Delayed Autonomic Regulation during Visceral Placebo Analgesia in Patients with Irritable Bowel Syndrome

Large placebo effect is common in the treatment of irritable bowel syndrome (IBS). Autonomic dysregulation, which can be measured by heart rate variability (HRV), may play a role in the IBS pathogenesis. We aimed to compare the HRV changes during visceral placebo analgesia between healthy controls and IBS. Thirteen IBS patients and 12 sex-/age- matched controls received twice rectal balloon distension to induce visceral pain. The placebo treatment consisted of a standardized oral statement of the effectiveness of a newly-developed intravenous drug (saline actually) to relieve the visceral pain. HRV parameters, including the low frequency (LF), high frequency (HF), and ratio of LF to HF (LF/ HF), were recorded at the baseline, saline and placebo sessions. Both controls and IBS patients achieved comparable placebo effects showing similar VAS reduction after the placebo treatment. Visceral pain induced an increased LF and LF/HF (enhanced sympathetic activity and sympathovagal balance) and decreased HF (diminished vagal activity) in both groups, in which HRV changes were reversed by placebo treatment. The HRV changes upon placebo treatment were promptly observed at the first rectal balloon distension in healthy volunteers, but not until the second distension in the IBS patients. IBS patients and healthy controls can achieve comparable placebo analgesia. Both groups have similar HRV responses during visceral stimulation and placebo treatment, but with delayed HRV changes in IBS patients. Autonomic control may be impaired during visceral placebo analgesia in IBS patients.

並列關鍵字

heart rate variability ； irritable bowel syndrome ； placebo ； visceral pain

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