Background: Pain perception ratings in irritable bowel syndrome (IBS) patients suggest that they present either hypoalgesia or hyperalgesia. However, little is known about the physiologic responses these patients present to a somatic painful stimulus.
Goals: The main goal of this project was to study autonomic nervous system responses and the cardiac response to experimental pain in IBS patients.
Study: This was addressed by exposing 27 women, 14 IBS, and 13 healthy controls (HCs), to a cold water (7 degrees C) immersion test of the forefoot for 2 minutes. Pain perception, galvanic skin responses (GSR), and heart rate (HR) were monitored during and after the immersion.
Results: For comparable pain perception, a significant group difference (P<0.02) in the cardiac response was observed during the immersion where the peak rise in HR was much higher for HCs, reaching 22%, whereas it only reached 8% for IBS patients. Moreover, HR variability analysis demonstrated that IBS and HCs had opposite autonomic cardiac reactivity to pain, where IBS had increased parasympathetic/decreased sympathetic reactivity.
Conclusions: For comparable pain perception, IBS subject demonstrated different autonomic nervous system response to pain, which supports the view of autonomic dysregulation in IBS.