Alison Bentley

Sensitivity of sleep stages to painful thermal stimuli

Many modalities of both acute and chronic pain have been shown to disrupt sleep. Any differences in the intensity of thermal noxious stimulus required to produce arousal from stage 2, slow‐wave sleep (SWS) and rapid eye movement (REM) sleep is unclear. An assessment of reactions of seven male (age 22 ± 2.9 years) and three female subjects (age 21.0 ± 1.0 years) to a range of gradually increasing temperatures was used both when awake and asleep. When awake, subjects assigned five different descriptors to the increasing heat stimulus. During the different stages of sleep, temperatures were increased over the same range as when awake until the subjects aroused from sleep. The possible fluctuations in pain perception due to a time‐of‐night effect were assessed in awake subjects over a 12‐h period from 19:00 to 07:00 hours. During sleep, arousals occurred at significantly higher temperatures during SWS (P < 0.01) and REM sleep (P < 0.05) than during stage 2 sleep. The temperatures causing arousals during SWS and REM sleep were not significantly different and were equivalent to temperatures causing pain tolerance when awake. No changes in pain perception due to time of night were observed. The results show that a higher intensity of thermal noxious stimulus is required to cause arousal from SWS and REM sleep when compared with stage 2 sleep. This would confirm the suspicion that REM sleep and SWS are relatively, and possibly equally, resistant to disruption by noxious stimuli.

Reduced quality of life when experiencing menstrual pain in women with primary dysmenorrhea

Primary dysmenorrhea is the most common gynecological condition among women of reproductive age. Although dysmenorrhea has been reported to affect the ability of women to carry out daily activities, the impact of primary dysmenorrheic pain specifically on quality of life (QoL), has yet to be elucidated. We investigated whether QoL varies between women with and without severe primary dysmenorrhea, and whether QoL is impaired only during menstruation or also during pain‐free phases of the menstrual cycle. Twelve women with severe primary dysmenorrhea and nine control women completed the quality of life enjoyment and satisfaction questionnaire (Q‐LES‐Q‐SF) during menstruation and during the late follicular phase. Women with dysmenorrhea had a significant reduction in Q‐LES‐Q‐SF scores (mean ± SD: 54 ± 18%, percentage of the total maximum possible score) when they were experiencing severe menstrual pain compared with their own pain‐free follicular phase (80 ± 14%, p < 0.0001) and compared with controls during menstruation (81 ± 10%, p < 0.0001). They also rated their overall life satisfaction and contentment as poorer during menstruation. Severe menstrual pain associated with primary dysmenorrhea, therefore, impacts health‐related of QoL.

Women with dysmenorrhea are hypersensitive to experimental deep muscle pain across the menstrual cycle.

UNLABELLED Primary dysmenorrhea is a common painful condition in women that recurs every month across the reproductive years. The recurrent nociceptive input into the central nervous system that occurs during menstruation each month in women with dysmenorrhea is hypothesized to lead to increased sensitivity to painful stimuli. We investigated whether women with primary dysmenorrhea are hyperalgesic to deep muscle pain induced by a cleanly nociceptive method of hypertonic saline injection. Pain stimulation was applied both within an area of referred menstrual pain (lower back) and at a remote site outside of referred menstrual pain (forearm) in 12 healthy women with severe dysmenorrhea and 9 healthy women without dysmenorrhea, at 3 phases of the menstrual cycle: menstruation and follicular and luteal phases. Women rated their pain severity on a 100-mm visual analog scale every 30 seconds after injection until the pain subsided. In both groups of women, menstrual cycle phase had no effect on the reported intensity and duration of muscle pain. However, women with dysmenorrhea had increased sensitivity to experimental muscle pain both at the site of referred pain and at a remote nonpainful site, as assessed by peak pain severity visual analog scale rating, area under the visual analog scale curve, and pain duration, compared to women without dysmenorrhea. These data show that women with severe primary dysmenorrhea, who experience monthly menstrual pain, are hyperalgesic to deep muscle pain compared to women without dysmenorrhea. PERSPECTIVE Our findings that dysmenorrheic women are hyperalgesic to a clinically relevant, deep muscle pain in areas within and outside of referred menstrual pain indicates lasting changes in pain sensitivity outside of the painful period during menstruation.

Can the sensory symptoms of restless legs syndrome be assessed using a qualitative pain questionnaire

ObjectivesThe sensations of restless legs syndrome (RLS) are described as paresthesias and dysesthesias, sensations which also occur in neuropathic pain. Whether validated pain assessment tools can be used to measure the quality and severity of RLS sensations has not been explored. MethodsPatients with RLS (n=25) completed the RLS severity scale of the International Restless Legs Syndrome Study Group, the McGill Pain Questionnaire (MPQ), and a Visual Analog Scale. Words chosen frequently were also compared with those describing different pain types. ResultsThe International Restless Legs Syndrome Study Group RLS severity scale score correlated significantly with the Pain Rating Index, and number of words chosen derived from the MPQ, but not with the visual analog scale estimate of pain intensity. The words chosen by patients with RLS showed no significant correlation with words chosen by patients with either neuropathic or nociceptive pain. DiscussionThe quality and severity of the sensation of RLS can be measured on the MPQ, and severity calculated from MPQ indices correlates significantly with a standard RLS severity measure. Thus the nonpainful sensations of RLS appear to be a subclinical form of pain.

Part 1. International Classification of Functioning, Disability and Health (ICF) Core Sets for persons with sleep disorders: Results of the consensus process integrating evidence from preparatory studies

BACKGROUND/OBJECTIVES The International Classification of Functioning, Disability and Health (ICF) provides a comprehensive and universally accepted framework to classify changes in functioning related to health conditions. Comprehensive and Brief Core Sets have been defined for various disorders but not for sleep disorders. Such a Core Set would greatly enhance the techniques available to describe the impact of sleep disorders on patients. The overarching purpose of this paper is to report on phase 1 of the international and World Health Organization (WHO) endorsed consensus process in identifying ICF Core Sets for sleep disorders. METHODS A formal decision-making and consensus process which integrated evidence gathered from preparatory studies was carried out. Relevant ICF categories were selected by a sample of international experts from different backgrounds using the nominal group technique. RESULTS Twenty-six experts from 22 countries and different professional backgrounds attended the consensus conference. Altogether 120 second- or third-level ICF categories were included in the Comprehensive ICF Core Set with the following ICF component split: 49 categories from body functions, 8 from body structures, 31 from activities and participation and 32 from environmental factors. The Brief ICF Core Set included a total of 15 second-level categories: 5 body functions (sleep, energy and drive, attention, consciousness, respiration functions); 3 body structures (brain, respiratory system, pharynx); 4 activities and participation (focusing attention, driving, handling stress and other psychological demands, carrying out daily routine); and 3 environmental factors (immediate family; health services, systems, and policies; and health professionals). CONCLUSION A formal consensus process integrating evidence and expert opinion led to the first version of the ICF Core Sets for persons with sleep disorders. Further validation of the Core Set is needed.

Perception of experimental pain is reduced after provoked waking from rapid eye movement sleep.

Patients with chronic pain often complain of pain when they wake at night, but the accuracy of their perception of the pain after waking at night is unknown. While cognitive functions are reduced for a short time after waking from sleep, a situation known as sleep inertia, it is unclear how sleep inertia may affect the perception of pain. We investigated the effects of sleep inertia on the perception of experimentally induced pain. Fourteen male volunteers were exposed to a randomized thermal heat stimulus of 43.1 °C ‘hot’ and 46.5 °C ‘hurting’ during provoked waking from Stage 2 sleep, slow wave sleep and rapid eye movement (REM) sleep. Subjects rated their pain on awakening on a Visual Analogue Scale at 30 s after awakening and each minute thereafter for 5 min. We found no change in pain perception over the 5‐min period irrespective of temperature used or sleep stage. However, perceived pain when awoken abruptly from REM sleep was significantly lower than the awake score for both the hot (P = 0.0069) and hurting (P = 0.0025) temperatures. Pain perception when woken from Stage 2 sleep or slow wave sleep was not significantly different from perception when awake. Our findings indicate that sleep inertia reduces pain perception when awoken abruptly from REM. This suggests that patients who wake up in pain either perceive accurately the pain they are experiencing, or at worst underestimate the level of pain if woken from REM sleep.

A validation study of the PAWPER XL tape: accurate estimation of both total and ideal body weight in children up to 16 years of age

Background: The PAWPER tape has proved to be one of the most accurate weight estimation systems available, but its reduced accuracy in obese children and relative shortness (153cm) limit its functioning. The PAWPER tape was redeveloped as the PAWPER XL tape, to provide additional capacity for estimating weight in obese children and taller children (for extra-length and extra-large children). The aim of this study was to evaluate the accuracy of the PAWPER XL tape in estimating total body weight (TBW) and ideal body weight (IBW) in a population with a high prevalence of underweight and obese children. Methods: Estimations of TBW and IBW were obtained using the Broselow tape, the Mercy method, the original PAWPER tape and the new PAWPER XL tape in a convenience sample of 332 Emergency Department children. These predicted weights were compared to actual weight and calculated IBW. Results: The percentage of TBW estimates within 10% of actual weight (PW10) for the PAWPER XL tape, the PAWPER tape, the Mercy method and the Broselow tape was 83.4%, 81.8%, 63.9% and 57.1% respectively. For IBW the PW10 for the PAWPER XL tape, the PAWPER tape and the Broselow tape was 87.9%, 86.7% and 80.0% respectively. Conclusions: The PAWPER XL tape estimated both TBW and IBW extremely accurately, significantly better than the other weight estimation systems. The increased length and number of habitus score categories of the PAWPER XL tape enabled it to outperform the PAWPER tape in children >153cm in length and in severely obese children. Correspondence to: Mike Wells, Division of Emergency Medicine, Faculty of Health Sciences, University of the Witwatersrand, 5 York Road, Parktown Johannesburg, South Africa, Tel: +27824910369; E-mail: mike.wells@emergencymedicine.co.za

Gender and site of injection do not influence intensity of hypertonic saline-induced muscle pain in healthy volunteers

The aim of the study was to determine whether the same stimulus to different muscles results in comparable pain and whether gender has any influence on the pain. We compared the quality and intensity of muscle pain induced by a hypertonic saline injection into the tibialis anterior (leg) muscle to that after an injection into the lumbar erector spinae (back) muscle in both male (n=10) and female (n=10) volunteers. Hypertonic or isotonic saline was injected into the leg and back muscles and pain intensity (visual analogue scale, VAS) and pain quality (McGill Pain Questionnaire) were measured. Pressure pain tolerance around the site of injection and on the contralateral side was measured. Hypertonic saline injection induced significant muscle pain in the back and leg compared to isotonic saline (P<0.05, ANOVA). The site of injection did not influence the quality of pain but there was a gender bias in the descriptive words chosen (chi(2) test, P<0.05) and female subjects were more sensitive to pressure than male subjects. Experimentally induced muscle pain is equivalent in intensity and quality in the leg and back muscle. Gender does not influence muscle pain intensity but does influence sensitivity to pressure and the description of pain.

Symptomatology of Peripheral Neuropathy in an African Language

The terminology used to describe neuropathic pain appears to be conserved across languages, which facilitates the translation of validated neuropathic pain screening tools into other languages. However, this assumption has not been assessed in an African language. Therefore we investigated the terminology used by 54 patients whose native language was isiZulu, a major Bantu language of Africa, when describing their symptomatic HIV-associated sensory neuropathy. Also, because English is a commonly spoken second-language in the region, we assessed these patients’ knowledge and understanding of 21 English terms commonly used to describe neuropathic pain. English translations of the most commonly used isiZulu symptom descriptors included: “hot/burning” (50%), “cramping” (35%), “painful/sore/aching” (32%), “itching” (22%), “numb” (22%), “cold/freezing” (17%), and “stabbing/pricking/pins-and-needles” (13%). Thus, the isiZulu terminology to describe neuropathic pain was very similar to that used in non-African languages. However, knowledge and understanding of English neuropathic pain descriptors by these non-native English speakers was highly variable. For example, knowledge of English terms ranged from>98% (“hot”, “cold/freezing”, “cramping”) to <25% (“pricking”, “radiating”, “throbbing”), and true understanding of English terms ranged from>90% (“hot”, “burning”, “cramping”) to <35% (“tingling”, “jumping”, “shooting”, “radiating”). In conclusion, we show significant similarity in the terms used to describe neuropathic pain in isiZulu compared to non-African languages, thus indicating that translation of existing neuropathic pain screening tools into this, and possibly other Bantu languages, is a viable option. However, the usefulness of English-language screening tools in this non-native English speaking population may be limited.

High-tech adjuncts to emergency weight estimation: Point-of-care ultrasound and point-of-care bioelectrical impedance measurements can increase the accuracy of length-based weight estimation in children

Introduction: An accurate and reliable method of estimating weight in sick obese children, for purposes of drug dosing calculations, has proved to be elusive. Incorporating the use of high-tech, point-of-care technology into weight-estimation methodology has not been evaluated before. We aimed to determine if ultrasound and bioelectrical impedance measurements could be used in combination with the PAWPER XL tape (PTXL) to increase the accuracy of total body weight (TBW), ideal body weight (IBW) and fat-free mass (FFM) estimation. Methods: A convenience sample of 332 children attending an academic Emergency Department was enrolled. Each child had their weight estimated with the PAWPER XL tape and underwent anthropometric, point-of-care ultrasound (PoCUS) and bioelectrical impedance (BI) measurements of parameters useful for body composition assessment. Dual X-ray absorptiometry (DXA) was measured and used as a reference for body composition. Multiple regression techniques were used to identify variables and variable-combinations that were strongly associated with TBW, IBW and DXA-measured FFM. Low-tech combinations including anthropometric measurements only were compared with models including high-tech measurements. Results: The PTXL alone, with no lowor high-tech adjunct, provided the most accurate estimate of IBW. Estimates of TBW based on anthropometric measurements were significantly improved with the addition of poCUS or BI to the prediction models, especially in underweight and obese children. Similarly, high-tech models significantly outperformed the low-tech models for estimating FFM. Conclusions: The use of PoCUS and BI significantly improved the accuracy of TBW and FFM estimation in children when compared with anthropometric-based methods. Correspondence to: Mike Wells, Division of Emergency Medicine, Faculty of Health Sciences, University of the Witwatersrand, 5 York Road, Parktown Johannesburg, South Africa, Tel: +27824910369; E-mail: mike.wells@emergencymedicine.co.za