The Relationship between Heart Rate Variability and Illness Severity

ABSTRACT

BACKGROUND: In severity of illness index, there is an acute physiologic and chronic health evaluation (APACHE) scoring system which was modified to APACHE III in 1990. Heart rate variability (HRV) studies for the intensive care unit (ICU) patients provides an indirect but noninvasive probe of autonomic cardiovascular control. Therefore, we intended to find out the relationship between the APACHE III score and the HRV variables in ICU patients. METHODS: We examined 22 patients in medical ICU of one college hospital from April to May of 2003, excluding patients with cardiac disorders, neurologic disorders or surgical diseases. We also examined 22 patients in general wards of family medicine. We checked the APACHE III during the 24 hours of admission, and examined the HRV on the second day of admission and then the total power (TP), normalized low frequency (LFnorm), low frequency/ high frequency ratio (LF/HF ratio) and approximate entropy (ApEn). RESULTS: The average of TP (msec2) were 538.9+/-896.7 in ICU patients and 1605.3+/-3091.8 in patients of general ward. The average APACHE III score was 35.9+/-18.5 and by Pearson correlation analysis, the correlation coefficient between the APACHE III score and the log (TP) was -0.58 (P=0.005). CONCLUSION: We found that the medical ICU patients had more decreased autonomic function than the patients of general ward, and there was a negative correlation with the APACHE III score and the disease severity.