Comparison of static and dynamic cerebral autoregulation under anesthesia influence in a controlled animal model

Abstract

The brain’s ability to maintain cerebral blood flow approximately constant despite cerebral perfusion pressure changes is known as cerebral autoregulation (CA) and is governed by vasoconstriction and vasodilation. Cerebral perfusion pressure is defined as the pressure gradient between arterial blood pressure and intracranial pressure. Measuring CA is a challenging task and has created a variety of evaluation methods, which are often categorized as static and dynamic CA assessments. Because CA is quantified as the performance of a regulatory system and no physical ground truth can be measured, conflicting results are reported. The conflict further arises from a lack of healthy volunteer data with respect to cerebral perfusion pressure measurements and the variety of diseases in which CA ability is impaired, including stroke, traumatic brain injury and hydrocephalus. To overcome these differences, we present a healthy non-human primate model in which we can control the ability to autoregulate blood flow through the type of anesthesia (isoflurane vs fentanyl). We show how three different assessment methods can be used to measure CA impairment, and how static and dynamic autoregulation compare under challenges in intracranial pressure and blood pressure. We reconstructed Lassen’s curve for two groups of anesthesia, where only the fentanyl anesthetized group yielded the canonical shape. Cerebral perfusion pressure allowed for the best distinction between the fentanyl and isoflurane anesthetized groups. The autoregulatory response time to induced oscillations in intracranial pressure and blood pressure, measured as the phase lag between intracranial pressure and blood pressure, was able to determine autoregulatory impairment in agreement with static autoregulation. Static and dynamic CA both show impairment in high dose isoflurane anesthesia, while low isoflurane in combination with fentanyl anesthesia maintains CA, offering a repeatable animal model for CA studies.

Continuous Time-Domain Cerebrovascular Reactivity Metrics and Discriminate Capacity for the Upper and Lower Limits of Autoregulation: A Scoping Review of the Animal Literature

“…Supplementary Appendix SD gives a general overview table of all 15 animal studies with primary and secondary outcomes of the study and its limitations. 19 , 20 , 25 , 34–45 Tables 1 , 2 , and 3 describe three categories of perturbation methods: arterial hypotension/hypertension, 19 , 25 , 34–41 ICP perturbation, 20 , 35 , 43 , 45 and other methods of inducing perturbation (such as cardiac arrest, hypothermia, etc. ), 25 , 37 , 38 , 40–42 , 44 , 45 respectively.…”

“… 19 , 20 , 25 , 34–45 Tables 1 , 2 , and 3 describe three categories of perturbation methods: arterial hypotension/hypertension, 19 , 25 , 34–41 ICP perturbation, 20 , 35 , 43 , 45 and other methods of inducing perturbation (such as cardiac arrest, hypothermia, etc. ), 25 , 37 , 38 , 40–42 , 44 , 45 respectively. Articles that used mixed methods will be found in more than one of Tables 1 , 2 , and 3 along with the study's conclusions regarding continuous indices.…”

“…To measure CBF, 12 studies used LDF, 19 , 20 , 25 , 34 , 35 , 38–44 two studies used laser Doppler index (LDx), 36 , 37 and one study used a diffusion coefficient measured with a custom-built diffusion coefficient spectroscopy. 45 All eligible studies reported the association between time-domain continuous metrics and the LLA aspect of the Lassen's autoregulatory curve. Only one study fully reconstructed the Lassen autoregulatory curve with both the LLA and ULA, but only related the continuous metrics to the curve's plateau (the region between LLA and ULA).…”

“…Only one study fully reconstructed the Lassen autoregulatory curve with both the LLA and ULA, but only related the continuous metrics to the curve's plateau (the region between LLA and ULA). 45 …”

Flujo sanguíneo cerebral y actividad metabólica cerebral. Una mirada desde la anestesiología

“…Los anestésicos inhalados son vasodilatadores directos y producen cambios del FSC según la dosis, en dosis menores a 1 MAC disminuyen el FSC y por acople deprimen la TMC, en dosis superiores a 1 MAC predomina su efecto vasodilatador aumentando el FSC [2], [4] (Figura 4). En modelos animales, tanto la autorregulación cerebral estática como la dinámica muestran un deterioro en la anestesia con isoflurano en dosis altas (> 1,5%), mientras que el isoflurano bajo (< 1%) en combinación con fentanilo mantiene la autorregulación cerebral [19]. 6.4 Relajantes musculares y FSC.…”