Effects of epidural morphine on gastrointestinal transit in unmedicated horses

ObjectiveTo evaluate the effect of epidural morphine on gastrointestinal (GI) motility in horses.Study designRandomly ordered crossover design.AnimalsSix healthy adult horses weighing 585 ± 48 kg (mean ± SD).MethodsHorses were randomly assigned to receive either 0.2 mg kg^?1 morphine or an equal volume (0.04 mL kg^?1) of saline epidurally (the first inter coccygeal space) with 2 weeks between treatments. The horses were stabled, fed a standardized diet and allowed water ad libitum throughout the duration of the study. Radiopaque spheres were administered by stomach tube. Xylazine 0.2 mg kg^?1 intravenously was administered prior to epidural injection. Heart rate, respiratory rate, GI sounds score and behavior score were recorded before drug administration and after epidural injection at 4, 8, 12, 18, 24 hours and every 12 hours thereafter for 6 days. Feces were weighed, radiographed and the number of spheres counted. Data were analyzed using a mixed effect model.ResultsAt no time did horses exhibit signs of colic or show significant differences between treatments regarding heart rate, respiratory rate, GI sounds score, behavior score, or cumulative number of spheres. The concentration of spheres per kg of feces was significantly lower (p < 0.05) for the morphine group at 18 and 24 hours. Using the centroid of the curves (spheres kg^?1 plotted versus time) the average transit time after saline epidural was 38 hours and after morphine it was 43 hours. The weight of feces hour^?1 was significantly lower (p < 0.05) at only 4 and 8 hours after morphine.Conclusions and clinical relevanceEpidural morphine, at a dose of 0.2 mg kg^?1, temporarily reduced GI motility but did not cause ileus or colic in this small group of healthy unfasted horses. Care should be taken when extrapolating these data to situations in which other factors may also affect GI motility.     

A comparison of epidural morphine with low dose bupivacaine versus epidural morphine alone on motor and respiratory function in dogs following splenectomy

ObjectiveTo compare post-operative motor function in dogs that received epidural morphine and low dose bupivacaine versus epidural morphine alone following splenectomy.Study designProspective, randomized study.Animals16 client owned dogs undergoing routine splenectomy.MethodsFollowing splenectomy dogs were randomly allocated into one of two groups. The morphine group (MOR) was administered epidural morphine (0.1 mg kg^?1); the morphine-bupivacaine group (MORB) received epidural morphine (0.1 mg kg^?1) and low dose bupivacaine [0.25 mg kg^?1, (0.167%)]. The adjusted final volume was 0.15 mL kg^?1 in both groups. Motor function and pain assessment were performed at pre-determined times using a simple numerical motor score and the University of Melbourne Pain Scale (UMPS) respectively. An arterial blood gas was performed 2 hours following epidural administration to check for respiratory compromise. If patients scored >7 on the UMPS or were deemed painful by the observer they were administered hydromorphone intravenously and dose and time of rescue analgesia were recorded.ResultsThere were no statistically significant differences in motor scores, pain scores, amount of rescue analgesia administered or PaCO₂ between treatment groups. No dogs demonstrated respiratory depression or profound motor dysfunction at any time point during the study. 9/16 (56%) dogs did not require rescue analgesia during the first 18 hours following splenectomy.Conclusions and clinical relevanceThe combination of low dose bupivacaine (0.25 mg kg^?1) and morphine (0.1 mg kg^?1) when administered epidurally has little effect on post-operative motor function. This combination can be used without concern of motor paralysis in healthy animals.     

The post-operative analgesic effects of epidurally administered morphine and transdermal fentanyl patch after ovariohysterectomy in dogs

ObjectiveTo investigate the analgesic and side effects of epidural morphine or a fentanyl patch after ovariohysterectomy in dogs.Study designProspective, randomized clinical study.AnimalsTwenty female mongrel dogs undergoing ovariohysterectomy.MethodsThe dogs were allocated to one of two groups: epidural morphine or transdermal fentanyl patch. Anaesthesia was induced with propofol and maintained with isoflurane. Morphine (0.1 mg kg^?1) was administered epidurally in the epidural morphine group and a transdermal fentanyl patch was applied 24 hours before the operation in the fentanyl patch group.The heart rate, respiratory rate, body temperature, plasma cortisol concentration, and sedation and analgesia scores were recorded during the 24 hour post-operative period. Adverse effects such as vomiting, anorexia, skin reactions, urinary retention, and time to start licking the surgical site were also recorded. p < 0.05 was considered significant. Statistical analyses utilized anova for repeated measures, Friedman tests, Mann-Whitney U-tests and independent sample t-tests as relevant.ResultsPain scores were lower in the epidural group than in the fentanyl group at all post-operative times. The dogs in the epidural morphine group were calm and relaxed, whereas discomfort and vocalization were recorded in the fentanyl patch group. The sedation scores were higher in the fentanyl patch group throughout the 12 hour period. Salivation and anorexia lasted longer in the fentanyl patch group than in the epidural morphine group. Plasma cortisol concentrations were high in the early post-operative period in both groups. The fentanyl patch group had higher cortisol concentrations than the epidural morphine group. Slight erythema was recorded in two dogs when the patches were removed.Conclusion and clinical relevanceEpidurally administered morphine provided better analgesia and caused fewer adverse effects than the fentanyl patch after ovariohysterectomy in dogs.     

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.     

Evaluation of the perioperative stress response from dexmedetomidine infusion alone,with butorphanol bolus or remifentanil infusion compared with ketamine and morphine infusions in isoflurane-anesthetized horses

ObjectiveTo evaluate perioperative stress-related hormones in isoflurane-anesthetized horses administered infusions of dexmedetomidine alone or with butorphanol or remifentanil, compared with ketamine–morphine.Study designRandomized, prospective, nonblinded clinical study.AnimalsA total of 51 horses undergoing elective surgical procedures.MethodsHorses were premedicated with xylazine, anesthesia induced with ketamine–diazepam and maintained with isoflurane and one of four intravenous infusions. Partial intravenous anesthesia (PIVA) was achieved with dexmedetomidine (1.0 μg kg^–1 hour^–1; group D; 12 horses); dexmedetomidine (1.0 μg kg^–1 hour^–1) and butorphanol bolus (0.05 mg kg^–1; group DB; 13 horses); dexmedetomidine (1.0 μg kg^–1 hour^–1) and remifentanil (3.0 μg kg^–1 hour^–1; group DR; 13 horses); or ketamine (0.6 mg kg^–1 hour^–1) and morphine (0.15 mg kg^–1, 0.1 mg kg^–1 hour^–1; group KM; 13 horses). Infusions were started postinduction; butorphanol bolus was administered 10 minutes before starting surgery. Blood was collected before drugs were administered (baseline), 10 minutes after ketamine–diazepam, every 30 minutes during surgery and 1 hour after standing. Mean arterial pressure (MAP), pulse rate, end-tidal isoflurane concentration, cortisol, nonesterified fatty acids (NEFA), glucose and insulin concentrations were compared using linear mixed models. Significance was assumed when p < 0.05.ResultsWithin D, cortisol was lower at 120–180 minutes from starting surgery compared with baseline. Cortisol was higher in KM than in D at 60 minutes from starting surgery. Within all groups, glucose was higher postinduction (except DR) and 60 minutes from starting surgery, and insulin was lower during anesthesia and higher after standing compared with baseline. After standing, NEFA were higher in KM than in DB. In KM, MAP increased at 40–60 minutes from starting surgery compared with 30 minutes postinduction.Conclusions and clinical relevanceDexmedetomidine suppressed cortisol release more than dexmedetomidine–opioid and ketamine–morphine infusions. Ketamine–morphine PIVA might increase catecholamine activity.     

Comparison of bupivacaine femoral and sciatic nerve block versus bupivacaine and morphine epidural for stifle surgery in dogs

ObjectiveTo evaluate the efficacy of combined femoral and sciatic nerve blocks as an alternative to epidural anesthesia and analgesia in dogs undergoing stifle surgery under general anesthesia.Study designProspective, blinded, randomized, clinical comparison.AnimalsTwenty dogs weighing 37 ± 11 (mean ± SD) kg, aged 3 (1–8) [median (minimum–maximum)] years undergoing elective unilateral tibial-plateau leveling osteotomy.MethodsDogs were assigned randomly to receive either epidural anesthesia (bupivacaine 0.5%, 0.5 mg kg^?1 + morphine 0.1%, 0.1 mg kg^?1, in 0.2 mL kg^?1; EPID) or femoral and sciatic nerve blocks (Bupivacaine 0.5%, 0.1 mL kg^?1, was administered at each site; F + S) guided by electrolocation. All patients received a standard general anesthesia technique. Pain and sedation were scored (on scales of 0–10 and 0–3, respectively) pre-operatively, at extubation, and at 1, 4 and then every 4 hours thereafter up to 24 hours. Postoperatively, hydromorphone was administered to any patient with a pain score of >5 or whenever the blinded caregiver determined that more hydromorphone was necessary. Intraoperative heart rate (HR), mean arterial pressure (MAP), end tidal isoflurane (FE′ISO), body temperature, post-operative pain scores, time to first hydromorphone dose after surgery, time to first feeding, time to first drinking, time to first urination, time to first ambulation (walk on a lead) and cumulative dose of hydromorphone were recorded.ResultsIntra-operatively, FE′ISO and MAP were significantly lower in the EPID group (p = 0.05 and p = 0.04, respectively). Postoperatively, the cumulative hydromorphone consumption (p = 0.04) and the incidence of urinary retention (p = 0.03) were higher in the EPID group.Conclusion and clinical relevance F + S is a practical alternative to EPID that produces less urine retention and reduces opioid consumption in the 24 hours after surgery. EPID might be associated with a lower isoflurane requirement and lower systemic blood pressure.     

A comparison of epidural buprenorphine plus detomidine with morphine plus detomidine in horses undergoing bilateral stifle arthroscopy

ObjectiveTo compare the analgesic efficacy of buprenorphine plus detomidine with that of morphine plus detomidine when administered epidurally in horses undergoing bilateral stifle arthroscopy.Study designProspective, randomized, blinded clinical trial.AnimalsTwelve healthy adult horses participating in an orthopedic research study. Group M (n = 6) received morphine (0.2 mg kg^?1) and detomidine (0.15 mg kg^?1) epidurally; group B (n = 6) received buprenorphine (0.005 mg kg^?1) and detomidine (0.15 mg kg^?1) epidurally.MethodsHorses received one of two epidural treatments following induction of general anesthesia for bilateral stifle arthroscopy. Heart rate (HR), mean arterial blood pressure (MAP), end-tidal CO₂ (Pe’CO₂), and end-tidal isoflurane concentrations (E’Iso%) were recorded every 15 minutes following epidural administration. Post-operative assessment was performed at 1, 2, 3, 6, 9, 12, and 24 hours after standing; variables recorded included HR, respiratory rate (f_R), abdominal borborygmi, defecation, and the presence of undesirable side effects. At the same times post-operatively, each horse was videotaped at a walk and subsequently assigned a lameness score (0-4) by three ACVS diplomates blinded to treatment and who followed previously published guidelines. Nonparametric data were analyzed using Wilcoxon’s rank-sum test. Inter- and intra-rater agreement were determined using weighted kappa coefficients. Statistical significance was set at p = 0.05.ResultsNo statistically significant differences were found between groups with respect to intra-operative HR, MAP, E’Iso%, or post-operative HR, gastrointestinal function and cumulative median lameness scores. Post-operative f_R in group B [24 (12-30), median (range)] breaths per minute was significantly higher than in group M [18 (15-20)] breaths per minute, p = 0.04.Conclusions and clinical relevanceIn horses undergoing bilateral stifle arthroscopy, these doses of buprenorphine plus detomidine injected epidurally produced analgesia similar in intensity and duration to that of morphine plus detomidine injected epidurally.     

Comparison of cervical epidural morphine with intravenous morphine administration on antinociception in adult horses using thermal threshold testing

ObjectiveTo compare the antinociceptive effects of morphine administered via cervical epidural catheter to intravenously administered morphine using a thermal threshold (TT) testing model in healthy adult horses.Study designProspective, randomized, blinded experimental study.AnimalsA total of six university-owned adult horses.MethodsHorses were instrumented with a cervical (C1–C2) epidural catheter and TT testing device with probes at withers and thoracic limb coronary bands. All horses underwent three TT testing cycles including cervical epidural morphine administration (treatment EpiM; 0.1 mg kg^–1), systemic morphine administration (treatment SystM; 0.1 mg kg^–1) and no morphine administration (treatment Control). Baseline TT was established prior to treatments, and TT was tested at 15, 30, 60, 90, 120, 150, 180, 240, 300, 360, 420, 480, 600 and 720 minutes following treatment. Horses underwent a 5 day washout period between treatments and the order of treatment was randomized. Differences between treatments were analyzed with repeated measures anova.ResultsSystemic and epidural morphine administration resulted in significantly higher TT values compared with baseline and control treatment. The duration of effect was significantly longer in treatment EpiM (10–12 hours) than in treatment SystM (1.5–2.0 hours). Horses in treatment EpiM had significantly higher TT values at time points 180–600 minutes (withers) and 300–600 minutes (coronary band) than horses in treatment SystM.Conclusions and clinical relevanceCervical epidural administration of morphine provided antinociceptive effects as measured by increased TT for 10–12 hours compared with 1.5–2.0 hours for intravenously administered morphine. No complications or adverse effects were noticed following epidural placement of a C1–C2 catheter and administration of morphine. The use of a cervical epidural catheter can be considered for analgesia administration in treatment of thoracic limb and cervical pain in the horse.     

Comparison of analgesic efficacy of epidural methadone or ropivacaine/methadone with or without pre‐operative oral tepoxalin in dogs undergoing tuberositas tibiae advancement surgery

ObjectiveTo investigate the clinical efficacy of four analgesia protocols in dogs undergoing tibial tuberosity advancement (TTA).Study designProspective, randomized, blinded study.AnimalsThirty-two client owned dogs undergoing TTA-surgery.MethodsDogs (n= 8 per treatment) received an oral placebo (PM and PRM) or tepoxalin (10 mg kg^?1) tablet (TM and TRM) once daily for 1 week before surgery. Epidural methadone (0.1 mg kg^?1) (PM and TM) or the epidural combination methadone (0.1 mg kg^?1)/ropivacaine 0.75% (1.65 mg kg^?1) (PRM and TRM) was administered after induction of anaesthesia. Intra-operative fentanyl requirements (2 μg kg^?1 IV) and end-tidal isoflurane concentration after 60 minutes of anaesthesia (Fe′ISO₆₀) were recorded. Post-operative analgesia was evaluated hourly from 1 to 8 and at 20 hours post-extubation with a visual analogue scale (VAS) and the University of Melbourne Pain Scale (UMPS). If VAS > 50 and/or UMPS > 10, rescue methadone (0.1 mg kg^?1) was administered IV. Analgesic duration (time from epidural until post-operative rescue analgesia) and time to standing were recorded. Normally distributed variables were analysed with an F-test (α = 0.05) or t-test for pairwise inter-treatment comparisons (Bonferonni adjusted α = 0.0083). Non-normally distributed data were analysed with the Kruskall–Wallis test (α = 0.05 or Bonferonni adjusted α = 0.005 for inter-treatment comparison of post-operative pain scores).ResultsMore intra-operative analgesia interventions were required in PM [2 (0–11)] [median (range)] and TM [2 (1–2)] compared to PRM (0) and TRM (0). Fe′ISO₆₀ was significantly lower in (PRM + TRM) compared to (PM + TM). Analgesic duration was shorter in PM (459 ± 276 minutes) (mean ± SD) and TM (318 ± 152 minutes) compared to TRM (853 ± 288 minutes), but not to PRM (554 ± 234 minutes). Times to standing were longer in the ropivacaine treatments compared to TM.Conclusions and clinical relevanceInclusion of epidural ropivacaine resulted in reduction of Fe′ISO₆₀, avoidance of intra-operative fentanyl administration, a longer duration of post-operative analgesia (in TRM) and a delay in time to standing compared to TM.     

A comparison of epidural buprenorphine with epidural morphine for postoperative analgesia following stifle surgery in dogs

Objective To compare the efficacy of epidural buprenorphine with epidural morphine for post‐operative pain relief in dogs undergoing cranial cruciate ligament rupture repair. Study design A randomized, double blind clinical trial. Animals Twenty client‐owned dogs with cranial cruciate ligament rupture. Methods Dogs were randomly assigned to receive either epidural buprenorphine (4 µg kg^?1) or epidural morphine (0.1 mg kg^?1) in a total volume of 0.2 mL kg^?1. Epidural injections were performed immediately after induction of anesthesia. End‐tidal halothane and CO₂ were recorded every 15 minutes from the time of epidural administration of drug to extubation. A numerical rating pain score system was used by a blinded observer to evaluate analgesia beginning at extubation and continuing at specific intervals for 24 hours after surgery. Heart rate, respiratory rate, and blood pressure were recorded noninvasively at the same times. If pain score indicated moderate discomfort, rescue morphine at 1.0 mg kg^?1 was administered intramuscularly. Results There were no significant differences between groups with respect to pain score, heart rate, respiratory rate, indirect blood pressure, end‐tidal halothane or end‐tidal CO₂ at any time point. Fifty percent of dogs in the buprenorphine group and 50% of dogs in the morphine group required rescue analgesic medication. Time of systemic rescue morphine administration did not differ significantly between the two groups. There were no clinically observable side‐effects from epidural administration of either drug in any of the dogs of this study. Conclusions Epidural buprenorphine is as effective as epidural morphine for the relief of postoperative hindlimb orthopedic pain in dogs. Clinical relevance Buprenorphine appears to be an effective opioid for epidural use in healthy dogs. Buprenorphine may offer certain advantages over morphine for epidural use, such as lower abuse potential and, in some clinics, reduced cost and less wastage of drug.     

Neuraxial morphine induced pruritus in two cats and treatment with sub anaesthetic doses of propofol

HistoryTwo cats were presented for orthopaedic surgery.Physical ExaminationWith the exception of the orthopaedic injuries found, clinical examination showed no abnormality.ManagementAs part of anaesthetic management, one cat received intrathecal morphine, the other epidural morphine. Following recovery, intense grooming was observed. After ensuring adequate analgesia this behaviour was interpreted as pruritus.In the first cat, pruritus was initially managed with medetomidine constant rate infusion (CRI) at 1 and 1.5 μg kg^?1 hour^?1. The lower dose produced sedation and no relief from pruritus, the higher dose ablated pruritus but induced sedation. Two propofol (lipid emulsion formulation) boli of 0.1 mg kg^?1 ablated pruritus without causing sedation. The second cat was successfully treated with four boli of 0.1 mg kg^?1 propofol over 20 minutes.Follow–upFollowing treatment with propofol, pruritus did not recur in either cat and both were discharged from the hospital.ConclusionsThis is the first clinical report of morphine–induced pruritus in cats and management with low–dose propofol. These cases suggest an antipruritic mechanism for lipid–formulation propofol.     

Post-operative analgesic effects of butorphanol or firocoxib administered to dogs undergoing elective ovariohysterectomy

ObjectiveTo compare the post-operative analgesic effects of butorphanol or firocoxib in dogs undergoing ovariohysterectomy.Study designProspective, randomized, blinded, clinical trial.AnimalsTwenty-five dogs >1 year of age.MethodsDogs received acepromazine intramuscularly (IM), 0.05 mg kg^?1 and either butorphanol IM, 0.2 mg kg^?1 (BG, n = 12) or firocoxib orally (PO), 5 mg kg^?1 (FG, n = 13), approximately 30 minutes before induction of anesthesia with propofol. Anesthesia was maintained with isoflurane. Ovariohysterectomy was performed by the same surgeon. Pain scores using the dynamic and interactive visual analog scale (DIVAS) were performed before and at 1, 2, 3, 4, 6, 8 and 20 hours after the end of surgery by one observer, blinded to the treatment. Rescue analgesia was provided with morphine (0.5 mg kg^?1) IM and firocoxib, 5 mg kg^?1 (BG only) PO if DIVAS > 50. Groups were compared using paired t-tests and Fisher’s exact test (p < 0.05). Data are presented as mean ± SD.ResultsThe BG required significantly less propofol (BG: 2.6 ± 0.59 mg kg^?1; FG: 5.39 ± 0.7 mg kg^?1) (p < 0.05) but the anesthesia time was longer (BG: 14 ± 6, FG: 10 ± 4 minutes). There were no differences for body weight (BG: 7.9 ± 5.0, FG: 11.5 ± 4.6 kg), sedation scores, and surgery and extubation times (BG: 10 ± 2, 8 ± 5 minutes; FG: 9 ± 3, 8 ± 4 minutes, respectively) (p > 0.05). The FG had significantly lower pain scores than the BG at 1, 2 and 3 hours following surgery (p < 0.05). Rescue analgesia was administered to 11/12 (92%) and 2/13 (15%) dogs in the BG and FG, respectively (p < 0.05).Conclusion and clinical relevanceFirocoxib produced better post-operative analgesia than butorphanol. Firocoxib may be used as part of a multimodal analgesia protocol but may not be effective as a sole analgesic.     

Cardiopulmonary and isoflurane‐sparing effects of epidural or intravenous infusion of dexmedetomidine in cats undergoing surgery with epidural lidocaine

ObjectiveTo compare the cardiorespiratory, anesthetic-sparing effects and quality of anesthetic recovery after epidural and constant rate intravenous (IV) infusion of dexmedetomidine (DEX) in cats given a low dose of epidural lidocaine under propofol-isoflurane anesthesia and submitted to elective ovariohysterectomy.Study designRandomized, blinded clinical trial.AnimalsTwenty-one adult female cats (mean body weight: 3.1 ± 0.4 kg).MethodsCats received DEX (4 μg kg^?1, IM). Fifteen minutes later, anesthesia was induced with propofol and maintained with isoflurane. Cats were divided into three groups. In GI cats received epidural lidocaine (1 mg kg^?1, n = 7), in GII cats were given epidural lidocaine (1 mg kg^?1) + DEX (4 μg kg^?1, n = 7), and in GIII cats were given epidural lidocaine (1 mg kg^?1) + IV constant rate infusion (CRI) of DEX (0.25 μg kg^?1 minute^?1, n = 7). Variables evaluated included heart rate (HR), respiratory rate (f_R), systemic arterial pressures, rectal temperature (RT), end-tidal CO₂, end-tidal isoflurane concentration (e′ISO), arterial blood gases, and muscle tone. Anesthetic recovery was compared among groups by evaluation of times to recovery, HR, f_R, RT, and degree of analgesia. A paired t-test was used to evaluate pre-medication variables and blood gases within groups. anova was used to compare parametric data, whereas Friedman test was used to compare muscle relaxation.ResultsEpidural and CRI of DEX reduced HR during anesthesia maintenance. Mean ± SD e′ISO ranged from 0.86 ± 0.28% to 1.91 ± 0.63% in GI, from 0.70 ± 0.12% to 0.97 ± 0.20% in GII, and from 0.69 ± 0.12% to 1.17 ± 0.25% in GIII. Cats in GII and GIII had longer recovery periods than in GI.Conclusions and clinical relevanceEpidural and CRI of DEX significantly decreased isoflurane consumption and resulted in recovery of better quality and longer duration, despite bradycardia, without changes in systemic blood pressure.     

A preliminary investigation comparing pre-operative morphine and buprenorphine for postoperative analgesia and sedation in cats

Objective To compare the postoperative analgesic and sedative properties of buprenorphine and morphine in cats. Study Design Prospective, randomized, blinded study. Animals Thirty‐two domestic cats undergoing surgery. Methods Cats received pre‐anaesthetic medication with acepromazine (0.05 mg kg^?1) given intramuscularly and were randomly allocated to group M and given morphine (0.1 mg kg^?1) intramuscularly (IM) or to group B and given buprenorphine (0.01 mg kg^?1) IM. Anaesthesia was induced with propofol and maintained with halothane in oxygen and nitrous oxide. Pain and sedation scores using visual analogue scales, and heart and respiratory rates, were measured immediately before, and 30, 60, 120, 180, 300 and 420 minutes after anaesthesia. Results Pain scores were significantly lower at 60, 120 and 180 minutes after anaesthesia in group B. Group B also had higher heart rates at 30 minutes. There were no other statistically significant differences between the groups. Clinical relevance Buprenorphine (0.01 mg kg^?1) appeared to provide better postoperative analgesia than morphine (0.1 mg kg^?1) and may also have a longer duration of action.     

Plasma histamine concentrations in horses administered sodium penicillin,guaifenesin–xylazine–ketamine and isoflurane with morphine or butorphanol

ObjectiveVarious drugs administered to horses undergoing surgical procedures can release histamine. Histamine concentrations were evaluated in horses prepared for surgery and administered butorphanol or morphine intraoperative infusions.Study designProspective studies with one randomized.AnimalsA total of 44 client-owned horses.MethodsIn one study, anesthesia was induced with xylazine followed by ketamine–diazepam. Anesthesia was maintained with guaifenesin–xylazine–ketamine (GXK) during surgical preparation. For surgery, isoflurane was administered with intravenous (IV) morphine (group M: 0.15 mg kg^–1 and 0.1 mg kg^–1 hour^–1; 15 horses) or butorphanol (group B: 0.05 mg kg^–1 and 0.01 mg kg^–1 hour^–1; 15 horses). Histamine and morphine concentrations were measured using enzyme-linked immunoassay before opioid injection (time 0), and after 1, 2, 5, 30, 60 and 90 minutes. In a subsequent study, plasma histamine concentrations were measured in 14 horses before drug administration (baseline), 15 minutes after IV sodium penicillin and 15 minutes after starting GXK IV infusion. Statistical comparison was performed using anova for repeated measures. Pearson correlation compared morphine and histamine concentrations. Data are presented as mean ± standard deviation. Significance was assumed when p ≤ 0.05.ResultsWith histamine, differences occurred between baseline (3.2 ± 2.4 ng mL^–1) and GXK (5.2 ± 7.1 ng mL^–1) and between baseline and time 0 in group B (11.9 ± 13.4 ng mL^–1) and group M (11.1 ± 12.4 ng mL^–1). No differences occurred between baseline and after penicillin or between groups M and B. Morphine concentrations were higher at 1 minute following injection (8.1 ± 5.1 ng mL^–1) than at 30 minutes (4.9 ± 3.1 ng mL^–1) and 60 minutes (4.0 ± 2.5 ng mL^–1). Histamine correlated with morphine at 2, 30 and 60 minutes.Conclusions and clinical relevanceGXK increased histamine concentration, but concentrations were similar with morphine and butorphanol.     

Evaluation of perfusion index as a noninvasive tool to determine epidural anesthesia effectiveness in dogs

ObjectiveTo evaluate perfusion index (PI) as a noninvasive tool to determine effectiveness and onset of epidural anesthesia in dogs.Study designProspective clinical trial.AnimalsA total of 21 adult dogs, aged 6.5 ± 3 years and weighing 34.9 ± 6.4 kg, undergoing a tibial plateau leveling osteotomy.MethodsDogs were premedicated intramuscularly with acepromazine (0.03 mg kg^–1) and hydromorphone (0.1 mg kg^–1) and anesthetized with intravenous propofol (to effect) and isoflurane in oxygen. A surface transflectance probe was secured to the tail base to monitor PI and a dorsal pedal artery catheter was placed for invasive blood pressure monitoring. A lumbosacral epidural was performed with the dog in sternal recumbency. Dogs were randomly assigned for inclusion of epidural morphine (0.1 mg kg^–1) or morphine (0.1 mg kg^–1) and lidocaine (4 mg kg^–1). PI was recorded following instrumentation of each dog just prior to the epidural (baseline), at 10 minute intervals for 30 minutes, before and after the surgical skin incision and before and after completion of the osteotomy. Physiological variables and end-tidal isoflurane were recorded at the same time points.ResultsThere was no significant difference in PI between the groups at any time point. There was a significant change in end-tidal isoflurane before and after the skin incision in the epidural morphine and epidural morphine–lidocaine groups (p = 0.04, p = 0.05, respectively) and before and after the osteotomy in each group for heart rate (p = 0.001, p = 0.04), diastolic (p = 0.01, p = 0.01) and mean arterial blood pressure (p = 0.03, p = 0.05).Conclusions and clinical relevancePI did not provide an objective means for determining the onset or effectiveness of epidural anesthesia in anesthetized dogs and alternate methods of noninvasive assessment should be investigated.     

Cardiopulmonary effects of an infusion of remifentanil or morphine in horses anesthetized with isoflurane and dexmedetomidine

ObjectiveTo examine the cardiopulmonary effects of infusions of remifentanil or morphine, and their influence on recovery of horses anesthetized with isoflurane and dexmedetomidine.Study designRandomized crossover study with 7-day rest periods.AnimalsSix adult horses (507 ± 61 kg).MethodsAfter the horses were sedated with xylazine, anaesthesia was induced with ketamine and diazepam, and maintained with isoflurane. After approximately 60 minutes, a dexmedetomidine infusion was started (0.25 μg kg^?1 then 1.0 μg^?1 kg^?1 hour^?1) in combination with either saline (group S), morphine (0.15 mg kg^?1 then 0.1 mg kg^?1 hour^?1; group M), or remifentanil (6.0 μg kg^?1 hour^?1; group R) for 60 minutes. Mean arterial pressure, heart rate, end-tidal carbon dioxide tension, and end-tidal isoflurane concentration were recorded every 5 minutes. Core body temperature, cardiac output, right ventricular and arterial blood-gas values were measured every 15 minutes. Cardiac index, systemic vascular resistance (SVR), intrapulmonary shunt fraction, alveolar dead space, oxygen delivery and extraction ratio were calculated. Recoveries were videotaped and scored by two observers blinded to the treatment. Data were analyzed using repeated measures anova followed by Dunnett’s or Bonferroni’s significant difference test. Recovery scores were analyzed using a Kruskal–Wallis test.ResultsNo significant differences were found among groups. Compared to baseline, heart rate decreased and SVR increased significantly in all groups, and cardiac index significantly decreased in groups S and M. Hemoglobin concentration, oxygen content and oxygen delivery significantly decreased in all groups. The oxygen extraction ratio significantly increased in groups M and R. Lactate concentration significantly increased in group S. Recovery scores were similar among groups.Conclusions and clinical relevanceDexmedetomidine alone or in combination with remifentanil or morphine infusions was infused for 60 minutes without adverse effects in the 6 healthy isoflurane-anesthetized horses in this study.     

Comparison of isoflurane inhalation anaesthesia, injection anaesthesia and high volume caudal epidural anaesthesia for umbilical surgery in calves; metabolic, endocrine and cardiopulmonary effects

ObjectiveTo compare three anaesthetic protocols for umbilical surgery in calves regarding adequacy of analgesia, and cardiopulmonary and hormonal responses.Study designProspective, randomised experimental study.AnimalsThirty healthy German Holstein calves (7 female, 23 male) aged 45.9 ± 6.4 days.MethodsAll calves underwent umbilical surgery in dorsal recumbency. The anaesthetic protocols were as follows: group INH (n = 10), induction 0.1 mg kg^?1 xylazine IM and 2.0 mg kg^?1 ketamine IV, maintenance isoflurane in oxygen; Group INJ (n = 10), induction 0.2 mg kg^?1 xylazine IM and 5.0 mg kg^?1 ketamine IV, maintenance 2.5 mg kg^?1 ketamine IV every 15 minutes or as required; group EPI (n = 10), high volume caudal epidural anaesthesia with 0.2 mg kg^?1 xylazine diluted to 0.6 mL kg^?1 with procaine 2%. All calves received peri-umbilical infiltration of procaine and pre-operative IV flunixin (2.2 mg kg^?1). Cardiopulmonary variables were measured at preset intervals for up to 2 hours after surgery. The endocrine stress response was determined. Intra-operative nociception was assessed using a VAS scale. Data were compared between groups using appropriate statistical tests. A value of p < 0.05 was considered significant.ResultsAll three protocols provided adequate anaesthesia for surgery although, as judged by the VAS scale, intra-operative response was greatest with INJ. Lowest mean cortisol levels during surgery occurred in EPI. Heart rate and cardiac output did not differ between groups, but mean arterial blood pressure, systemic vascular resistance, and partial pressure of carbon dioxide were higher and arterial pH lower in groups INH and INJ than in Group EPI. Group INJ became hypoxaemic and had a significantly greater vascular shunt than did the other groups.Conclusion and clinical relevanceGroups INH and EPI both proved acceptable protocols for calves undergoing umbilical surgery, whilst INJ resulted in variable anti-nociception and in hypoxaemia. High volume caudal epidural anaesthesia provides a practical inexpensive method of anaesthesia for umbilical surgery.     

Comparison of analgesia provided by lidocaine, lidocaine-morphine or lidocaine-tramadol delivered epidurally in dogs following orchiectomy

ObjectiveTo evaluate and compare the postoperative analgesia provided by epidural lidocaine, lidocaine/morphine or lidocaine/tramadol in dogs following elective orchiectomy.Study designProspective experimental trial.AnimalsThirty-six mongrel dogs aged 2-8 years old, weighing 6.6-22 kg.MethodsThe dogs received 6.0 mg kg^?1 of lidocaine combined with 1.0 mg kg^?1 of tramadol, 0.1 mg kg^?1 of morphine or 0.01 mL kg^?1 of 0.9% NaCl epidurally. Analgesia was assessed at 4, 8, 12, 18 and 24 hours (T4, T8, T12 and T24) after the offset of lidocaine using a scale composed of physiologic and behavioral parameters. Rescue analgesia with morphine (0.2 mg kg^?1, IM) was performed if the evaluation score exceeded 10 during the postoperative period. The scores over time were analyzed using the Friedman’s two-way analysis of variance and the comparison between groups was made by the Kruskal-Wallis test with statistical significances accepted if p = 0.05.ResultsThere were no differences in the pain scores between the morphine and tramadol groups over time and no rescue analgesia was administered. In the NaCl group, rescue analgesia was needed at T4, T8 and T12. Within this group, the final evaluation times (T18 and T24) had lower pain scores than at T4, T8 and T12.Conclusions and clinical relevanceEpidural lidocaine/tramadol provided an analgesic effect comparable to that of epidural lidocaine/morphine during the first 12 hours after surgical castration without substantial side effects, suggesting that tramadol may be an effective postoperative analgesic in dogs submitted to this surgical procedure.     

Observations of the potency and duration of vecuronium in isoflurane-anesthetized horses

ObjectiveTo evaluate the potency and duration of three subparalyzing doses of vecuronium (VEC) in isoflurane-anesthetized horses.Study designProspective experimental study.AnimalsThirteen healthy adult horses undergoing arthroscopic surgery.MethodsDuring isoflurane anesthesia, horses received one of three doses of vecuronium (25, 50, or 100 μg kg^?1). Neuromuscular transmission was monitored with acceleromyography (AMG) with train-of-four (TOF) stimulation of the radial nerve. Maximal depression of the first twitch (T1), and onset time were recorded for each dose. Recovery time to a TOF ratio >90% was also evaluated.ResultsVecuronium 25 μg kg^?1 produced no observable T1 depression in four horses. VEC 50 μg kg^?1 (n = 5) produced a maximal T1 depression of [median (min, max)] 41 (20, 71) % in four horses, and no neuromuscular block was seen in the fifth. VEC 100 μg kg^?1 was given to four horses and produced a T1 depression of 73 (64, 78) %. Of the four horses in which VEC 50 μg kg^?1 produced a measurable neuromuscular block, three recovered spontaneously 43 (40, 52) minutes after VEC administration; a fourth subject received edrophonium to reverse residual block at the end of the surgery. Spontaneous recovery after VEC 100 μg kg^?1 occurred by 112 minutes in one horse, and had to be facilitated by edrophonium in the remaining three horses, more than 2 hours after VEC had been given.Conclusions and clinical relevanceA dose of 100 μg kg^?1 VEC in isoflurane anesthetized horses failed to produce complete paralysis. The partial neuromuscular block lasted at least 2 hours after this dose had been administered. Edrophonium was required to reverse the neuromuscular block in three of four horses. It is likely that more than 100 μg kg^?1 VEC would be necessary for complete neuromuscular blockade in horses, and that this dose will last >2 hours.