Czosnyka, Peter Smielewski, R. Blaine Easley

Research output: Contribution to journalArticle

Abstract

BACKGROUND: Cerebrovascular autoregulation monitoring is often desirable for critically ill patients in whom intracranial pressure (ICP) is not measured directly. Without ICP, arterial blood pressure (ABP) is a substitute for cerebral perfusion pressure (CPP) to gauge the constraint of cerebral blood flow across pressure changes. We compared the use of ABP versus CPP to measure autoregulation in a piglet model of arterial hypotension. METHODS: Our database of neonatal piglet (5-7 days old) experiments was queried for animals with naïve ICP that were made lethally hypotensive to determine the lower limit of autoregulation (LLA). Twenty-five piglets were identified, each with continuous recordings of ICP, regional cerebral oximetry (rSO2), and cortical red cell flux (laser Doppler). Autoregulation was assessed with the cerebral oximetry index (COx) in 2 ways: linear correlation between ABP and rSO2 (COxABP) and between CPP and rSO2 (COxCPP). The lower limits of autoregulation were determined from plots of red cell flux versus ABP. Averaged values of COxABP and COxCPP from 5 mm Hg ABP bins were used to show receiver operating characteristics for the 2 methods. RESULTS: COxABP and COx CPP yielded identical receiver operating characteristic curve areas of 0.91 (95% confidence interval [CI], 0.88-0.95) for determining the LLA. However, the thresholds for the 2 methods differed: a threshold COx ABP of 0.5 was 89% sensitive (95% CI, 81%-94%) and 81% specific (95% CI, 73%-88%) for detecting ABP below the LLA. A threshold COxCPP of 0.42 gave the same 89% sensitivity (95% CI, 81%-94%) with 77% specificity (95% CI, 69%-84%). CONCLUSIONS: The use of ABP instead of CPP for autoregulation monitoring in the naïve brain with COx results in a higher threshold value to discriminate ABP above from ABP below the LLA. However, accuracy was similar with the 2 methods. These findings support and refine the use of near-infrared spectroscopy to monitor autoregulation in patients without ICP monitors.

Original languageEnglish (US)
Pages (from-to)191-195
Number of pages5
JournalAnesthesia and Analgesia
Volume111
Issue number1
DOIs
StatePublished - Jul 2010

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Intracranial Pressure
Cerebrovascular Circulation
Arterial Pressure
Homeostasis
Oximetry
Brain
Confidence Intervals
ROC Curve
Near-Infrared Spectroscopy
Critical Illness
Hypotension
Lasers
Databases
Pressure

ASJC Scopus subject areas

  • Anesthesiology and Pain Medicine

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Noninvasive autoregulation monitoring with and without intracranial pressure in the naïve piglet brain. / Brady, Ken M.; Mytar, Jennifer O.; Kibler, Kathleen K.; Hogue, Charles W.; Lee-Summers, Jennifer; Czosnyka, Marek; Smielewski, Peter; Easley, R. Blaine.

In: Anesthesia and Analgesia, Vol. 111, No. 1, 07.2010, p. 191-195.

Research output: Contribution to journalArticle

Brady, KM, Mytar, JO, Kibler, KK, Hogue, CW, Lee-Summers, J, Czosnyka, M, Smielewski, P & Easley, RB 2010, 'Noninvasive autoregulation monitoring with and without intracranial pressure in the naïve piglet brain', Anesthesia and Analgesia, vol. 111, no. 1, pp. 191-195. https://doi.org/10.1213/ANE.0b013e3181e054ba
Brady, Ken M. ; Mytar, Jennifer O. ; Kibler, Kathleen K. ; Hogue, Charles W. ; Lee-Summers, Jennifer ; Czosnyka, Marek ; Smielewski, Peter ; Easley, R. Blaine. / Noninvasive autoregulation monitoring with and without intracranial pressure in the naïve piglet brain. In: Anesthesia and Analgesia. 2010 ; Vol. 111, No. 1. pp. 191-195.
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AU - Brady, Ken M.

AU - Mytar, Jennifer O.

AU - Kibler, Kathleen K.

AU - Hogue, Charles W.

AU - Lee-Summers, Jennifer

AU - Czosnyka, Marek

AU - Smielewski, Peter

AU - Easley, R. Blaine

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N2 - BACKGROUND: Cerebrovascular autoregulation monitoring is often desirable for critically ill patients in whom intracranial pressure (ICP) is not measured directly. Without ICP, arterial blood pressure (ABP) is a substitute for cerebral perfusion pressure (CPP) to gauge the constraint of cerebral blood flow across pressure changes. We compared the use of ABP versus CPP to measure autoregulation in a piglet model of arterial hypotension. METHODS: Our database of neonatal piglet (5-7 days old) experiments was queried for animals with naïve ICP that were made lethally hypotensive to determine the lower limit of autoregulation (LLA). Twenty-five piglets were identified, each with continuous recordings of ICP, regional cerebral oximetry (rSO2), and cortical red cell flux (laser Doppler). Autoregulation was assessed with the cerebral oximetry index (COx) in 2 ways: linear correlation between ABP and rSO2 (COxABP) and between CPP and rSO2 (COxCPP). The lower limits of autoregulation were determined from plots of red cell flux versus ABP. Averaged values of COxABP and COxCPP from 5 mm Hg ABP bins were used to show receiver operating characteristics for the 2 methods. RESULTS: COxABP and COx CPP yielded identical receiver operating characteristic curve areas of 0.91 (95% confidence interval [CI], 0.88-0.95) for determining the LLA. However, the thresholds for the 2 methods differed: a threshold COx ABP of 0.5 was 89% sensitive (95% CI, 81%-94%) and 81% specific (95% CI, 73%-88%) for detecting ABP below the LLA. A threshold COxCPP of 0.42 gave the same 89% sensitivity (95% CI, 81%-94%) with 77% specificity (95% CI, 69%-84%). CONCLUSIONS: The use of ABP instead of CPP for autoregulation monitoring in the naïve brain with COx results in a higher threshold value to discriminate ABP above from ABP below the LLA. However, accuracy was similar with the 2 methods. These findings support and refine the use of near-infrared spectroscopy to monitor autoregulation in patients without ICP monitors.

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