Spreading pattern of epidurally administered contrast medium in rabbits

Lumbar Epidural: Anatomical and Clinical Study in Dogs Submitted to Ovariohysterectomy

Epidural anesthesia minimizes perioperative pain in dogs. It is considered that epidural solution dispersion in cadavers is similar to alive dogs. The objective of the anatomical study was to compare the dispersion of 0.2 mL/kg 0.25% bupivacaine and iohexol via lumbar epidural (L1–L2) under fluoroscopic guidance in 10 thawed cadavers (GC) and 13 female dogs (G0.25) (5–15 kg; body score 4/5). The objective of the clinical study was to evaluate postoperative analgesic consumption and sedation for 6 h after extubation of dogs submitted to ovariohysterectomy when using 0.25% (G0.25; n = 10) bupivacaine with the intraoperative use of fentanyl (GF; n = 10). Parametric data were compared by the t-test and non-parametric data by the Mann Whitney test. Pain and sedation scores were evaluated over time by the Friedman test, followed by the Dunn test. Alive dogs presented greater epidural dispersion (17 ± 3 vertebrae) than thawed cadavers (11 ± 4 vertebrae; p = 0.002). All dogs treated with fentanyl and only one dog treated with 0.25% epidural bupivacaine presented pain scores above the cut-off point of the Glasgow Composite Measure Pain Scale Short-Form (GCMPS-SF) and required postoperative rescue analgesia up to 6 h after extubation. The sedation score was higher at all postoperative moments compared to preoperative moments in the G0.25 and GF, except for evaluations performed at 5 and 6 h after extubation in the GF. Greater sedation was observed immediately after extubation in the GF compared to the G0.25, and there was greater sedation in the G0.25 compared to the GF from 3 to 6 h after extubation. The conclusion of the anatomical study was that L1–L2 epidural bupivacaine dispersion is lower in canine thawed cadavers than in alive dogs. Conclusion of the clinical study was that lumbar epidural anesthesia improved postoperative analgesia and produced longer postoperative sedation when compared to fentanyl.

Comparison of Clinical Outcomes of Different Rates of Infusion in Caudal Epidural Steroid Injection: A Randomized Controlled Trial

Study Design

Prospective randomized controlled equivalence trial.

Purpose

To compare the clinical outcomes between patients with lumbosacral radiculopathy that received caudal epidural steroid injection (CESI) at injection rates of 40 mL/min (fast rate) and 20 mL/min (slow rate) and to identify the complications associated with these different CESI rates.

Overview of Literature

CESI is widely used for chronic low back pain with lumbar radiculopathy. However, the influence of CESI rates on clinical outcomes has not been well studied.

Methods

Ninety patients were randomized into two CESI groups. Two patients did not complete the study. Eighty-eight were included in the final analysis: 44 patients were in the fast infusion group, and 44 patients were in the slow infusion group. Intragroup and intergroup comparisons were conducted with regard to the Visual Analog Scale (VAS), Roland 5-point pain scale, standing tolerance test, walking tolerance test, and patient satisfaction scale at pre-injection, 2 weeks, 6 weeks, and 12 weeks post-injection. Complications associated with the different rates were recorded.

Results

Both groups demonstrated clinical improvement in all parameters, except for VAS, after injection. There were no statistically significant differences in any outcomes at each time point between the two groups. One patient in the fast rate group and no patients in the slow rate group experienced nausea and vomiting after injection (p=0.320). Eight patents in the fast rate group and two patients in the slow rate group experienced pain at the injection site (p=0.044).

Conclusions

Although there were no significant differences between injection rates in the short-term clinical improvement outcomes, the fast injection rate group experienced more pain at the injection site, suggesting that the use of the slow injection rate may be considered.

The Differential Flow of Epidural Local Anaesthetic via Needle or Catheter: A Prospective Randomized Double-blind Study

The extent of epidural anaesthesia and pattern of spread of contrast medium, using different injection techniques, has not been well documented. Therefore, in this prospective, randomized, double-blind study, the extent of anaesthesia and pattern of spread of contrast medium following an epidural bolus injection, via either a Tuohy needle or an epidural catheter, were compared.

The study had two parts. In the first, 59 of 79 patients scheduled for a lower extremity operation under epidural anaesthesia were randomly allocated to one of the two groups. Anaesthesia was achieved with an epidural injection of 10 to 15 ml (including a 3 ml test dose) of 0.75% ropivacaine and fentanyl 25 μg via either a Tuohy needle (Group N, n=31) or a catheter (Group C, n=28). The level of sensory anaesthesia was recorded. In the second part, the remaining 20 patients were randomized to initially receive 5 ml of contrast medium via either a Tuohy needle (Group NE, n=10) or a catheter (Group CE, n=10). The extent of spread was recorded radiologically.

Unilateral or missed blocks and additional dose requirement were absent in Groups N and C. No differences were found in the extent of sensory anaesthesia or the spread of contrast medium. Twenty per cent of catheter tips lay outside the lateral margins of the vertebral bodies.

We found that an epidural bolus injection, via either a Tuohy needle or a catheter, made no difference in regard to spread of local anaesthetic or contrast medium in the epidural space.

Preliminary study on contrast flow analysis of thoracic transforaminal epidural block

Background

The thoracic transforaminal epidural block (TTFEB) is usually performed to treat herpes zoster or postherpetic neuralgia (PHN). Especially, multiple segmental involvements and approximate contrast medium spread range, according to volume, help to choose the proper drug volume in the transforaminal epidural block. This study investigated the contrast medium spread patterns of 1-ml to 3-ml TTFEBs.

Methods

A total of 26 patients with herpes zoster or PHN were enrolled in this study. All participants received 1 ml, 2 ml, or 3 ml of contrast medium. Results were divided into Groups A, B and C based on the volume (1, 2, or 3 ml), with n = 26 for each group. After the injection of contrast medium, the spread levels were estimated in both the lateral and anteroposterior (AP) images using fluoroscopy.

Results

The cephalad spread of contrast medium in the lateral image as expressed by the median (interquartile range) was 2.00 levels (1.00-2.00) for Group A, 2.50 (2.00-3.00) for Group B, and 3.00 (2.00-4.00) for Group C. The caudal spread level of contrast medium was 1.00 (1.00-2.00) for Group A, 2.00 (2.00-3.00) for Group B, and 2.00 (2.00-3.00) for Group C. There was ventral and dorsal spread of the 3-ml contrast medium injection in 88% (23/26) of cases in the lateral image.

Conclusions

Injection of 3 ml of contrast medium through the foramina spread 6 levels in a cephalocaudal direction. Spread patterns revealed a cephalad preference. TTFEB resulted in dorsal and ventral spread in a high percentage of cases. This procedure may be useful for transferring drugs to the dorsal and ventral roots.

The Neurological Safety of an Epidurally Administered Lipo-PGE1 Agonist in Rats

BACKGROUND AND OBJECTIVE

Liposomal prostaglandin E1 (Lipo-PGE1) can inhibit platelet aggregation and vasodilatation and has been found to be therapeutic in ischemia and spinal diseases including stenosis. However, the neurologic safety of epidural administration of lipo-PGE1 requires further study. We investigated the neurotoxicity of epidurally administered lipo-PGE1 agonist in rats.

METHODS

Twenty-seven rats were randomly divided into three groups: Epidural isotonic sodium chloride solution administration (negative control, group N, n = 9); epidural lipo-PGE1 agonist (group L, n = 9); and epidural alcohol (positive control, group A, n = 9). A single 3-mL injection of lipo-PGE1 agonist (0.3 mL, 0.15 μg/kg), 40% ethanol, or isotonic sodium chloride solution was administered. Neurologic assessments were performed 3, 7, and 21 days after the injection. Histopathologic data were evaluated by one pathologist via light microscopy.

RESULTS

All rats in groups N and L, except one rat in group L, demonstrated normal response to neurologic assessments. Histopathologic findings showed no evidence of degenerative myelopathy, chromatolysis, or myelin loss in group N or L at any time point. However, all rats in group A revealed sensory and motor deficits as well as histopathologic abnormalities.

CONCLUSION

Liposomal prostaglandin E1 agonist did not cause any apparent neurologic abnormalities in the spinal cord or dorsal root ganglion, suggesting it is neurologically safe for epidural injection in this species. Additional mammalian study is warranted.

Analysis of thoracic epidurography and correlating factors affecting the extent of contrast medium spread

Background

Thoracic epidural anesthesia is frequently used to maintain intraoperative and postoperative analgesia. Frequently, 3 ml of local anesthetic is used as a test dose, or for intermittent epidural injection. We assessed the extent of the spread of 3 ml of contrast medium in the thoracic epidural space and attempted to identify any correlating factors affecting the epidurography.

Methods

A total of 70 patients were enrolled in the study, and thoracic epidural catheterizations were performed under fluoroscopic guidance. Using 3 ml of contrast medium, epidurography was evaluated to confirm the number of spinal segments covered by the contrast medium. Correlation analysis was performed between patient characteristics (sex, age, body mass index, weight, height, and location of catheter tip) and the extent of the contrast spread.

Results

The mean number of vertebral segments evaluated by contrast medium was 7.9 ± 2.2 using 3 ml of contrast medium. The contrast spread in the cranial direction showed more extensive distribution than that in the caudal direction, with statistical significance (P < 0.01). Patient height demonstrated a negative correlation with the extent of distribution of contrast medium (r = −0.311, P < 0.05).

Conclusions

Thoracic epidurography using 3 ml of contrast medium results in coverage of a mean of 7.9 ± 2.2 spinal segments, with more extensive cranial spread, and patient height showed a weak negative correlation with the distribution of contrast medium.

Therapeutic effect of epidurally administered lipo-prostaglandin e1 agonist in a rat spinal stenosis model

BACKGROUND

A lipo-prostaglandin E1 agonist is effective for the treatment of neurological symptoms of spinal stenosis when administered by an oral or intravenous route. we would like to reveal the therapeutic effect of an epidural injection of lipo-prostaglandin E1 on hyperalgesia in foraminal stenosis.

METHODS

A total of 40 male Sprague-Dawley rats were included. A small stainless steel rod was inserted into the L5/L6 intervertebral foramen to produce intervertebral foraminal stenosis and chronic compression of the dorsal root ganglia (DRG). The rats were divided into three groups: epidural PGE1 (EP) (n = 15), saline (n = 15), and control (n = 10). In the EP group, 0.15 µg.kg-1 of a lipo-PGE1 agonist was injected daily via an epidural catheter for 10 days from postoperative day 3. In the saline group, saline was injected. Behavioral tests for mechanical hyperalgesia were performed for 3 weeks. Then, the target DRG was analyzed for the degree of chromatolysis, chronic inflammation, and fibrosis in light microscopic images.

RESULTS

From the fifth day after lipo-PGE1 agonist injection, the EP group showed significant recovery from mechanical hyperalgesia, which was maintained for 3 weeks (P < 0.05). Microscopic analysis showed much less chromatolysis in the EP group than in the saline or control groups.

CONCLUSIONS

An epidurally administered lipo-PGE1 agonist relieved neuropathic pain, such as mechanical hyperalgesia, in a rat foraminal stenosis model, with decreasing chromatolysis in target DRG. We suggest that epidurally administered lipo-PGE1 may be a useful therapeutic candidate for patients with spinal stenosis.

Distribution of contrast medium epidurally injected at thoracic and lumbar vertebral segments

The epidural distribution of iohexol (0.2 ml/kg) administered at thoracic vertebrae (Thoracic group) and lumbar vertebrae (Lumbar group) was compared by computed tomographic (CT) epidurography in dogs. The total spread of iohexol was similar between the 2 groups upon reaching a similar cranial level. The maximal CT values were higher at the C7/T1 and T4/T5 levels in Thoracic group, but they were higher at the T13/L1 and L4/L5 levels in Lumbar group (P<0.05). This result suggests that the distribution pattern of the drug administered epidurally at thoracic vertebrae and lumbar vertebrae is different in dogs.

Use of electrical stimulation to monitor lumbosacral epidural and intrathecal needle placement in rabbits

OBJECTIVE

To determine the minimal electric threshold of neurostimulation dorsally and ventrally to the interarcuate ligament in the lumbosacral area necessary to cause muscle contraction of the hind limb or tail and determine whether a continuous electrical stimulation applied to an insulated needle during lumbosacral epidural needle placement could be used to distinguish the epidural from the intrathecal space in rabbits.

ANIMALS

24 New Zealand white rabbits.

PROCEDURES

Rabbits received iohexol (0.2 mL/kg) either dorsally (group 1) or ventrally to the interarcuate ligament in the lumbosacral area (groups 2 and 3). Correct placement of the needle was determined by use of the loss of resistance to injection technique (group 2) or a continuous electrical stimulation (group 3) and confirmed by examination of the iohexol distribution pattern on radiographs.

RESULTS

In all rabbits of group 1, iohexol was injected in the lumbosacral area, outside the epidural space. In groups 2 and 3, iohexol was injected intrathecally. No pure iohexol epidural migration of iohexol was observed. Mean ± SD minimal electric threshold to elicit a motor response was 1.2 ± 0.3 mA, 0.3 ± 0.1 mA, and 0.3 ± 0.1 mA in groups 1, 2, and 3, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Neurostimulation was a useful technique to determine correct intrathecal needle placement in rabbits but failed to detect the lumbosacral epidural space when the common technique, used in dogs and cats for the lumbosacral epidural approach, was used.

Evaluation of the Neurological Safety of Epidural Milnacipran in Rats

Background

Milnacipran is a balanced serotonin norepinephrine reuptake inhibitor with minimal side effects and broad safety margin. It acts primarily on the descending inhibitory pain pathway in brain and spinal cord. In many animal studies, intrathecal administration of milnacipran is effective in neuropathic pain management. However, there is no study for the neurological safety of milnacipran when it is administered neuraxially. This study examined the neurotoxicity of epidural milnacipran by observing behavioral and sensory-motor changes with histopathological examinations of spinal cords in rats.

Methods

Sixty rats were divided into 3 groups, with each group receiving epidural administration of either 0.3 ml (3 mg) of milnacipran (group M, n = 20), 0.3 ml of 40% alcohol (group A, n = 20), or 0.3 ml of normal saline (group S, n = 20).

Results

There were no abnormal changes in the behavioral, sensory-motor, or histopathological findings in all rats of groups M and S over a 3-week observation period, whereas all rats in group A had abnormal changes.

Conclusions

Based on these findings, the direct epidural administration of milnacipran in rats did not present any evidence of neurotoxicity in behavioral, sensory-motor and histopathological evaluations.

Effects of epidural TNF-α inhibitor injection: analysis of the pathological changes in a rat model of chronic compression of the dorsal root ganglion

OBJECTIVES

To evaluate the efficacy of a single direct epidural injection of tumor necrosis factor (TNF)-α inhibitor to reduce the pathological changes in nerve fiber injuries in a rat model of chronic compression of the dorsal root ganglion (CCD).

MATERIALS AND METHODS

A surgical procedure for CCD was performed in 17 adult male F-344 rats. The effects of the epidural TNF-α inhibitors on CCD-induced pathological changes were investigated. Three groups of rats (n = 17) were used: (1) CCD + saline (n = 4), (2) CCD + triamcinolone (n = 5), and (3) CCD + TNF-α inhibitors (n = 8). Their dorsal root ganglia and nerve roots were removed on postoperative day 14. The intraneural edema, demyelination, and Wallerian degeneration of all 17 rats were scored pathologically.

RESULTS

The pathology scores of the rats in the TNF-α inhibitor treatment group (1.38 ± 0.74) indicated a mild degree of intraneural edema compared to the saline treatment group (2.25 ± 0.50, p = 0.041). In addition, rats in the TNF-α inhibitor treatment group (2.13 ± 0.35) had a mild degree of demyelination compared to the saline treatment group (2.75 ± 0.50, p = 0.038) and the triamcinolone treatment group (2.80 ± 0.45, p = 0.019). The differences in the pathology scores for Wallerian degeneration were not statistically significant in all three study groups (p = 0.658).

CONCLUSION

The epidural injection of a TNF-α inhibitor was more effective than a placebo and comparable to triamcinolone in reducing pathological nerve injury progression.

Evaluation of the neurological safety of epidurally-administered pregabalin in rats

Background

The primary site of action of pregabalin, i.e. the α-2-δ subunit of the voltage-dependent calcium channel, is located at the dorsal root ganglion and dorsal horn of the spinal cord. Therefore, the epidural administration of pregabalin could have advantages over oral administration. However, the possibility of its neurotoxicity should be excluded before any attempt at epidural administration. We evaluated the neuronal safety of epidurally-administered pregabalin by observing the sensory/motor changes and examining the histopathology of spinal cord in rats.

Methods

Sixty rats of 180-230 g were divided into three groups; 3 mg of pregabalin dissolved in 0.3 ml saline (group P, n = 20), 0.3 ml 40% alcohol (group A, n = 20), or 0.3 ml normal saline (group N, n = 20) was administered epidurally to the rats in each group. Pinch-toe test, motor function evaluation, and histopathologic examination of vacuolation, chromatolysis, meningeal inflammation, and neuritis were performed at the 1st, 3rd, 7th, and 21st day after each epidural administration.

Results

All rats enrolled in group P, like those in group N, showed neither sensory/motor dysfunction nor any histopathological abnormality over the 3-week observation period. In contrast, in group A, 80% of the rats showed abnormal response to the pinch-toe test and all rats showed decreased motor function during the entire evaluation period. In addition, all histopathologic findings of neurotoxicity were observed exclusively in group A.

Conclusions

The epidurally administered pregabalin (about 15 mg/kg) did not cause any neurotoxic evidence, in terms of both sensory/motor function evaluation and histopathological examination in rats.

The neurological safety of epidural parecoxib in rats

Epidural injection of cyclooxygenase-2 inhibitors has been suggested as a useful therapeutic modality in pain management in animal studies and clinical settings. Direct epidural administration of parecoxib, a highly selective cyclooxygenase-2 inhibitor, may have advantages over its parenteral administration regarding required dose, side effects, and efficacy. However, no animal studies have been performed to investigate the possible neurotoxicity of epidurally injected parecoxib. Therefore, the present study was performed to assess the neurotoxicity of epidurally injected parecoxib in rats. Rats (n=45) were randomly divided into three groups: normal saline group (group N, n=15), ethanol group (group E, n=15), and parecoxib group (group P, n=15). 0.3 mL of epidural parecoxib (6 mg) and the same volume of epidural ethanol or normal saline were injected into the epidural space. Neurologic assessment was performed 3, 7 and 21 days after the injection by pinch toe testing. Histologic changes were evaluated for vacuolation of the dorsal funiculus, chromatolytic changes of the motor neurons, neuritis, and meningeal inflammation. All rats in groups N and P showed normal response to pinch-toe testing and had a normal gait at each observation point. Histological examination showed no evidence suggestive of neuronal body or axonal lesions, gliosis, or myelin sheet damage in group N or P at any time. However, all rats in group E showed sensory-motor dysfunction, behavioral change, or histopathological abnormalities. No neurotoxicity on the spinal cord or abnormalities in sensorimotor function or behavior was noted in rats that received epidural parecoxib.

The neurological safety of epidural pamidronate in rats

Background

Pamidronate is a potent inhibitor of osteoclast-mediated bone resorption. Recently, the drug has been known to relieve bone pain. We hypothesized that direct epidural administration of pamidronate could have various advantages over oral administration with respect to dosage, side effects, and efficacy. Therefore, we evaluated the neuronal safety of epidurally-administered pamidronate.

Methods

Twenty-seven rats weighing 250-350 g were equally divided into 3 groups. Each group received an epidural administration with either 0.3 ml (3.75 mg) of pamidronate (group P), 0.3 ml of 40% alcohol (group A), or 0.3 ml of normal saline (group N). A Pinch-toe test, motor function evaluation, and histopathologic examination of the spinal cord to detect conditions such as chromatolysis, meningeal inflammation, and neuritis, were performed on the 2nd, 7th, and 21st day following administration of each drug.

Results

All rats in group A showed an abnormal response to the pinch-toe test and decreased motor function during the entire evaluation period. Abnormal histopathologic findings, including neuritis and meningeal inflammation were observed only in group A rats. Rats in group P, with the exception of 1, and group N showed no significant sensory/motor dysfunction over a 3-week observation period. No histopathologic changes were observed in groups P and N.

Conclusions

Direct epidural injection of pamidronate (about 12.5 mg/kg) showed no neurotoxic evidence in terms of sensory/motor function evaluation and histopathologic examination.

Spreading pattern of contrast medium in the high thoracic epidural space in rabbits: the effect of neck flexion and extension

Background

Neck flexion has been shown to increase cranial spread of contrast agent when a small fixed volume was injected into the high thoracic epidural space. The purpose of this study was to evaluate the effect of volume of contrast medium on its distribution through the high thoracic epidural space during neck extension and flexion using the rabbit model.

Methods

An epidural catheter was introduced into the epidural space of New Zealand white rabbits with the tip located at the T3-4 intervertebral level. The neck was extended or flexed (n = 8 for each group), and the contrast medium was injected with the volume increasing by increments of 0.1 ml/kg, up to 0.3 ml/kg. The spread of contrast medium was determined by counting the number of vertebral body units using lateral epidurographic images.

Results

In both groups, the total spread of contrast medium was similar, increasing continuously with injected volume. The cranial spread was greater in the flexion group than the extension group. However, the caudal spread was greater in the extension than in the flexion group. In the extension group, the contrast medium spread caudally about twice as far as it spread cranially, but there was no statistically significant difference between cranial and caudal spread in the flexion group.

Conclusions

In the high thoracic epidural space of rabbit, the contrast medium of varying doses showed limited cranial spread. The flexion of the neck increased cranial spread and extension of the neck increased caudal spread.

Time-dependent effect of epidural steroid on pain behavior induced by chronic compression of dorsal root ganglion in rats

Although epidural steroid injection has been commonly used to treat radicular pain, its clinical efficacy remains controversial. In a rat model of radicular pain induced by chronic compression of lumbar dorsal root ganglion (CCD), we examined the effect of epidural steroid on CCD-induced pain behavior. Triamcinolone [a glucocorticoid receptor (GR) agonist] or RU38486 (a GR antagonist) was given epidurally once either on day 3 (early treatment) or day 10 (late treatment) after CCD. The results showed that 1) early treatment with triamcinolone and RU38486 alone, respectively, reduced and exacerbated mechanical allodynia and thermal hyperalgesia, 2) late treatment with triamcinolone alone failed to improve mechanical allodynia and only transiently attenuated thermal hyperalgesia, and 3) late treatment with RU38486 alone improved mechanical allodynia and thermal hyperalgesia in CCD rats. Moreover, a second dose of triamcinolone given on day 10 paradoxically exacerbated pain behavior in CCD rats that received a first dose of triamcinolone on day 3. These results indicate that the effect of epidural steroid on radicular pain may be time-dependent. Clinical implications for epidural steroid treatment are discussed in light of these preclinical findings.

The Neurological Safety of Epidural Gabapentin in Rats: A Light Microscopic Examination

Gabapentin acts primarily on the central nervous system. Therefore, we hypothesized that the direct epidural administration of gabapentin could have various advantages over its oral administration with respect to required dose, side effects, and efficacy. However, before administering gabapentin into the epidural space in a clinical setting, its neurotoxicity must be examined in animals. Thus, we evaluated neurotoxicity of epidural gabapentin by observing behavioral and sensory-motor changes, and by histopathological examinations of spinal cords and dorsal root ganglia in the rat. Twenty-seven rats were randomly divided into 3 groups, which were administered 0.3 mL (30 mg) of epidural gabapentin (group G, n = 9) and the same volume of epidural alcohol (group A, n = 9) or normal saline (group N, n = 9). No rats in groups G and N showed sensory-motor dysfunction, behavioral change, or histopathological abnormalities over a 3-wk observation period, whereas all rats in group A showed abnormalities. We conclude that the direct epidural injection of gabapentin in rats did not show any neurotoxic evidence in terms of sensory-motor functions and behavior, or by a microscopic histopathological evaluation. This study represents a first promising step toward the trial of epidural gabapentin in a clinical setting.

Anesthetic effect of epidural anesthesia with cephalad or caudad catheterization for ankle surgery or hemorrhoidectomy

BACKGROUND

The larger size of the first sacral nerve root has been reported to be an unfavorable factor leading to sacral sparing in epidural anesthesia. Previous studies have shown that an adequate analgesic effect of the epidural block was achieved with the catheter placement in the caudal direction. In this study, the anesthetic effect of epidural anesthesia with catheter placement of a cephalic or caudad direction was compared in ankle and hemorrhoid surgery.

METHODS

Twenty-one ASA physical status I or II patients undergoing surgery for ankle fractures with epidural anesthesia were enrolled and randomized into two groups. The epidural catheter was placed either to a cephalad (AU group) or caudal (AD group) direction. Another 21 patients undergoing hemorrhoidectomy were also randomized into two groups to receive epidural anesthesia in a similar way (HU and HD groups). The onset for, duration of, and recovery time from epidural anesthesia and the incidence of analgesic request were recorded.

RESULTS

No significant differences were demonstrated when age, height, weight or sex were compared between the four study groups. The onset time of the block and the incidence of intrasurgical analgesic request were lower in the caudal subgroup when the ankle surgery patients were compared. Otherwise, there were no significant differences in the duration of anesthesia and time to recovery or level of anesthesia.

CONCLUSION

Injection of local anesthetic solution through a caudally oriented epidural catheter produces faster onset and superior quality of anesthesia in comparison with the injection through the cephaladly oriented catheter in ankle surgery, but not hemorrhoidectomy.

The Neurotoxicity of Epidural Hyaluronic Acid in Rabbits: A Light and Electron Microscopic Examination

Because hyaluronic acid (HA) has an antiinflammatory effect and prevents and/or reduces tissue adhesion, we believed it possible that epidurally-administered HA during epidural adhesiolysis procedures could alleviate pain in patients with chronic lower back pain. Therefore, we performed this pre-clinical trial evaluation of epidurally-administered HA neurotoxicity by light microscopy (LM) and electron microscopy (EM) in rabbits. Twenty rabbits were randomly divided into two groups, a normal saline (NS) group (n = 10) and a HA group (n = 10). Saline (0.2 mL/kg of 0.9% solution) and the same volume of HA were injected into the epidural space. No rabbits showed any sensory-motor or behavior change during the 3-wk period, except for one rabbit in the NS group that showed decreased appetite, activity, and weight loss. By LM, two rabbits in the NS group showed abnormal findings considered to be the result of trauma and infection associated with epidural catheterization. EM findings showed no significant neurotoxic findings in either group. In conclusion, epidurally-administered HA did not cause neurotoxicity in rabbits.

IMPLICATIONS

We performed a pre-clinical trial evaluation on the neurotoxicity of hyaluronic acid administered epidurally by light microscopy and electron microscopy in rabbits. Epidurally-administered hyaluronic acid did not produce any sign of neurotoxicity in rabbits.

Thoracic epidural catheters placed by the caudal route in infants: the importance of radiographic confirmation

BACKGROUND

Cephalad advancement of epidural catheters to the thoracic region via the caudal route has been shown to be feasible in neonates and small infants. This has allowed many young infants to receive thoracic level epidural analgesia with dilute local anaesthetic solutions using the simpler caudal approach. Since radiographic confirmation of the catheter tip is routine at this institution, we wished to determine how often radiographic studies led to adjustment or replacement of the epidural catheter.

METHODS

After institutional review board approval, we retrospectively reviewed the medical records of neonates and infants less than 6 months of age who had thoracic or lumbar epidural analgesia via the caudal route between August 1995 and January 2000. Demographic data were recorded, including age, weight and type of surgery. The epidural catheter type, tip location by radiograph and any manipulation of the catheter after the radiograph were also noted.

RESULTS

During the study period, a total of 115 infants were identified as having received caudal placement of a thoracic catheter. Radiographic studies were available for 86 of these infants. The position of 28 (32%) of the epidural catheters was considered to be inadequate after review of the confirmatory radiograph. Ten of these catheters were determined to be in the high thoracic or cervical region and were pulled back to the desired level. Seventeen of these catheters were coiled in the lumbosacral area and 15 of these were replaced at an adequate level. One catheter was found to be outside the epidural space in the presacral area. No correlation could be found between age, weight, type of catheter or type of surgery and the need for catheter manipulation.

CONCLUSIONS

Even in young infants, radiographic determination of the catheter tip appears warranted when thoracic catheters are placed via the caudal route.