Autonomic dysfunction in ICU-acquired weakness: a prospective observational pilot study
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- Wieske, L., Chan Pin Yin, D.R.P.P., Verhamme, C. et al. Intensive Care Med (2013) 39: 1610. doi:10.1007/s00134-013-2991-z
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.
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.
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.
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.