Slessarev Marat, Mahmoud Ossama, McIntyre Christopher W, Ellis Christopher G
Department of Medicine, Western University, London, ON, Canada.
Department of Medical Biophysics, Western University, London, ON, Canada.
Front Med (Lausanne). 2021 Jan 20;7:615318. doi: 10.3389/fmed.2020.615318. eCollection 2020.
Ischemic and hyperemic injury have emerged as biologic mechanisms that contribute to cognitive impairment in critically ill patients. Spontaneous deviations in cerebral blood flow (CBF) beyond ischemic and hyperemic thresholds may represent an insult that contributes to this brain injury, especially if they accumulate over time and coincide with impaired autoregulation. We used transcranial Doppler to measure the proportion of time that CBF velocity (CBFv) deviated beyond previously reported ischemic and hyperemic thresholds in a cohort of critically ill patients with respiratory failure and/or shock within 48 h of ICU admission. We also assessed whether these CBFv deviations were more common during periods of impaired dynamic autoregulation, and whether they are explained by concurrent variations in mean arterial pressure (MAP) and end-tidal PCO (PetCO). We enrolled 12 consecutive patients (three females) who were monitored for a mean duration of 462.6 ± 39.8 min. Across patients, CBFv deviated by more than 20-30% from its baseline for 17-24% of the analysis time. These CBFv deviations occurred equally during periods of preserved and impaired autoregulation, while concurrent variations in MAP and PetCO explained only 13-21% of these CBFv deviations. CBFv deviations beyond ischemic and hyperemic thresholds are common in critically ill patients with respiratory failure or shock. These deviations occur irrespective of the state of dynamic autoregulation and are not explained by changes in MAP and CO. Future studies should explore mechanisms responsible for these CBFv deviations and establish whether their cumulative burden predicts poor neurocognitive outcomes.
缺血性损伤和充血性损伤已成为导致危重症患者认知障碍的生物学机制。脑血流量（CBF）自发偏离缺血和充血阈值可能代表一种导致脑损伤的损害，特别是如果它们随着时间累积并与自动调节功能受损同时出现。我们使用经颅多普勒测量了一组入住重症监护病房（ICU）48小时内发生呼吸衰竭和/或休克的危重症患者中，脑血流速度（CBFv）偏离先前报道的缺血和充血阈值的时间比例。我们还评估了这些CBFv偏差在动态自动调节功能受损期间是否更常见，以及它们是否可以通过平均动脉压（MAP）和呼气末二氧化碳分压（PetCO）的同时变化来解释。我们连续纳入了12例患者（3名女性），平均监测时间为462.6±39.8分钟。在所有患者中，CBFv在分析时间的17 - 24%内偏离基线超过20 - 30%。这些CBFv偏差在自动调节功能正常和受损期间出现的频率相同，而MAP和PetCO的同时变化仅解释了这些CBFv偏差的13 - 21%。在患有呼吸衰竭或休克的危重症患者中，CBFv偏离缺血和充血阈值的情况很常见。这些偏差的出现与动态自动调节状态无关，也不能通过MAP和CO的变化来解释。未来的研究应探索导致这些CBFv偏差的机制，并确定它们的累积负担是否预示着不良的神经认知结果。
