Relationships between Irritable Bowel Syndrome Pain, Skin Temperature Indices of Autonomic Dysregulation, and Sensitivity to Thermal Cutaneous Stimulation.

Fong Wong,Andre P Mauderli,Charles J Vierck,Siegfried Schmidt,Christopher D King,Anthony C Rodrigues,Joseph L Riley

doi:10.1155/2010/949027

Abstract

This study evaluated relationships between irritable bowel syndrome (IBS) pain, sympathetic dysregulation, and thermal pain sensitivity. Eight female patients with diarrhea-predominant IBS and ten healthy female controls were tested for sensitivity to thermal stimulation of the left palm. A new method of response-dependent thermal stimulation was used to maintain pain intensity at a predetermined level (35%) by adjusting thermal stimulus intensity as a function of pain ratings. Clinical pain levels were assessed prior to each testing session. Skin temperatures were recorded before and after pain sensitivity testing. The temperature of palmar skin dropped (1.5°C) when the corresponding location on the opposite hand of control subjects was subjected to prolonged thermal stimulation, but this response was absent for IBS pain patients. The patients also required significantly lower stimulus temperatures than controls to maintain a 35% pain rating. Baseline skin temperatures of patients were significantly correlated with thermode temperatures required to maintain 35% pain ratings. IBS pain intensity was not significantly correlated with skin temperature or pain sensitivity. The method of response-dependent stimulation revealed thermal hyperalgesia and increased sympathetic tone for chronic pain patients, relative to controls. Similarly, a significant correlation between resting skin temperatures and thermal pain sensitivity for IBS but not control subjects indicates that tonic sympathetic activation and a thermal hyperalgesia were generated by the chronic presence of visceral pain. However, lack of a significant relationship between sympathetic tone and ratings of IBS pain casts doubt on propositions that the magnitude of IBS pain is determined by psychological stress.

Highlights

Irritable bowel syndrome (IBS) is a functional pain disorder with no known etiology but an association with psychological stress [1,2,3]
The present study found that abnormal autonomic responses of IBS patients are revealed by painful somatic stimulation of a small area of the skin, as long as the stimulus is of sufficient duration
A repeated measures design was utilized for evaluation of clinical pain ratings, skin temperatures, and psychophysical ratings of thermal pain sensitivity across 4 series within 3 separate tests of a relatively homogeneous sample of IBS patients

Summary

Introduction

Irritable bowel syndrome (IBS) is a functional pain disorder with no known etiology but an association with psychological stress [1,2,3]. Because autonomic output systems of central stress circuits control essential functions of the gut [4,5,6], stress has been suspect as a cause of IBS [1, 5, 7]. Numerous factors can change relationships between diagnoses of IBS and levels of autonomic activation including age, duration of chronic pain, gender, profiles of gut disturbance (e.g., abdominal pain with constipation or diarrhea), magnitude of IBS pain, skin temperature, and the method of autonomic stimulation. Relationships between the presence of pain and autonomic dysfunction in IBS patients have been shown in models that used blood pressure, heart rate variability, and heart rate as indicators [10, 28, 29]. We hypothesize that abnormal autonomic responsivity (skin thermoregulation) can be revealed by prolonged focal thermocutaneous stimulation. Several minutes long episodes of thermocutaneous pain were induced with a new stimulation method that makes the procedure safe and tolerable for the subjects [30]

Methods

Results

Conclusion