Heart rate variability (HRV) may provide an estimation of the autonomous nervous system
(ANS) integrity in critically ill patients. Disturbances of cerebral autoregulation
(CAR) may share common pathways of ANS dysfunction.
To explore whether changes in HRV and CAR index correlate in critically ill septic
Prospectively collected data on septic adult (> 18 years) patients admitted into a
mixed Intensive Care between February 2016 and August 2019 with a recorded transcranial
doppler CAR assessment. CAR was assessed calculating the Pearson's correlation coefficient
(i.e. mean flow index, Mxa) between the left middle cerebral artery flow velocity
(FV), insonated with a 2-MHz probe, and invasive blood pressure (BP) signal, both
recorded simultaneously through a Doppler Box (DWL, Germany). MATLAB software was
used for CAR assessment using a validated script; a Mxa >0.3 was considered as impaired
CAR. HRV was assessed during the same time period using a specific software (Kubios
HRV 3.2.0) and analyzed in both time-domain and frequency domain methods. Correlation between HRV-derived variables and Mxa were assessed using the Spearman's
A total of 141 septic patients was studied; median Mxa was 0.35 [0.13–0.60], with
77 (54.6 %) patients having an impaired CAR. Mxa had a significant although weak correlation
with HRV time domain (SDNN, r = 0.17, p = 0.04; RMSSD, r = 0.18, p = 0.03; NN50, r = 0.23, p = 0.006; pNN50, r = 0.23, p = 0.007), frequency domain (FFT-HF, r = 0.21; p = 0.01; AR-HF, r = 0.19; p = 0.02), and non-linear domain (SD1, r = 0.18, p = 0.03) parameters. Impaired CAR patients had also all of these HRV-derived parameters
higher than those with intact CAR.
In this exploratory study, a potential association of ANS dysfunction and impaired
CAR during sepsis was observed.