Examination of cardiovascular and peripheral autonomic function in the ICU: a pilot study

Critical illness may affect the autonomic nervous system. Decreased cardiovascular autonomic function measured by heart rate variability (HRV) has been reported in critically ill patients but limited information exists about other autonomic functions. The cold face test (CFT) and skin wrinkle test (SWT) have never been investigated in critically ill patients. Feasibility and safety of the CFT and SWT were investigated in critically ill patients. Exclusion criteria: polyneuropathy, autonomic neuropathy, admission after stroke, spinal cord injury or cardiac arrest. For the CFT, a cold pack was applied to the forehead to measure the maximal increase in RR interval. The simulated SWT was used and wrinkling was assessed on a five-point scale. HRV was investigated using power spectral analysis of continuous 5-min ECG recordings. Twelve critically ill patients were included (mean age 54). No adverse effects for the CFT and SWT were noted. The CFT could be performed in 10 patients and showed an abnormal response in 9. The SWT could be performed in 11 patients; results were abnormal in 6. HRV analysis showed decreased HRV in all patients. CFT and HRV responses were correlated with each other, no correlation was found between SWT and CFT or HRV results. The CFT and SWT are feasible and safe in critically ill patients. Cardiovascular dysfunction may be more prevalent in critical illness than peripheral sympathetic dysfunction. Influence of confounders and further validation of these tests needs to be investigated.