Cardiovascular effects of epidural administration of methadone, ropivacaine 0.75% and their combination in isoflurane anaesthetized dogs

ObjectiveTo compare the cardiovascular effects of four epidural treatments in isoflurane anaesthetised dogs.Study designProspective, randomized. experimental study.AnimalsSix female, neutered Beagle dogs (13.3 ± 1.0 kg), aged 3.6 ± 0.1 years.MethodsAnaesthesia was induced with propofol (8.3 ± 1.1 mg kg^?1) and maintained with isoflurane in a mixture of oxygen and air [inspiratory fraction of oxygen (FiO₂) = 40%], using intermittent positive pressure ventilation. Using a cross-over model, NaCl 0.9% (P); methadone 1% 0.1 mg kg^?1 (M); ropivacaine 0.75% 1.65 mg kg^?1 (R) or methadone 1% 0.1 mg kg^?1 + ropivacaine 0.75% 1.65 mg kg^?1 (RM) in equal volumes (0.23 mL kg^?1) using NaCl 0.9%, was administered epidurally at the level of the lumbosacral space. Treatment P was administered to five dogs only. Cardiovascular and respiratory variables, blood gases, and oesophageal temperature were recorded at T-15 and for 60 minutes after epidural injection (T0).ResultsMean overall heart rate (HR in beats minute^?1) was significantly lower after treatment M (119 ± 16) (p = 0.0019), R (110 ± 18) (p < 0.0001) and RM (109 ± 13) (p < 0.0001), compared to treatment P (135 ± 21). Additionally, a significant difference in HR between treatments RM and M was found (p = 0.04). After both ropivacaine treatments, systemic arterial pressures (sAP) were significantly lower compared to other treatments. No significant overall differences between treatments were present for central venous pressure, cardiac output, stroke volume, systemic vascular resistance, oxygen delivery and arterial oxygen content (CaO₂). Heart rate and sAP significantly increased after treatment P and M compared to baseline (T-15). With all treatments significant reductions from baseline were observed in oesophageal temperature, packed cell volume and CaO₂. A transient unilateral Horner’s syndrome occurred in one dog after treatment R.Conclusions and clinical relevanceClinically important low sAPs were observed after the ropivacaine epidural treatments in isoflurane anaesthetised dogs. Systemic arterial pressures were clinically acceptable when using epidural methadone.     

Comparison of respiratory function during TIVA (romifidine,ketamine, midazolam) and isoflurane anaesthesia in spontaneously breathing ponies Part I: blood gas analysis and cardiorespiratory variables

ObjectiveTo compare pulmonary function and gas exchange in ponies during maintenance of anaesthesia with isoflurane or by a total intravenous anaesthesia (TIVA) technique.Study designExperimental, cross–over study.AnimalsSix healthy ponies weighing mean 286 (range 233–388) ± SD 61 kg, age 13 (9-16) ± 3 years.MethodsThe ponies were anaesthetized twice, a minimum of two weeks apart. Following sedation with romifidine [80 μg kg^?1 intravenously (IV)], anaesthesia was induced IV with midazolam (0.06 mg kg^?1) and ketamine (2.5 mg kg^?1), then maintained either with inhaled isoflurane (Fe’Iso = 1.1 vol%) (T-ISO) or an IV infusion of romifidine (120 μg kg^?1 hour^?1), midazolam (0.09 mg kg^?1 hour^?1 IV) and ketamine (3.3 mg kg^?1 hour^?1) (T-TIVA). Ponies were placed in lateral recumbency. Breathing was spontaneous and Fi’O₂ 60%. After an instrumentation/stabilisation period of 30 minutes, arterial and mixed venous blood samples were taken simultaneously every 10 minutes for 60 minutes and analysed immediately. Oxygen extraction ratio (O₂ER) and venous admixture were calculated. Tidal volume (TV), minute volume (MV), respiratory rate (f_R), packed cell volume (PCV), arterial blood pressure and heart rate (HR) were measured and recorded. Data were analysed with mixed model anova (a = 0.05). Treatments were compared overall and at two selected time points (T30 and T60) using Bonferroni correction.ResultsArterial and mixed venous partial pressures of O₂ and CO₂, and TV were significantly lower and MV and f_R were higher in T-TIVA compared to T-ISO. Venous admixture did not differ between treatments. O₂ER was significantly higher in T-TIVA. Mean arterial pressure was higher and HR was lower in T-TIVA compared to T-ISO.Conclusions and clinical relevanceWhilst arterial CO₂ was within an acceptable range during both protocols, the impairment of oxygenation was more pronounced with the T-TIVA evidenced by lower arterial and venous oxygen partial pressures.     

Postanesthetic Neuropathy/Myopathy in the Nondependent Forelimb in 4 Horses

Postanesthetic lameness in the form of myopathy or neuropathy is a well-known complication associated with equine general anesthesia and is most often reported in the dependent limb of horses treated in lateral recumbency. The aim of this case series was to report clinical data of 4 horses treated under general anesthesia in lateral recumbency and that developed postanesthetic neuropathy/myopathy in the nondependent forelimb. With anti-inflammatory and analgesic medical treatment, locomotor problems associated with neuropathy/myopathy resolved after 12–24 hours in all cases. The pathogenesis remains unclear. A first hypothesis may be the decreased hydrostatic pressure in limb vessels elevated above the level of the heart, and consequent reduction of muscle perfusion. Second, abduction and/or endorotation of the upper forelimb may have caused injury to the brachial plexus. Therefore, positioning of the nondependent forelimb should be done judiciously and may be the subject of further research.     

The synergistic necrohemorrhagic action of Clostridium perfringens perfringolysin and alpha toxin in the bovine intestine and against bovine endothelial cells

Bovine necrohemorrhagic enteritis is a major cause of mortality in veal calves. Clostridium perfringens is considered as the causative agent, but there has been controversy on the toxins responsible for the disease. Recently, it has been demonstrated that a variety of C. perfringens type A strains can induce necrohemorrhagic lesions in a calf intestinal loop assay. These results put forward alpha toxin and perfringolysin as potential causative toxins, since both are produced by all C. perfringens type A strains. The importance of perfringolysin in the pathogenesis of bovine necrohemorrhagic enteritis has not been studied before. Therefore, the objective of the current study was to evaluate the role of perfringolysin in the development of necrohemorrhagic enteritis lesions in calves and its synergism with alpha toxin. A perfringolysin-deficient mutant, an alpha toxin-deficient mutant and a perfringolysin alpha toxin double mutant were less able to induce necrosis in a calf intestinal loop assay as compared to the wild-type strain. Only complementation with both toxins could restore the activity to that of the wild-type. In addition, perfringolysin and alpha toxin had a synergistic cytotoxic effect on bovine endothelial cells. This endothelial cell damage potentially explains why capillary hemorrhages are an initial step in the development of bovine necrohemorrhagic enteritis. Taken together, our results show that perfringolysin acts synergistically with alpha toxin in the development of necrohemorrhagic enteritis in a calf intestinal loop model and we hypothesize that both toxins act by targeting the endothelial cells.     

Prevalence and molecular characterisation of Cryptosporidium and Giardia in lambs and goat kids in Belgium

The prevalence of Cryptosporidium and Giardia was studied on 10 intensively reared sheep and goat farms in the province of East Flanders, Belgium. Random faecal samples were collected and examined using the Merifluor((R)) immunofluorescence assay. Cryptosporidium positive samples were withheld for molecular identification using primers targeting the 18S rDNA, 70 kDa heat shock protein and 60 kDa glycoprotein gene. For the molecular identification of Giardia the beta-giardin gene and a recently developed assemblage specific PCR based on the triose phosphate isomerase gene were used. The prevalence of Cryptosporidium in lambs was 13.1% (18/137), on 4 out of 10 farms. In goat kids the Cryptosporidium prevalence was 9.5% (14/148), on 6 out of 10 farms. The molecular characterisation of Cryptosporidium positive isolates indicated that in lambs (n=10) the cervine genotype was predominant, whereas in the goat kids (n=11) only C. parvum was identified, with subgenotypes IIaA15G2R1 and IIdA22G1. The Giardia prevalence was 25.5% (35/137) in lambs with all 10 farms being positive, and 35.8% (53/148) in goat kids with 8 out of the 10 farms being positive. Both in the goat kids and in the lambs the host specific assemblage E was most commonly identified. However, the zoonotic assemblage A was identified in 6 out of 28 goat kids and in 2 out of 8 lambs, based on the beta-giardin sequence alignment. Using the assemblage specific PCR, mixed assemblage A and E infections were additionally identified in 2 lambs and in 5 goat kids. The results of the present study indicate that both Cryptosporidium and Giardia are common parasites on intensively reared sheep and goat farms in the province of East Flanders, Belgium, and that they are a potential source for zoonotic infections.     

Cardiovascular effects of enoximone in isoflurane anaesthetized ponies

OBJECTIVE: Enoximone is a phosphodiesterase III inhibitor frequently used to improve cardiac output (CO) in man. As the use of enoximone has not been reported in horses, the effects of this inodilator were examined in isoflurane anaesthetized ponies. STUDY DESIGN: Prospective, randomised, experimental study. ANIMALS: Six healthy ponies, weighing 286 (212-367) +/- 52 kg, aged 5.0 +/- 1.6 years (4-6.5). METHODS: After sedation with romifidine [80 microg kg(-1) intravenously (IV)], general anaesthesia was induced with midazolam (0.06 mg kg(-1) IV) and ketamine (2.2 mg kg(-1) IV) and maintained with isoflurane in oxygen (Et Iso 1.7%). The ponies were ventilated to maintain eucapnia (PaCO(2) 4.66-6.00 kPa). Each pony was anaesthetized twice with an interval of 3 weeks; receiving enoximone 0.5 mg kg(-1) IV (E) or saline (S) 90 minutes post-induction. Heart rate (HR), arterial (AP) and right atrial pressure (RAP) were measured before treatment, every 5 minutes between T0 (treatment) and T30 and then every 10 minutes until T120. Cardiac output measurements (lithium dilution technique) and blood gas analysis (arterial and central venous samples) were performed before T0 and at T5, T10, T20, T40, T60, T80, T100 and T120. Stroke volume (SV), systemic vascular resistance (SVR), venous admixture (Qs/Qt) and oxygen delivery (DO(2)) were calculated. RESULTS: Enoximone induced significant increases in HR, CO, SV, Qs/Qt and DO(2) and a significant decrease in RAP. No significant differences were detected for AP, SVR and blood gases. No cardiac arrhythmias or other side effects were observed. CONCLUSIONS AND CLINICAL RELEVANCE: The present results suggest that in isoflurane anaesthetized ponies, enoximone has beneficial effects on CO and SV without producing significant changes in blood pressure. Despite an increase in Qs/Qt, DO(2) to the tissues was improved.