Continuous Measurement of Autoregulation by Spontaneous Fluctuations in Cerebral Perfusion Pressure

Brady, Kenneth Martin; Lee, Jennifer K.; Kibler, Kathleen K.; Easley, R. Blaine; Koehler, Raymond C.; Shaffner, Donald H.

doi:10.1161/strokeaha.108.514877

Cited by 177 publications

(170 citation statements)

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“…The group LLA was 29.7 mmHg (26.1-36.4 mmHg), and hemispheric differences were small (3.9 mmHg; 1.2-5.9 mmHg). These values are similar to our previously reported LLA determinations in neonatal swine (3)(4)(5)13). Intact autoregulation above LLA was verified by static rate of autoregulation of 0.79 (0.51-0.87), suitable for defining health in a ROC analysis.…”

Section: Resultssupporting

confidence: 92%

“…Previous studies comparing PRx against LLA have demonstrated accuracy, and PRx is linked to outcome in multiple studies (3,6,13,18). This study was not designed to detect a difference in accuracy among PRx, iPRx, and ABP-ICP phase shift but rather to report the accuracy obtained with PEEP oscillation.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, positive ABP-ICP correlation (positive PRx) indicates pressure-passive cerebral vasculature, a state seen when cerebral perfusion pressure (CPP) is either excessive or inadequate for cerebrovascular autoregulation. Conversely, negative ABP-ICP correlation (negative PRx) indicates pressurereactive cerebral vasculature, which is found when CPP is within range of the cerebrovascular autoregulation plateau (3). PRx monitoring can delineate optimal CPP for patients after traumatic brain injury (7,18).…”

mentioning

confidence: 99%

“…Cortical laser Doppler flux recordings during hemorrhage were used to delineate the LLA by a previously published method, commonly used in our lab (3,4,13,15). Flux measurements are plotted across CPP, and the LLA is determined by piece-wise linear regression as the intersection of the two best-fit lines with the lowest residual error squared.…”

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confidence: 99%

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Positive end-expiratory pressure oscillation facilitates brain vascular reactivity monitoring

Brady

Easley

Kibler

et al. 2012

Journal of Applied Physiology

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Brady KM, Easley RB, Kibler K, Kaczka DW, Andropoulos D, Fraser CD 3rd, Smielewski P, Czosnyka M, Adams GJ, Rhee CJ, Rusin CG. Positive end-expiratory pressure oscillation facilitates brain vascular reactivity monitoring. J Appl Physiol 113: 1362-1368, 2012. First published September 13, 2012 doi:10.1152/japplphysiol.00853.2012.-The pressure reactivity index (PRx) identifies optimal cerebral perfusion pressure after traumatic brain injury. We describe a method to improve PRx precision by induced variations in arterial blood pressure (ABP) using positive end-expiratory pressure (PEEP) modulation (iPRx). Neonatal swine (n ϭ 10) were ventilated with static PEEP and then with PEEP oscillated between 5 and 10 cmH2O at a frequency of 1/min. PRx was recorded as a moving correlation coefficient between ABP and intracranial pressure (ICP) from spontaneous ABP activity (0.05-0.003 Hz) during static PEEP. iPRx was similarly recorded with PEEP oscillation-induced ABP waves. The lower limit of autoregulation (LLA) was delineated with continuous cortical laser Doppler flux monitoring. PEEP oscillation increased autoregulation-monitoring precision. The ratios of median absolute deviations to range of possible values for the PRx and iPRx were 9.5% (8.3-13.7%) and 6.2% (4.2-8.7%), respectively (P ϭ 0.006; median, interquartile range). The phase-angle difference between ABP and ICP above LLA was 161°(150°-166°) and below LLA, Ϫ31°(Ϫ42°to 12°, P Ͻ 0.0001). iPRx above LLA was Ϫ0.42 (Ϫ0.67 to Ϫ0.29) and below LLA, 0.32 (0.22-0.43, P ϭ 0.0004). A positive iPRx was 97% specific and 91% sensitive for perfusion pressure below LLA. PEEP oscillation caused stable, low-frequency ABP oscillations that reduced noise in the PRx. Safe translation of these findings to clinical settings is expected to yield more accurate and rapid delineation of individualized optimal perfusion-pressure goals for patients. cerebrovascular autoregulation; pressure reactivity; positive end-expiratory pressure; neonatal CEREBROVASCULAR PRESSURE AUTOREGULATION is a vital, homeostatic mechanism in the mammalian brain that constrains cerebral blood flow (CBF) during changes in arterial blood pressure (ABP). Dynamic cerebrovascular resistance (CVR), also known as pressure reactivity, mediates autoregulation.The pressure reactivity index (PRx) was first described in 1997 as a means of monitoring cerebrovascular reactivity by moving correlation between slow waves (0.05-0.008 Hz) of ABP and intracranial pressure (ICP) (9). When autoregulation is intact, vascular constriction occurs during increased ABP, and vascular dilatation occurs during decreased ABP. Dilatation and constriction of the cerebral vasculature due to autoregulation can be trended by ICP monitoring: ICP increases during vasodilation and decreases during vasoconstriction (13). Therefore, positive ABP-ICP correlation (positive PRx) indicates pressure-passive cerebral vasculature, a state seen when cerebral perfusion pressure (CPP) is either excessive or inadequate for cerebrovascular autoregulation. Convers...

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Positive end-expiratory pressure oscillation facilitates brain vascular reactivity monitoring

Brady

Easley

Kibler

et al. 2012

Journal of Applied Physiology

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“…Furthermore, THRT in prospective observational studies was shown to be useful in predicting clinical deterioration after SAH. 2,6 However, while clinical and experimental data exist supporting the validity of Sxa and TOxa, 13,23,25,31,32,34 neither index has been evaluated for its power to predict DCI. The mean flow index, Mx, which is derived from mean FV and CPP and its noninvasive version, Mxa, where ABP is used instead of CPP, have been previously investigated in patients with SAH.…”

Section: Methodological Considerationsmentioning

confidence: 99%

Cerebral Autoregulation after Subarachnoid Hemorrhage: Comparison of Three Methods

Budohoski

Czosnyka

Smielewski

et al. 2012

J Cereb Blood Flow Metab

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In patients after subarachnoid hemorrhage (SAH) failure of cerebral autoregulation is associated with delayed cerebral ischemia (DCI). Various methods of assessing autoregulation are available, but their predictive values remain unknown. We characterize the relationship between different indices of autoregulation. Patients with SAH within 5 days were included in a prospective study. The relationship between three indices of autoregulation was analyzed: two indices calculated using spontaneous blood pressure fluctuations, Sxa (based on transcranial Doppler) and TOxa (based on near-infrared spectroscopy); and transient hyperemic response test (THRT) where a brief compression of the common carotid artery is used. The predictive value of indices was assessed using data from the first 5 days. Overall there was only moderate correlation between indices. However, both Sxa and TOxa showed good accuracy in predicting impaired autoregulation evidenced by a negative THRT (area under the curve (AUC): 0.788, 95% CI: 0.723 to 0.854 and AUC: 0.827, 95% CI: 0.769 to 0.885, respectively). All indices proved accurate in predicting DCI when 0-to 5-day data were used (AUC: 0.801, 95% CI: 0.660 to 0.942; AUC: 0.857, 95% CI: 0.731 to 0.984, AUC: 0.796, 95% CI: 0.658 to 0.934 for THRT, Sxa, and TOxa, respectively). Combining all three indices had 100% specificity for predicting DCI. While multiple colinearities exist between the assessed methods, multimodal monitoring of cerebral autoregulation can aid in predicting DCI.

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Point‐of‐Care Noninvasive Assessments of Cerebrovascular Reactivity in Traumatic Brain Injury: Integrating the Physiome with Clinical Phenotype

Zeiler

2021

Annals of Neurology

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Continuous Measurement of Autoregulation by Spontaneous Fluctuations in Cerebral Perfusion Pressure

Cited by 177 publications

References 18 publications

Positive end-expiratory pressure oscillation facilitates brain vascular reactivity monitoring

Positive end-expiratory pressure oscillation facilitates brain vascular reactivity monitoring

Cerebral Autoregulation after Subarachnoid Hemorrhage: Comparison of Three Methods

Point‐of‐Care Noninvasive Assessments of Cerebrovascular Reactivity in Traumatic Brain Injury: Integrating the Physiome with Clinical Phenotype

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