Intra-subject variability in pain scoring and the consequences for analgesia treatment.

Predicting the analgesic effect of pain medication is an important topic in chronic pain research, especially in the field of neuropathic pain. A recent finding of major interest was that the amount of pain relief produced by capsaicine patches could be predicted by the amount of variability of the pre-treatment spontaneous pain scores of the patients. Therefore, we want to further explore the predictability of pre-treatment pain variability on the probability to experience pain relief. To this end we will determine variability on experimentally induced heat and electrical pain stimuli to determine its predictive potential for opioid-induced analgesia (i.e. alfentanil). Furthermore, variability tests will be repeated after opioid administration to evaluate the effect of opioids on pain variability.



The aims of the study are:

1. To evaluate individual pain variability in the study groups;

2. To evaluate the predictive properties of pain variability on alfentanil analgesia;

3. To evaluate the effect of alfentanil on pain variability.

28-3-2014: Most important changes in the Vapaana protocol:
• Quantitative Sensory Testing (QST) and corneal confocal microscopy measurements were added to the protocol for fibromyalgia patients.
• A group of 40 obese patients (BMI > 35) was added to the patient groups in the protocol, and their measurements include QST as is done in the fibromyalgia group.
• Outcome measures are the QST data (as described by Rolke et al. 2006).

Healthy volunteers and patients with a high variability in pain scores have a high probability to experience pain relief from alfentanil opposed to volunteers and patients with a low variability in pain scores.

Measurements by the VAS or NRS for pain. To measure variability 10 scores will be taken. This will be done 2 times, under placebo and under alfentanil condition.

Analgetic drug (alfentanil = 100ng/ml) infusion. Subjects will score thermal and electrical pain before and during alfentanil and placebo infusion (crossover design). We will assess whether the variability in pain scores prior to infusion can predict the amount of analgesia by alfentanil.