The Effect of Data Length on the Assessment of Dynamic Cerebral Autoregulation with Transfer Function Analysis in Neurological ICU Patients

Abstract

Background Cerebral autoregulation plays an important role in safeguarding adequate cerebral perfusion and reducing the risk of secondary brain injury, which is highly important for patients in the neurological intensive care unit (neuro-ICU). Although the consensus white paper suggests that a minimum of 5 min of data are needed for assessing dynamic cerebral autoregulation with transfer function analysis (TFA), it remains unknown if the length of these data is valid for patients in the neuro-ICU, of whom are notably different than the general populations. We aimed to investigate the effect of data length using transcranial Doppler ultrasound combined with invasive blood pressure measurement for the assessment of dynamic cerebral autoregulation in patients in the neuro-ICU. Methods Twenty patients with various clinical conditions (severe acute encephalitis, ischemic stroke, subarachnoid hemorrhage, brain injury, cerebrovascular intervention operation, cerebral hemorrhage, intracranial space-occupying lesion, and toxic encephalopathy) were recruited for this study. Continuous invasive blood pressure, with a pressure catheter placed at the radial artery, and bilateral continuous cerebral blood flow velocity with transcranial Doppler ultrasound were simultaneously recorded for a length of 10 min for each patient. TFA was applied to derive phase shift, gain, and coherence function at all frequency bands from the first 2, 3, 4, 5, 6, 7, 8, 9, and 10 min of the 10-min recordings in each patient on both hemispheres. The variability in the autoregulatory parameters in each hemisphere was investigated by repeated measures analysis of variance. Results Forty-one recordings (82 hemispheres) were included in the study. According to the critical values of coherence provided by the Cerebral Autoregulation Research Network white paper, acceptable rates for the data were 100% with a length ≥ 7 min. The final analysis included 68 hemispheres. The effects of data length on trends in phase shift in the very low frequency (VLF) band ( F 1.801,120.669 = 6.321, P = 0.003), in the LF band ( F 1.274,85.343 = 4.290, P = 0.032), and in the HF band ( F 1.391,93.189 = 3.868, P = 0.039) were significant for 3–7 min, for 4–7 min, and for 5–8 min, respectively. Effects were also significant on the gain in the VLF band ( F 1.927,129.134 = 3.215, P = 0.045) for 2–8 min and on the coherence function in all frequency bands (VLF F 2.846,190.671 = 90.247, P < 0.001, LF F 2.515,168.492 = 55.770, P < 0.001, HF F 2.411, 161.542 =...

Association of Blood Pressure Variability With Death and Discharge Destination Among Critically Ill Patients With and Without Stroke

“…As techniques for monitoring cerebral autoregulation improve, 50 studies should examine whether damage to autonomic cerebral control centers and stroke severity are associated with worse cerebral autoregulation. Prospective studies with a timeline of clinician-driven changes, details of stroke severity and location, and outcomes are needed to help to elucidate whether the association seen between high BPV and poor outcomes in critically ill patients with stroke is truly a modifiable risk factor or merely a biomarker of severe strokes and systemic critical illness.…”

Cerebral Autoregulation Assessment Using the Near Infrared Spectroscopy ‘NIRS-Only’ High Frequency Methodology in Critically Ill Patients: A Prospective Cross-Sectional Study

“…In a sepsis model in eleven healthy subjects, the baseline LF-phase shift values of 16.2° (q1–q3 3.0–52.6) decreased to 3.9° (q1–q3 2.0–8.8) after endotoxin infusion. Zhang et al obtained the CA status in neurological ICU patients using ABP and TCD recordings and found an average LF-phase shift of about 30° in twenty patients [ 12 ]. This might suggest that in our critically ill and sedated/comatose population with high disease severity scores, the CA status was somehow impaired in general.…”

“…The Cerebrovascular Research Network (CARNet) recommends a minimum duration of five minutes for reliable CA estimations with TCD recordings [ 8 ]. Zhang et al showed that after seven minutes of spontaneous ABP oscillations, the TCD-based CA-parameters became stable in an intensive care unit (ICU) population [ 12 ].…”

Impaired dynamic cerebral autoregulation in young adults with mild depression

“…The appropriate finger cuff was placed on the middle phalanx of the left middle finger. According to our previous study of data length (Zhang et al, 2021), CBFV and BP were recorded for 8 min. The participants were instructed to breathe normally when recording to obtain a stable end-tidal CO 2 level.…”