Individualized mean arterial pressure targets in critically ill patients guided by non-invasive cerebral-autoregulation: a scoping review

Abstract

Background: Current guidelines recommend a uniform mean arterial pressure (MAP) target for resuscitating critically ill patients; for example, 65 mmHg for patients with sepsis and post-cardiac arrest. However, since cerebral autoregulation capacity likely varies widely in patients, uniform target may be insufficient in maintaining cerebral perfusion. Personalized MAP targets, based on a non-invasive determination of cerebral autoregulation, may optimize perfusion and reduce complications.

Objectives: This scoping review summarizes the numerical values, feasibility, and clinical data on personalized MAP targets in critically ill patients. The focus is on non-invasive monitoring, such as near-infrared spectroscopy and transcranial doppler ultrasound, due to their safety, practicality and applicability to patients with- and without brain injury.

Methods: Following PRISMA-ScR guidelines, a systematic search of Ovid MedLine, Embase (Ovid), and the Cochrane Library (Wiley) was conducted on September 28, 2023. Two independent reviewers screened titles, abstracts, and full texts for eligibility and manually reviewed references.

Results: Of 7,738 studies were identified, 49 met the inclusion criteria. Of these, 45 (92%) were observational and 4 (8%) were interventional. Patient populations included cardiac surgery (26, 53%), non-cardiac major surgery (4, 8%), cardiac arrest (8, 16%), brain injury (7, 14%), respiratory failure and shock (3, 6%), and sepsis (3, 6%). Optimal MAP was reported in 24 (49%), lower limit of autoregulation in 23 (47%), and upper limit of autoregulation in 10 studies (20%). Thirty-four studies reported partial data loss due to software failures, anomalous data, insufficient natural MAP fluctuation, and workflow barriers. Available randomized controlled trials (RCT) identified challenges with maintaining patients within their target range. Studies explored the associations between personalized MAP targets and a wide range of neurological and non-neurological outcomes, with the most significant and consistent associations identified for acute kidney injury and major morbidity and mortality. Ten studies investigated demographic predictors identifying only few predictors of personalized targets.

Conclusion: Preliminary investigations suggest considerable variability in personalized MAP targets, which may explain differences in clinical outcomes among critically ill populations. Key gaps remain, including a lack of observational studies in critically ill subpopulations other than cardiac surgery and well-designed RCTs. Resolving identified feasibility barriers might be crucial to successfully carrying out future studies.

Keywords: Arterial pressure; Autoregulation; Big data; Cerebral vascular circulation; Near-infrared spectroscopy; Precision medicine; Transcranial Doppler ultrasonography.

Fig. 1

PRISMA Flow chart

Fig. 2

MAPopt values reported across studies. Note that some studies reported multiple values corresponding to different participant sub-groups/MAPopt calculation methods used. Secondary aggregation of these datapoints to one single value are oftentimes not possible or appropriate, hence they are listed as reported in the study. D = Day, Cox = Cerebral Oximetry Index, Mx = Mean Blood Velocity Index, HVx = Haemoglobin Volume Reactivity Index, CFVx = Cerebral Flow Velocity Index, CPC = Cerebral Performance Category, TBI = Traumatic Brain Injury, AIS = Acute Ischemic Stroke, ICH = Intracranial Hemorrage, aSAH = Aneurysmal Subarachnoid Hemorrhage, TCD = Transcranial Doppler Ultrasound, NIRS = Near Infared Spectroscopy, UT-NIRS = Ultra-sound tagged Near Infared Spectoscopy

Fig. 3

The magnitude of target MAP range reported across studies. POD = post-operative day. For which day 1 is the day patients complete their surgery

Fig. 4

Diagram overview of factors associated with autoregulation-guided MAP targets. *MAC positively correlates with ULA but not LLA. Low PaCo2 and high MAP treatment associates with a larger MAP area below LLA