title: Autonomic dysfunction in ICU-acquired weakness: a prospective observational pilot study.
abstract: OBJECTIVE
  Intensive care unit-acquired weakness (ICU-AW) is a frequent complication of critical illness. It is unknown if patients with ICU-AW also have autonomic dysfunction, another frequent neurological complication of critical illness. We hypothesized that patients who develop ICU-AW also develop autonomic dysfunction. Furthermore, we hypothesized that patients with ICU-AW are more prone to develop autonomic dysfunction compared to patients without ICU-AW.
  
  
  METHODS
  This was an observational cohort study of patients newly admitted to the ICU. Autonomic dysfunction was measured daily using heart rate variability (HRV) to a maximum of 15 days after admission. ICU-AW was diagnosed using the Medical Research Council score. Abnormal HRV was defined using age-matched reference values. The association between ICU-AW and HRV was analyzed using linear mixed effects models.
  
  
  RESULTS
  We included 83 patients, 15 (18 %) of whom were diagnosed with ICU-AW. Of 279 HRV measurements, 204 could be analyzed. Abnormal HRV was found in all critically ill patients irrespective of the presence of ICU-AW (ICU-AW 100 % (IQR 71-100) vs. no ICU-AW 100 % (IQR 40-100); p = 0.40). Mechanical ventilation, sedation, norepinephrine, heart rate, and HRV artifacts were identified as confounders for HRV. ICU-AW was not associated with HRV.
  
  
  CONCLUSIONS
  Abnormal HRV is frequent in critically ill patients, both with and without ICU-AW. It is unlikely that patients with ICU-AW are more prone to develop abnormal HRV. However, we found that abnormal HRV may not be an accurate indicator of autonomic dysfunction because of confounders.
authors.affiliation: Department of Intensive Care Medicine, Academic Medical Center, University of Amsterdam, Meibergdreef 9, Room G3-228, P.O. Box 22700, 1105 AZ, Amsterdam, The Netherlands. L.Wieske@amc.uva.nl
authors.forename: L
authors.initials: L
authors.lastname: Wieske
authors.forename: D R P P
authors.initials: DR
authors.lastname: Chan Pin Yin
authors.forename: C
authors.initials: C
authors.lastname: Verhamme
authors.forename: M J
authors.initials: MJ
authors.lastname: Schultz
authors.forename: I N
authors.initials: IN
authors.lastname: van Schaik
authors.forename: J
authors.initials: J
authors.lastname: Horn
mesh_terms: D001341:Autonomic Nervous System / Q000503:physiopathology*; D015331:Cohort Studies; D016638:Critical Illness; D005260:Female; D006339:Heart Rate; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000503:physiopathology*; D009422:Nervous System Diseases / Q000503:physiopathology*; D010865:Pilot Projects; D011446:Prospective Studies