Chien-Chuan Chen

Association between human opioid receptor genes polymorphisms and pressure pain sensitivity in females

This study examined the association between pressure pain sensitivity and various single nucleotide polymorphisms (SNPs) of human μ‐, κ‐, and δ‐opioid receptor (i.e. OPRM1, OPRK1, and OPRD1) genes in 72 healthy adult Taiwanese women of Han Chinese race. Pressure pain threshold and tolerance were measured by an algometer and polymorphisms of the opioid receptor genes determined from blood samples. Our data revealed that pressure pain threshold, but not tolerance, in subjects with the minor allele (termed ‘GA’) genotype of the IVS2+31G>A polymorphism of the OPRM1 gene was significantly higher than those with major allele (termed ‘GG’) genotype. Neither pressure pain threshold nor tolerance between major and minor alleles of other SNPs of the OPRM1, OPRK1, and OPRD1 genes were significantly different. These data suggest an association between the IVS2+31G>A SNP of the OPRM1 gene and pressure pain sensitivity in healthy adult females.

Premedication with mirtazapine reduces preoperative anxiety and postoperative nausea and vomiting.

BACKGROUND:Mirtazapine is a new antidepressant that blocks 5-HT2 and 5-HT3 receptors. With this receptor profile, it is possible that mirtazapine could provide both anxiolysis and efficacy for postoperative nausea and vomiting (PONV). We therefore tested the hypothesis that premedication with mirtazapine can reduce preoperative anxiety and PONV. METHODS:Eighty female patients with at least two PONV risk factors scheduled for gynecological surgery were enrolled. Dexamethasone 8 mg was given before induction of anesthesia and patients were randomly assigned to group M + D (mirtazapine plus dexamethasone) or group dexamethasone. An oral disintegrating mirtazapine 30 mg or placebo tablet was given 1 h before surgery. Preoperative anxiety level was assessed by a visual analog scale (VAS) before mirtazapine administration and 1 h thereafter. General anesthesia was induced with 1% propofol at the rate of 200 mL/h (until loss of consciousness) and was then maintained with sevoflurane in oxygen and air. An auditory evoked potentials index monitor was used to titrate sevoflurane. The incidence of PONV, the use of rescue antiemetic, complete response, postoperative Ramsay Sedation Scores, and VAS pain scores were assessed 1, 2, and 24 h after surgery and compared. RESULTS:The VAS anxiety scale was lower in group M + D after mirtazapine administration. There were no differences in the induction dose of propofol, the concentrations of sevoflurane during anesthesia, and recovery times between the two groups. The incidence of complete response to PONV over 0–24 h was lower in group M + D (80% vs 50%, P < 0.01). CONCLUSIONS:Premedication with mirtazapine 30 mg reduces the level of preoperative anxiety and the risk of PONV in moderate and high-risk female patients.

Chronic intrathecal infusion of gabapentin prevents nerve ligation-induced pain in rats

BACKGROUND Gabapentin is an anticonvulsant and adjuvant analgesic. It is effective in several pain studies. Neuropathic pain is the most difficult type of pain to treat. In this study, we examined if intrathecal gabapentin could prevent nerve injury-induced pain. METHODS Under isoflurane anaesthesia, male Sprague-Dawley rats (200-250 g) underwent right L5/6 spinal nerve ligation and placement of an intrathecal catheter connected to an infusion pump. After surgery, intrathecal saline or gabapentin (20 µg h(-1)) was given for 7 days (n=8 per group). The right hind paw withdrawal threshold to von Frey filament stimuli and withdrawal latency to radiant heat were determined before (baseline) and once daily for 7 days after surgery. Haematoxylin and eosin and toluidine blue staining were used to evaluate the neurotoxicity of gabapentin (40 µg h(-1)). RESULTS Seven days after nerve ligation, the affected paw withdrawal threshold and latency of saline-treated rats decreased from the baseline 11.7 (11.7-22.2) [median (inter-quartile range)] to 1.6 (0.9-3.2) g and 10.8 (10.5-11.2) to 4.3 (4.2-7) s, respectively. Rats receiving gabapentin (20 µg h(-1)) had higher withdrawal threshold [9.9 (9.9-19.3) g] and latency [11.5 (9.7-11.9) s] on day 7 after ligation. No obvious histopathological change or growth retardation was detected after intrathecal gabapentin (40 µg h(-1)) infusion. CONCLUSIONS We showed a preventative effect of intrathecal gabapentin on the development of nerve injury-induced mechanical allodynia and thermal hyperalgesia. Our data suggest that continuous intrathecal gabapentin may be considered as an alternative for the prevention of nerve injury-induced pain.

Treating a patient with intractable paralytic ileus using thoracic epidural analgesia

Postoperative ileus is considered an undesirable response to major abdominal surgery that leads to discomfort, complications, morbidity, and the prolongation of hospital stays. Although thoracic epidural analgesia has been introduced to prevent and/or reduce postoperative ileus, it is rarely used as a way to treat postoperative ileus. A 65-year-old man developed paralytic ileus after undergoing a colectomy. Despite conservative and surgical management, postoperative morbidity persisted. A continuous infusion of 0.2% levobupivacaine at a rate of 4 mL/hour was administered for 4 days via a thoracic epidural catheter that had been percutaneously tunneled into the T11-T12 epidural space. With this treatment, daily drainage from a nasogastric tube was gradually decreased and flatus was noted. A week later, the patient could start receiving a liquid diet. Therefore, thoracic epidural analgesia can be used to treat or alleviate paralytic ileus.

Treatment of Spontaneous Intracranial Hypotension Secondary to Sacral Perineural Cysts by Caudal Epidural Blood Patch-a Case Report

Spontaneous intracranial hypotension (SIN), an uncommon reason of postural headache, is usually resulted from a spontaneous spinal cerebrospinal fluid (CSF) leak. However the mechanisms of the spontaneous CSF leak are unclear, and may be related to factors that cause dural sac weakness, such as sacral perineural cysts, the anatomical variations of the meninges in the lumbo-sacral region. In this report, we presented a female patient suffered from a postural headache. Sacral perineural cysts were noted according to her image study, and SIH was diagnosed. She was treated with the caudal epidural blood patch because of failed traditional treatments. We inserted a non-kinking catheter into the sacral epidural space under ultrasound-guidance and confirmed the location of catheter by the enhancement of contrast medium with fluoroscopy. After the treatment, the positional headache improved dramatically. In the discussion, we reviewed the clinical features, diagnosis, and managements of SIN and postural headache. We also discussed the possible pathophysiology of STH and mechanisms of the effect of epidural blood patch.

Ultrasound-Guided Pulsed Radiofrequency of Suprascapular Nerve for Chronic Shoulder Pain: A Case Report

Suprascapular nerve (SSN) blockade improves pain, range of motion, and disability in acute and chronic shoulder pain. Pain relief usually lasts several hours with local anesthetic. If steroids are added, the relief lasts several weeks. Since repetitive steroid exposure is associated with several hazards, alternative long-term therapies would be desirable. Pulsed radiofrequency (PRF) is a non-destructive, safe, and repeatable long-term pain control therapy. We report a case, wherein using ultrasound guidance and fluoroscopy and nerve stimulation confirmation, SSN PRF treatment was performed. It provided 9-10 months of pain relief and improvement in shoulder function, without deterioration in muscle strength.

Ultrasound-Guided Intercostal Nerve Block for Intractable Right Upper Quadrant Abdominal Pain: A Case Report

Abdominal visceral organ pathology is commonly the source of abdominal pain. However, some abdominal pain may originate from the abdominal wall muscles and be somatic in origin. Transversus Abdominis Plane (TAP) block is an effective block to offer analgesia for abdominal somatic pain. Intercostal nerve (ICN) blockade is also an useful diagnostic and therapeutic tool to manage pain covered by the distribution of thoracic nerves. Chronic abdominal wall pain can often be missed as a differential diagnosis for patients suffering with abdominal pain. We present a case of intractable right upper quadrant (RUQ) abdominal pain managed successfully with ultrasound-guided TAP and ICN block.