Dag Lemming

Biochemical alterations in the trapezius muscle of patients with chronic whiplash associated disorders (WAD) – A microdialysis study

The mechanisms behind the development of chronic trapezius myalgia in patients with whiplash associated disorders (WAD) appear to involve both peripheral and central components, but the specific contribution of alterations in muscle is not clear. Female patients with WAD and involvement of trapezius (N=22) and female controls (N=20; CON) were studied during an experiment compromised of rest (baseline), 20min repetitive low‐force exercise and 120min recovery. Their interstitial concentrations of serotonin (5‐HT), glutamate, lactate, pyruvate, potassium, interleukin‐6 (IL‐6), and blood flow were determined in the trapezius muscle using a microdialysis technique. Pressure pain thresholds (PPT) over trapezius and tibialis anterior muscles were also assessed. In WAD, we found signs of generalized hypersensitivity according to PPT. The WAD group had significantly higher interstitial [IL‐6] and [5‐HT] in the trapezius than the CON. [Pyruvate] was overall significantly lower in WAD, and with lactate it showed another time‐pattern throughout the test. In the multivariate regression analysis of pain intensity [5‐HT] was the strongest regressor and positively correlated with pain intensity in WAD. In addition, blood flow, [pyruvate], and [potassium] influenced the pain intensity in a complex time dependent way. These findings may indicate that peripheral nociceptive processes are activated in WAD with generalized hypersensitivity for pressure and they are not identical with those reported in chronic work‐related trapezius myalgia, which could indicate different pain mechanisms.

Widespread pain hypersensitivity and facilitated temporal summation of deep tissue pain in whiplash associated disorder: an explorative study of women.

OBJECTIVE Widespread deep tissue pain hyperalgesia was evaluated in women with chronic whiplash associated disorder (n = 25) and controls (n = 10) using computerized cuff pressure algometry and hypertonic saline infusion. METHODS A pneumatic double-chamber cuff was placed around: (i) the arm and (ii) the leg. Cuff inflation rate was constant and the pain intensity was registered continuously on a visual analogue scale (VAS); thresholds of detection and tolerance were extracted. For assessment of spatial summation the protocol was repeated with a single-chamber cuff inflated around the leg. Temporal summation of pain was assessed from the leg with constant cuff pressure stimulation at 2 different pressure intensities for 10 min. Hypertonic saline was infused in the tibialis anterior muscle. RESULTS Cuff pressure pain thresholds were lower in subjects with whiplash associated disorder compared with controls (p < 0.05). Tonic pressure stimulation evoked higher maximal VAS and larger areas under the VAS curve in subjects with whiplash associated disorder compared with controls (p < 0.05). The pain threshold and tolerance were higher during single cuff than double cuff stimulation. The area under the VAS curve after intramuscular saline infusion was larger in whiplash associated disorder (p < 0.05). CONCLUSION The results indicated widespread hyperalgesia in chronic whiplash associated disorder and facilitated temporal summation outside the primary pain area, suggesting involvement of central sensitization.

The Responses to Pharmacological Challenges and Experimental Pain in Patients With Chronic Whiplash-associated Pain

Objectives:This study evaluates the analgesic responses to intravenous administration of morphine, lidocaine, and ketamine and their relations to duration of chronic pain after whiplash trauma. In addition, experimental muscle pain sensitivity and its correlation to pain duration and pharmacological responses were assessed. Methods:Thirty-three patients with diagnosed whiplash-associated disorder grade II in the chronic stage, according to the Quebec classification, were included. The pharmacological evaluation was performed in a randomized, double-blind, cross-over design and consisted of a 30-minute period of intravenous administration of morphine (0.3 mg/kg), lidocaine (5 mg/kg), ketamine (0.3 mg/kg), or placebo (isotonic saline). Intensity ratings of habitual pain on a visual analogue scale were taken before, during, and after the infusion. The patients were classified as nonresponders, placebo-responders, or responders (minimum 50% decrease of pain intensity) of the drugs. Pressure pain thresholds and intramuscular and cutaneous electrical stimulation pain thresholds were measured. The pain intensity during experimental muscle pain by intramuscular hypertonic saline was also recorded. Experimental pain assessments were performed on the lower legs outside the habitual painful area. Results:Thirty patients completed the study; 2 were placebo responders and 10 were nonresponders. Of 18 responders, there were 15 morphine responders, 11 lidocaine responders, and 14 ketamine responders. In the patients with whiplash-associated disorder duration less than 2 years, 7 responded to morphine, 5 to lidocaine, and 8 to ketamine. In the patients with pain duration longer than 2 years, 8 responded to morphine, 6 to lidocaine, and 6 to ketamine. Thus, no pattern with respect to pain duration was found. Seventeen patients participated in the experimental pain assessment, and no significant differences in the variables of the intramuscular and cutaneous stimulation and intramuscular-induced pain with respect to response to the pharmacological challenges or whiplash-associated disorder duration existed. Discussion:The pharmacological challenges identified subgroups of patients with chronic whiplash-associated disorder that might be considered before instituting therapeutic interventions or research. However, the pattern of responses to the pharmacological challenges did not show any clear relationships with pain duration or the experimental pain tests.

Single-Point but Not Tonic Cuff Pressure Pain Sensitivity Is Associated with Level of Physical Fitness - A Study of Non-Athletic Healthy Subjects

Exercise is often used for pain rehabilitation but the link between physical activity level and pain sensitivity is still not fully understood. Pressure pain sensitivity to cuff algometry and conditioned pain modulation (CPM) were evaluated in highly active men (n=22), normally active men (n=26), highly active women (n=27) and normally active women (n=23) based on the Godin Leisure-Time Exercise Questionnaire. Cuff pressure pain sensitivity was assessed at the arm and lower leg. The subjects scored the pain intensity on an electronic Visual Analogue Scale (VAS) during ten minutes with 25 kPa constant cuff pressure and two minutes with zero pressure. The maximal VAS score and area under the VAS-curve were extracted. Pressure pain thresholds (PPT) were recorded by manual pressure algometry on the ipsilateral tibialis anterior muscle before, during and after the tonic arm stimulation. Tonic cuff stimulation of the arm and leg resulted in higher VAS peak scores in women compared with men (p<0.04). In all groups the PPTs were reduced during and after the cuff stimulation compared with baseline (p=0.001). PPT were higher in men compared with women (p=0.03) and higher in highly physical active compared with normal active (p=0.048). Besides the well-known gender difference in pressure pain sensitivity this study demonstrates that a high physical fitness degree in non-athletic subjects is associated with increased pressure pain thresholds but does not affect cuff pressure pain sensitivity in healthy people.

Cuff pressure pain detection is associated with both sex and physical activity level in nonathletic healthy subjects

Purpose The aim of this study was to evaluate pressure pain sensitivity on leg and arm in 98 healthy persons (50 women) using cuff algometry. Furthermore, associations with sex and physical activity level were investigated. Method Normal physical activity level was defined as Godin Leisure-Time Exercise Questionnaire (GLTEQ) score ≤ 45 and high activity level as GLTEQ > 45. A pneumatic double-chamber cuff was placed around the arm or leg where a single chamber was inflated. The cuff inflation rate (1 kPa/s) was constant, and pain intensity was registered continuously on a 10 cm electronic visual analogue scale (VAS). The pain detection threshold (PDT) was defined as when the pressure was perceived as painful, and pain tolerance (PTT) was when the subject terminated the cuff inflation. For PTT, the corresponding VAS score was recorded (VAS-PTT). The protocol was repeated with two chambers inflated. Result Only single cuff results are given. For women compared with men, the PDT was lower when assessed in the arm ( P = 0.002), PTTs were lower in the arm and leg ( P < 0.001), and the VAS-PTT was higher in the arm and leg ( P < 0.033). Highly active participants compared with less active had higher PDT ( P = 0.027) in the leg. Women showed facilitated spatial summation ( P < 0.014) in the arm and leg and a steeper VAS slope (i.e., the slope of the VAS pressure curve between PDT and PPT) in the arm and leg ( P < 0.003). Conclusion This study indicates that reduced pressure pain sensitivity is associated both with male sex and physical activity level.

Use of an adjustable hand plate in studying the perceived horizontal plane during simulated flight.

BACKGROUND Quantitative data on spatial orientation would be valuable not only in assessing the fidelity of flight simulators, but also in evaluation of spatial orientation training. In this study a manual indicator was used for recording the subjective horizontal plane during simulated flight. METHODS In a six-degrees-of-freedom hexapod hydraulic motion platform simulator, simulating an F-16 aircraft, seven fixed-wing student pilots were passively exposed to two flight sequences. The first consisted in a number of coordinated turns with visual contact with the landscape below. The visually presented roll tilt was up to a maximum 670. The second was a takeoff with a cabin pitch up of 100, whereupon external visual references were lost. The subjects continuously indicated, with the left hand on an adjustable plate, what they perceived as horizontal in roll and pitch. There were two test occasions separated by a 3-d course on spatial disorientation. RESULTS Responses to changes in simulated roll were, in general, instantaneous. The indicated roll tilt was approximately 30% of the visually presented roll. There was a considerable interindividual variability. However, for the roll response there was a correlation between the two occasions. The amplitude of the response to the pitch up of the cabin was approximately 75%; the response decayed much more slowly than the stimulus. DISCUSSION With a manual indicator for recording the subjective horizontal plane, individual characteristics in the response to visual tilt stimuli may be detected, suggesting a potential for evaluation of simulation algorithms or training programs.