Segmental epidural and subarachnoid analgesia in conscious horses: a comparative study

Six adult horses were used to compare the effects of segmental epidural analgesia (SEA) and segmental subarachnoid analgesia (SSA). A 17-gauge Huber point directional needle was used to place a catheter with stylet into the epidural space or the subarachnoid space at the lumbosacral intervertebral junction and to catheterize the thoracolumbar epidural or subarachnoid space. The position of the catheter was confirmed radiographically. A 2% solution of mepivacaine hydrochloride was used at average doses of 80 mg (4 ml) to produce SEA and 30 mg (1.5 ml) to produce SSA. Onset of analgesia in response to superficial and deep muscular pinprick stimulations was significantly (P less than 0.05) faster in horses with SSA than with SEA (8.0 +/- 1.9 minutes vs 15.8 +/- 3.8 minutes). Maximal thoracolumbar analgesia extended from spinal cord segments T14 to L3 on both sides of the spinal column during SSA and from T12 to L2 on one or both sides during SEA. Duration of analgesia lasted significantly (P less than 0.05) longer in horses with SEA than in those with SSA (80.8 +/- 16.9 minutes vs 44.8 +/- 14.5 minutes). There was a significant (P less than 0.05) increase in subcutaneous temperature at the right and left 18th thoracic (T18) dermatomes and decreases of respiratory rate and rectal temperatures in horses with SEA. Respiratory rate and rectal temperature were not significantly (P greater than 0.05) decreased in horses with SSA.(ABSTRACT TRUNCATED AT 250 WORDS)     

Continuous caudal epidural and subarachnoid anesthesia in mares: a comparative study

A new technique for producing continuous caudal epidural analgesia (CEA) and caudal subarachnoid analgesia (CSA) in adult horses (mares) without causing loss of pelvic limb function is described. A modified 17-gauge Huber-point directional needle was used to place a catheter with stylet into either the epidural or subarachnoid space at the lumbosacral intervertebral junction. The catheter was positioned at either the midsacral (S2-3) subarachnoid space or caudal portion of the sacral (S-3 to S-5) epidural space in 7 mares. The position of the catheter was confirmed radiographically. A 2% solution of mepivacaine HCl was used at an average dose of 0.061 +/- 0.013 mg/kg (1.3 +/- 0.3 ml) to produce CSA and 0.196 +/- 0.034 mg/kg (4.1 +/- 0.7 ml) to produce CEA. Onset of analgesia to superficial and deep muscular pinprick stimulation was faster with CSA than it was with CEA (8.2 +/- 2.4 minutes vs 21.4 +/- 3.8 minutes). Maximal caudal analgesia extended from spinal cord segments S-1 to coccyx during CSA and CEA. Periods of analgesia were shorter with CSA than with CEA (70.0 +/- 21.8 minutes vs 102.1 +/- 13.2 minutes). Perineal (S-4 to S-5) dermatome subcutaneous temperature was increased after epidural and subarachnoid injections of mepivacaine HCl solution. Heart rate, respiratory rate, systolic, diastolic, and mean arterial blood pressures, pulse pressure, rectal temperature, arterial blood gas tensions (PaCO2, PaO2), pHa, hematocrit, and total solid concentrations did not change significantly (P greater than 0.05) from base-line values after injection. The benefits and potential complications of CSA and CEA in horses are discussed.     

Combined spinal-epidural anesthesia in a dog

OBJECTIVE: To report use of combined spinal epidural anesthesia for tail resection and surgical exploration of the pelvic canal and the perineal-pararectal area in a dog. ANIMAL: A 4-month-old, 13 kg male Collie dog. METHODS: Under inhalant anesthesia, an epidural catheter was threaded through a Tuohy needle at L5-L6. Then using a Whitacre spinal needle bupivacaine and fentanyl were administered in the subarachnoid space at L6-L7 level. Fifteen minutes later, morphine was administered epidurally. Bupivacaine and morphine were administered epidurally 4 hours after the subarachnoid injection. RESULTS: No cardiorespiratory response to surgical stimulation was observed. Postoperative analgesia was satisfactory, and the catheter was removed 30 hours later. No complications or neurologic sequelae occurred before discharge or were noted 10 days later. CONCLUSION: Combined spinal-epidural anesthesia provided excellent intraoperative anesthesia and perioperative analgesia in a dog undergoing surgery involving the pelvic canal. CLINICAL RELEVANCE: Combined spinal-epidural anesthesia can be performed in dogs, and its use should be considered in major surgeries caudal to the diaphragm, as the epidural catheter allows cranial extension of the block, providing excellent intraoperative anesthesia and perioperative analgesia.     

Plasma mepivacaine concentrations after caudal epidural and subarachnoid injection in the horse: comparative study

The venous plasma concentrations of mepivacaine were determined in 7 adult mares (420 +/- 17.1 kg) given an injection of a 2% solution of the hydrochloride at either the sacral (S2-3 to S5-C1) epidural space or the midsacral (S2-3) subarachnoid space. An average dose of 91.4 +/- 15.7 mg (4.6 +/- 0.8 ml) was needed to produce caudal epidural analgesia (CEA) and 26.7 +/- 5.4 mg (1.3 +/- 0.3 ml) to produce caudal subarachnoid analgesia (CSA). Maximal caudal analgesia extended from spinal cord segments S-1 to coccyx during CEA and CSA. The onset of analgesia as measured by response to superficial and deep muscular pinprick stimulations was significantly (P less than 0.05) faster in mares with CSA than with CEA (8.3 +/- 2.4 minutes vs 21.4 +/- 3.8 minutes). The period of analgesia was significantly (P less than 0.05) longer in mares with CEA than with CSA (80.0 +/- 11.5 minutes vs 67.4 +/- 26.3 minutes). The rate of vascular absorption of mepivacaine from the epidural space was significantly (P less than 0.05) faster than from the subarachnoid space. Maximum venous plasma concentrations of mepivacaine were similar (P greater than 0.05) after epidural and subarachnoid injections (0.05 +/- 0.03 micrograms/ml and 0.05 +/- 0.03 micrograms/ml) at the same times after mepivacaine administration (51.4 +/- 33.4 minutes and 53.6 +/- 24.3 minutes).(ABSTRACT TRUNCATED AT 250 WORDS)     

Spinal fluid concentrations of mepivacaine in horses and procaine in cows after thoracolumbar subarachnoid analgesia

The CSF concentrations of mepivacaine in 10 Standardbred horses and of procaine in 10 Holstein cows given the drugs by thoracolumbar subarachnoid injection were determined. Mepivacaine hydrochloride was injected into the horses (502 +/- 60.5 kg) at an average dosage of 30 mg (1.5 ml of 20 mg/ml solution). Analgesia was produced 7.5 +/- 4.3 minutes after injection, extended between spinal cord segments T13 and L3 on both sides of the spinal column, and lasted 47 +/- 18.7 minutes at the T18 dermatome. Procaine hydrochloride was injected into cows (614 +/- 51.5 kg) at a dosage ranging between 75 mg and 100 mg (1.5 ml and 2 ml of 50 mg/ml solution). Analgesia was produced 8.2 +/- 2.0 minutes after injection, extended between spinal cord segments T11 and L4 on both sides of the spinal column, and lasted 47 +/- 17.5 minutes at the T13 dermatome. The critical CSF concentrations of local anesthetics required to eliminate response to pinprick stimulation were 204.4 +/- 90.3 micrograms of mepivacaine/ml in horses and 197.0 +/- 86.1 micrograms of procaine/ml in cows. Average CSF concentrations at 120 minutes after injections were made were 16.8 +/- 15.5 micrograms of mepivacaine/ml and 30.6 +/- 17.1 micrograms of procaine/ml. In in vitro experiments to determine the rates of hydrolysis of mepivacaine and procaine in CSF, significant changes (P greater than 0.05) were not seen in the CSF concentrations of mepivacaine in horses and procaine in cattle after a 120-minute incubation (37 C). The analgesic threshold concentrations of mepivacaine in CSF of horses and procaine in CSF of cows were similar.(ABSTRACT TRUNCATED AT 250 WORDS)     

Hemodynamic effects of unilateral segmented lumbar epidural analgesia in cattle.

Hemodynamic measurements, arterial and mixed venous blood gas tensions, and pH were determined in 12 adult cows (mean weight 538 kg) following the injection of 8 ml of 5% procaine between the first and the second lumber vertebra into the epidural space. Comparison of base-line data with obtained during unilateral segmented lumbar analgesia between T(13) and L(3) segments indicated significant decreases (P is less than 0.05) in total peripheral resistance and diastolic and mean arterial blood pressures, and significant increases (P is less than 0.05) in heart rate and cardiac output. Arterial and mixed venous blood gas tensions and pH, O(2)-uptake, stroke volume, left ventricular stroke work, left ventricular minute work and hematocrit did not change significantly (P is less than 0.05). Cardiovascular and respiratory values in two cows (mean weight 700 kg) given xylazine (50 mg, IM), were depressed from base-line data, but did not change significantly (P is less than 0.05) during unilateral segmental epidural analgesia of segments T(13 to L(3). The nonsedated healthy cow tolerates sympathetic vasomotor blockade between T(13) and L(3) segments well and is able to mobilize circulatory mechanisms effectively.     

Evaluation of analgesic and physiologic effects of epidural morphine administered at a thoracic or lumbar level in dogs undergoing thoracotomy

ObjectiveTo evaluate the analgesic and physiological effects of epidural morphine administered at the sixth and seventh lumbar or the fifth and sixth thoracic vertebrae in dogs undergoing thoracotomy.Study designProspective, randomized, blinded trial.AnimalsFourteen mixed-breed dogs, weighing 8.6 ± 1.4 kg.MethodsThe animals received acepromazine (0.1 mg kg^?1) IM and anesthesia was induced with propofol (4 mg kg^?1) IV. The lumbosacral space was punctured and an epidural catheter was inserted up to the region between the sixth and seventh lumbar vertebrae (L, n = 6) or up to the fifth or sixth intercostal space (T, n = 8). The dogs were allowed to recover and after radiographic confirmation of correct catheter position, anesthesia was reinduced with propofol IV and maintained with 1.7% isoflurane. Following stabilization of monitored parameters, animals received morphine (0.1 mg kg^?1) diluted in 0.9% NaCl to a final volume of 0.25 mL kg^?1 via the epidural catheter, and after 40 minutes, thoracotomy was initiated. Heart rate and rhythm, systolic, mean and diastolic arterial pressures, respiratory rate, arterial hemoglobin oxygen saturation, partial pressure of expired CO₂ and body temperature were measured immediately before the epidural administration of morphine (0 minute) and every 10 minutes during the anesthetic period. The Melbourne pain scale and the visual analog scale were used to assess post-operative pain. The evaluation began 3 hours after the epidural administration of morphine and occurred each hour until rescue analgesia.ResultsThere were no important variations in the physiological parameters during the anesthetic period. The post-operative analgesic period differed between the groups, being longer in T (9.9 ± 1.6 hours) compared with L (5.8 ± 0.8 hours).ConclusionsThe use of morphine, at a volume of 0.25 mL kg^?1, administered epidurally over the thoracic vertebrae provided longer lasting analgesia than when deposited over the lumbar vertebrae.Clinical relevanceThe deposition of epidural morphine provided longer lasting analgesia when administered near to the innervation of the injured tissue without increasing side effects.     

Relationship between intervertebral joint morphology and mobility in the equine thoracolumbar spine

The anatomical features of 21 equine thoracolumbar spines, obtained from horses with clinically normal backs, were examined and the results compared with recent data on the mobility of the joint complexes of the horse's spine. The thoracolumbar spine can be divided into four regions based upon the morphology of the joint complexes: the first thoracic intervertebral joint (T1-2), the cranial and mid thoracic region (T2-T16), the caudal thoracic and lumbar region (T16-L6) and the lumbosacral joint. The mobility of the intervertebral joints in each of these regions can be related to their morphology, particularly the shape, size and orientation of the articular facets and the presence and frequent fusion of the lateral joints of the lumbar spine. The shape and thickness of the intervertebral discs also appear to be of importance.     

Analgesic and systemic effects of ketamine,xylazine, and lidocaine after subarachnoid administration in goats

OBJECTIVE: To determine the effects of ketamine hydrochloride, xylazine hydrochloride, and lidocaine hydrochloride after subarachnoid administration in goats. ANIMALS: 6 healthy goats. PROCEDURE: In each goat, ketamine (3 mg/kg), xylazine (0.1 mg/kg), lidocaine (2.5 mg/kg), and saline (0.9% NaCI) solution were injected into the subarachnoid space between the last lumbar vertebra and first sacral vertebra (time 0). Analgesic, ataxic, sedative, cardiovascular, and respiratory effects and rectal temperature were evaluated before (baseline) and 2, 5, 10, 15, and 30 minutes after administration and at 30-minute intervals thereafter as needed. RESULTS: Administration of anesthetics induced varying degrees of analgesia. Onset of the analgesic effect was more delayed for xylazine (mean +/- SD, 9.5 +/- 2.6 minutes) than for ketamine (6.7 +/- 2.6 minutes) or lidocaine (3.5 +/- 1.2 minutes). Duration of analgesia induced by xylazine (88.3 +/- 15 minutes) was twice as long as the duration of analgesia induced by ketamine (48.8 +/- 13.5 minutes) but similar to that induced by lidocaine (66.5 +/- 31 minutes). Xylazine induced bradycardia, whereas ketamine caused a nonsignificant increase in heart rate. Xylazine induced a reduction in arterial pressure, whereas ketamine or lidocaine did not affect arterial pressure. CONCLUSIONS AND CLINICAL RELEVANCE: Subarachnoid administration of xylazine in goats resulted in longer duration of analgesia of the tail, perineum, hind limbs, flanks, and caudodorsal rib areas than administration of ketamine or lidocaine. However, xylazine caused bradycardia and respiratory depression. Additional studies are needed to determine whether the analgesia would be sufficient to allow clinicians to perform surgical procedures.     

Comparison of the width of the intervertebral disk space and radiographic changes before and after intervertebral disk fenestration in dogs

Intervertebral disk space widths were measured on lateral radiographs of 73 anesthetized dogs. Weight was found to have a significant (P less than 0.01) effect on disk space width. Using weight-adjusted disk space width measurements for all subsequent studies, older (7- to 16-year-old) dogs and males had consistently, but not significantly, wider, disk spaces than did alternative groups. Cervical and lumbar intervertebral disk spaces tended to be wider than those in the caudal thoracic region. The widest cervical intervertebral disk spaces were C4-5 and C5-6 and the narrowest was C2-3. In the lumbar region, L2-3 was the widest disk space and L4-5 was the narrowest. Dachshunds generally had greater mean intervertebral disk space width than did other breeds of dogs. Cervical (n = 6 dogs) and thoracolumbar (n = 6 dogs) disk fenestration resulted in narrow intervertebral disk spaces, regardless of breed. When a ventral approach was used in thoracolumbar fenestration, the mean intervertebral disk space was narrower than that resulting from use of a dorsolateral approach. Spondylosis was found radiographically 1 to 4 years after intervertebral disk fenestration in 3 of 6 dogs that had cervical fenestrations and in 5 of 6 dogs that underwent thoracolumbar fenestration.     

Intervertebral disk disease in 10 cats.

The medical records of 10 cats diagnosed with intervertebral disk disease were reviewed. No apparent sex or breed predilection was found. The mean age of cats in the study was 9.8 years. Clinical signs included back pain, difficulty ambulating, and incontinence. Radiographs revealed narrowed disk spaces, mineralized intervertebral disks, and evidence of extradural compression on myelography or computed tomography. All intervertebral disk herniations occurred in the thoracolumbar spine, with a peak incidence at the fourth to fifth lumbar (L4-L5) intervertebral disk space. Eight cats had Hansen's type I intervertebral disk herniation. Surgery was performed in seven cats. All cats judged to have an excellent outcome had undergone surgical decompression.     

Caudal epidural analgesia induced by xylazine administration in cows

Xylazine (0.05 mg/kg of body weight diluted to a 5-ml volume, using 0.9% NaCl) or 5 ml of 0.9% NaCl was administered epidurally into the first caudal intervertebral space (Co1-Co2) in 8 cows (mean +/- SD body weight, 583 +/- 150 kg). Cows were observed for responses to deep needle pricking of the caudal dermatomes (S3 to Co), sedation, and ataxia. Heart rate, respiratory rate, body temperature, rate of ruminal contractions, coccygeal arterial blood pressure, pHa, blood gas tension (PaO2, PaCO2), base excess, total solids concentration, and PCV were determined before and after xylazine administration. Epidurally administered xylazine induced sedation and selective (S3 to Co) analgesia for at least 2 hours. Mild ataxia of hind limbs was observed in 6 cows, but all cows remained standing. Heart rate, respiratory rate, rate of ruminal contractions, arterial blood pressure, PaO2, PCV, and total solids concentration were significantly (P less than 0.05) decreased, and PaCO2, base excess, and bicarbonate concentration were significantly (P less than 0.05) increased after xylazine administration. Epidurally administered 0.9% NaCl did not alter sensory perception to needle pricking and did not affect any of the physiologic variables determined. Although epidural administration of xylazine induced analgesia and sedation in healthy cows, it should be avoided for epidural analgesia in cattle with heart disease, lung disease, and/or gastrointestinal disease because of its potent cardiopulmonary and ruminal depressant effects.     

Comparison of feasibility and safety of epidural catheterization between cranial and caudal lumbar vertebral segments in dogs

To compare the technical difficulty and safety of epidural catheterization between cranial and caudal lumbar region, thirteen dogs were randomly assigned to a cranial lumbar group (group CraL, n=6) or a caudal lumbar group (group CauL, n=6) depending on different epidural sites, and one dog was used as a negative control without catheterization. After general anesthesia, an epidural catheter was advanced 10 cm cranially from the interspace of L1-L2 in group CraL or from lumbosacral space in group CauL. Dogs were euthanized and catheter position and tip location were confirmed by laminectomy. Spinal cord samples were examined by macro- and microscopic observations. Success rate, time taken for epidural space confirmation and catheter insertion were compared, and overall technical difficulty was evaluated subjectively. Epidural catheter was inserted successfully in all dogs. Time needed from needle skin puncture to catheter placement and saline injection was 226 ± 63 and 229 ± 26 sec in groups CraL and CauL without significant differences. Three dogs in group CraL suffered subcutaneous blood, but no spinal cord injuries were found. Subjective evaluation score of the overall technical difficulty was slightly but significantly higher in group CraL than in group CauL (P=0.009). Epidural catheterization in cranial lumbar region could be performed as feasible and safe as that at the caudal lumbar vertebral region in medium or large dogs.     

Evaluation of electrical nerve stimulation for epidural catheter positioning in the dog

ObjectiveTo evaluate the accuracy of epidural catheter placement at different levels of the spinal cord guided solely by electrical nerve stimulation and resultant segmental muscle contraction.Study designProspective, experiment.AnimalsSix male and two female Beagles, age (1 ± 0.17 years) and weight (12.9 ± 1.1 kg).MethodsAnimals were anesthetized with propofol and maintained with isoflurane. An insulated epidural needle was used to reach the lumbosacral epidural space. A Tsui epidural catheter was inserted and connected to a nerve stimulator (1.0 mA, 0.1 ms, 2 Hz) to assess positioning of the tip at specific spinal cord segments. The catheter was advanced to three different levels of the spinal cord: lumbar (L2–L5), thoracic (T5–T10) and cervical (C4–C6). Subcutaneous needles were previously placed at these spinal levels and the catheter was advanced to match the needle location, guided only by corresponding muscle contractions. Catheter position was verified by fluoroscopy. If catheter tip and needle were at the same vertebral body a score of zero was assigned. When catheter tip was cranial or caudal to the needle, positive or negative numbers, respectively, corresponding to the number of vertebrae between them, were assigned. The mean and standard deviation of the number of vertebrae between catheter tip and needle were calculated to assess accuracy. Results are given as mean ± SD.ResultsThe catheter position in relation to the needle was within 0.3 ± 2.0 vertebral bodies. Positive predictive values (PPV) were 57%, 83% and 71% for lumbar, thoracic and cervical regions respectively. Overall PPV was 70%. No significant difference in PPV among regions was found.Conclusion and clinical relevancePlacement of an epidural catheter at specific spinal levels using electrical nerve stimulation was feasible without radiographic assistance in dogs. Two vertebral bodies difference from the target site may be clinically acceptable when performing segmental epidural regional anesthesia.     

Distribution of new methylene blue injected into the lumbosacral epidural space in cats

OBJECTIVE: To determine the effects of injection volume and vertebral anatomy on the spread of new methylene blue (NMB) injected into the lumbosacral epidural space in cats. STUDY DESIGN: Prospective experimental study. SAMPLE POPULATION: Sixteen cats. METHODS: Cats were randomly assigned to four groups and received from 0.1 to 0.4 mL kg(-1) of 0.12% NMB in 0.9% saline. Injection was made into the lumbosacral epidural space using a dorsal approach with the cats in sternal recumbency. The extent of cranial migration of the dye as indicated by the staining of epidural fat and dura mater was measured. RESULTS: The mean +/- SD (range) number of stained vertebrae in the 0.3 and 0.4 mL kg(-1) groups, were 11.5 +/- 1.5 (T7-T11) and 12.4 +/- 1.8 (T6-T10), respectively. This was significantly greater than the number in the 0.1 and 0.2 mL kg(-1) groups, 4.3 +/- 0.6 (L3-L4) and 6.0 +/- 0.7 (L1-L2) vertebrae, respectively (p < 0.001). Linear regression analysis showed that the volume injected correlated significantly with the number of stained vertebrae (R2 = 0.83, p < 0.001). In the dorsal and lateral aspect of the spinal cord, NMB solution distributed between epidural fat and dura mater. Migration under the spinal cord occurred along the two longitudinal epidural veins. CONCLUSIONS AND CLINICAL RELEVANCE: The larger the volume of solution injected into the lumbosacral epidural space in cats, the greater the spread.     

Comparison of lidocaine, xylazine, and xylazine/lidocaine for caudal epidural analgesia in horses.

Caudal epidural analgesia was achieved in 6 adult horses on 3 successive occasions at weekly intervals by injection of lidocaine, xylazine, and a combination of lidocaine/xylazine through indwelling epidural catheters. Analgesia was defined as a lack of response to pinprick and hemostat pressure in the skin of the perineal area. A significant (P < 0.05) difference was not found for time of onset of analgesia between lidocaine (4.3 +/- 0.8 minutes, mean +/- SEM) and the lidocaine/xylazine combination (5.3 +/- 1.3 minutes). Time to onset of analgesia after administration of xylazine was significantly (P < 0.05) longer (32.0 +/- 3.4 minutes) than that for either of the other 2 treatments. Duration of analgesia was significantly (P < 0.05) longer for the combination (329.8 +/- 6.2 minutes) than for either drug used alone (lidocaine, 87.2 +/- 7.5 minutes; xylazine, 204.2 +/- 12.9 minutes). Pulse and respiratory rates were not significantly altered by any of the drugs. Neurologic sequelae were not clinically apparent after administration of the drugs or after chronic epidural catheterization.     

Distribution of new methylene blue injected into the dorsolumbar epidural space in cows

Objective To describe the effect of injection volume and anatomy on the spread of new methylene blue (NMB) injected into the epidural space between the first and second lumbar vertebrae in cows. Study Design Prospective experimental study. Sample Population Thirteen nonpregnant cows. Methods Cows were randomly assigned to two groups. Group 1 received 5 mL and Group 2 received 10 mL of 0.12% NMB in 0.9% saline. The injection was made into the first interlumbar epidural space using a dorsal approach. The extent of cranial and caudal migration of the dye, as manifested by the staining of the epidural fat and dura mater, was measured. Results Mean ± SEM number (range) of stained vertebrae was significantly greater in the 10‐mL group than in the 5‐mL group, 4.4 ± 0.6 (T11 to L5) and 3.0 ± 0.2 (T12 to L3), respectively (p < 0.05). Linear regression analysis showed that the volume was significantly correlated with the number of stained vertebrae (R² = 0.42, p = 0.016). In the dorsal and lateral aspect of the spinal cord, there were two types of distribution of NMB along the surface of the epidural fat: between the periosteum and epidural fat; and between the epidural fat and dura mater. Migration under the spinal cord occurred along the two longitudinal epidural veins. Conclusions and Clinical Relevance The larger the volume of solution injected into the first interlumbar epidural space, the greater the spread. Intrinsic anatomic factors, such as characteristics of epidural fat and veins, influence the epidural spread of injected solution and, consequently, epidural analgesia.     

Functional outcome in dogs after surgical treatment of caudal lumbar intervertebral disk herniation.

Caudal lumbar disk herniations (i.e., third lumbar [L3] to seventh lumbar [L7] intervertebral spaces) represent approximately 15% of surgically treated thoracolumbar disk herniations in dogs. A retrospective case-control study was conducted to determine the postoperative outcome of this subset of dogs in the authors' neurosurgical practice. Medical records (1985 through 1996) were reviewed for dogs with caudal lumbar disk herniation confirmed at surgery. Thirty-six cases were identified. For each case, two dogs that underwent surgical treatment for upper motor neuron thoracolumbar disk herniation (tenth thoracic [T10] to L3 intervertebral spaces) were selected as controls. Probabilities of functional recovery for cases and controls were 81% and 85%, respectively (p value of 0.49). In dogs with caudal lumbar disk herniation, complete sensorimotor loss was the only significant predictor of functional recovery (p value of 0.005). Disk herniations that occur at the thoracolumbar junction and those that occur in the caudal lumbar region should not be considered to be different in terms of surgical treatment and postoperative outcome. The lower motor neuron signs that often accompany caudal lumbar disk herniation reflect the site of spinal cord injury and do not necessarily predict a poor prognosis.     

Multivariate regression analysis of epidural pressure in cattle

OBJECTIVE: To evaluate the effects of growth, maturity, and pregnancy on epidural pressure in cattle. ANIMALS: 50 healthy Holstein cattle (18 heifers, 23 lactating cows, and 9 pregnant nonlactating cows). PROCEDURE: Each of the cattle was restrained in a standing position. Height of the second lumbar vertebra's transverse process (2LTP) and humeral tuberosity (HT) on the right side as well as abdominal girth (AG) were measured in each animal, and body condition score (BCS) was ascertained. Skin caudal to the first lumbar spinous process was aseptically prepared, and anesthetic was injected. After inserting a 16-gauge 120-mm Tuohy needle in the ligamentum flavum, a calibrated pressure transducer was connected to the needle. Then, the needle was introduced into the epidural space, and epidural pressure was recorded. RESULTS: Mean +/- SD residual epidural pressure of heifers (-9.3+/-3.3 mm Hg) was significantly higher than that of lactating (-174+/-5.5 mm Hg) or nonlactating (-14.5+/-2.4 mm Hg) cows. Stepwise regression of 5 variables revealed that only the difference in height between 2LTP and HT (2LTP - HT) in heifers and only BCS in lactating cows were significantly correlated with residual epidural pressure. For all cattle, the optimal equation (R2 = 0.47) describing the relationship was y = -12.7 + 6.3x, - 0.4x2 - 0.1x3, where y is epidural pressure, x1 is BCS, x2 is 2LTP - HT, and x3 is age. CONCLUSIONS AND CLINICAL RELEVANCE: Negative epidural pressure was detected in standing cattle. Growth, maturity, and pregnancy affect epidural pressure in cattle.