Epidural injection of ketamine for perineal analgesia in the horse

Outcome of epidural catheterization for delivery of analgesics in horses: 43 cases (1998-2001)

OBJECTIVE

To determine reasons for epidural catheter placement among horses examined at a veterinary teaching hospital, efficacy of epidural administration of analgesics, duration of catheter placement, reasons for catheter removal, and complications encountered.

DESIGN

Retrospective study.

ANIMALS

43 horses.

PROCEDURE

Medical records were reviewed.

RESULTS

A total of 50 epidural catheters were placed in the 43 horses. Underlying conditions included fractures, lacerations, septic arthritis, myositis, perineal injuries, and cellulitis. Horses ranged from 2 to 21 years old and weighed between 365 and 795 kg (803 and 1,749 lb). Median duration of catheter placement was 96 hours (range, 1.5 to 480 hours). The response to epidural drug administration was reported as positive in 34 horses and negative in 4. There was no apparent response in 2 horses, and response could not be determined in 3. Three temporary patient-related complications associated with epidural catheter administration were observed. Technical problems associated with the epidural catheters included dislodgement of the catheter itself (7 catheters) or of the adapter or filter (5), obstruction (5), and leakage (5). Twenty-two catheters were removed because of resolution of the underlying condition, and 10 were removed because of complications. For 6 catheters, the reason for catheter removal was not recorded. The remaining 12 catheters were in place when the horses were euthanatized.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that epidural catheterization can be used successfully for repeated epidural delivery of analgesics and anesthetics in horses with various clinical conditions. Complications associated with epidural catheters or epidural drug administration were infrequent and transient.

Evaluation of the local analgesic effect of ketamine in the palmar digital nerve block at the base of the proximal sesamoid (abaxial sesamoid block) in horses

OBJECTIVE

To evaluate the local analgesic effect of ketamine in a palmar digital nerve block at the base of the proximal sesamoid (abaxial sesamoid block) in horses.

ANIMALS

36 mature healthy Andalusian horses.

PROCEDURE

Horses were randomly assigned to 4 groups of 9 horses each and received an abaxial sesamoid block in a randomly chosen forelimb with 1 of the following: saline (0.9% NaCl) solution, 1% ketamine solution, 2% ketamine solution, or 3% ketamine solution. To determine analgesia, the radiant heat lamp-hoof withdrawal model was used as a noxious thermal stimulus. Before each nerve block, baseline hoof withdrawal reflex latency (HWRL, time between lamp illumination and withdrawal of the hoof) was determined; after the nerve block, local analgesic effects were determined by measuring HWRL at 2 and 5 minutes after injection and then every 5 minutes for a total period of 1 hour.

RESULTS

Significant differences in HWRL were found between baseline values and values at 2 to 15 minutes following a nerve block with ketamine. Significant differences were found between HWRL values at every time point from 2 to 10 minutes following a nerve block with saline solution, compared with 1 or 2% ketamine solution. Similarly, significant differences were found between HWRL values at every time point from 2 to 15 minutes following a nerve block with saline solution, compared with 3% ketamine solution.

CONCLUSIONS AND CLINICAL RELEVANCE

Abaxial sesamoid block with ketamine ensures adequate analgesia in horses with an onset of action of 2 minutes and a maximal duration of action of 15 minutes.

Perineal analgesic actions of epidural clonidine in cattle

OBJECTIVE

To determine the analgesic, sedative, motor, cardiac and respiratory effects of epidural clonidine in cattle.

STUDY DESIGN

Prospective randomized study.

ANIMAL POPULATION

Six healthy male cattle weighing between 236 and 365 kg.

METHODS

To investigate the effect of epidural clonidine, the animals received 2 and 3 μg kg^-1 of clonidine diluted to 8 mL with 0.9% saline. Two treatments were utilized as controls. The animals from the first control treatment received 2% lidocaine (0.4 mg kg^-1) and those from the second received an equal volume of 0.9% saline. Each animal received each treatment in random order. Evaluations of analgesia, sedation, muscle relaxation, heart rate, respiratory rate and rectal temperature were obtained at 0 (basal), 2, 5, 10, 15 and 30 minutes after epidural injection, and then at 30-minute intervals until loss of analgesia occurred. All the animals received a standard noxious stimulus consisting of needle insertion into the skin and deep muscle; a 4-point scale was used to score the response. A second scale was used to score sedation and a third for muscle relaxation.

RESULTS

Both doses of clonidine were effective in producing analgesia of the tail, perineum, and upper hindlimb. Complete analgesia was present before (mean ± SE = 9 ± 4 vs. 19 ± 9 minutes) and lasted longer (311 ± 33 vs. 192 ± 27 minutes) for the 3 μg kg^-1versus the 2 μg kg^-1 dose, respectively. A dose-dependent sedative effect of clonidine was also observed, with a peak effect between 60 and 180 minutes. No effects on heart or respiratory rates were observed with either dose of clonidine.

CONCLUSIONS

Epidural administration of 2 and 3 μg kg^-1 of clonidine in cattle in this study provided bilateral perineal analgesia/anesthesia with a dose-dependent onset and duration of action.

CLINICAL RELEVANCE

Further studies are required to determine whether the analgesia is sufficient for surgery.

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.

Injeção epidural de morfina ou cetamina em cães: avaliação do efeito analgésico pelo emprego de filamentos de von Frey

Utilizaram-se 14 cães mestiços, com idade inferior a cinco anos e peso médio de 12,5kg, com o objetivo de se avaliar os efeitos da injeção epidural de morfina ou cetamina sobre a dor pós-operatória. Os cães foram anestesiados com sevoflurano por meio de máscara facial, e em ato contínuo, receberam injeção epidural de morfina (0,1mg/kg; G1) ou cetamina (0,2mg/kg; G2) diluídas em 0,3ml/kg de solução salina. A incisão experimental de 1,5cm foi realizada no coxim plantar e suturada com fio de náilon. Interrompida a anestesia inalatória e decorridos 30 minutos iniciou-se a avaliação da dor peri-incisional, aplicando-se os filamentos de von Frey a 0,3cm equidistantes da incisão. O procedimento foi repetido a intervalos de 30 minutos até 120 minutos, e posteriormente às 3, 4, 5, 6 e 24 horas do período pós-incisional. Os animais de G1 não responderam à estimulação com os filamentos e apoiaram o membro incindido normalmente durante todo o período de avaliação. No G2 observou-se aumento progressivo da resposta à estimulação pelos filamentos de von Frey desde os 90 minutos até 24 horas. A morfina reduziu a dor pós-incisional por 24 horas, mostrando-se mais efetiva do que a cetamina para o controle da dor.

Epidural anesthesia and analgesia in horses

Intercoccygeal, or caudal, epidural injection of local anesthetics is a convenient method of producing analgesia and local anesthesia of the tail and perineal structures in conscious standing horses. This technique has been further developed to provide long duration analgesia and anesthesia by placement of catheters into the epidural space of horses. More recently, opioid, alpha-2 adrenergic agonists, ketamine and other analgesic agents have been administered by caudal epidural injection, providing pain relief in both conscious, standing and anesthetized, recumbent horses. This chapter describes the development of different anesthetic and analgesic epidural techniques in horses, methods for epidural injection and catheterization, and reviews the current literature related to epidural analgesia and pain control in horses.

Analgesic, hemodynamic, and respiratory effects induced by caudal epidural administration of meperidine hydrochloride in mares

OBJECTIVE

To determine the analgesic, hemodynamic, and respiratory effects induced by caudal epidural administration of meperidine hydrochloride in mares.

ANIMALS

7 healthy mares.

PROCEDURE

Each mare received meperidine (5%; 0.8 mg/kg of body weight) or saline (0.9% NaCl) solution via caudal epidural injection on 2 occasions. At least 2 weeks elapsed between treatments. Degree of analgesia in response to noxious electrical, thermal, and skin and muscle prick stimuli was determined before and for 5 hours after treatment. In addition, cardiovascular and respiratory variables were measured and degree of sedation (head position) and ataxia (pelvic limb position) evaluated.

RESULTS

Caudal epidural administration of meperidine induced bilateral analgesia extending from the. coccygeal to S1 dermatomes in standing mares; degree of sedation and ataxia was minimal. Mean (+/- SD) onset of analgesia was 12 +/- 4 minutes after meperidine administration, and duration of analgesia ranged from 240 minutes to the entire 300-minute testing period. Heart and respiratory rates, rectal temperature, arterial blood pressures, Hct, PaO2, PaCO2, pHa, total solids and bicarbonate concentrations, and base excess were not significantly different from baseline values after caudal epidural administration of either meperidine or saline solution.

CONCLUSIONS AND CLINICAL RELEVANCE

Caudal epidural administration of meperidine induced prolonged perineal analgesia in healthy mares. Degree of sedation and ataxia was minimal, and adverse cardiorespiratory effects were not detected. Meperidine may be a useful agent for induction of caudal epidural analgesia in mares undergoing prolonged diagnostic, obstetric, or surgical procedures in the anal and perineal regions.

Combined xylazine and ketamine as an analgesic regimen in sheep

OBJECTIVE

To determine whether low dose xylazine with ketamine reduces the concentrations of cortisol and prolactin in sheep postoperatively and to characterise the effects of the drugs on behaviour during recovery.

DESIGN

Analysis of variance was used to compare the effects of anaesthesia, surgery and combined ketamine/xylazine treatment on the plasma cortisol and prolactin concentrations and on behavioural variables in pregnant ewes subjected to abdominal surgery.

PROCEDURE

Twelve ewes were randomly assigned to receive either ketamine/xylazine or placebo in association with anaesthesia and surgery. Both groups of ewes underwent anaesthesia alone followed a week later by anaesthesia with laparotomy and hysterotomy. Plasma cortisol and prolactin concentrations were assayed during these procedures and for 5 days afterwards. Behavioural observations were made remotely during recovery from anaesthesia and anaesthesia plus surgery.

RESULTS

The concentrations of cortisol in the plasma of pregnant ewes undergoing surgery were increased by preoperative handling and the onset of thiopentone/halothane anaesthesia, with a further increase during surgery (P = 0.033). Cortisol concentrations decreased over the first four postoperative hours (P = 0.029) and were normal by 24 h. The drug treatment did not affect the immediate responses of ewes to anaesthesia or surgery, although treated ewes had lower cortisol concentrations than saline-treated controls over the first five postoperative days (P = 0.018). Prolactin concentrations increased in response to anaesthesia (P = 0.047), but were not affected by surgery or the drug treatment. Drug-treated ewes had prolonged sleeping time after surgery (P = 0.002), but they took no longer to stand than saline-treated controls and required fewer attempts to stand successfully (P = 0.025).

CONCLUSION

At the doses used, ketamine and xylazine did not mitigate the immediate endocrine consequences of surgery but the behavioural data provide a basis for further investigations that may lead to improvements in analgesic treatments.

Evaluation of the analgesic effects of epidurally administered morphine, alfentanil, butorphanol, tramadol, and U50488H in horses

OBJECTIVE

To evaluate and compare effects of epidurally administered morphine, alfentanil, butorphanol, tramadol, and U50488H on avoidance threshold to noxious electrical stimulation over the dermatomes of the perineal, sacral, lumbar, and thoracic regions in horses.

ANIMALS

5 healthy adult horses.

PROCEDURE

Using a Latin square complete repeated-measures design, horses were randomly assigned to receive 1 of 6 treatments (morphine, alfentanil, butorphanol, tramadol, U50488H, or sterile water) at intervals of at least 7 days. Agents were injected epidurally at the first intercoccygeal epidural space, and electrical stimulation was applied at repeated intervals for 24 hours to the dermatomes of the perineal, sacral, lumbar, and thoracic regions. Avoidance threshold to electrical stimulation was recorded.

RESULTS

Administration of butorphanol, U50488H, and sterile water did not induce change in avoidance threshold. Alfentanil increased avoidance threshold during the first 4 hours, but not significantly. Tramadol and morphine significantly increased threshold and analgesic effects. Complete analgesia (avoidance threshold, >40 V) in the perineal and sacral areas was achieved 30 minutes after tramadol injection, compared with 6 hours after morphine injection. Duration of complete analgesia was 4 hours and 5 hours after tramadol and morphine injections, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Epidural administration of tramadol and morphine induces long-lasting analgesia in healthy adult horses. Epidural administration of opioids may provide long-lasting analgesia in horses without excitation of the CNS.