title: Heart rate variability parameters do not correlate with pain intensity in healthy volunteers.
abstract: OBJECTIVE
  When patients cannot indicate pain, physiological parameters may be useful. We tested whether heart rate variability (HRV) parameters, as reflection of sympathetic and vagal tone, can be used to quantify pain intensity.
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  A standardized heat stimulus was applied to the forearm in 75 healthy volunteers during three study periods of 2 minutes.
  
  
  METHODS
  Before and after each application, pain intensity was measured by a visual analog scale (VAS) and inter beat interval (IBI) was recorded. Standard deviation of normal to normal beat intervals (SDNN) of the IBI, the power of the low (LF, 0.07-0.14 Hz) and high frequency (HF, 0.15-0.50 Hz) band, and LF/HF ratio were calculated. Log transformation resulted in normal distribution. Correlation between HRV parameters and pain intensity was assessed by Pearson's correlation coefficient.
  
  
  RESULTS
  Data from 73 volunteers (44 women) could be analyzed. The mean age was 30 ± 11 years. Compared with baseline, during all heat periods, pain intensity measured by VAS increased from 2 ± 3 mm, 3 ± 5 mm, and 2 ± 4 mm, to 40 ± 20 mm, 42 ± 21 mm, and 44 ± 22 mm, respectively. Log transformed SDNN (lnSDNN) and LF (lnLF) decreased; lnSDNN from 4.0 ± 0.4 to 3.9 ± 0.5, P = 0.002; 4.0 ± 0.4 to 3.9 ± 0.5, P = 0.016; and 4.1 ± 0.4 to 3.9 ± 0.4, P = 0.004, respectively; lnLF from 6.3 ± 1.0 to 6.1 ± 1.2, P = 0.001; 6.4 ± 1.0 to 6.2 ± 1.1, P = 0.019; and 6.5 ± 1.0 to 6.2 ± 1.1, P = 0.020, respectively. No correlation of any HRV parameter with VAS score was found.
  
  
  CONCLUSIONS
  HRV parameters may detect responses to heat pain, but are not suitable to assess pain intensity.
authors: Department of Internal Medicine, University of Groningen, University Medical Centre Groningen, Groningen, The Netherlands.
authors: Jan J
authors: JJ
authors: Meeuse
authors: Marco S P
authors: MS
authors: Löwik
authors: Sabine A M
authors: SA
authors: Löwik
authors: Eline
authors: E
authors: Aarden
authors: Arie M
authors: AM
authors: van Roon
authors: Reinold O B
authors: RO
authors: Gans
authors: Marten
authors: M
authors: van Wijhe
authors: Joop D
authors: JD
authors: Lefrandt
authors: Anna K L
authors: AK
authors: Reyners
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001341:Autonomic Nervous System / Q000503:physiopathology; D023381:Endpoint Determination; D005260:Female; D064368:Healthy Volunteers; D006339:Heart Rate / Q000502:physiology*; D006358:Hot Temperature; D006801:Humans; D008297:Male; D010146:Pain / Q000503:physiopathology*; D010147:Pain Measurement; D015203:Reproducibility of Results; D018401:Sample Size
keywords: Autonomic Nervous System; Experimental Pain; Heart Rate; Heat Pain; Pain Measurement