title: Demarcation of secondary hyperalgesia zones: Punctate stimulation pressure matters.
abstract: BACKGROUND
  Secondary hyperalgesia is increased sensitivity in normal tissue near an injury, and it is a measure of central sensitization reflecting injury-related effects on the CNS. Secondary hyperalgesia areas (SHAs), usually assessed by polyamide monofilaments, are important outcomes in studies of analgesic drug effects in humans. However, since the methods applied in demarcating the secondary hyperalgesia zone seem inconsistent across studies, we examined the effect of a standardized approach upon the measurement of SHA following a first degree burn injury (BI).
  
  
  METHODS
  The study was a two-observer, test-retest study with the two sessions separated by 6wk. An observer-blinded design adjusted to examine day-to-day and observer-to-observer variability in SHA was used. In 23 healthy volunteers (12 females/11 males) a BI was induced by a contact thermode (47.0°C, 420s, 2.5×5.0cm(2)). The SHA, demarcated by polyamide monofilaments (bending force: 0.2, 69 and 2569mN) and a "weighted-pin" stimulator (512mN), were assessed 45 to 75min after each BI.
  
  
  RESULTS
  A random effect, linear mixed model demonstrated a logarithmic correlation between elicited skin pressures (mN/mm(2)) and the SHAs (P<0.0001). No day-to-day or observer-to-observer differences in SHAs were observed. Intraclass correlation coefficients, in the range of 0.51 to 0.84, indicated a moderate to almost perfect reliability between observers.
  
  
  METHODS
  No standardized approach in SHA-assessment has hitherto been presented.
  
  
  CONCLUSIONS
  This is the first study to demonstrate that demarcation of secondary hyperalgesia zones depends on the developed pressure of the punctate stimulator used.
authors: Neuroscience Center, Rigshospitalet, Copenhagen University Hospitals, Multidisciplinary Pain Center 7612, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark. Electronic address: thomaskringsted@hotmail.com.
authors: Thomas K
authors: TK
authors: Ringsted
authors: Neuroscience Center, Rigshospitalet, Copenhagen University Hospitals, Multidisciplinary Pain Center 7612, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark.
authors: Casper
authors: C
authors: Enghuus
authors: Research Unit, Department of Palliative Care, Bispebjerg Hospital, Copenhagen University Hospitals, Copenhagen, Denmark.
authors: Morten A
authors: MA
authors: Petersen
authors: Neuroscience Center, Rigshospitalet, Copenhagen University Hospitals, Multidisciplinary Pain Center 7612, Rigshospitalet, Blegdamsvej 9, 2100 Copenhagen, Denmark.
authors: Mads U
authors: MU
authors: Werner
mesh_terms: D002056:Burns / Q000150:complications / Q000503:physiopathology; D005260:Female; D006358:Hot Temperature; D006801:Humans; D006930:Hyperalgesia / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D010812:Physical Stimulation / Q000379:methods*; D011312:Pressure; D015203:Reproducibility of Results; D016037:Single-Blind Method; D055815:Young Adult
keywords: Burn injury; Mechanical hyperalgesia; Monofilaments; Punctate hyperalgesia; Secondary hyperalgesia; Sensitization