Facilitated Central Pain Mechanisms Across the Menstrual Cycle in Dysmenorrhea and Enlarged Pain Distribution in Women With Longer Pain History

Dysmenorrhea (DYS), or recurrent menstrual pain, is a highly prevalent pain condition among otherwise healthy women. However, the progression of DYS over time and the influence of the menstrual cycle phases need to be better understood. While the location and distribution of pain have been used to assess pain mechanisms in other conditions, they are unexplored in DYS. Thirty otherwise healthy women with severe DYS and 30 healthy control women were recruited into 3 subgroups (n = 10) according to the length of their menstrual history (<5, 5-15, or>15 years since menarche). The intensity and distribution of menstrual pain were recorded. Pressure pain thresholds at abdominal, hip, and arm sites, pressure-induced pain distribution, temporal summation of pain, and pain intensity after pressure cessation over the gluteus medius were assessed at 3 menstrual cycle phases. Compared with the healthy control women, those with DYS showed lower pressure pain thresholds in every site and menstrual cycle phase (P < .05), enlarged pressure-induced pain areas during menstruations (P < .01), and increased temporal summation and pain intensity after pressure cessation in the overall menstrual cycle (P < .05). Additionally, these manifestations were enhanced during the menstrual and premenstrual phases compared to ovulation in women with DYS (P < .01). Women with long-term DYS demonstrated enlarged pressure-induced pain distribution, enlarged menstrual pain areas, and more days with severe menstrual pain compared to the short-term DYS subgroup (P < .01). Pressure-induced and menstrual pain distributions were strongly correlated (P < .001). These findings suggest that severe DYS is a progressive condition underscored by facilitated central pain mechanisms associated with pain recurrence and exacerbation. PERSPECTIVE: Enlarged pressure-induced pain areas occur in DYS, associated with the length of the condition and the distribution of menstrual pain. Generalized hyperalgesia is present throughout the entire menstrual cycle and intensifies during premenstrual and menstrual phases.

Comparing what the clinician draws on a digital pain map to that of persons who have greater trochanteric pain syndrome

OBJECTIVES

To assess the agreements and differences in pain drawings (pain area, shape and location) between individuals who have greater trochanteric pain syndrome (GTPS) and their clinician.

METHODS

In this study, 23 patients with GTPS (21 female, pain duration range 8-24 months) underwent clinical evaluation by a registered physiotherapist. Digital 2d full body pain drawings were independently performed by the clinician during the subjective examination and by the patient following the physical examination. Levels of agreement [LoA] in the pain area were assessed with Bland-Altman plots. Differences in pain drawings were assessed visually by overlaying images, and by quantifying the differences in shape and location with the bounding box, and Jaccard index, respectively.

RESULTS

Pain areas (/total pixels of the charts) did not differ in size (LoA mean difference less than -0.5%; range -2.35-1.56%) or shape (bounding box p>0.17). However, there was minimal overlap in location (Jaccard index range 0.09-0.18/1 for perfect overlap).

CONCLUSIONS

Patients and the clinician displayed differences in location of pain areas, but not size or shape, when they independently performed digital pain drawings. The reasons that underlie and the clinical impact of these differences remains unclear.

Spatiotemporal patterns of pain distribution and recall accuracy: a dose-response study

OBJECTIVES

Clinical decisions rely on a patient's ability to recall and report their pain experience. Monitoring pain in real-time (momentary pain) may reduce recall errors and optimize the clinical decision-making process. Tracking momentary pain can provide insights into detailed changes in pain intensity and distribution (area and location) over time. The primary aims of this study were (i) to measure the temporal changes of pain intensity, area, and location in a dose-response fashion and (ii) to assess recall accuracy of the peak pain intensity and distribution seven days later, using a digital pain mapping application. The secondary aims were to (i) evaluate the influence of repeated momentary pain drawings on pain recall accuracy and (ii) explore the associations among momentary and recall pain with psychological variables (pain catastrophizing and perceived stress).

METHODS

Healthy participants (N=57) received a low (0.5 ml) or a high (1.0 ml) dose of hypertonic saline (5.8%) injection into the right gluteus medius muscle and, subsequently, were randomized into a non-drawing or a drawing group. The non-drawing groups reported momentary pain intensity every 30-s. Whereas the drawing groups reported momentary pain intensity and distribution on a digital body chart every 30-s. The pain intensity, area (pixels), and distribution metrics (compound area, location, radiating extent) were compared at peak pain and over time to explore dose-response differences and spatiotemporal patterns. All participants recalled the peak pain intensity and the peak (most extensive) distribution seven days later. The peak pain intensity and area recall error was calculated. Pain distribution similarity was determined using a Jaccard index which compares pain drawings representing peak distribution at baseline and recall. The relationships were explored among peak intensity and area at baseline and recall, catastrophizing, and perceived stress.

RESULTS

The pain intensity, area, distribution metrics, and the duration of pain were lower for the 0.5 mL than the 1.0 mL dose over time (p<0.05). However, the pain intensity and area were similar between doses at peak pain (p>0.05). The pain area and distribution between momentary and recall pain drawings were similar (p>0.05), as reflected in the Jaccard index. Additionally, peak pain intensity did not correlate with the peak pain area. Further, peak pain intensity, but not area, was correlated with catastrophizing (p<0.01).

CONCLUSIONS

This study showed differences in spatiotemporal patterns of pain intensity and distribution in a dose-response fashion to experimental acute low back pain. Unlike pain intensity, pain distribution and area may be less susceptible in an experimental setting. Higher intensities of momentary pain do not appear to influence the ability to recall the pain intensity or distribution in healthy participants.

IMPLICATIONS

The recall of pain distribution in experimental settings does not appear to be influenced by the intensity despite differences in the pain experience. Pain distribution may add additional value to mechanism-based studies as the distribution reports do not vary with pain catastrophizing. REC# N-20150052.

Local hyperalgesia, normal endogenous modulation with pain report beyond its origin: a pilot study prompting further exploration into plantar fasciopathy

Background and aims Persistent tendinopathies were previously considered solely as peripheral conditions affecting the local tendinous tissue until quantitative sensory testing identified involvement of altered pain processing. In similar fashion, pain in patients with persistent plantar fasciopathy may also involve more than local tissue. The aim of this pilot study was to investigate potential differences in conditioned pain modulation and pressure and thermal pain thresholds, between individuals with PF and healthy pain-free controls, as a precursor to a larger-scale study. Methods We assessed 16 individuals with plantar fasciopathy and 11 pain-free controls. Plantar fasciopathy diagnosis was: palpation pain of the medial calcaneal tubercle or the proximal plantar fascia, duration ≥3 months, pain intensity ≥2/10, and ultrasound-measured plantar fascia thickness ≥4 mm. Quantitative sensory tests were performed locally at the plantar heel and remotely on the ipsilateral elbow. Assessments included pain thresholds for pressure, heat and cold, and conditioned pain modulation measured as change in local resting pressure pain threshold with cold water hand immersion. Participants rated pain intensity at pain threshold. Additionally, the area and distribution of plantar fasciopathy pain was drawn on a digital body chart of the lower limbs. Descriptive analyses were performed and between-group differences/effects expressed as standardised mean differences (d). Results There was no conditioned pain modulation difference between participants with plantar fasciopathy and controls (d = 0.1). Largest effects were on local pressure pain threshold and reported pain intensity on pressure pain threshold (d > 1.8) followed by pain intensity for heat and cold pain thresholds (d = 0.3-1.5). According to the digital body chart, pain area extended beyond the plantar heel. Conclusions The unlikelihood of a difference in conditioned pain modulation yet a pain area extending beyond the plantar heel provide a basis for exploring altered pain processing in a larger-scale study. Implications This was the first study to investigate the presence of altered pain processing in individuals with plantar fasciopathy using a conditioned pain modulation paradigm and thermal pain thresholds. We found no indication of an altered pain processing based on these measures, however, patients rated pain higher on thresholds compared to controls which may be important to clinical practice and warrants further exploration in the future.

Healthy Pain-Free Individuals with a History of Distal Radius Fracture Demonstrate an Expanded Distribution of Experimental Referred Pain Toward the Wrist

OBJECTIVE

Nociception caused by injuries may sensitize central mechanisms causing expanded pain areas. After recovery, the status of such pain distribution and sensitivity mechanisms is unknown. The present study investigated whether individuals who have fully recovered from a distal radius fracture demonstrate increased pain sensitivity and expanded distribution of pressure-induced pain.

DESIGN

Cross-sectional single-blinded study.

SETTING

Clinical setting.

SUBJECTS

Twenty-three pain-free individuals with a history of painful distal radius fracture and 22 nonfractured, age/gender-matched controls participated in two experimental sessions (day 0, day 1) 24 hours apart.

METHODS

Pressure pain thresholds (PPTs) were recorded bilaterally at the extensor carpi radialis longus (ECRL), infraspinatus, and gastrocnemius muscles. Spatial distribution of pain was assessed following 60-second painful pressure stimulation at the ECRL (bilateral) and the infraspinatus muscles on the fractured or dominant side. Participants drew pain areas on a body map. After day 0 assessments, prolonged pain was induced by eccentric exercise of wrist extensors on the fractured/dominant side.

RESULTS

Compared with controls, pressure-induced ECRL pain in the fracture group referred more frequently toward the distal forearm (P < 0.005) on day 0. Both groups showed larger pain areas on day 1 compared with day 0 (P < 0.005), although the fracture group showed a larger relative change between days (P < 0.005). The fracture group showed larger pain areas on the fracture side compared with the contralateral side on both days (P < 0.005).

CONCLUSIONS

Prolonged pain and recovered prior painful injuries like fractures may sensitize pain mechanisms manifested as expanded pain distribution. Pressure-induced referred pain can be a simple pain biomarker for clinical use.

Digital Pain Mapping and Tracking in Patients With Chronic Pain: Longitudinal Study

Background

Digital pain mapping allows for remote and ecological momentary assessment in patients over multiple time points spanning days to months. Frequent ecological assessments may reveal tendencies and fluctuations more clearly and provide insights into the trajectory of a patient’s pain.

Objective

The primary aim of this study is to remotely map and track the intensity and distribution of pain and discomfort (eg, burning, aching, and tingling) in patients with nonmalignant spinal referred pain over 12 weeks using a web-based app for digital pain mapping. The secondary aim is to explore the barriers of use by determining the differences in clinical and user characteristics between patients with good (regular users) and poor (nonregular users) reporting compliance.

Methods

Patients (N=91; n=53 women) with spinal referred pain were recruited using web-based and traditional in-house strategies. Patients were asked to submit weekly digital pain reports for 12 weeks. Each pain report consisted of digital pain drawings on a pseudo–three-dimensional body chart and pain intensity ratings. The pain drawings captured the distribution of pain and discomfort (pain quality descriptors) expressed as the total extent and location. Differences in weekly pain reports were explored using the total extent (pixels), current and usual pain intensity ratings, frequency of quality descriptor selection, and Jaccard similarity index. Validated e-questionnaires were completed at baseline to determine the patients’ characteristics (adapted Danish National Spine Register), disability (Oswestry Disability Index and Neck Disability Index), and pain catastrophizing (Pain Catastrophizing Scale) profiles. Barriers of use were assessed at 6 weeks using a health care–related usability and acceptance e-questionnaire and a self-developed technology-specific e-questionnaire to assess the accessibility and ease of access of the pain mapping app. Associations between total extent, pain intensity, disability, and catastrophizing were explored to further understand pain. Differences between regular and nonregular users were assessed to understand the pain mapping app reporting compliance.

Results

Fluctuations were identified in pain reports for total extent and pain intensity ratings (P<.001). However, quality descriptor selection (P=.99) and pain drawing (P=.49), compared using the Jaccard index, were similar over time. Interestingly, current pain intensity was greater than usual pain intensity (P<.001), suggesting that the timing of pain reporting coincided with a more intense pain experience than usual. Usability and acceptance were similar between regular and nonregular users. Regular users were younger (P<.001) and reported a larger total extent of pain than nonregular users (P<.001).

Conclusions

This is the first study to examine digital reports of pain intensity and distribution in patients with nonmalignant spinal referred pain remotely for a sustained period and barriers of use and compliance using a digital pain mapping app. Differences in age, pain distribution, and current pain intensity may influence reporting behavior and compliance.

Modifiable motion graphics for capturing sensations

Objective

The purpose of this study was to assess the relationship between an embodied sensory experience and the ability to translate the perception of this experience visually using modifiable motion graphics.

Methods

A custom-designed software was developed to enable users to modify a motion graphic in real-time. The motion graphics were designed to depict realistic visualizations of pain quality descriptors, such as tingling and burning. Participants (N = 34) received an electrical stimulation protocol known to elicit sensations of tingling. The protocol consisted of eight stimulation intensities ranging from 2—6mA delivered, in a randomized fashion and repeated three times, to the index finger. Immediately after each stimulus, participants drew the area of the evoked sensation on a digital body chart of the hand. Participants then modified the motion graphic of tingling by adjusting two parameters, namely the speed (rate of dots disappearing and re-appearing) and density of these dots in the drawn area. Then, participants rated the perceived intensity and selected the most appropriate pain quality descriptor.

Results

There was an increase in the area, density, and perceived intensity ratings as the electrical stimulation intensity increased (P<0.001). The density of the motion graphic, but not speed, correlated with perceived intensity ratings (0.69, P<0.001) and electrical stimulation intensities (0.63, P<0.01). The descriptor ‘tingling’ was predominantly selected in the range of 3–4.5mA and was often followed by ‘stabbing’ as the electrical intensity increased.

Discussion

The motion graphic tested was perceived to reflect a tingling sensation, the stimulation protocol elicited a tingling sensation, and participants adjusted one of the two motion graphic features systematically. In conclusion, an embodied sensation, such as tingling, maybe visually represented similarly between individuals. These findings create research, clinical, and commercial opportunities that utilize psychophysics to explore, visualize, and quantify changes in embodied sensory experiences in response to known stimuli.

Capturing patient-reported area of knee pain: a concurrent validity study using digital technology in patients with patellofemoral pain

BACKGROUND

Patellofemoral pain (PFP) is often reported as a diffuse pain at the front of the knee during knee-loading activities. A patient's description of pain location and distribution is commonly drawn on paper by clinicians, which is difficult to quantify, report and compare within and between patients. One way of overcoming these potential limitations is to have the patient draw their pain regions using digital platforms, such as personal computer tablets.

OBJECTIVE

To assess the validity of using computer tablets to acquire a patient's knee pain drawings as compared to paper-based records in patients with PFP.

METHODS

Patients (N = 35) completed knee pain drawings on identical images (size and colour) of the knee as displayed on paper and a computer tablet. Pain area expressed as pixel density, was calculated as a percentage of the total drawable area for paper and digital records. Bland-Altman plots, intraclass correlation coefficient (ICC), Pearson's correlation coefficients and one-sample tests were used in data analysis.

RESULTS

No significant difference in pain area was found between the paper and digital records of mapping pain area (p = 0.98), with the mean difference = 0.002% (95% CI [-0.159-0.157%]). A very high agreement in pain area between paper and digital pain drawings (ICC = 0.966 (95% CI [0.93-0.98], F = 28.834, df = 31, p < 0.001). A strong linear correlation (R2 = 0.870) was found for pain area and the limits of agreement show less than ±1% difference between paper and digital drawings.

CONCLUSION

Pain drawings as acquired using paper and computer tablet are equivalent in terms of total area of reported knee pain. The advantages of digital recording platforms, such as quantification and reporting of pain area, could be realized in both research and clinical settings.

A Comparison of Oral Sensory Effects of Three TRPA1 Agonists in Young Adult Smokers and Non-smokers

This study profiled intra-oral somatosensory and vasomotor responses to three different transient receptor potential (TRP) channels, subfamily A, member 1 (TRPA1) agonists (menthol, nicotine, and cinnamaldehyde) in smoking and non-smoking young adults. Healthy non-smokers (N = 30) and otherwise healthy smokers (N = 25) participated in a randomized, double-blinded, cross-over study consisting of three experimental sessions in which they received menthol (30 mg), nicotine (4 mg), or cinnamaldehyde (25 mg) chewing gum. Throughout a standardized 10 min chewing regime, burning, cooling, and irritation intensities, and location were recorded. In addition, blood pressure, heart rate and intra-oral temperature were assessed before, during, and after chewing. Basal intra-oral temperature was lower in smokers (35.2°C ± 1.58) as compared to non-smokers (35.9°C ± 1.61) [F_{(1, 52)} = 8.5, P = 0.005, post hoc, p = 0.005]. However, the increase in temperature, heart rate, and blood pressure in response to chewing menthol, nicotine, and cinnamaldehyde gums were similar between smokers and non-smokers. Although smoking status did not influence the intensity of burning, cooling, and irritation, smokers did report nicotine burn more often (92%) than non-smokers (63%) [χ(1, N=55)2 = 6.208, P = 0.013]. Reports of nicotine burn consistently occurred at the back of the throat and cinnamaldehyde burn on the tongue. The cooling sensation of menthol was more widely distributed in the mouth of non-smokers as compared to smokers. Smoking alters thermoregulation, somatosensory, and possibly TRPA1 receptor responsiveness and suggests that accumulated exposure of nicotine by way of cigarette smoke alters oral sensory and vasomotor sensitivity.

Distribution and symmetrical patellofemoral pain patterns as revealed by high-resolution 3D body mapping: a cross-sectional study

Background

Detailed pain mapping of extent and distribution in individuals with patellofemoral pain (PFP) within and around a complex structure such as the knee has yet to be explored.

Methods

Perceptions of on-going pain from adolescents and young adults (N = 35) with long-standing (>10 months) PFP were collected on high-resolution 3D digital body-schema of the knees. Location, area of pain, pain intensity, laterality, worse side of knee pain, symptom duration, and symmetry in bilateral knee pain were recorded. A threshold for naturally occurring variations in symmetrical knee pain drawings were collected from 18 healthy controls and used in combination with the development a symmetry index (0–1) to create a fuzzy rule for classifying symmetrical and non-symmetrical PFP patterns as compared to a PFP expert. The symmetry index was computed and tested using a correlation coefficient alone or in combination with the Jaccard index and the true and false positive rates (TPR and FPR, respectively) determined.

Results

The peripatellar region was the common report of pain location however, novel and nonconforming PFP patterns were identified and the majority of individuals (22 of 27) with bilateral PFP expressed highly-symmetric mirror-image pain. Individuals with symptom duration of 5 years or more had a greater area of pain, compared to those with symptoms for less than 5 years. The total area of pain was correlated to symptom duration for those with extended symptoms durations and a progression towards an “O” shaped pattern emerged. A TPR of 100% for identifying symmetrical knee pain patterns was found however the expert PFP tended to be stricter, as reflected in FPR of 20%.

Conclusions

A high proportion of PFP patterns or symptoms occur in mirrored locations and are exceptionally symmetrical, and long duration of symptoms appear to converge to an ‘O’ shape. Classifying symmetrical pain patterns is subjective however simple fuzzy rules and correlations can be used to increase objectivity. This study highlights a gap in knowledge of PFP symptom presentation, reveals what may be a natural progression of symptoms, and provides valuable clinical insight for both pain management and treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12891-017-1521-5) contains supplementary material, which is available to authorized users.

A Test-Retest Reliability Study of Human Experimental Models of Histaminergic and Non-histaminergic Itch

Numerous exploratory, proof-of-concept and interventional studies have used histaminergic and non-histaminergic human models of itch. However, no reliability studies for such surrogate models have been conducted. This study investigated the test-retest reliability for the response to histamine- and cowhage- (5, 15, 25 spiculae) induced itch in healthy volunteers. Cowhage spiculae were individually applied with tweezers and 1% histamine was applied with a skin prick test (SPT) lancet, both on the volar forearm. The intensity of itch was recorded on a visual analogue scale and self-reported area of itch was assessed 5 and 10 min after itch provocation. Reliability of the evoked itch (area under the curve and peak intensity) was assessed by the coefficient of variation (CV), intra-class correlation coefficient (ICC), and sample size estimation for parallel and cross-over designs. Cowhage (ICC = 0.57-0.77, CVbetween = 97%, CVwithin = 41%) and histamine: (ICC = 0.83-0.93, CVbetween = 97%, CVwithin = 20%) exhibited moderate-to-excellent intra-individual reliability and moderate inter-individual reliability for the itch intensity. For a test-retest observation period of one week, SPT-delivered histamine and application of cowhage-spiculae are reproducible human models of itch. The high inter-individual and low intra-individual variability suggests cross-over designed studies when applicable.

Psychophysical and Vasomotor Responses of the Oral Tissues: A Nicotine Dose-Response and Menthol Interaction Study

INTRODUCTION

This study implemented an intra-oral test-platform to assess the sensory, psychophysical, and vasomotor responses to nicotine and menthol, alone or in combination.

METHODS

Two double-blinded, placebo-controlled, randomized, cross-over studies, including healthy nonsmoking participants were performed. Study I: A dose-response relationship (N = 20) between 0, 2, and 4 mg nicotine gum. Study II: An interaction response (N = 22) to 30 mg menthol and 4 mg nicotine alone or in combination. Heart rate, blood pressure, tactile and thermosensory thresholds, intra-oral blood flow and temperature, pain/irritation intensities/locations, McGill Pain Questionnaire, and taste experience were assessed before, during or after the completion of a standardized chewing regime.

RESULTS

A dose-response elevation in heart rate was attenuated when nicotine was combined with menthol. Blood flow, temperature, and warm-detection thresholds, as assessed on the tongue, similarly increased for all gums. Pain intensity and taste experiences were similar between nicotine doses. Nicotine attenuated the sweet, cooling, and freshening sensation of menthol. Within the first 4 minutes, menthol reduced the intensity but not the area of nicotine-induced pain and irritation. The 4-mg nicotine dose led to a continued increase in the intensity and area of irritation in the throat post-chewing. Moreover, one-half of participants responded to menthol as an irritant, and these individuals demonstrated larger areas of nicotine-induced irritation in the throat post-chewing.

CONCLUSIONS

The intra-oral test platform provides a basis to optimize the assessment of nicotine-related taste and sensory experiences and can be used in future studies for profiling nicotine gum.

Creation of a gilded trap by the high economic value of the Maine lobster fishery

Unsustainable fishing simplifies food chains and, as with aquaculture, can result in reliance on a few economically valuable species. This lack of diversity may increase risks of ecological and economic disruptions. Centuries of intense fishing have extirpated most apex predators in the Gulf of Maine (United States and Canada), effectively creating an American lobster (Homarus americanus) monoculture. Over the past 20 years, the economic diversity of marine resources harvested in Maine has declined by almost 70%. Today, over 80% of the value of Maine's fish and seafood landings is from highly abundant lobsters. Inflation-corrected income from lobsters in Maine has steadily increased by nearly 400% since 1985. Fisheries managers, policy makers, and fishers view this as a success. However, such lucrative monocultures increase the social and ecological consequences of future declines in lobsters. In southern New England, disease and stresses related to increases in ocean temperature resulted in more than a 70% decline in lobster abundance, prompting managers to propose closing that fishery. A similar collapse in Maine could fundamentally disrupt the social and economic foundation of its coast. We suggest the current success of Maine's lobster fishery is a gilded trap. Gilded traps are a type of social trap in which collective actions resulting from economically attractive opportunities outweigh concerns over associated social and ecological risks or consequences. Large financial gain creates a strong reinforcing feedback that deepens the trap. Avoiding or escaping gilded traps requires managing for increased biological and economic diversity. This is difficult to do prior to a crisis while financial incentives for maintaining the status quo are large. The long-term challenge is to shift fisheries management away from single species toward integrated social-ecological approaches that diversify local ecosystems, societies, and economies.

Tip of the tongue selectivity and motor learning in the palatal area

This study assessed the ability of the tongue tip to accurately select intraoral targets embedded in an upper palatal tongue-computer interface, using 18 able-bodied volunteers. Four performance measures, based on modifications to Fitts's Law, were determined for three different tongue-computer interface layouts. The layouts differed with respect to number and location of the targets in the palatal interface. Assessment of intraoral target selection speed and accuracy revealed that performance was indeed dependent on the location and distance between the targets. Performances were faster and more accurate for targets located farther away from the base of the tongue in comparison to posterior and medial targets. A regression model was built, which predicted intraoral target selection time based on target location and movement amplitude better than the predicted by using a standard Fitts's Law model. A 30% improvement in the speed and accuracy over three daily practice sessions of 30 min emphasizes the remarkable motor learning abilities of the tongue musculature and provides further evidence that the tongue is useful for operating computer-interface technologies.

Vascular and psychophysical effects of topical capsaicin application to orofacial tissues

AIMS

To characterize and contrast human sensory and vascular changes produced by topical application of the algesic chemical capsaicin to the glabrous lips and tongue.

METHODS

Applications of 1% capsaicin or vehicle cream to the glabrous lips and tongue were randomized between two two-trial sessions. The capsaicin trial followed the vehicle trial for each session. Before and 5, 15, and 30 minutes after capsaicin or vehicle cream application, six parameters were recorded from the glabrous lips or the tongue dorsum: (1) burning pain intensity, as measured on a visual analog scale; (2) burning pain area, as indicated by subjects on an orofacial drawing; (3) mechanical sensitivity, as measured by a von Frey filament; (4) visual flare; (5) blood flow and temperature, as measured by laser-Doppler imaging and thermography, respectively; and (6) areas of increased temperature (hot spots), as calculated by a digital tracer from the thermographs. Data were analyzed by ANOVAs and Pearson's correlations.

RESULTS

Compared to vehicle application, capsaicin elicited burning pain, increases in blood flow and temperature, but no change in mechanical sensitivity in the glabrous lips or tongue. Greater increases in blood flow and temperature paralleled more intense burning pain and larger areas of perceived pain for the lips compared to the tongue. The location of distinct areas of increased temperature within the orofacial area differed between the capsaicin-lip and capsaicin-tongue trials.

CONCLUSION

The several differences between these responses to noxious stimulation of the glabrous lips and tongue may have implications for examinations of orofacial somatosensory functions.

Video-assisted thoracoscopic ligation of patent ductus arteriosus in children

Video-assisted thoracoscopic surgery is a new approach that offers an alternative to open surgical ligation of the patient ductus arteriosus. Advanced video technology precise pediatric instrumentation, and innovative surgical techniques have facilitated the development of this approach. From April 1993 to February 1995, this procedure was performed at a large pediatric medical center on more than 100 pediatric patients with a wide range of ages and weights. There was a collaborative effort among all disciplines, and perioperative nurses on the cardiac OR team were challenged to become proficient with this new procedure through inservice sessions, ongoing education, and hands-on experience.