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Rapid induction analgesia for the alleviation of procedural pain during burn care

Wright, Bernadette R (1996) Rapid induction analgesia for the alleviation of procedural pain during burn care. PhD thesis, Murdoch University.

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Burn patients often have to endure intense pain during their regular dressing changes. Burn care procedures typically include washing wound sites, debridement, topical application of medication and dressing change - all requiring necessary stimulation of highly sensitized nociceptors on the periphery of burn injury areas. Complete analgesia through administration of narcotic analgesics is rarely attained; thus, psychological therapy for pain management may have a role as an adjunct to opioid therapy. The primary objective of this study was to alleviate procedural pain (in terms of its sensory and affective components) by using Rapid Induction Analgesia, or RIA (Barber, 1977) - a technique for hypnotic analgesia. An independent groups and within-subjects design was used in three separate studies to investigate the effect of RIA on pain perception. All but Study (3) were conducted in the laboratory on healthy volunteer subjects.

The purpose of Study (1) was to estimate the extent to which RIA can increase pain threshold and pain tolerance on mild pain, experimentally induced by capsaicin - the active compound in hot peppers. Upon application of this substance on 30 volunteer subjects, capsaicin induced hyperalgesia and increased nociceptor sensitivity to otherwise non-painful stimulation, thus simulating actual burn pain. Primary hyperalgesia at the locus of injury and secondary hyperalgesia around the wound periphery are common physiological responses to burn injuries. A common objective of Study (1) and Study (2) was also to test the differential effects of RIA on primary and secondary hyperalgesia, which are typical physiological characteristics of nociceptor reaction to noxious stimulation. Cutaneous nociceptive fibres are sensitized to low levels of stimulation which, under normal conditions, would not cause pain. This enhanced sensitivity results in a reduction in pain threshold and tolerance. Thus, for Study (1) and Study (2) it was predicted that RIA would alter the sensory and affective responses to pain induced by mechanical stimulation produced by a pressure algometer. Study (1) also set out to evaluate RIA with post-induction suggestions for analgesia. In all three studies, RIA was made available only to half the subject sample. In addition to comparing differences in pain perception between groups, each subject's pre-treatment pain measures were also compared with their post-treatment ratings of pain. Dependent variables were measured with separate visual analogue scales (VAS) for the sensory and affective components of pain and a VAS for relaxation measures. Analyses of Study (1) revealed that relaxation levels reported by experimental subjects increased but significant increases in pain threshold and tolerance were not detected. Furthermore, alterations in pain perception in terms of its sensory and affective components were relatively modest.

In Study (2) capsaicin was topically applied on the forearm of 27 healthy volunteer subjects to induce pain, but the protocol for hypnotic induction was altered in an attempt to enhance treatment efficacy. Experimental subjects were not aroused from the hypnotic state prior to pain assessment. An expected effect of this shorter time interval was a more enhanced capsaicin inflammatory effect. Dependent variables measured were identical to those of Study (1). It was again predicted that the extent of reported pain reduction would differ between areas of primary and secondary hyperalgesia for subjects on whom hypnotic analgesia had been induced. Data analyses of Study (2) revealed that RIA had an impact on pain perception when the suggestions for analgesia were maintained during pain assessment. Furthermore, RIA-treated subjects experienced a significant increase in their relaxation level relative to their pre-induction relaxation scores. A significant difference in relaxation scores was not detected for control subjects. RIA did not alter the intensity of the pressure stimulus required to achieve threshold or tolerance levels of pain. However, at pain tolerance limits, RIA significantly influenced the sensory and affective perception of pain in both primary and secondary hyperalgesic areas, particularly the affective ratings. Moreover, pain perception in areas of secondary hyperalgesia was consistently lower than at the primary hyperalgesic site.

Study (3) investigated the effect of RIA on resting and procedural pain perception, anticipatory anxiety, relaxation levels, and medication consumption of 30 in-patients in the Burn Unit at a major teaching hospital. Dependent variables were measured over 4 burn care sessions. Hypnotic induction was conducted twice on experimental patients. The perception of patients' pain by staff was also investigated to determine the extent to which patients' self-reports differed from staff perception, in light of RIA. RIA significantly reduced the sensory and affective component of pain, and increased relaxation state during burn care. RIA also resulted in a progressive and significant reduction of anticipatory anxiety and in affective pain perception at rest. Of interest, no significant relationship was found between aptitude for absorption and treatment efficacy. The promising outcome of this study confirms RIA as a viable technique for burn pain control during burn care.

Item Type: Thesis (PhD)
Murdoch Affiliation: School of Social Sciences
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Drummond, Peter
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