Effects of different anesthetic techniques on the incidence of phantom limb pain after limb amputation: a population-based retrospective cohort study

Background

General anesthesia (GA) has been considered the anesthetic technique which most frequent leads to phantom limb pain (PLP) after a limb amputation. However, these prior reports were limited by small sample sizes. The aims of this study were to evaluate the incidence of PLP according to the various anesthetic techniques used for limb amputation and also to compare the occurrence of PLP according to amputation etiology using the Korean Health Insurance Review and Assessment Service for large-scale demographic information.

Methods

The claims of patients who underwent limb amputation were reviewed by analyzing the codes used to classify standardized medical behaviors. The patients were categorized into three groups—GA, neuraxial anesthesia (NA), and peripheral nerve block (PNB)—in accordance with the anesthetic technique. The recorded diagnosis was confirmed using the diagnostic codes for PLP registered within one year after the limb amputation.

Results

Finally, 7,613 individuals were analyzed. According to the recorded diagnoses, 362 patients (4.8%) developed PLP after amputation. Among the 2,992 patients exposed to GA, 191 (6.4%) were diagnosed with PLP, whereas 121 (4.3%) of the 2,840 patients anesthetized with NA, and 50 (2.8%) of the 1,781 patients anesthetized under PNB developed PLP. The relative risks were 0.67 (95% confidence interval [CI], 0.53–0.84; P < 0.001) for NA and 0.43 (95% CI, 0.32–0.59; P < 0.001) for PNB.

Conclusions

In this retrospective cohort study, using large-scale population-based databases, the incidence rates of PLP after limb amputations were, in the order of frequency, GA, NA, and PNB.

Clinical experiences of performing transforaminal balloon adhesiolysis in patients with failed back surgery syndrome: two cases report

Epidural fibrosis is a contributing factor to the persistent pain that is associated with failed back surgery syndrome (FBSS) and other pathophysiologies, particularly as it inhibits the passage of regional medications to areas responsible for pain. Therefore, effective mechanical detachment of epidural fibrosis can contribute to pain reduction and improve function in FBSS patients. In this report, we describe the successful treatment of FBSS patients with epidural adhesiolysis using a Fogarty catheter via the transforaminal approach.

The effects of gabapentin pretreatment on brain injury induced by focal cerebral ischemia/reperfusion in the rat

Background

Experimental studies have shown that gabapentin can reduce neuronal injury in the setting of cerebral ischemia, but the mechanisms have not yet been clearly determined. This study was conducted to determine whether gabapentin pretreatment altered expression levels of heat shock protein 70 and reduced acute phase neuronal injury in rats subjected to transient focal cerebral ischemia/reperfusion.

Methods

Forty male Sprague-Dawley rats (260-300 g) were randomly assigned to one of four groups (saline-treated, or 0.1, 0.5, or 5 mg/kg gabapentin group). In all animals, focal cerebral ischemia was induced by intraluminal middle cerebral artery occlusion for 1 hour. The animals of the gabapentin groups were pretreated with a single intravenous administration of gabapentin 20 minutes before ischemic insults. The infarct volume, brain edema and motor behavior deficits were analyzed 24 hours after ischemic insult. Caspase-3-reactive cells and cells showing Hsp70 activity were counted in the caudoputamen and fronto-parietal cortex.

Results

The infarction ratio was significantly decreased in the 5 mg/kg gabapentin group (P < 0.05) and brain edema ratios were significantly reduced in the 0.1 mg/kg, 0.5 mg/kg, and 5 mg/kg gabapentin groups 24 hours after ischemia/reperfusion injury (P < 0.05). There were more Hsp70-reactive cells in the 5 mg/kg gabapentin group than in the saline group in both the caudoputamen and fronto-parietal cortex (P < 0.05).

Conclusions

These results indicate that gabapentin may have a neuroprotective effect and can reduce early neuronal injury caused by focal cerebral ischemia/reperfusion; this may be mediated by expression of Hsp70. However, gabapentin pretreatment did not prevent caspase-dependent apoptosis.

Changes in magnesium concentration in the serum and cerebrospinal fluid of neuropathic rats

BACKGROUND

Central sensitization of neuropathic pain is associated with an influx of extracellular calcium via the opening of N-methyl-D-aspartate (NMDA) receptor-gated ion channels, which are usually blocked by magnesium plugs. As magnesium-deficient rats develop a mechanical hyperalgesia and intrathecal or intraperitoneal magnesium suppresses neuropathic pain, the magnesium concentrations in serum and cerebrospinal fluid may be altered in neuropathic pain. We therefore compared the magnesium concentrations in serum and cerebrospinal fluid of neuropathic rats with those in injured rats without symptoms of neuropathic pain and normal rats.

METHODS

Mechanical allodynia was induced in male Sprague-Dawley rats by tight ligature of the left lumbar fifth and sixth spinal nerves. The threshold of paw withdrawal was evaluated by the up-down method using withdrawal response to stimulus with a von Frey filament on the third, seventh and 14th days. Rats with a threshold of less than 4 g were selected as the symptomatic group and compared with an asymptomatic group, an unoperated control group and a sham-operated group. On the 16th day, the Mg2+ concentrations in serum and cerebrospinal fluid were measured.

RESULTS

The magnesium concentrations in the serum and cerebrospinal fluid of symptomatic neuropathic rats did not differ from those in the injured rats without symptoms of neuropathic pain, sham-operated rats and normal rats.

CONCLUSION

Our results suggest that physiologic homeostasis is maintained by active transport through the blood-brain barrier despite the activation of NMDA receptor-gated ion channels. However, rats with neuropathic pain may be in a magnesium-deficient condition at the effector site, such that magnesium treatment can decrease neuropathic pain.

Nonsteroidal Antiinflammatory Drugs Suppress Pain-Related Behaviors, but Not Referred Hyperalgesia of Visceral Pain in Mice

Visceral pain is characterized by spontaneous pain and referred hyperalgesia. After inducing visceral pain in mice using intracolonic mustard oil administration, we examined the effects of various nonsteroidal antiinflammatory drugs (NSAIDs) on pain-related behavior and on Evans blue dye extravasation. Animals were given one of the following: saline, ethanol, dimethylsulfoxide (DMSO), morphine, ketoprofen, ketorolac, or DFU (a cyclooxygenase-2 inhibitor). After drug treatment, mice underwent intracolonic administration of 50 microL 1.5% mustard oil. Spontaneous pain-related responses were assessed for the next 20 min. The frequency of withdrawal responses to the application of von Frey hairs to the abdomen, foot, and tail was determined. After completion of the behavioral tests, Evans blue was injected into the animals via the tail vein. Two hours later, the colon was removed postmortem and Evans blue content was measured. Spontaneous pain behaviors were significantly less in animals administered 3 and 10 mg/kg morphine, 50 mg/kg ketorolac, 100 mg/kg ketoprofen, and 20 mg/kg DFU (P < 0.05). Response frequencies to the application of von Frey hairs were lower in mice administered 3 and 10 mg/kg morphine (P < 0.05) but were not affected by ketorolac, ketoprofen, or DFU treatment. Colonic Evans blue content was smaller in mice given 100 mg/kg ketoprofen and 20 mg/kg DFU (P < 0.05). We concluded that NSAIDs reduced pain behavior and inflammation but had little effect on referred hyperalgesia.

Inflammation induces ectopic mechanical sensitivity in axons of nociceptors innervating deep tissues

A variety of seemingly diverse pain syndromes are characterized by movement-induced pain radiating in the distribution of a peripheral nerve or nerve root. This could be explained by the induction of ectopic mechanical sensitivity in intact sensory axons. Here we show that inflammation led to mechanical sensitivity of the axons of a subset of mechanically sensitive primary sensory neurons. Dorsal root recordings were made from 194 mechanically sensitive neurons that innervated deep and cutaneous structures and had C, Adelta, and Aalphabeta conduction velocities. No axons of any category were mechanically sensitive in control experiments. However, the axons of neurons innervating deep structures and having C- or Adelta-conduction velocities became mechanically sensitive during the neuritis, and also exhibited an increased incidence of spontaneous discharge. The incidence of mechanical sensitivity followed a distinct time course. In some cases, paw withdrawal thresholds were obtained after neuritis induction. The time course of the resultant hypersensitivity was not directly related to the time course of the axonal mechanical sensitivity. Ectopic axonal mechanical sensitivity could explain some types of radiating, nerve-related pain coexisting with diseases of seemingly diverse etiologies.

Mid-axonal tumor necrosis factor-alpha induces ectopic activity in a subset of slowly conducting cutaneous and deep afferent neurons

After injuries to the musculoskeletal system, peripheral nerve axons are exposed to numerous inflammatory mediators, including tumor necrosis factor-alpha (TNF). Exposure of sensory axons to TNF can cause behavioral hypersensitivity in the peripheral innervation territory of the affected axons. The hypothesis that TNF activates nociceptor axons was tested by using teased fiber techniques in the rat. Recordings were made of single nociceptors innervating both deep and cutaneous receptive fields supplied by the sciatic nerve. The axons proximal to the receptive field were exposed to ascending concentrations of TNF (0.01 to 1 ng/mL). In 21% of cutaneous and 9% of deep neurons, TNF rapidly evoked a transient response. There was no difference between deep and cutaneous nociceptors in the incidence of TNF responses. The majority of neurons responded to TNF injected into their receptive fields. Our data support that TNF can induce ectopic electrogenesis in a minority of nociceptor axons that innervate both deep and cutaneous tissues. This activity may correlate to the human perception of radiating pain that often accompanies neuritis.