Vet Anaesth Analg [journal]
- Ampakine CX1942 attenuates opioid-induced respiratory depression and corrects the hypoxaemic effects of etorphine in immobilized goats (Capra hircus). [Journal Article]
- Vet Anaesth Analg 2016 Sep; 43(5):528-38.
To determine whether CX1942 reverses respiratory depression in etorphine-immobilized goats, and to compare its effects with those of doxapram hydrochloride.A prospective, crossover experimental trial conducted at 1753 m.a.s.l.Eight adult female Boer goats (Capra hircus) with a mean ± standard deviation mass of 27.1 ± 1.6 kg.Following immobilization with 0.1 mg kg(-1) etorphine, goats received one of doxapram, CX1942 or sterile water intravenously, in random order in three trials. Respiratory rate, ventilation and tidal volume were measured continuously. Arterial blood samples for the determination of PaO2 , PaCO2 , pH and SaO2 were taken 2 minutes before and then at 5 minute intervals after drug administration for 25 minutes.Doxapram corrected etorphine-induced respiratory depression but also led to arousal and hyperventilation at 2 minutes after its administration, as indicated by the low PaCO2 (27.8 ± 4.5 mmHg) and ventilation of 5.32 ± 5.24 L minute(-1) above pre-immobilization values. CX1942 improved respiratory parameters and corrected etorphine's hypoxaemic effects more gradually than did doxapram, with a more sustained improvement in PaO2 and SaO2 in comparison with the control trial.CX1942 attenuated opioid-induced respiratory depression and corrected the hypoxaemic effects of etorphine in immobilized goats.Ampakines potentially offer advantages over doxapram, a conventional treatment, in reversing etorphine-induced respiratory depression without causing unwanted side effects, particularly arousal, in immobilized animals.
- Isoflurane MAC determination in dogs using three intensities of constant-current electrical stimulation. [Journal Article]
- Vet Anaesth Analg 2016 Sep; 43(5):464-71.
To compare isoflurane minimum alveolar concentrations (MACs) in dogs determined using three intensities of constant-current electrical stimulation applied at the tail, and thoracic and pelvic limbs, and to compare isoflurane MACs obtained with all combinations of electrical stimulation and anatomic site with those obtained using the tail clamp as the noxious stimulus.Randomized trial.Six mixed-breed, adult female dogs aged 1-2 years and weighing 11.1 ± 4.4 kg.In each dog, MAC was determined by the bracketing method with the tail clamp (MACTAILCLAMP ), and three electrical currents (10 mA, 30 mA, 50 mA) at three anatomic sites (thoracic limb, pelvic limb, tail). Each MAC achieved with electrical stimulation was compared with MACTAILCLAMP using a mixed-model anova and Dunnett's procedure for multiple comparisons. The effects of current intensity and anatomic site on isoflurane MAC were tested using a mixed-model anova followed by Tukey's test for multiple comparisons (p < 0.05).Mean MACTAILCLAMP was 1.69%. MACs achieved with currents of 30 mA and 50 mA did not differ independently of anatomic site. When currents of 10 mA were applied to the tail and thoracic limb, resulting MACs were lower than those obtained using currents of 30 mA and 50 mA. Currents of 30 mA and 50 mA provided MACs that did not differ from those of MACTAILCLAMP , whereas a current of 10 mA achieved the same result only for the pelvic limb.Isoflurane MAC is affected by current intensity and anatomic site. Current intensities of 30 mA and 50 mA provided consistent results when applied to the tail, and thoracic and pelvic limbs that did not differ from those obtained using the tail clamp. Consequently, they can be used in place of the tail clamp in MAC studies in dogs.
- Regional distribution of ventilation in horses in dorsal recumbency during spontaneous and mechanical ventilation assessed by electrical impedance tomography: a case series. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2016 Aug 2.
To evaluate the regional distribution of ventilation in horses during spontaneous breathing and controlled mechanical ventilation (CMV) using electrical impedance tomography (EIT).Prospective, experimental case series.Four anaesthetized experimental horses.Horses were anaesthetized with isoflurane in an oxygen-air mixture and medetomidine continuous rate infusion, placed in dorsal recumbency with an EIT belt around the thorax, and allowed to breathe spontaneously until PaCO2 reached 13.3 kPa (100 mmHg), when volume CMV was started. For each horse, the EIT signal was recorded for at least 2 minutes immediately before (T1), and at 30 (n = 3) or 60 (n = 1) minutes after the start of CMV (T2). The centre of ventilation (CoV), dependent silent spaces (DSS) (likely to represent atelectatic lung areas), non-dependent silent spaces (NSS) (likely to represent lung areas with low ventilation) and total ventilated area (TVA) were evaluated. Cardiac output (CO) was measured and venous admixture and oxygen delivery (DO2 ) were calculated at T1 and T2. Data are presented as median and range.After the initiation of CMV, the CoV moved ventrally towards the non-dependent lung by 10% [from 57.4% (49.6-60.2%) to 48.3% (41.9-54.4%)]. DSS increased [from 4.1% (0.2-13.9%) to 18.7% (7.5-27.5%)], while NSS [21.7% (9.4-29.2%) to 9.9% (1.0-20.7%)] and TVA [920 (699-1051) to 837 (662-961) pixels] decreased. CO, venous admixture and DO2 also decreased.In spontaneously breathing anaesthetized horses in dorsal recumbency, ventilation was essentially centred within the dependent dorsal lung regions and moved towards non-dependent ventral regions as soon as CMV was started. This shows a major lack of ventilation in the dependent lung, which may be indicative of atelectasis.
- Pharmacokinetics and pharmacodynamics of intravenous romifidine and propranolol administered alone or in combination for equine sedation. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2016 Jul 18.
Propranolol has been suggested for anxiolysis in horses, but its sedation efficacy and side effects, both when administered alone and in combination with α2 -adrenoceptor agonists, remain undetermined. This study aimed to document the pharmacokinetics and pharmacodynamics of propranolol, romifidine and their combination.Randomized, crossover study.Six adult horses weighing 561 ± 48 kg.Propranolol (1 mg kg(-1) ; treatment P), romifidine (0.1 mg kg(-1) ; treatment R) or their combination (treatment PR) were administered intravenously with a minimum of 1 week between treatments. Alertness, behavioral responsiveness (visual and tactile) and physiologic variables were measured before and up to 960 minutes after drug administration. Blood was collected for blood gas and acid-base analyses and measurement of plasma drug concentrations. Data were analyzed using repeated-measures analysis of variance or Friedman with Holm-Sidak and Wilcoxon rank-sum tests (p < 0.05).Systemic clearance significantly decreased and the area under the concentration-time curve significantly increased for both drugs in PR compared with P and R. Both PR and R decreased behavioral responsiveness and resulted in sedation for up to 240 and 480 minutes, respectively. Sedation was deeper in PR for the first 16 minutes. Heart rate significantly decreased in all treatments for at least 60 minutes, and PR significantly increased the incidence of severe bradycardia (<20 beats minute(-1) ).Although not associated with reduced behavioral responsiveness or sedation alone, propranolol augmented romifidine sedation, probably through alterations in romifidine pharmacokinetics, in horses administered PR. The occurrence of severe bradycardia warrants caution in the co-administration of these drugs at the doses studied.
- Gastro-oesophageal reflux in large-sized, deep-chested versus small-sized, barrel-chested dogs undergoing spinal surgery in sternal recumbency. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2016 Jul 7.
The aim of this study was to investigate whether an increased frequency of gastro-oesophageal reflux (GOR) is more common in large-sized, deep-chested dogs undergoing spinal surgery in sternal recumbency than in small-sized, barrel-chested dogs.Prospective, cohort study.Nineteen small-sized, barrel-chested dogs (group B) and 26 large-sized, deep-chested dogs (group D).All animals were premedicated with intramuscular (IM) acepromazine (0.05 mg kg(-1) ) and pethidine (3 mg kg(-1) ) IM. Anaesthesia was induced with intravenous sodium thiopental and maintained with halothane in oxygen. Lower oesophageal pH was monitored continuously after induction of anaesthesia. Gastro-oesophageal reflux was considered to have occurred whenever pH values > 7.5 or < 4 were recorded. If GOR was detected during anaesthesia, measures were taken to avoid aspiration of gastric contents into the lungs and to prevent the development of oesophagitis/oesophageal stricture.The frequency of GOR during anaesthesia was significantly higher in group D (6/26 dogs; 23.07%) than in group B (0/19 dogs; 0%) (p = 0.032). Signs indicative of aspiration pneumonia, oesophagitis or oesophageal stricture were not reported in any of the GOR cases.In large-sized, deep-chested dogs undergoing spinal surgery in sternal recumbency, it would seem prudent to consider measures aimed at preventing GOR and its potentially devastating consequences (oesophagitis/oesophageal stricture, aspiration pneumonia).
- Evaluation of a new handheld point-of-care blood gas analyser using 100 equine blood samples. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2016 Jul 7.
To determine whether the Enterprise point-of-care blood analysis system (EPOC) produces results in agreement with two other blood gas analysers in regular clinical use (i-STAT and Radiometer ABL77) and to investigate the precision of the new machine when used with equine whole blood.Prospective, randomized, non-blinded, comparative laboratory analyser study.Horses admitted to a university teaching hospital requiring arterial or venous blood gas analysis as part of their routine clinical management.One hundred equine blood samples were run immediately, consecutively and in randomized order on three blood gas analysers. Results of variables common to all three analysers were tested for agreement and compared with guidelines used in human medicine. These require 80% of results from the test analyser to fall within a defined range or percentage of results from the comparator devices to achieve acceptability. Additionally, 21 samples were run twice in quick succession on the EPOC analyser to investigate precision.Agreement targets were not met for haematocrit, haemoglobin and base excess for either i-STAT or ABL77 analysers. EPOC precision targets were not met for partial pressure of carbon dioxide, ionized calcium, haematocrit and haemoglobin. Overall comparative performance of the EPOC was good to excellent for pH, oxygen tension, potassium, bicarbonate and oxygen saturation of haemoglobin, but marginal to poor for other parameters.The EPOC may be useful in performing analysis of equine whole blood, but trend analysis of carbon dioxide tension, ionized calcium, haematocrit and haemoglobin should be interpreted with caution. The EPOC should not be used interchangeably with other blood gas analysers.
- Cardiovascular effects of dexmedetomidine, with or without MK-467, following intravenous administration in cats. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2016 Jul 5.
To characterize the cardiovascular effects of dexmedetomidine, with or without MK-467, following intravenous (IV) administration in cats.Prospective Latin square experimental study.Six healthy adult purpose-bred cats.Cats were anesthetized with desflurane in oxygen for instrumentation with a carotid artery catheter and a thermodilution catheter in the pulmonary artery. One hour after discontinuation of desflurane, cats were administered dexmedetomidine (25 μg kg(-1) ), MK-467 (600 μg kg(-1) ), or dexmedetomidine (25 μg kg(-1) ) and MK-467 (600 μg kg(-1) ). All treatments were administered IV as a bolus. Cardiovascular variables were measured prior to drug administration and for 8 hours thereafter. Only data from the dexmedetomidine and dexmedetomidine-MK-467 treatments were analyzed.Dexmedetomidine produced significant decreases in heart rate, cardiac index and right ventricular stroke work index, and significant increases in arterial blood pressure, central venous pressure, pulmonary artery pressure and systemic vascular resistance index. Dexmedetomidine combined with MK-467 resulted in significant but transient decrease in blood pressure and right ventricular stroke work index.Following IV co-administration, MK-467 effectively attenuated dexmedetomidine-induced cardiovascular effects in cats. The drug combination resulted in transient reduction in arterial blood pressure, without causing hypotension.
- Professor Emeritus E. Wynn Jones MRCVS, FRCVS, PhD. [Journal Article]
- Vet Anaesth Analg 2016 Sep; 43(5):1.
- Clinical evaluation of intranasal medetomidine-ketamine and medetomidine-S(+)-ketamine for induction of anaesthesia in rabbits in two centres with two different administration techniques. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2016 Jul 4.
The aim was to compare efficacy and side effects of induction with medetomidine-ketamine or medetomidine-S(+)-ketamine by intranasal (IN) instillation in rabbits and to evaluate both protocols during subsequent isoflurane anaesthesia.Prospective, blinded, randomized experimental study in two centres.Eighty-three healthy New Zealand White rabbits undergoing tibial or ulnar osteotomy.Medetomidine (0.2 mg kg(-1) ) with 10 mg kg(-1) ketamine (MK) or 5 mg kg(-1) S(+)-ketamine (MS) was administered IN to each rabbit in a randomized fashion. In Centre 1 (n = 42) rabbits were held in sternal recumbency, and in Centre 2 (n = 41) in dorsal recumbency, during drug instillation. Adverse reactions were recorded. If a rabbit swallowed during endotracheal intubation, half of the initial IN dose was repeated and intubation was re-attempted after 5 minutes. Anaesthesia was maintained with isoflurane. Heart rate, blood pressure, end-tidal carbon dioxide concentration and blood gases were recorded. Data were analysed using Student's t-test, Mann-Whitney test and Fisher's exact test.In all, 39 animals were assigned to the MK group and 44 to the MS group. Two rabbits in the MS group held in dorsal recumbency died after instillation of the drug. Eight (MK) and 11 rabbits (MS) were insufficiently anaesthetized and received a second IN dose. One rabbit in MK and three in MS required an isoflurane mask induction after the second IN dose. There were no significant differences between treatments for induction, intraoperative data, blood gas values and recovery data.This study indicated that medetomidine-ketamine and medetomidine-S(+)-ketamine were effective shortly after IN delivery, but in dorsal recumbency IN administration of S(+)-ketamine led to two fatalities. Nasal haemorrhage was noted in both cases; however, the factors leading to death have not been fully elucidated.
- Ultrasound-guided vessel catheterization in adult Yorkshire cross-bred pigs. [JOURNAL ARTICLE]
- Vet Anaesth Analg 2016 Jul 4.
To describe an ultrasound-guided approach for venous and arterial vascular access and catheterization in anesthetized adult Yorkshire cross-bred pigs.Prospective experimental study.Ten adult female Yorkshire cross-bred pigs, weighing 78.4 ± 5.6 kg (mean ± standard deviation).Using ultrasound guidance and the Seldinger technique, a 7 Fr, 20 cm triple-lumen central venous catheter was placed in the external jugular vein and an 18 gauge, 16 cm catheter was placed in the femoral artery. The success rate of catheterization and the incidence of catheter patency over 24 hours of general anesthesia were recorded.Catheterization of the external jugular vein was successful in 10 out of 10 pigs and catheterization of the femoral artery was successful in eight out of 10 pigs. A surgical dissection technique on the femoral artery was performed in two pigs. Venous and arterial catheter patency was maintained in all pigs over the 24 hour study period.Ultrasound guidance resulted in success rates of 100% for catheterization of the external jugular vein and 80% for catheterization of the femoral artery in anesthetized adult Yorkshire cross-bred pigs. This technique is a noninvasive, easily performed alternative to surgical exposure of the vessels in large pigs undergoing surgical instrumentation for biomedical device testing.