Tramadol relieves thermal hyperalgesia in rats with chronic constriction injury of the sciatic nerve.

The present study was designed to test whether tramadol is effective in the control of neuropathic pain in rats. Chronic constriction injury (CCI) of the sciatic nerve was induced over the left hind limb in male Sprague-Dawley rats. Identical surgery was performed on the opposite side except that the sciatic nerve was not ligated (sham surgery). Paw withdrawal latency (PWL) to heat was tested for each hind paw 1 day before surgery and on the 4th day after surgery to ensure the development of thermal hyperalgesia. In the acute treatment groups, saline or tramadol was administered subcutaneously at doses of 10, 20 or 30 mg/kg, and PWLs were measured 30, 60, 90, 120, 150 and 180 min after treatment. In the semi-chronic treatment groups, continuous systemic administration of tramadol 40 mg/kg/day or saline for 7 days was provided at a uniform rate via osmotic mini pumps. Tramadol reversed PWL in a dose-dependent manner in the acute treatment groups. PWLs were significantly reversed at 2 days after tramadol infusion, and this effect was sustained throughout the remainder of the treatment period in comparison with the saline group. Tramadol also resulted in a decreased sensitivity to thermal stimulus on the sham limb both in acute and semi-chronic administration. We conclude that both acute and semi-chronic tramadol treatment relieves thermal hyperalgesia effectively in rats with CCI of the sciatic nerve. This indicates that tramadol shows promise as a potential treatment for relief of neuropathic pain in humans.

Axillary brachial plexus block with patient controlled analgesia for complex regional pain syndrome type I: a case report.

BACKGROUND AND OBJECTIVES: Brachial plexus block (BPB) has been cited as a treatment modality for complex regional pain syndrome type I (CRPS I) of the upper limb. However, there are no reports using axillary BPB with patient controlled analgesia (PCA) for the treatment of CRPS I. This report is based on the retrospective observations of the outcome and effects of axillary BPB with PCA in a patient with CRPS I. CASE REPORT: A 32-year-old man suffered from CRPS I of the right upper limb after surgical release of carpal tunnel syndrome of the right hand. Symptoms and signs over the right hand were alleviated under rehabilitation and conventional pharmacological management, but severe painful swelling of the right wrist persisted. Axillary BPB with PCA was performed on the 32nd postoperative day, which soon resulted in significant reduction of pain with gradual improvement of function of the right wrist. CONCLUSIONS: Axillary BPB with PCA may provide patients with CRPS I of the upper limb a feasible and effective treatment. .

Prolonged morphine treatment relieves thermal hyperalgesia in rats with sciatic nerve constriction injury.

We examined the effects of chronic morphine treatment with regular intermittent administration in a modified chronic constriction injury (CCI) model of the rat sciatic nerve originally introduced by Bennett and Xie. A painful neuropathy was induced over the left hind limb with sciatic nerve ligation, and sham surgery was done on the opposite side in male Sprague-Dawley rats. Paw-with-drawal latency (PWL) was obtained one day before surgery (pre-op baseline) and on the fourth day after surgery (post-op) to assure the development of thermal hyperalgesia. Morphine hydrochloride (5, 10, 15, and 20 mg/kg per day) was subcutaneously administered for 7 days to four experimental groups. The control group received normal saline rather than morphine under the same injection protocol. PWLs were evaluated on days 5, 7, 9, and 11 of the treatment. PWL decreased to 50-60% of the pre-op baseline or sham limb on the fourth day after surgery. Morphine's ability to reverse PWL appeared dose-related, and no tolerance developed during treatment with chronic intermittent administration. This may indicate that prolonged use of intermittently-administered morphine can be a feasible regimen for relief of neuropathic pain.

Subarachnoid fentanyl with diluted small-dose bupivacaine for cesarean section delivery.

BACKGROUND: The use of neuraxial opioid was very popular in recent years, and they may augment the analgesia produced by local anesthetic through direct binding with the spinal opioid receptors. Hemodynamic stability is very important during Cesarean section. Theoretically, the reduction of local anesthetic by addition of fentanyl would provide better hemodynamic stability and good anesthetic status. METHODS: Thirty healthy parturients undergoing Cesarean section were assessed in a randomized fashion. They were divided into two groups. Each subject received 5 mg hyperbaric bupivacaine plus 25 micrograms fentanyl (0.5 ml) and cerebrospinal fluid (CSF) 0.6 ml (Group M + F) or 8 mg hyperbaric bupivacaine plus 0.5 ml of CSF (Group M). The effects of hemodynamic stability, side effects, and complete analgesic duration were observed. RESULTS: It was disclosed that the hemodynamic status was more stable in group M + F. The incidence of nausea and vomiting appeared to be not statistically significant between groups. The incidence of pruritus was apparently higher in group M + F (93.5% vs. 0) but the incidence of shivering was much lower in group M + F (0 vs. 33.3%). The complete analgesic duration was longer in group M + F (146 +/- 47 min vs. 104 +/- 44 min). There were no significant differences in the anesthetic and surgical status, 1-min and 5-min Apgar scores, and the time of regression of sensory level to T10. CONCLUSIONS: The combination of small-dose bupivacaine with fentanyl could provide more stable hemodynamic status, longer postoperative analgesia, and lower incidence of shivering. The incidence of pruritus in group M + F was high, but it was usually mild.

Patient-controlled epidural analgesia for postherpetic neuralgia in an HIV-infected patient as a therapeutic ambulatory modality.

A 43-year-old HIV-positive male was referred to our pain clinic one month after his fourth attack of herpes zoster infection. He complained of intermittent intolerable sharp and lancinating pain accompanied by numbness over the inner aspect of the left upper extremity, left anterior chest wall and the back. Physical examination revealed allodynia over the left T1 and T2 dermatomes without any obvious skin lesion. The pain was treated with epidural block made possible by a retention epidural catheter placed via the T2-3 interspace. After the administration of 8 ml of 1% lidocaine in divided doses, the pain was completely relieved for 4 h without significant change of blood pressure or heart rate. A pump (Baxter API) for patient-controlled analgesia (PCA) filled with 0.08% bupivacaine was connected to the epidural catheter on the next day and programmed at a basal rate of 2 ml/h, PCA dose 2 ml, lockout interval 15 min, with an one-hour dose limit of 8 ml. He was instructed to report his condition by telephone every weekday. The pump was refilled with drug and the wound of catheter entry was checked and managed every 3 or 4 days. The epidural catheter was replaced every week. During treatment, the pain intensity was controlled in the range from 10 to 0-2 on the visual analogue scale. He was very satisfied with the treatment and reported only slight hypoesthesia over the left upper extremity in the early treatment period. Epidural PCA was discontinued after 28 days. He did not complain of pain thereafter but reported a slight numb sensation still over the lesion site for a period of time. In conclusion, postherpetic neuralgia in an HIV-infected man was successfully treated with ambulatory therapeutic modality of epidural PCA for 28 days.

Acquired tracheomalacia--a case report.

Tracheomalacia is a condition characterized by weakness of the tracheal walls and supporting cartilage. It may be congenital, occurring in association with other lesions, such as vascular ring, tracheoesophageal fistula, dyschondroplasia, congenital cysts or tumors, or it may be acquired, most commonly as a result of protracted endotracheal intubation and less often of irradiation, trauma or neoplasm. We present a case of acquired tracheomalacia in a 15-year-old boy, a victim of Proteus syndrome (hemihypertrophy, subcutaneous tumors, and macrodactyly), who had congenital scoliosis with secondary chronic restrictive pulmonary disease, for which he was admitted to our hospital for surgical correction of the spine. Unfortunately, his conditions, particularly of respiratory, worsened after the operation, which called for an emergent tracheostomy. During the procedure, high airway pressure and CO2 retention developed, and an extreme narrowing of the tracheal lumen was revealed by fiberoptic bronchoscopy. Acquired tracheomalacia was diagnosed. The probable mechanisms, diagnostic tests, and treatments of tracheomalacia are hereunder discussed.

The dose effect of propofol on cerebrovascular reactivity to carbon dioxide in rabbits.

BACKGROUND: Propofol has several properties beneficial to intracranial operation such as reduction in cerebral metabolic rate and cerebral blood flow (CBF) in a dose-dependent manner while leaving autoregulation intact. Several studies have demonstrated that the responsiveness of CBF to changes in arterial carbon dioxide tension (PaCO2) is maintained during propofol anesthesia in both humans and animals. These studies showed a significant difference in the CBF-CO2 reactivity slope between awake and propofol anaesthetized groups, but no comparison with different doses of propofol was made. To determine the dose effect of propofol on cerebrovascular CO2 reactivity, we used laser Doppler flowmetry (LDF) to detect the changes of CBF during propofol anesthesia. METHODS: Ten rabbits were studied using LDF on the parietal cortex. After surgical preparation, anesthesia was maintained with 66% N2O in O2, morphine 10 mg/kg and pancuronium. Three experimental conditions were studied sequentially with intravenous administration of the following drugs: (1) normal saline (control), (2) propofol 20 mg/kg/h i.v., (3) propofol 40 mg/kg/h i.v. Mean arterial pressure, rectal temperature and hematocrit were kept constant. The arterial carbon dioxide tension (PaCO2) was adjusted to three levels during each condition: 20-25 mmHg (hypocapnia), 35-40 mmHg (normocapnia) and 45-50 mmHg (hypercapnia). CBF was measured continuously and recorded after the target PaCO2 had been reached. RESULTS: There were no differences among all conditions in mean arterial pressure and heart rate. The changes of CBF as PaCO2 increased at the three different CO2 levels during each of the conditions were significantly different. The slope of CBF-CO2 reactivity among three different propofol doses was not significantly different. CONCLUSIONS: These data indicate that cerebral vasomotor responsiveness to CO2 during propofol anesthesia is preserved and that the slope of CBF-CO2 reactivity is independent of propofol doses as mean arterial blood pressure is maintained.