The role of negative expectations on the development of secondary hyperalgesia in healthy volunteers: A pilot study

Details

Supervisors

Mouraux, André ; van den Broeke, Emanuel

Faculty

Faculté des sciences de la motricité

Degree label

Master [120] en sciences de la motricité, orientation générale

Abstract

It is known that during a surgery, psychological factors such as fear, pain catastrophizing or state anxiety are associated with increased risk for developing post-operative chronic pain. During surgery, cutaneous tissue lesions can lead to an increase in pain sensitivity in the area of the damage (“primary hyperalgesia”) and in the surrounding uninjured skin (“secondary hyperalgesia”). It is assumed that secondary hyperalgesia refers to central sensitization, whereas primary hyperalgesia is the result of peripheral and central sensitization, the latter could be the source of chronic pain. In the present pilot study performed on healthy volunteers, we assess, if negative expectations about the painfulness of HFS will increase the magnitude of secondary hyperalgesia. The first aim of this pilot study was to determine the feasibility. The second aim was to generate data that can be used to calculate the effect size and importantly, to determine the sample size. In a between–subject design, healthy volunteers were randomly allocated to either a nocebo condition or a control condition. Both conditions received high-frequency burstlike electrical stimulation (HFS) to induce secondary hyperalgesia at the ventral forearm. Before HFS participants received a written instruction about HFS, which was extended in the nocebo group by the statement that HFS would be painful. The primary outcome was the length of secondary hyperalgesia. All participants could endure HFS and, thus, the protocol seems feasible. We found that the mean length of proximal-distal axe of the area of secondary hyperalgesia on the volar forearm was 97.25 ± 29.61 mm (mean ± sd) for the control group, and 83.38 ± 41.69 mm for the nocebo group. The effect of the written suggestion that HFS will be painful leaded to an effect size of 0.383 regarding the length of secondary hyperalgesia. The number of participants to be recruited would be N>89 per group. This result has prompt us to revise the protocol to achieve a stronger and better-controlled nocebo effect.