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Christine N Sang

Publications and source records attributed to Christine N Sang.

7 recordsLinked to original sources
PubMed2005

Advances and limitations in the evaluation of analgesic combination therapy.

Combination therapy using multiple drugs or modalities that target multiple mechanisms is common practice in the treatment of chronic pain. The benefit of combination therapy is purported to lie in its ability to provide improved efficacy with reduced toxicity. However, there are few published trials evaluating combination analgesics. Therefore, clinical choices regarding treatments, doses, and schedules tend to be determined empirically from innumerable drug combinations and permutations. Synergism is in part dependent on the pain condition, drug-drug interactions, and dose responses of the individual treatment components (among known and unknown factors), and a quantification of synergistic interactions would enable a rational approach to the use of combination analgesic therapy. Traditionally, drug interactions were evaluated by first establishing dose-response relationships of the individual component drugs and the combination in fixed dose ratios, followed by constructing isobolograms that would then allow a detailed statistical analysis. This strategy is at best challenging to perform in chronic analgesic trials. This article discusses the gold standard analytic approach to evaluating combination therapies (isobolograms), various permutations of this approach in human subjects, and the challenges of designing randomized controlled clinical trials that assess synergism between two therapies.

Analgesics↗
PubMed2003

Stability and reliability of detection thresholds for human A-Beta and A-delta sensory afferents determined by cutaneous electrical stimulation.

Activity in primary afferent fibers that usually mediate fine touch can evoke sensations of pain in conditions in which there is sensitization of central neurons. Input from these large diameter Abeta afferents may also sustain and exacerbate these central mechanisms. The role of these fibers in clinical pain syndromes can be evaluated by applications of electrical stimuli that preferentially activate Abeta axons. This study assessed the stability and reliability of a method of electrical stimulation (ES) useful for clinical evaluation. Monopolar constant-current rectangular pulses were delivered to 5 equi-spaced sites on the volar aspect of the left forearm along a transverse line 5 cm distal to the antecubital crease. Current intensity was gradually increased to determine detection threshold and pain detection threshold. This study determined: 1) Effect of pulse duration (1, 2, and 5 msec); 2) the variation of detection threshold and pain threshold over repeated stimulation; 3) the effect of electrode position with respect to distance from the trunk of underlying ulnar or median nerves; and 4) the effect of re-positioning the electrode on variability of detection threshold and pain threshold. There was no significant variability over time for either detection threshold (DT) or pain threshold (PT) at any of the 3 pulse durations tested. There was also no significant effect on variability of shifting the electrode between sites, nor was there a significant difference in variability between sites when placed either over or adjacent to peripheral nerves. Under simulated clinical conditions of electrode re-positioning, the mean detection threshold in 300 trials and ten subjects was 0.30 mA with an overall standard error of 0.007, standard errors of 0.014 over the 10 subjects, 0.003 over the 6 trials, and 0.012 over the 5 locations. Similarly, mean pain threshold in these 300 trials was 3.24 +/- 0.093, with standard errors of 0.12 over the 10 subjects, 0.023 over the 6 trials, and 0.13 over the 5 locations. Mean ratio of pain threshold divided by detection threshold ratio was 10.9 +/- 0.25 with a range of 2.0-28.3. Single pulse, constant current electrical stimulation of the skin at threshold levels is a quantifiable and reliable sensory method that is repeatable within and between testing sessions. Our results suggest that in skin unaffected by allodynia, a ratio of the two sensory thresholds (pain threshold and detection threshold) of less than 2.0 is uncommon. We propose that, in the presence of mechanical allodynia, a pain threshold/detection threshold of less than 2.0 suggests that altered central nervous system processing of Abeta input may contribute to allodynia.

Adult↗
PubMed2002

The role of fluoroscopy in cervical epidural steroid injections: an analysis of contrast dispersal patterns.

STUDY DESIGN: A multicenter, retrospective analysis of cervical epidurograms. OBJECTIVES: To determine the effectiveness of the loss of resistance (LOR) technique in identifying the cervical epidural space. To delineate the pattern of epidural contrast spread during cervical epidural steroid injections. BACKGROUND: Previous studies have shown that if performed without fluoroscopy, the LOR technique can result in inaccurate needle placement in up to 30% of lumbar epidural steroid injections. To date, no study has examined accuracy of LOR technique and pattern of radiographic contrast spread in cervical epidural levels. METHODS: Epidurograms of 38 cervical epidural steroid injections in 31 patients were reviewed. The number of LOR attempts and pattern of contrast spread was analyzed. The effects of age, gender, MRI results, previous cervical laminectomy, and the physician's level of training were correlated with results. RESULTS: The authors found a 53% rate of false LOR during the first attempt to enter the epidural space. Unilateral epidural contrast spread was found in 51% and ventral epidural spread was found in 28% of cases. The average number of cervical vertebral levels covered with 2 mL of contrast was 3.14, with significantly wider spread noted in those patients who had not undergone previous cervical laminectomy. Other variables did not influence the accuracy of needle placement and pattern of epidural contrast spread. CONCLUSIONS: The loss of resistance technique may not be an adequate method for ensuring accurate needle placement in blindly performed cervical epidural injections. The use of epidurography can improve the accuracy of needle placement and medication delivery to targeted areas of pathology.

Adult↗
PubMed2002

The technical aspects of epidural steroid injections: a national survey.

UNLABELLED: Although epidural steroid injections (ESIs) are a common treatment for chronic pain conditions, it is not clear whether there is consensus on their technical aspects. The current literature suggests that variations in technical aspects may affect ESI outcomes. The goal of the survey was to help establish a standard frame of reference for the performance of ESIs. We analyzed survey results from 68 academic anesthesia programs and 28 private practices in the United States. The main finding in this survey is that there is no clear-cut consensus as to the ideal method to perform ESI. There is a wide variation among individual practices in almost every technical aspect of ESI. Private practices use significantly more fluoroscopy than academic centers. The large difference was found in the cervical region where 73% of private practices and only 39% of academic institutions polled perform the ESIs with fluoroscopic guidance (P = 0.005). A similar discrepancy was found in approaches to the epidural space after laminectomy where 61% of private practices, but only 15% of academic centers, use the transforaminal approach. The study results indicate that there is no consensus, and that there is a wide variation in current practices. IMPLICATIONS: A national survey of practices performing epidural steroid injections was conducted. The purpose was to establish whether consensus exists on technical aspects of this procedure. The study results indicate that there is no consensus, and that there is a wide variation in current practices.

Analgesia, Epidural↗
PubMed2002

Dextromethorphan and memantine in painful diabetic neuropathy and postherpetic neuralgia: efficacy and dose-response trials.

BACKGROUND: There are few repeated dose-controlled trials of N-methyl-d-aspartate glutamate receptor antagonists in patients with neuropathic pain. The authors sought to evaluate two low-affinity N-methyl-d-aspartate antagonists using a novel two-stage design. METHODS: The authors studied patients with painful diabetic neuropathy (DN) and postherpetic neuralgia (PHN) in two crossover trials: (1) efficacy trial (dextromethorphan vs. memantine vs. active placebo [lorazepam]) and (2) dose-response trial of the preferred active drug in responders from the first study (0% vs. 25% vs. 50% vs. 100% of each patient's maximally tolerated dose). Pain intensity was measured on a 20-point scale. RESULTS: Nineteen of 23 DN patients and 17 of 21 PHN patients completed the efficacy trial. Median doses for DN and PHN were 400 and 400 mg/day dextromethorphan, 55 and 35 mg/day memantine, and 1.8 and 1.2 mg/day lorazepam. In the efficacy trial, among patients with DN, dextromethorphan reduced pain intensity by a mean of 33% from baseline, memantine reduced pain intensity by a mean of 17%, and lorazepam reduced pain intensity by a mean of 16%; the proportions of subjects achieving greater than moderate pain relief were 68% with dextromethorphan, 47% with memantine, and 37% with lorazepam. Mean reductions in pain intensity in patients with PHN were 6% with dextromethorphan, 2% with memantine, and 0% with lorazepam. No comparison with placebo reached statistical significance in the efficacy trial. In the 10 DN subjects who responded to dextromethorphan, there was a significant dose-response effect on pain intensity (P = 0.035), with the highest dose significantly better than that of lorazepam (P = 0.03). CONCLUSIONS: Dextromethorphan is effective in a dose-related fashion in selected patients with DN. This was not true of PHN, suggesting a difference in pain mechanisms. Selective approaches to pain-relevant N-methyl-d-aspartate receptors are warranted.

Adult↗