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BACKGROUND: Bradycardia and dysautonomia observed during SARS-Cov2 infection suggests involvement of the autonomic nervous system (ANS). Limited data exists on ANS dysregulation and its association with outcomes in patients with acute respiratory distress syndrome (ARDS) related to COVID-19 (C-ARDS) or other etiologies (NC-ARDS). OBJECTIVES: We aimed to explore sympathovagal balance, assessed by heart rate variability (HRV), and its clinical prognostic value in C-ARDS compared with NC-ARDS. METHODS: A single-center, prospective case-control study was conducted. Consecutive patients meeting ARDS criteria between 2020 and 2022 were included. HRV was assessed using 1-hour electrographic tracing during a stable, daytime period. RESULTS: Twenty-four patients with C-ARDS and 19 with NC-ARDS were included. Age, sex and ARDS severity were similar between groups. The median heart rate was markedly lower in the C-ARDS group than in the NC-ARDS group (60 [53-72] versus 101 [91-112] bpm, p<.001). Most of HRV parameters were significantly increased in patients with C-ARDS. HRV correlated with heart rate only in patients with C-ARDS. A positive correlation was found between the low-to high-frequency ratio (LF/HF) and length of intensive care unit stay (r = 0.576, p<.001). CONCLUSION: This study confirmed that C-ARDS was associated with marked bradycardia and severe ANS impairment, suggesting a sympathovagal imbalance with vagal overtone. Poor outcomes appeared to be more related to sympathetic rather than parasympathetic hyperactivation.
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INTRODUCTION: Low cardiac output and hypovolemia are candidate macrocirculatory mechanisms explanatory of de novo anuria in intensive care unit (ICU) patients undergoing continuous renal replacement therapy (CRRT). We aimed to determine the hemodynamic parameters and CRRT settings associated with the longitudinal course of UO during CRRT. METHODS: This is an ancillary analysis of the PRELOAD CRRT observational, single-center study (NCT03139123). Enrolled adult patients had severe acute kidney injury treated with CRRT for less than 24 h and were monitored with a calibrated continuous cardiac output monitoring device. Hemodynamics (including stroke volume index [SVI] and preload-dependence, identified by continuous cardiac index variation during postural maneuvers), net ultrafiltration (UFNET), and UO were reported 4-hourly, over 7 days. Two study groups were defined at inclusion: non-anuric participants if the cumulative 24 h UO at inclusion was ≥0.05 mL kg-1 h-1, and anuric otherwise. Quantitative data were reported by its median [interquartile range]. RESULTS: Forty-two patients (age 68 [58-76] years) were enrolled. At inclusion, 32 patients (76%) were not anuric. During follow-up, UO decreased significantly in non-anuric patients, with 25/32 (78%) progressing to anuria within 19 [10-50] hours. Mean arterial pressure (MAP) and UFNET did not significantly differ between study groups during follow-up, while SVI and preload-dependence were significantly associated with the interaction of study group and time since inclusion. Higher UFNET flow rates were significantly associated with higher systemic vascular resistances and lower cardiac output during follow-up. Multivariate analyses showed that (1) lower UO was significantly associated with lower SVI, lower MAP, and preload-independence; and (2) higher UFNET was significantly associated with lower UO. CONCLUSIONS: In ICU patients treated with CRRT, those without anuria showed a rapid loss of diuresis after CRRT initiation. Hemodynamic indicators of renal perfusion and effective volemia were the principal determinants of UO during follow-up, in relation with the hemodynamic impact of UFNET setting.
