[Measuring pressure pain thresholds. Comparison of an electromechanically controlled algometer with established methods]

Interferential current intensity influences the hypoalgesic response in healthy subjects under mechanically-induced pain: A randomized controlled trial

BACKGROUND

Interferential current (IFC) is a non-pharmacological therapy often used to reduce pain intensity. However, there is no scientific evidence of the biological effects of the adjustment of IFC intensity of stimulation.

OBJECTIVE

To investigate whether the adjustment of IFC intensity influences pain on cutaneous sensory threshold (CST), pressure pain threshold (PPT) and pain intensity in healthy subjects under mechanically induced pain.

METHODS

This is a placebo-controlled randomized trial. One hundred and two healthy university students blinded to intervention were randomized using opaque sealed envelopes to the following groups: 1) sensory IFC (n = 24); 2) fixed motor IFC (n = 26); 3) adjusted motor IFC (n = 27); and 4) placebo IFC (n = 25). After 40 minutes of stimulation or placebo, subjects were evaluated by an investigator blinded to group allocation. CST (von Frey filaments), PPT (algometry), and pain intensity (11-point numerical scale) were measured.

RESULTS

Adjusted motor IFC promoted a significant reduction of CST (hand: mean difference (MD) = 2.39, confidence intervals (CI) = 1.39-3.38; and forearm: MD = 3.01, CI = 2.87-3.14) compared to placebo. Adjusted motor IFC increased PPT significantly (hand: MD = 27.59, CI = 26.80-28.37; and forearm: MD = 34, CI = 25.74-42.25) when compared to placebo. Adjusted motor IFC reduced pain intensity by 4.01 points (CI = 3.64-4.55) when compared to placebo. No adverse events were observed.

CONCLUSIONS

Adjusted motor IFC intensity increased PPT and CST and also reduced pain intensity in healthy subjects under mechanically induced pain.

The influence of opioid blockage on the sexual response cycle: A randomized placebo-controlled experiment with relevance for the treatment of Compulsive Sexual Behavior Disorder (CSBD)

The use of opioid antagonists is discussed as a feasible and tolerable treatment of Compulsive Sexual Behavior Disorder (CSBD). However, little is known about the influence of opioid blockage on relevant physiological functions such as sexual arousal, pain perception as well as disgust sensitivity during the sexual response cycle (SRC). Healthy participants (N = 64, n = 32 women) were invited to the laboratory twice using a double-blind, randomized cross-over design, with an interval of four weeks between sessions. Participants were randomly subjected to an SRC condition (including an erotic audio play and masturbation to orgasm) and a control condition. Participants received either naltrexone (50 mg, n = 32) or placebo at both sessions. Self-reported sexual arousal and physiological measures of arousal as well as pain perception, odor disgust sensitivity, and prolactin levels were assessed along the SRC. Naltrexone increased prolactin levels and blunted the orgasm-induced prolactin rise. Naltrexone also reduced self-reported sexual arousal throughout the sexual response cycle and blunted respiration rate during masturbation. However, naltrexone did not affect other markers of physiological arousal, pressure pain ratings and odor disgust sensitivity. These findings suggest that naltrexone has an acute negative effect on sexual arousal. Since prolactin levels mediate sexual satiation, we propose that a prolactin-induced increase in sexual satiation could explain the positive effects reported for naltrexone in the treatment of CSBD.

Immediate analgesic effect of transcutaneous electrical nerve stimulation (TENS) and interferential current (IFC) on chronic low back pain: Randomised placebo-controlled trial

OBJECTIVE

To compare the immediate analgesic effect of transcutaneous nerve stimulation (TENS) and interferential current (IFC), with different combinations of parameters, in individuals with chronic low back pain (CLBP).

METHODOLOGY

280 individuals with CLBP were included in the study, both genders, randomized in 8 groups: GI2KHz/100Hz, GI2KHz/2Hz, GI4KHz/100Hz, GI4KHz/2Hz, placebo interferential group (GIP), GT100Hz, GT2Hz, and placebo TENS group (GTP). All individuals underwent a single application of TENS or IFC for 30min. The assessments were carried out prior to the intervention, as well as immediately after, with the following outcomes: pain intensity (Numeric Pain Rating Scale-NPRS), qualitative pain characteristics (McGill Pain Questionnaire-MPQ), and pressure pain threshold (PPT) by pressure algometry (PA) in 4 points of the low back region.

RESULTS

In the intergroup comparison of NPRS, all intervention groups showed greater pain reduction compared to GTP (p < 0.05). In the total MPQ score, the groups that obtained significant results (p < 0.05) when compared to GTP were GT100Hz and GT2Hz, while the groups GT100Hz and GI4KHz/100Hz were significant when compared to GIP. In the PA, GI4KHz/100Hz showed an increase in the PPT in all points compared to GTP and GI2KHz/100Hz.

CONCLUSION

Both TENS and IFC presented immediate analgesic effect in CLBP, with emphasis on the interferential current of 4 KHz modulated at 100Hz.

The virtue of optimistic realism - expectation fulfillment predicts patient-rated global effectiveness of total hip arthroplasty

BACKGROUND

Emerging evidence highlights the importance of preoperative expectations in predicting patient-reported outcomes of orthopedic surgeries. To date, it is still a matter of controversy whether patient satisfaction can be maximized by promoting either optimistic or realistic outcome expectations before surgery. Adjusting overly optimistic outcome expectancies in favor of a more realistic outlook on the limitations of total hip arthroplasty could reduce the risk of disappointment and lead to greater satisfaction with surgery outcomes. Our prospective cohort study was aimed at comparing the relative predictive influence of baseline expectations, expectation fulfillment and symptomatic improvement on the global effectiveness of total hip arthroplasty.

METHODS

Ninety patients (49 female, 41 male; mean age: 63 ± 12.87 years) fulfilled inclusion criteria and completed a comprehensive preoperative assessment comprising sociodemographic, clinical, functional and psychological phenotypes. Moreover, the strengths of preoperative expectations for improvements in eight pain-related and functional domains were recorded on a 5-point Likert-scale. At 12 months after surgery, patients were asked to rate perceived improvements in each of these domains as well as the global effectiveness of the total hip replacement on a 5-point Likert-scale. To evaluate the relative impact of preoperative expectations, symptom improvement and the fulfillment of expectations on the global effectiveness of surgery, a sequential multiple regression analysis was performed.

RESULTS

Compared with the actual improvement at 12-months follow-up, prior expectations had been overly optimistic in about 28% of patients for hip pain, in about 45% for walking ability and around 60% for back pain, independence in everyday life, physical exercise, general function social interactions and mental well-being. An optimistic hip pain expectation, walking ability at baseline and the fulfillment of expectations for walking ability, general function and independence in everyday life were found to independently predict global effectiveness ratings.

CONCLUSIONS

Positive expectation about pain and the fulfillment of expectations concerning functional domains predicted higher global effectiveness ratings. In line with many authors investigating the relationship between the fulfillment of expectations and satisfaction with medical interventions, we suggest that professionals should explicitly address their patients' expectations during the preoperative education and consultation.

The beta-adrenergic receptor agonist, terbutaline, reduces UVB-induced mechanical sensitization in humans

OBJECTIVES

Previously, we found in cultures of primary neurons and in animals that sensitized primary neurons can be desensitized by treatment with e.g. beta-adrenergic receptor agonists. We now tested whether also in human sensitization such as UVB-radiation induced sunburn-like hyperalgesia can be reduced by intradermal injection of the beta-adrenergic receptor agonist terbutaline.

METHODS

In our prospective randomized study, 17 participants received an individual UVB dose to cause a defined local sunburn-like erythema at four locations, two on each forearm. Twenty-four hours later, the sensitized four areas were injected intradermally with terbutaline pH 4.3, terbutaline pH 7.0, saline pH 4.3 or saline pH 7.0, respectively. Pain thresholds were examined before and after induction of UVB-sensitization, and 15, 30 and 60 min after injection of the respective solution. Mechanical pain thresholds of the skin and of deeper tissues were determined by pinprick and pressure algometer measurements, respectively.

RESULTS

UVB-irradiation decreased mechanical pain thresholds for pinprick and pressure algometer measurements demonstrating a successful sunburn-like sensitization. Intradermal injection of terbutaline pH 7.0 into the sensitized skin reduced the sensitization for all measured timepoints as determined by pinprick measurements. Pinprick measurements of sensitization were not reduced by injection of terbutaline pH 4.3, saline solution pH 7.0 or saline solution pH 4.3. Also, sensitization of deeper tissue nociceptors were not altered by any of the injections as measured with the pressure algometer.

CONCLUSIONS

Similar to our cellular observations, also in humans beta-adrenergic agonists such as terbutaline can reduce the sensitization of primary neurons in the skin.

SIGNIFICANCE

We previously showed in model systems that beta-adrenergic stimulation can not only sensitize but also desensitize nociceptors. Our study shows that also in humans beta-adrenergic agonists desensitize if injected into UVB-sensitized skin. This indicates an analgesic activity of adrenergic agonists in addition to their vasoconstrictory function.

Vibration and rotation during biaxial pressure algometry is related with decreased and increased pain sensations

OBJECTIVE

During palpation, the pressure intensity and direction include minor deviations suggesting that standardized variations of the pressure intensity during pressure algometry may optimize the stimulus efficacy. This study examined the perceived pain outcome and reliability of a biaxial (bidirectional) algometer exerting rotational and vibratory stimulation on top of the basic pressure.

METHODS

In 24 healthy subjects, pressure pain thresholds (PPTs) were recorded with a linear pressure gradient (30 kPa/s) applied by a 1-cm(2) probe bilaterally on the tibialis anterior muscle via biaxial and handheld algometers. During constant pressure stimulation (5 seconds, 75%, 100%, 125% PPT), rotational (45°, 90°, and 180°), linear vibrational (15, 25, and 50 Hz), and radial vibrational stimulations (5, 15, and 25 Hz) were applied randomly via regular and fanning rounded probes (1 cm(2)). Subjects rated perceived pain on a 10-cm visual analogue scale on two occasions separated by 1 week period.

RESULTS

Repeated measures analysis of variance revealed enhanced effect of rotation angle (P < 0.001), probe (P < 0.001), and radial vibration frequency (P < 0.02), and suppressing effect of axial vibration frequency (P < 0.03) on pain perception, relative to basic pressure alone. PPT reliability of biaxial and handheld algometers showed averaged intraclass correlation coefficient of 0.94 and 0.945, and coefficient of variations of 15.4 and 13.5%, respectively.

CONCLUSIONS

PPT assessment and multidirectional stimulations can be exerted reliably via biaxial algometer. Linear vibrational stimulation effect on pressure pain perception verified the inhibitory interaction between simultaneous pressure stimulation of low-threshold mechanoreceptors and nociceptors, while radial vibration and rotational stimulation showed facilitatory effects.

Algometry with a clothes peg compared to an electronic pressure algometer: a randomized cross-sectional study in pain patients

BACKGROUND

Hypersensitivity of the central nervous system is widely present in pain patients and recognized as one of the determinants of chronic pain and disability. Electronic pressure algometry is often used to explore aspects of central hypersensitivity. We hypothesized that a simple pain provocation test with a clothes peg provides information on pain sensitivity that compares meaningfully to that obtained by a well-established electronic pressure algometer. "Clinically meaningful" was defined as a medium (r = 0.3-0.5) or high (r > 0.5) correlation coefficient according to Cohen's conventions.

METHODS

We tested 157 in-patients with different pain types. A calibrated clothes peg was applied for 10 seconds and patients rated the pain intensity on a 0 to 10 numerical rating scale. Pressure pain detection threshold (PPdt) and pressure pain tolerance threshold (PPtt) were measured with a standard electronic algometer. Both methods were performed on both middle fingers and ear lobes. In a subgroup of 47 patients repeatability (test-retest reliability) was calculated.

RESULTS

Clothes peg values correlated with PPdt values for finger testing with r = -0.54 and for earlobe testing with r = -0.55 (all p-values < 0.001). Clothes peg values also correlated with PPtt values for finger testing with r = -0.55 (p < 0.001). Test-retest reliability (repeatability) showed equally stable results for clothes peg algometry and the electronic algometer (all r-values > 0.89, all p-values < 0.001).

CONCLUSIONS

Information on pain sensitivity provided by a calibrated clothes peg and an established algometer correlate at a clinically meaningful level.

Reliability and usefulness of the pressure pain threshold measurement in patients with myofascial pain

Objective

To assess the usefulness of a pressure algometer to measure pressure pain threshold (PPT) for diagnosis of myofascial pain syndrome (MPS) in the upper extremity and trunk muscles.

Method

A group of 221 desk workers complaining of upper body pain participated in this study. Five physiatrists made the diagnosis of MPS using physical examination and PPT measurements. PPT measurements were determined for several muscles in the back and upper extremities. Mean PPT data for gender, side, and dominant hand groups were analyzed. Sensitivity and specificity of Fischer's standard method were evaluated. PPT cut-off values for each muscle group were determined using an ROC curve.

Results

Cronbach's alpha for each muscle was very high. The PPT in men was higher than in females, and the PPT in the left side was higher than in the right side for all muscles tested (p<0.05). There was no significant difference in PPT for all muscles between dominant and non-dominant hand groups. Diagnosis of MPS based on Fischer's standard showed relatively high specificity and poor sensitivity.

Conclusion

The digital pressure algometer showed high reliability. PPT might be a useful parameter for assessing a treatment's effect, but not for use in diagnosis or even as a screening method.