Analgesic management of an eight-year-old Springer Spaniel after amputation of a thoracic limb

Analgesic agents were administered perioperatively to an eight-year-old Springer Spaniel undergoing amputation of its right thoracic limb. The amputation was carried out due to a painful, infiltrative and poorly differentiated sarcoma involving the nerves of the brachial plexus. A combination of pre-emptive and multimodal perioperative analgesic strategies was used; including intravenous (IV) infusions of fentanyl, morphine, lidocaine and ketamine.     

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.     

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.     

Presumed generalised seizure following caudal epidural administration of morphine and detomidine in a pony

A 9-year-old show pony mare became acutely lame following removal of a bone sequestrum of the distal phalanx of the right thoracic limb. The mare also suffered from ongoing right dorsal colitis secondary to previous long-term nonsteroidal anti-inflammatory drug (NSAID) use. To avoid further NSAID use, a protocol for caudal epidural administration of morphine and detomidine in an increased volume was used to provide analgesia to the thoracic limbs. A total volume of 50 mL (0.2 mL/kg bwt) was administered over approximately 90 s. Immediately following the injection, the pony collapsed into lateral recumbency and experienced an apparent generalised seizure characterised by loss of consciousness and frantic paddling of all four limbs. The pony recovered rapidly without intervention, and no residual neurological deficits were noted. The epidural analgesia resulted in a marked improvement in comfort levels. The speed of injection is thought to have caused a change in epidural and intracranial pressures resulting in a generalised seizure and highlights the importance of administering large volumes slowly.     

Inhibition of motility in isolated horse small intestine is mediated by κ but not µ opioid receptors

The effects of preferential μ (morphine), selective μ (fentanyl), selective κ (compound U69593) opioid receptor agonists, and nonselective (naloxone) and selective μ (naloxonazine) antagonists on equine small intestinal motility were evaluated in vitro. Samples of circular muscle from equine jejunum were placed in isolated organ baths and drug-induced modifications of both spontaneous and electrically evoked contractile activity were measured. None of the opioid agonists induced a significant change in spontaneous contractions. Fentanyl and U69593 reduced electrically induced contractions, whereas morphine reduced them only slightly. Naloxone competitively antagonised U69593, but both naloxone and naloxonazine were unable to counteract the inhibition of contractions induced by fentanyl. The inhibition of contractions shown by fentanyl is therefore probably not mediated by opioid receptors, but due to an anticholinergic activity of this drug. In summary, these data showed an inhibitory effect exerted by κ receptors on equine small intestinal motility, whereas the role of μ receptors seemed marginal and would need further characterisation.     

Minimum end‐tidal sevoflurane concentration necessary to prevent movement during a constant rate infusion of morphine,or morphine plus dexmedetomidine in ponies

ObjectiveTo compare the effects of a constant rate infusion (CRI) of dexmedetomidine and morphine to those of morphine alone on the minimum end-tidal sevoflurane concentration necessary to prevent movement (MAC_NM) in ponies.Study designProspective, randomized, crossover, ‘blinded’, experimental study.AnimalsFive healthy adult gelding ponies were anaesthetized twice with a 3-week washout period.MethodsAfter induction of anaesthesia with sevoflurane in oxygen (via nasotracheal tube), the ponies were positioned on a surgical table (T0), and anaesthesia was maintained with sevoflurane (Fe‘SEVO 2.5%) in 55% oxygen. Monitoring included pulse oximetry, electrocardiography and measurement of anaesthetic gases, arterial blood pressure and body temperature. The ponies were mechanically ventilated and randomly allocated to receive IV treatment M [morphine 0.15 mg kg^?1 (T10-T15) followed by a CRI (0.1 mg kg^?1 hour^?1)] or treatment DM [dexmedetomidine 3.5 μg kg^?1 plus morphine 0.15 mg kg^?1 (T10-T15) followed by a CRI of dexmedetomidine 1.75 μg kg^?1 hour^?1 and morphine 0.1 mg kg^?1 hour^?1]. At T60, a stepwise MAC_NM determination was initiated using constant current electrical stimuli at the skin of the lateral pastern region. Triplicate MAC_NM estimations were obtained and then averaged in each pony. Wilcoxon signed-rank test was used to detect differences in MAC between treatments (a = 0.05).ResultsSevoflurane-morphine MAC_NM values (median (range) and mean ± SD) were 2.56 (2.01–4.07) and 2.79 ± 0.73%. The addition of a continuous infusion of dexmedetomidine significantly reduced sevoflurane MAC_NM values to 0.89 (0.62–1.05) and 0.89 ± 0.22% (mean MAC_NM reduction 67 ± 11%).Conclusion and clinical relevanceCo-administration of dexmedetomidine and morphine CRIs significantly reduced the MAC_NM of sevoflurane compared with a CRI of morphine alone at the reported doses.     

Effects of extradural morphine on end-tidal isoflurane concentration and physiological variables in pigs undergoing abdominal surgery: a clinical study

OBJECTIVE: To evaluate the effects of preoperative extradural morphine on the end-tidal isoflurane (Fe'ISO) concentration and on physiological variables in pigs undergoing abdominal surgery. STUDY DESIGN: Prospective, randomized, blinded study. ANIMALS: Fourteen healthy pigs (20 +/- 4 kg) undergoing intestinal cannulation. MATERIALS AND METHODS: Anaesthesia was induced with a combination of medetomidine (50 microg kg(-1)) and tiletamine-zolazepam (2.5 mg kg(-1)) injected intramuscularly, and was maintained with isoflurane in air and oxygen (FiO(2) = 50% O(2)). In the first group, morphine (0.1 mg kg(-1)) was administered extradurally before surgery. The second group received an equivalent volume of extradural saline as control. During the experiment, heart and respiratory rates, mean arterial blood pressure, tidal volume and minute ventilation were recorded every 10 minutes. The concentration of Fe'ISO was adjusted, according to the depth of anaesthesia, by an experienced animal nurse. Within treatment groups, time-related changes in Fe'ISO and physiological variables were analysed using a repeated measurement anova. Differences in data between treatment groups were analysed at specific time points using a Mann-Whitney U-test. Results are presented as mean +/- SD; p < 0.05 was considered as significant. RESULTS: After the onset of action of the morphine, the Fe'ISO required to maintain anaesthesia was significantly lower in the extradural morphine group compared with control. During the expected maximal effect of the drug, Fe'ISO was significantly lower in the morphine group (0.6 +/- 0.2%) than in the control group (0.9 +/- 0.2%). The decrease in Fe'ISO indicated that the onset of action of morphine was approximately 30 minutes after injection. No significant differences in other clinical variables were found between the groups. CONCLUSION: Pigs that received extradural morphine before abdominal surgery achieved surgical anaesthetic depth at a lower Fe'ISO concentration. CLINICAL RELEVANCE: Extradural morphine allows abdominal surgery to be performed at a lower Fe'ISO concentrations.     

Thoracic epidural analgesia via the lumbosacral approach using multiport catheters with a low concentration of bupivacaine and morphine in sheep

ObjectiveTo determine the analgesic and systemic effects of thoracic epidural administration of bupivacaine (BP) and morphine (MP) in conscious sheep.Study designRandomized, crossover, experimental study.AnimalsSix healthy castrated sheep weighing between 40 and 50 kg.MethodsEach sheep received, via the lumbosacral approach, BP (0.5 mg kg^?1), MP (0.1 mg kg^?1), and BP plus MP (BPMP; 0.25 mg kg^?1 + 0.05 mg kg^?1) in a randomized order. Heart rate, blood pressure, respiratory rate, blood gas analysis, skin temperature, rectal temperature, analgesia, sedation, and motor blockade were determined before treatment and at predetermined intervals until analgesia had disappeared.ResultsThe main areas of complete analgesia for the BP and BPMP treatments were the thorax and forelimb bilaterally. The median duration of analgesia was shorter with MP treatment (45 minutes; score 2) than with BP treatment (70 minutes) and BPMP treatment (140 minutes; p < 0.05). The BP and BPMP treatments caused motor block, and MP and BPMP treatments showed mild sedation. Significant decreases in systolic and diastolic arterial blood pressures were observed only with the BP treatment (p < 0.05). Epidural MP combined with the BP local anesthetic depressed ventilation but within acceptable limits in these clinically healthy sheep.ConclusionsThoracic epidural administration of BPMP to sheep resulted in longer duration of analgesia of the thorax and forelimbs bilaterally in conscious sheep than the administration of MP or BP alone. The incidence of complications was low, but side-effects such as depressed ventilation and muscle paralysis occurred and require appropriate management.Clinical relevanceThis technique should be considered as another method for the relief of postoperative pain after thoracic surgery in sheep.     

Effects of peri-operative morphine administration during halothane anaesthesia in horses

OBJECTIVE: To study the effects of morphine on haemodynamic variables, blood gas values and the requirement for additional anaesthetic drugs in horses undergoing surgery. STUDY DESIGN: Prospective randomized study. METHODS: Thirty-eight client-owned horses, ASA(American Society of Anesthesiologists) category I or II, undergoing elective surgical procedures, were studied. Horses were divided between two groups, and were paired according to operation, anaesthetist, body position during surgery, mass and breed. Group M+ received morphine by intravenous (IV) injection (0.15 mg kg(-1)) before induction of anaesthesia and then by infusion (0.1 mg kg(-1) hour(-1)) throughout anaesthesia. Group M- received the same anaesthetic technique (pre-anaesthetic medication with romifidine (100 microg kg(-1)) IV; induction with ketamine (2.2 mg kg(-1)) and diazepam (50 microg kg(-1)) IV; maintenance with halothane), except that morphine was excluded. Both groups received flunixin IV (1.1 mg kg(-1)) before surgery. Both groups also received 50% nitrous oxide for the first 10 minutes of anaesthesia. During anaesthesia, end-tidal halothane was maintained at 0.9% (+/-0.1%) in both groups. Heart rate (HR) and respiratory rate (fr), systolic, mean and diastolic arterial pressures were recorded every 5 minutes. Arterial blood samples were analysed every 20 minutes. Additional anaesthetics (ketamine and midazolam) were administered whenever the horse moved. Dobutamine was infused to maintain mean arterial pressure (MAP) > 58 mm Hg, but was discontinued when MAP reached 68 mm Hg. Mechanical ventilation was imposed when PaCO(2) exceeded 9.3 kPa (70 mm Hg). RESULTS: Haemodynamic data (HR and MAP) and blood gas measurements were analysed using repeated measure analysis using a mixed covariance pattern model (SAS version 8.2). A Student's t-test was used to investigate differences between groups in the doses of additional anaesthetics required. There were no significant differences between M+ or M- groups in MAP (p = 0.65), HR (p = 0.74), PaO2 (p = 0.40) or PaCO2 (p = 0.20). Fewer horses in the M+ group received additional anaesthetics (15.8% compared to 21.1% in M- group), and the mean dose of ketamine required was higher in the M- group (mean +/- SD: M-, 0.93 +/- 0.70; M+, 0.45 +/- 0.17). These differences were not statistically significant (p = 0.28). CONCLUSIONS: Pre-anaesthetic and peri-operative morphine administration is not associated with significant haemodynamic or ventilatory changes. Horses receiving morphine tended to receive fewer and lower doses of additional anaesthetic drugs, although this was not statistically significant.