A method for overcoming the ceiling effect of bounded pain scales

Thiopental Does Not Produce Hyperalgesia: A Laboratory Study Using Two Human Experimental Pain Models

Objective

Past investigations assessing the effects of thiopental on pain are conflicting. Although several studies demonstrate hyperalgesia as a result of barbiturate administration, others show analgesia. Our objective was to assess the effects of an infusion of the GABAA agonist thiopental, compared with placebo, in healthy participants on two subjective experimental pain paradigms: noxious electrical stimulation and intradermal capsaicin.

Methods

For electrical stimulation, the milliamps required to achieve pain threshold and tolerance were recorded, and the percent change from baseline was determined for each infusion condition. In the intradermal capsaicin condition, the area of hyperalgesia was determined by von Frey technique pre- and postinfusion, and the percent change in the area of hyperalgesia was calculated.

Results

Though thiopental infusion resulted in an increase in the electrical stimulation current required to elicit pain threshold or reach pain tolerance when compared with baseline, this finding was not statistically significant. In the intradermal capsaicin condition, there was a statistically significant difference in overall pre- and postinfusion pain interpretation, as measured by the McGill Pain Questionnaire (P < 0.05), but there was no significant difference in area of hyperalgesia.

Conclusions

In this human study of thiopental’s effects on two experimental pain models, our results show that thiopental does not induce hyperalgesia.

Moving beyond the limitations of the visual analog scale for measuring pain: novel use of the general labeled magnitude scale in a clinical setting

OBJECTIVE

Quantifying pain intensity is challenging, particularly for patients with chronic pain. The visual analog scale (VAS) is limited by ceiling effects that often leave patients with no ability to quantify worsening pain. The goal of this study was to determine whether the general Labeled Magnitude Scale (gLMS) can be feasibly used to measure pain clinically while overcoming limitations of the VAS.

DESIGN

Eighty patients (mean age, 53.7 yrs) scheduled for evaluation of a painful complaint were asked to rate their current pain using the gLMS and the VAS. The time necessary to administer the gLMS was recorded to determine feasibility. The difference in rating between the two scales (VAS and gLMS) was the main outcome measure.

RESULTS

After scaling and rounding off the gLMS scores for direct comparison, it was found that the gLMS scores were significantly lower than the corresponding VAS scores by a mean of 1.78 (P < 0.001). The mean time to administer the gLMS was 2.66 mins.

CONCLUSIONS

These results suggest that the gLMS has great potential and can be feasibly used to measure pain intensity clinically. The gLMS scores were consistently lower than the VAS scores, thus reducing the ceiling effect and allowing range at the high end of the scale for rating worsening pain.

Analgesic effects of ethanol are influenced by family history of alcoholism and neuroticism

BACKGROUND

Although personality factors and family history of substance abuse influence how individuals experience pain and respond to analgesics, the combined effects of those factors have not been extensively studied. The objective of this study was to consider the possible role of personality trait of neuroticism and family history of alcoholism on the experience of pain and their role in the analgesic response to an ethanol challenge.

METHODS

Forty-eight healthy subjects participated in this study; thirty-one had a positive family history of alcoholism (FHP), seventeen had a negative family history of alcoholism (FHN). They were also categorized based on their neuroticism (N) scores (low N = 28, and high N = 20). This was a double-blind, placebo-controlled, randomized, within-subject design study of intravenous administration of three doses of ethanol. The testing consisted of 3 separate test days scheduled at least 3 days apart. Test days included a placebo day (saline solution), low-exposure ethanol day (targeted breathalyzer = 0.040 g/dl), and high-exposure ethanol day (targeted breathalyzer = 0.100 g/dl). Noxious electrical stimulation and pain assessments were performed prior to start of infusion and at the 60-minute infusion mark.

RESULTS

The analgesic effect of ethanol was mediated by an interaction between the personality trait of neuroticism and family history. Individuals with family history of alcoholism and high N scores reported significantly more analgesia on low dose of ethanol than those with low N scores. There was no difference in the analgesic response to ethanol among FHNs with low and high N scores.

CONCLUSION

These findings support the conclusion that neuroticism and family history of alcoholism both influence the analgesic response of alcohol. Individuals with high N scores and FHP have the strongest response to ethanol analgesia particularly on the low exposure to alcohol.