Age and upper limb tension testing affects current perception thresholds.

Current perception threshold (CPT) testing was used to quantitatively measure the sensory response to upper limb tension testing (ULTT). The study addressed the ability of ULTT to tension the intended nerve, and the influence of age on CPT. Normal subjects (n=59) performed a randomized series of CPT tests at 5 and 2,000 Hz in a resting position and in a median-nerve bias position using the Neurometer. Results indicate that ULTT impacts CPT in normal subjects, with greater effects observed in the ulnar nerve (p<0.05) than for median nerve (NS). Age was a significant covariate for CPT (2,000 Hz, p=0.032; 5 Hz, p=0.034), and Pearson correlations indicated a weak but significant correlation of age with CPT. Age had a differential impact on CPT frequencies, suggesting differential impacts on nerve fibers, with a trend towards hypoesthesia at 2,000 Hz (r=0.10 to 0.30) and toward hyperesthesia at 5 Hz (r=-0.16 to -0.28). ULTT causes measurable effects in the sensory threshold of peripheral nerve, which are more pronounced with age; increased touch threshold and decreased pain thresholds can be expected. The specificity of nerve bias elicited by specific ULTT needs further exploration.     

Reproducibility of current perception threshold with the Neurometer® vs the Stimpod NMS450 peripheral nerve stimulator in healthy volunteers: an observational study

Purpose

Current methods of assessing nerve blocks, such as loss of perception to cold sensation, are subjective at best. Transcutaneous nerve stimulation is an alternative method that has previously been used to measure the current perception threshold (CPT) in individuals with neuropathic conditions, and various devices to measure CPT are commercially available. Nevertheless, the device must provide reproducible results to be used as an objective tool for assessing nerve blocks.

Methods

We recruited ten healthy volunteers to examine CPT reproducibility using the Neurometer^® and the Stimpod NMS450 peripheral nerve stimulator. Each subject’s CPT was determined for the median (second digit) and ulnar (fifth digit) nerve sensory distributions on both hands – with the Neurometer at 5 Hz, 250 Hz, and 2000 Hz and with the Stimpod at pulse widths of 0.1 msec, 0.3 msec, 0.5 msec, and 1.0 msec, both at 5 Hz and 2 Hz. Intraclass correlation coefficients (ICC) were also calculated to assess reproducibility; acceptable ICCs were defined as ≥ 0.4.

Results

The ICC values for the Stimpod ranged from 0.425-0.79, depending on pulse width, digit, and stimulation; ICCs for the Neurometer were 0.615 and 0.735 at 250 and 2,000 Hz, respectively. These values were considered acceptable; however, the Neurometer performed less efficiently at 5 Hz (ICCs for the second and fifth digits were 0.292 and 0.318, respectively).

Conclusion

Overall, the Stimpod device displayed good to excellent reproducibility in measuring CPT in healthy volunteers. The Neurometer displayed poor reproducibility at low frequency (5 Hz). These results suggest that peripheral nerve stimulators may be potential devices for measuring CPT to assess nerve blocks.     

The addition of epinephrine increases intensity of sensory block during epidural anesthesia with lidocaine

BACKGROUND AND OBJECTIVES: Little is known about the effect of adding epinephrine to local anesthetic solutions on the intensity of sensory block during epidural anesthesia. This study examined development of sensory block during lumbar epidural anesthesia using a cutaneous current perception threshold (CPT) quantitative sensory testing device. METHODS: Twenty ASA I patients who were randomly divided to receive 10 mL 1% lidocaine with (group E) or without (group P) epinephrine 1:200,000. Current perception threshold at 2,000, 250, and 5 Hz stimulation at the trigeminal (V), ninth thoracic (T9), and second lumbar (L2) dermatomes, and the dermatomal levels of block of light touch, temperature, and pinprick discrimination were measured before and every 5 minutes, until 60 minutes after injection of epidural lidocaine. RESULTS: After epidural administration of lidocaine with epinephrine, all CPT significantly increased at T9 and L2, whereas no increase was detected after epidural plain lidocaine. Areas under the curves, calculated to express overall magnitude and duration of CPT values, were significantly larger in group E than those in group P at 2,000 and 250 Hz at T9. No differences were observed in the maximal levels of loss of cold, pinprick, and touch sensations between both groups. CONCLUSIONS: These results suggest that lumbar epidural anesthesia using 10 mL 1% lidocaine with epinephrine produces a more intense block of both large and small diameter sensory nerve fibers than that with plain lidocaine. It appears, therefore, that the addition of epinephrine improves the quality of sensory block during epidural anesthesia with lidocaine.     

Adhesiolysis and targeted steroid/local anesthetic injection during epiduroscopy alleviates pain and reduces sensory nerve dysfunction in patients with chronic sciatica

PURPOSE: The aim of this study was to evaluate the effect of adhesiolysis followed by the injection of steroid and local anesthetic during epiduroscopy on sensory nerve function, pain, and functional disability in patients with chronic sciatica. METHODS: Epidural adhesiolysis, using epiduroscopy, followed by the injection of steroid and local anesthetic, was scheduled in 19 patients with chronic sciatica refractory to lumbar epidural block. Sensory nerve function in the legs was tested with a series of 2000-Hz (Abeta-fiber), 250-Hz (Adelta-fiber), and 5-Hz (C-fiber) stimuli, using the current perception threshold (CPT), and CPT values and intensity of pain and Roland Morris Disability Questionnaire (RMDQ) scores were assessed before and 1 and 3 months after the epiduroscopy. RESULTS: At all frequencies, the CPT values in the affected legs of patients before the epiduroscopy were significantly higher than those in the unaffected legs. Epidural adhesiolysis was successfully performed in 16 of the 19 patients. In these patients, the CPT values at 2000 and 250 Hz, and the pain and RMDQ scores 1 and 3 months after the epiduroscopy were significantly lower than those before the epiduroscopy, while the CPT value at 5 Hz did change. CONCLUSION: Epidural adhesiolysis followed by the injection of steroid and local anesthetic during epiduroscopy alleviated pain, and functional disability, and reduced dysfunction of Abeta and Adelta fibers in patients with chronic sciatica.     

The impact of wrist extension provocation on current perception thresholds in patients with carpal tunnel syndrome: a pilot study.

PURPOSE: To determine whether current perception threshold (CPT) varied between subjects with and without carpal tunnel syndrome (CTS) and whether positioning in wrist extension (reversed Phalen's test) was provocative. METHOD: Subjects (n=30) were tested using the Neurometer (Neutron, Inc., Baltimore, MD) at 5, 250, and 2,000 Hz in a rest and reverse Phalen's position. Group and positional differences were analyzed using analysis of variance. RESULTS: Higher CPT occurred at 2,000 Hz in both rest (p=0.02) and reverse Phalen's position (p=0.01) in CTS subjects. There was also a significant change in CPT in the CTS group following wrist extension, particularly at 2,000 Hz (p<0.05). CONCLUSION: A positional effect on sensibility was noted at 2,000 Hz in subjects with CTS. Further evaluation is required to determine the role and optimal test protocols for provocative-sensory testing in diagnosis and outcome assessment of CTS. For CPT these should focus on using the 2,000 Hz frequency.     

Evaluation of adhesive tape containing lidocaine using current perception threshold measurement

Lidocaine adhesive tape (Penles; Wyeth Lederle Japan, Ltd, Tokyo, Japan) is placed for pain relief prior to puncturing a vein with a needle. We investigated the optimal time interval from application of Penles to vein puncture by measuring current perception threshold (CPT) levels with a Neurometer, by which it was possible to measure the extent of nerve block in a non-invasive and quantitative manner with 3 electrical stimulus rates (2000 Hz, 250 Hz, and 5 Hz). Penles was applied to the dorsum of volunteers' hands for 1, 2, 4, 6 and 12 hours before measuring CPT levels. With a stimulation rate of 2000 Hz and 250 Hz, CPT, levels were found to increase 4 hours after the Penles application, while peak CPT levels for 5 Hz stimulation were observed from 6 to 12 hours after application. However, CPT levels tended to decrease 12 hours after application, regardless of the stimulus rate. From the result, we conclude that Penles provides maximum benefit when applied 6 hours prior to vein puncture.     

Aging and overactive bladder may be associated with loss of urethral sensation in women

AIMS: To compare current perception thresholds (CPT) in the urethra and bladder of women with idiopathic overactive bladder to asymptomatic controls. METHODS: Women with > or =1 urge urinary incontinence (UUI) episode per week on 7-day diary, seeking treatment for UUI underwent CPT testing using a Neurometer(R) CPT device (Neurotron, Inc., Baltimore, MD). Testing was done in the urethra and bladder at three frequencies 2,000, 250, and 5 Hz corresponding to A-beta, A-delta, and C fibers, respectively. CPT values from the women with UUI were compared to CPT values from a group of control women without lower urinary tract symptoms. RESULTS: Forty-eight controls without lower urinary tract symptoms and 13 women with UUI were included in the analysis. Women with UUI were significantly older (mean +/- SD age 62 +/- 14 and 44 +/- 15, P < 0.0005) and more likely to be vaginally parous (P = 0.007) than control women. Urethral CPT at 2,000, 250, and 5 Hz were significantly higher in women with UUI than controls, while bladder CPT were not different between groups. Using logistic regression, to control for age and parity, urethral CPT at 5 Hz remained significantly higher in women with UUI than controls (P = 0.013). CONCLUSION: Urethral sensation is significantly higher in older women, suggesting sensory neuropathy in the lower urinary tract increases with age and may contribute to the increase in overactive bladder seen with aging. These data reinforce the role of the urethra in lower urinary tract function.     

Urethral and bladder current perception thresholds: normative data in women

PURPOSE: Given increased evidence of sensory dysfunction in lower urinary tract pathology, we determined normative current perception threshold values in the lower urinary tract of asymptomatic women. MATERIALS AND METHODS: After receiving institutional review board approval women without lower urinary tract symptoms underwent current perception threshold testing of the urethra and bladder using a Neurometer constant current stimulator. Current perception threshold values were determined at 3 frequencies, including 2,000 Hz (corresponding to A-beta fibers), 250 Hz (corresponding to A-delta fibers) and 5 Hz (corresponding to C fibers). RESULTS: A total of 48 women with a mean age of 38 years (range 23 to 67) underwent current perception threshold testing. Normative values were established for the urethra and bladder at 2,000, 250 and 5 Hz. Median urethral current perception thresholds at 2,000, 250 and 5 Hz were 1.2 (IQR 0.76-1.5), 0.45 (IQR 0.33-0.56) and 0.11 mA (IQR 0.07-0.24), respectively. Median bladder current perception thresholds at 2,000, 250 and 5 Hz were 4.1 (IQR 2.0-6.3), 2.3 (IQR 0.87-5.5) and 1.4 mA (IQR 0.22-2.9), respectively. Urethral and bladder current perception thresholds increased significantly with subject age at all 3 frequencies (p<0.0005). Prior pelvic surgery was associated with an increased bladder current perception threshold at all 3 frequencies (p<0.005) but not with the urethral current perception threshold. CONCLUSIONS: We report urethral and bladder current perception thresholds for a large sample of asymptomatic women. These reference values may help elucidate changes in afferent nerve function in women with lower urinary tract dysfunction.     

Comparison between sensory testing modalities for the evaluation of afferent nerve functioning in the genital area

Determine the reproducibility and relationship between current perception threshold testing (CPT) and quantitative sensory testing (QST) in the genital area. Sixteen women underwent CPT and QST of the vagina. CPT was done at 2,000, 250, and 5 Hz (corresponding to A-β, A-δ, and C fibers, respectively), and QST testing was done using thermal (C fibers), vibratory (A-β fibers), and cold (A-δ and C fibers) sensation. Ten women underwent repeated testing 1 week later. Thermal and vibratory thresholds correlated with CPT at 5 and 2,000 Hz (ρ = 0.77, P = 0.002 and ρ = 0.6, P = 0.01, respectively). Repeated thermal, vibratory, and cold thresholds had good concordance correlation (rho__c = 0.83, rho__c = 0.96, rho__c = 0.77). CPT at 5 and 2,000 Hz were also strongly correlated (rho__c = 69, rho__c = .7). CPT and QST testing stimulate similar afferent nerve fiber populations in the vagina.     

Quantitative and selective assessment of sensory block during lumbar epidural anaesthesia with 1% or 2% lidocaine

We have examined sensory block during lumbar epidural anaesthesia using a cutaneous current perception threshold (CPT) sensory testing device in 20 patients who received 10 ml of either 1% or 2% lidocaine (lignocaine). CPT at 2000, 250 and 5 Hz stimulation at the trigeminal (V), ninth thoracic (T9) and second lumbar (L2) dermatomes, and dermatomal levels of block to light touch, temperature and pinprick discrimination were measured before and every 5 min until 60 min after epidural lidocaine. There were significant differences between 1% and 2% epidural lidocaine in all CPT at T9 and L2, in addition to maximal cephalad spread of the three sensory modalities. After 2% lidocaine, all CPT increased significantly at T9 and L2. In contrast, only at 250 and 5 Hz for L2 did epidural block with 1% lidocaine produce significant increases in CPT. Maximal level of loss of touch sensation after 1% lidocaine was significantly lower than that of cold and pinprick sensations. We conclude that the dose of lidocaine affected intensity of sensory block during lumbar epidural anaesthesia. In addition, differential neural block resulting from epidural anaesthesia appeared to be associated with a differential effect on nerve fibres of different sizes.      

Objective assessment of nerve injury after greater saphenous vein stripping.

AIM: The complication of nerve injury after greater saphenous vein stripping for varicosity is subjective, and a method for objective evaluation has never been established. The aim of this study was to evaluate postoperative sensory changes by quantitative assessment of current perception threshold (CPT), and to clarify the relation between CPT and symptoms. PATIENTS AND METHODS: Between January 2003 and August 2005, 27 limbs in 18 patients were enrolled. Quantitative sensory function was determined through CPT using a Neurometer (Neurotron, Inc., USA), with which saphenous nerve neural fiber selective minimum sensing values against three electrical stimuli (2000, 250, 5 Hz) were measured. CPT measurements were scheduled on the day before the operation, and 2-7 days, 1, 3, and 6 months after the operation. RESULTS: An increase in CPT value of more than 20% or decrease to below 50% compared to the preoperative value with at least two stimuli was defined as CPT abnormality. Subjective symptoms were observed in 13 limbs in the early postoperative period, and 10 limbs showed CPT abnormality. In 6 limbs with a CPT increase over 20% with all three stimuli, neurological symptoms continued for 6 months. CONCLUSIONS: CPT evaluation provides an objective indication of neurological symptoms in the lower limb following varicose vein surgery.     

Quantitative and selective evaluation of differential sensory nerve block after transdermal lidocaine

We evaluated the effect of transdermal lidocaine on differential sensory nerve block in 15 healthy volunteers. Lidocaine 10% gel was applied topically to a forearm and covered with a plastic film. Three types of sensory nerve fibers (Abeta, Adelta, and C fibers) were evaluated with a series of 2000-, 250-, and 5-Hz stimuli using current perception threshold (CPT) testing. Sensations of touch, pinprick, cold, and warmth were also measured. These measurements were made before the topical lidocaine (baseline), 60 min after the draping (T0), and at 1-h intervals until 5 h after T0 (T1 to T5). A significant increase in CPT compared with baseline was observed until T2 at 5 Hz and T4 at 250 Hz, whereas the increase in CPT at 2000 Hz continued throughout the study period. All subjects experienced the disappearance of pinprick and cold sensations, whereas touch and warmth sensations were detectable during the study period. We conclude that when lidocaine is applied transdermally, the sensitivity of nerves to local anesthetics is proportional to the axon diameters. However, pinprick and cold sensation are affected more strongly than other sensations at receptor sites. IMPLICATIONS: We evaluated the effect of transdermal lidocaine on differential sensory nerve block in healthy volunteers. Our results show that the sensitivity of nerves to local anesthetics is proportional to the axon diameter.     

Neuroselective current perception threshold evaluation of bladder mucosal sensory function

OBJECTIVE: To evaluate human bladder mucosal sensory function by neuroselective Current Perception Threshold (CPT) measures from healthy and neuropathic bladders. METHODS: Eight healthy volunteers and 38 patients with urinary symptoms underwent conventional urodynamic tests including water-filling cystometry and ice water test. Standardized neuroselective CPT measures were obtained from the left index finger and the mucosa of the posterior bladder wall. Three different CPTs were obtained from each test site using a constant alternating current sinusoid waveform electrical stimulus presented at 2000Hz, 250Hz and 5Hz stimulation frequencies, which could selectively reflect the functions of the large myelinated fibers (A-beta-fiber), the small myelinated fibers (A-delta-fiber), and the unmyelinated fibers (C-fiber), respectively. RESULTS: As the determination of CPT values on the finger skin, the CPT values in the bladder could be determined using the neuroselective measures in all patients but three who had no sensory response (absence of sensation) caused by complete spinal injury. In the 8 patients with detrusor hyperreflexia due to incomplete spinal cord injury (supra-sacral lesion), the bladder CPT value (4.0+/-1.9) at 5Hz was significantly lower (p<0.01) than that in the controls (26.2+/-17.7). In the neurogenic bladders determined to be underactive (n=11, including post pelvic surgery, post infra-sacral level spinal cord injury and diabetes patients), the higher CPT values of bladder mucosal sensory functions were found at 5Hz (p<0.05), 250Hz (p=0.07), and 2000Hz (p<0.05) compared to the controls. CONCLUSIONS: Quantitative neuroselective measurement of CPT values in the human bladder mucosal function was feasible. Hypersensitivity or hyposensitivity of the urinary sensory function could be determined using the CPT values in comparison to control. The quantitative neuroselective estimation of the bladder sensory functions in different types of sensory peripheral nerve fibers may contribute to the appropriate selection of therapeutic strategy in patients with urinary sensory dysfunction.     

Increased Sensitivity to Thermal Pain and Reduced Subcutaneous Lidocaine Efficacy in Redheads

Background: Anesthetic requirement in redheads is exaggerated, suggesting that redheads may be especially sensitive to pain. Therefore, the authors tested the hypotheses that women with natural red hair are more sensitive to pain and that redheads are resistant to topical and subcutaneous lidocaine.

Methods: The authors evaluated pain sensitivity in red-haired (n = 30) or dark-haired (n = 30) women by determining the electrical current perception threshold, pain perception, and maximum pain tolerance with a Neurometer CPT/C (Neurotron, Inc., Baltimore, MD). They evaluated the analogous warm and cold temperature thresholds with the TSA-II Neurosensory Analyzer (Medoc Ltd., Minneapolis, MN). Volunteers were tested with both devices at baseline and with the Neurometer after 1-h exposure to 4% liposomal lidocaine and after subcutaneous injection of 1% lidocaine. Data are presented as medians (interquartile ranges).

Results: Current perception, pain perception, and pain tolerance thresholds were similar in the red-haired and dark-haired women at 2,000, 250, and 5 Hz. In contrast, redheads were more sensitive to cold pain perception (22.6 [15.1-26.1] vs. 12.6 [0-20][degrees]C; P = 0.004), cold pain tolerance (6.0 [0-9.7] vs. 0.0 [0.0-2.0][degrees]C; P = 0.001), and heat pain (46.3 [45.7-47.5] vs. 47.7 [46.6-48.7][degrees]C; P = 0.009). Subcutaneous lidocaine was significantly less effective in redheads (e.g., pain tolerance threshold at 2,000-Hz stimulation in redheads was 11.0 [8.5-16.5] vs. > 20.0 (14.5 to > 20) mA in others; P = 0.005).     

Neuroselective measure of the current perception threshold of A‐delta and C‐fiber afferents in the lower urinary tract

Sensory dysfunction could be involved in various pathogeneses in the lower urinary tract including neurogenic bladder, overactive bladder, painful bladder syndrome and neuropathy as a result of endocrine disorders. The ability to diagnose sensory function more objectively is of increasing interest to clinicians. Afferent innervations of the lower urinary tract involve myelinated (A‐delta) and unmyelinated (C) fibers. The Neurometer (Neurotron, Baltimore, MD, USA) is the only reported commercially available device to evaluate afferent function by selectively depolarizing different subpopulations of afferent nerves, with 250 Hz activating A‐delta fibers and 5 Hz activating C‐fibers, to determine their current perception threshold (CPT) as a quantitative measure. Recently, increased evidence has suggested that measurement of CPT values of A‐delta and C‐fibers in the lower urinary tracts is feasible and shows significant correlation with clinical symptoms and conventional urodynamic variables, as well as the efficacy of various treatments. However, there are still controversial issues in the wider use of this technology in diagnosis and assessment of the therapeutic effectiveness of sensory dysfunction in the lower urinary tracts. In order to resolve the remaining challenges in the CPT test of the lower urinary tract, recent efforts include development of a new balloon‐type electro‐catheter with dual electrodes as an alternative sensory test for the bladder or urethra, which allows simultaneous performance of conventional urodynamic tests and urine collection, and future standardized techniques available for comparison with validated control values.     

Current perception thresholds and postoperative pain in schizophrenic patients

BACKGROUND AND OBJECTIVES: Schizophrenic patients may have less sensitivity to pain; however, pain insensitivity in schizophrenia has not been adequately evaluated. We investigated current perception threshold (CPT) and postoperative pain intensity in patients with long-standing and treated schizophrenia and control patients. METHODS: We measured CPTs for 2,000 Hz, 250 Hz, and 5 Hz and postoperative pain intensity using a visual analogue scale (VAS) in 50 chronic schizophrenic patients who were on chronic phenothiazine derivatives (> 10 years) and for 25 control patients. RESULTS: CPTs for 2,000 Hz, 250 Hz, and 5 Hz in schizophrenic patients were 334.2 +/- 112.2, 303.9 +/- 117.1, and 165.0 +/- 72.3, respectively. CPTs for 2,000 Hz, 250 Hz, and 5 Hz in schizophrenic patients were significantly higher than those of control patients. VAS pain scores of schizophrenic patients were 4.0 +/- 1.7 at 2 hours post-operatively and 3.8 +/- 1.5 at 5 hours postoperatively, which were significantly (P < .05) lower than those (5.0 +/- 1.6 and 5.1 +/- 1.9) of the control group. CONCLUSIONS: Chronic schizophrenic patients have increased current perception threshold and lower VAS pain scores in postoperative pain compared with control patients.     

Increased sensitivity to thermal pain and reduced subcutaneous lidocaine efficacy in redheads

BACKGROUND: Anesthetic requirement in redheads is exaggerated, suggesting that redheads may be especially sensitive to pain. Therefore, the authors tested the hypotheses that women with natural red hair are more sensitive to pain and that redheads are resistant to topical and subcutaneous lidocaine. METHODS: The authors evaluated pain sensitivity in red-haired (n = 30) or dark-haired (n = 30) women by determining the electrical current perception threshold, pain perception, and maximum pain tolerance with a Neurometer CPT/C (Neurotron, Inc., Baltimore, MD). They evaluated the analogous warm and cold temperature thresholds with the TSA-II Neurosensory Analyzer (Medoc Ltd., Minneapolis, MN). Volunteers were tested with both devices at baseline and with the Neurometer after 1-h exposure to 4% liposomal lidocaine and after subcutaneous injection of 1% lidocaine. Data are presented as medians (interquartile ranges). RESULTS: Current perception, pain perception, and pain tolerance thresholds were similar in the red-haired and dark-haired women at 2,000, 250, and 5 Hz. In contrast, redheads were more sensitive to cold pain perception (22.6 [15.1-26.1] vs. 12.6 [0-20] degrees C; P = 0.004), cold pain tolerance (6.0 [0-9.7] vs. 0.0 [0.0-2.0] degrees C; P = 0.001), and heat pain (46.3 [45.7-47.5] vs. 47.7 [46.6-48.7] degrees C; P = 0.009). Subcutaneous lidocaine was significantly less effective in redheads (e.g., pain tolerance threshold at 2,000-Hz stimulation in redheads was 11.0 [8.5-16.5] vs. > 20.0 (14.5 to > 20) mA in others; P = 0.005). CONCLUSION: Red hair is the phenotype for mutations of the melanocortin-1 receptor. Results indicate that redheads are more sensitive to thermal pain and are resistant to the analgesic effects of subcutaneous lidocaine. Mutations of the melanocortin-1 receptor, or a consequence thereof, thus modulate pain sensitivity.     

Chest tube insertion is one important factor leading to intercostal nerve impairment in thoracic surgery

Objectives

Chest tube insertion seems to be one important factor leading to intercostal nerve impairment. The purpose of this prospective study was to objectively evaluate intercostal nerve damage using current perception threshold testing in association with chest tube insertion.

Methods

Sixteen patients were enrolled in this study. Intercostal nerve function was assessed with a series of 2000-Hz (Aβ fiber), 250-Hz (Aδ fiber), and 5-Hz (C fiber) stimuli using current perception threshold testing (Neurometer CPT/C^®). Current perception threshold values at chest tube insertion were measured before surgery, during chest tube insertion and after removal of the chest tube. Intensities of ongoing pain were also assessed using a numeric rating scale (0–10).

Results

Current perception thresholds at each frequency after surgery were significantly higher than before surgery. Numeric rating scale scores for pain were significantly reduced from 3.3 to 1.9 after removal of the chest tube (p = 0.004). The correlation between current perception threshold value at 2000 Hz and intensity of ongoing pain was marginally significant (p = 0.058).

Conclusions

This is the first study to objectively evaluate intercostal nerve damage at chest tube insertion. The results confirmed that chest tube insertion has clearly deleterious effects on intercostal nerve function.     

The current perception thresholds vary between horizontal and 70 degrees tilt-up positions

We investigated the influence of posture on current perception threshold (CPT). The subjects consisted of 20 healthy male volunteers (23-31 yr old). At both the horizontal and the 70 degrees tilt-up position (TUP), the CPTs (5, 250, and 2000 Hz) of the middle finger were determined by using the Neurometer CPT/C (Neuropteran, Baltimore, MD). Autonomic nervous activities were evaluated by heart rate variability (HRV) analysis and spontaneous baroreflex sensitivity analysis at the two postures previously mentioned. The three CPTs at the 70 degrees TUP were significantly lower than those at the horizontal posture (5 Hz, P < 0.05; 250 Hz, P < 0.001; 2000 Hz, P < 0.05). The changes in HRV and spontaneous baroreflex sensitivity at the 70 degrees TUP indicated decreasing parasympathetic tone. The CPTs of 5 and 250 Hz were significantly correlated with mean systolic blood pressure at the 70 degrees TUP. The CPT of 2000 Hz was significantly correlated with the 0.15-0.4 Hz component in HRV at both postures. The regression analysis of the difference of 5 Hz CPT with that of the mean systolic blood pressure showed a significant correlation (P < 0.001). To evaluate the clinical course of peripheral nerve disorders, the comparison of CPTs measured during the same posture is important. This suggests that CPTs must be measured at the horizontal posture. Implications: Current perception thresholds at the 70 degrees tilt-up posture were significantly lower than those at the horizontal posture. When the compensatory mechanism for preserving blood pressure was emphasized, the current perception thresholds would have a relational connection to mean systolic blood pressure, similar to the concept of hypertension-induced hypoalgesia.     

Current perception threshold evaluation of the female urethra

The purpose of this study was to determine the feasibility of the current perception threshold (CPT) evaluation in the female urethra. Women without LUT dysfunction underwent CPT testing using a Neurometer (Neurotron, Inc., Baltimore, MD) connected to a ring electrode in the urethra. Testing was done in a standardized fashion at three frequencies, 2000, 250 and 5 Hz, to determine when subjects first perceived the stimuli and when perceived stimuli became painful. Current perception threshold testing was accomplished in all 10 subjects studied. The level at which subjects first perceived stimuli was significantly lower than that at which the stimuli became painful ( P<0.002). Mean perception thresholds at 2000, 250 and 5 Hz were 70 microA (range 14-230), 25 microA (4-80) and 17 microA (2-78), respectively, and mean pain thresholds were 229 microA (54-424), 91 microA (24-162) and 110 microA (25-200), respectively. There was no difference in subjects' perception thresholds at 250 and 5 Hz ( P=0.206). Perception thresholds and pain thresholds were significantly different at all other frequencies. Women without LUT dysfunction have lower perception thresholds than pain thresholds and can distinguish between most stimuli at different frequencies. Current perception threshold testing of the female urethra is technically feasible and may be useful for assessing the functional integrity of different afferent pathways.