Anaesthesia In Sheep Research Articles

Propofol-sparing and hemodynamic effects of guaifenesin in sheep

ObjectiveTo evaluate the propofol-sparing and hemodynamic effects of guaifenesin administered for co-induction of anesthesia in sheep. Study designProspective, blinded, two-way crossover experimental study. AnimalsThirteen healthy adult female sheep. MethodsAnesthesia was induced without premedication with intravenous (IV) guaifenesin 5% at 100 mg kg–1 (GGE) or an equivalent volume of physiologic saline (SAL), followed by IV propofol at a controlled rate (1 mg kg–1 min–1). Heart rate (HR), respiratory rate and oscillometric noninvasive arterial blood pressure (NIBP) were recorded at baseline after co-induction administration, following endotracheal intubation and every 2 minutes thereafter for 10 minutes. Propofol doses required to achieve intubation after each co-induction treatment were compared by independent Student’s t-test. Values of p < 0.05 were considered statistically significant. ResultsThe propofol dose required (mean ± standard deviation) to achieve intubation was significantly lower (p = 0.001) in the GGE treatment (3.40 ± 0.74 mg kg–1) than in the SAL treatment (5.94 ± 1.09 mg kg–1). HR was increased after anesthetic induction compared with baseline in both treatments. HR was generally lower in the GGE treatment than in the SAL treatment. NIBP did not vary between GGE and SAL treatments. Conclusions and clinical relevanceGuaifenesin, when administered as a co-induction agent with propofol in sheep, reduces propofol dose requirements and maintains hemodynamic variables within a clinically acceptable range.

A novel extraoral ultrasound-guided approach for mandibular nerve block in Rahmani sheep

BackgroundRegional anesthesia is the favored choice in ruminant animals compared to general anesthesia, primarily due to its high safety margin and reduced demand for cost-intensive equipment in addition to its field applicability. Ultrasound-guided nerve block has gained significant attention in the field of veterinary medicine. This study utilized twenty-seven sheep of the native Rahmani breed to both demonstrate and evaluate the effectiveness of the ultrasound guided inferior alveolar nerve block technique.MethodsThe research comprised three phases: Phase 1 involved an anatomical examination of mandibles and sheep heads to locate the mandibular foramen and delineate the mandibular nerve course. Phase 2 included ultrasound-guided injection of methylene blue dye at specific sites along the mandibular nerve in cadaveric sheep heads. In Phase 3, clinical implementation of ultrasound-guided inferior alveolar nerve blocks was conducted in 27 live sheep, assessing efficacy, onset, and duration.ResultsVertical extraoral ultrasound-guided nerve block was achieved successfully in 25 sheep (98%). A preliminary cadaveric study showed good distribution of the injectate at the mandibular nerve site. The mean onset time was 138 ± 18 s, and the mean duration time was 54 ± 4.1 min. Prominent analgesia of the ipsilateral mandible, medial surface of the cheek, and lateral border of the tongue was observed.ConclusionsUltrasound-guided mandibular nerve block holds promise as a technique for providing effective and safe anesthesia in sheep undergoing mandibular procedures.

Critical key points for anesthesia in experimental research involving sheep (Ovis aries)

Anesthesia and analgesia have a major impact on ensuring animal welfare and safety, resulting in reduced stress response and effective pain control, ensuring the comfort of the animal, promoting faster recovery, and reducing the risk of complications associated with various research procedures. Each stage of anesthesia in sheep is vital for maintaining the animal's welfare, ensuring procedural success, minimizing stress, risks, and complications, and optimizing the quality of research data. Proper attention to detail and adherence to best practices at each stage contribute to the overall success of anesthesia management in sheep. Anesthesia protocols should suit individual requirements for each sheep, in light of factors such as health status, procedure duration, and desired anesthesia depth. Meticulous monitoring, adherence to best practices, and prompt intervention are essential for minimizing the risks of complications during sheep anesthesia and ensuring the safety and welfare of the animals undergoing anesthesia for research purposes. This article presents the main key points that can improve anesthetic management for sheep involved in experimental research to minimize stress response and complications, enhancing animal safety, welfare, and comfort during and after procedures. Multimodal anesthesia approaches ensure effective pain relief, tailored to the specific needs of individual animals or procedures, optimizing outcomes and minimizing risks. Anesthesia management contributes to improved research data collection under conditions that enhance the validity and reliability of results. Sheep's impressive capacity to maintain homeostasis even during extended periods of anesthesia highlights the critical importance of upholding data quality in alignment with the universally accepted principles of Replacement, Reduction, and Refinement for ethical animal research. By adhering to these principles, researchers can minimize the number of animals used, reduce any potential discomfort or distress experienced by the animals, and refine procedures to optimize animal welfare while still achieving scientific objectives.

O estimulador de nervo periférico melhora a eficácia do bloqueio paravertebral proximal paravertebral proximal em ovelhas

ABSTRACT The purpose of this study was to compare the efficacy of proximal paravertebral anesthesia in sheep using a peripheral nerve stimulator and compare it to the Cambridge technique. Eight Santa Inês sheep, five females and three males aged 2 years and weighing 13kg were enrolled in the study. Right proximal paravertebral anesthesia was carried out using 2% lidocaine without vasoconstrictor, injected in the spaces between T13-L1, L1-L2 and L2-L3, with and without the aid of a peripheral nerve stimulator in two procedures with an interval of 7 days between treatments, which comprised: ST (stimulator treatment: 3mg kg-1 of lidocaine 2%) and CT (Cambridge control treatment, 6mg kg-1 of lidocaine 2%). Cardiorespiratory variables were recorded before the treatment (baseline, TB) and then at 15, 30, 45 and 60 minutes (T15, T30, T45 and T60, respectively) following local anesthesia. Effectiveness of the regional anesthesia was assessed by means of mechanical skin clamping at a point between the iliac crest and the lowest border of the last rib. Data were tested for normal distribution using the Shapiro-Wilk test and compared using Kruskal-Wallis followed by Dunn post-hoc test. Duration of the blockade was analyzed using a Kaplan-Meyer survival curve. Analyses were performed under 5% significance. ST took significantly longer and had greater success and greater duration. Positive response to skin clamping in CT was obtained in seven animals at T15 and one at T45, whereas in ST, one animal responded to skin clamping at T15, two at T30, four at T45 and one at T60. Duration was significantly longer in ST compared to CT according to the Kaplan-Meyer analysis. No changes were seen in cardiorespiratory variables throughout the study. In conclusion, the peripheral nerve stimulator increases the success of proximal paravertebral anesthesia using a lower dose of 2% lidocaine in healthy sheep.

Anatomical and topographic substantiation of mandibular anesthesia in sheep

This study presents an anatomical and topographic justification for performing mandibular anesthesia in sheep. The study was conducted on the basis of the Department of Anatomy and Histology of Animals named after Professor A. F. Klimov of the Moscow State Academy of Veterinary Medicine and Biotechnology – MBA named after K. I. Scriabin. The object of the study was sheep of the Romanov breed (n=20) aged 1-2 years without pronounced signs of pathology of the dental apparatus. The material for the study was the lower jaws (n=20) and survey radiographs of the head area (n=20). To achieve this goal, a comprehensive methodological approach was used, including: anatomical dissection and macromorphometry with the determination of skeletotopic and linear parameters of the mandible. Mandibular anesthesia is one of the most common manipulations in animal dentistry. For high-quality anesthesia of the mandibular branch of the trigeminal nerve, it is important to take into account the topical landmarks of the structures forming the mandibular canal. Based on the results of macromorphometry and rengenogrammetry, skeletotopic landmarks of the holes forming the mandibular canal are presented, which are important to take into account when performing anesthesia of the lower alveolar nerve. Comparative analysis of morphometric and rengenogrammetric parameters of the upper and lower jaws did not reveal significant differences in their linear parameters, which indicates the high informative value of the X-ray diagnostic method in assessing the morphofunctional state of the jaw bones and the channels located on them. The results obtained can be used in the development of new approaches to the mandibular branch of the trigeminal nerve during local anesthesia in veterinary and experimental dentistry.

Effects of cumulative duration of repeated anaesthesia exposure on foetal brain development in the ovine model

ObjectiveAnaesthesia is required in 0.4–1% of pregnant women, and prolonged and repeated exposures to anaesthesia may be required. It is unknown whether these exposures may result in foetal neurotoxicity in humans. As sheep have a gestation comparable to that of humans, the objective of this study was to analyse the neurodevelopmental outcome of ovine foetuses that had been exposed in utero to repeated and prolonged anaesthesia. DesignRandomized controlled preclinical study. SettingAnaesthesia for non-obstetric surgery during pregnancy. AnimalsTwenty-four healthy pregnant Swifter ewes. InterventionsThe ewes were randomized to no anaesthesia exposure (control-group), single exposure (at gestational age 68–70 days), or repeated exposure (at gestational age 68–70 days and 96–98 days) to 2.5 h of sevoflurane anaesthesia and maternal laparotomy. All lambs were delivered at approximately term gestation (gestational age: 140–143 days). MeasurementsThe primary outcome was neuron density in the frontal cortex 24 h after birth for the control-group versus the repeated-exposure-group. Key secondary outcome was the time needed to achieve the milestone of standing. Secondary outcomes included other neurobehavioural assessments (e.g., motoric milestones) and histological parameters quantified in multiple brain regions (neuron density, total cell density, proliferation, inflammation, synaptogenesis, astrocytes and myelination). Main resultsNeuron density in the frontal cortex did not differ between groups (mean ± standard deviation: control-group: 403 ± 39, single-exposure group: 436 ± 23 and repeated-exposure-group: 403 ± 40 neurons/mm2, control-group versus repeated-exposure-group: p = 0.986, control-group versus single-exposure-group: p = 0.097). No significant difference was observed for the time needed to achieve the milestone of standing. Only very limited differences were observed for other histological outcome parameters and neurobehavioural assessments. ConclusionsThere is no evidence for foetal neuronal injury or neurobehavioural impairments after a cumulative duration of 5 h repetitive prenatal anaesthesia in sheep.

Physiologic Effects of Prolonged Terminal Anesthesia in Sheep (Ovis gmelini aries).

The ruminant alimentary tract and its effects on blood homeostasis complicate prolonged terminal studies conducted under general anesthesia in sheep. We therefore studied 15 healthy female white alpine sheep that were undergoing prolonged anesthesia (> 30 h) for an unrelated terminal study. In the current study, all sheep developed a decreased hematocrit and hemoglobin concentration after induction of anesthesia, which fell further, along with a significant decrease in white blood cell count, over the course of anesthesia. Sheep also showed an initial hyponatremia, a persistent hypokalemia, hypocalcemia, and a progressive hyperchloremia. A significant drop in blood pH developed over time despite normal values of blood lactate and a marked decline in partial pressure of carbon dioxide over the course of the experiment. The latter consequently reduced the efficacy of mechanical ventilation, as reflected in a reduced oxygen partial pressure. A significant increase in lactate dehydrogenase and creatinine kinase was observed. Arterial blood pressure and heart rate significantly decreased over time, but remained within normotensive and normocardic limits. Central venous pressure rose significantly over the course of anesthesia. In conclusion, prolonged anesthesia in sheep is associated with a wide range of complex physi- ologic changes. An in-depth understanding of all metabolic compensatory mechanisms and their underlying cause during prolonged anesthesia is necessary for interpreting data from the primary study, with special considerations to account for ruminant-specific physiology.

Analysis of pH and electrolytes in blood and ruminal fluid, including kidney function tests, in sheep undergoing long-term surgical procedures

BackgroundThe physiology of sheep as small ruminants is remarkably different from monogastric animals especially regarding the forestomach system. Using sheep for surgical procedures during scientific research thereby presents an exceptional setting for the anaesthetist. Long-term anaesthesia generally demands deprivation of food to reduce the risk of bloat in sheep. This might influence the energy and electrolyte balance. In horses and companion animals, close monitoring of mean arterial blood pressure, capnography and blood gas analysis are common procedures during long-term surgery. However, few data are available on reference ranges for blood gas in sheep and these cover only short periods of anaesthesia. To the authors’ knowledge, there is no study available that includes the monitoring of electrolytes and pH in ruminal fluid and kidney function tests in sheep undergoing long term anaesthesia. Thereby, the aim of the present study was to gather data on blood parameters, and data on ruminal fluid and kidney function during long-term anaesthesia in sheep. Data were obtained from eight sheep undergoing the invasive surgical procedure of left pneumonectomy and auto-transplantation or isolated left lung perfusion. After a 19-h fasting period, the animals were administered xylazine and ketamine and then intubated and maintained in general anaesthesia under artificial ventilation using isoflurane in oxygen. Blood samples were evaluated during 9 h of anaesthesia; ruminal fluid and kidney function tests were evaluated during 7 h of anaesthesia.ResultsBlood parameters such as electrolytes and partial pressure of carbon dioxide revealed few changes, yet blood glucose decreased and beta-hydroxybutyric acid increased significantly. All animals showed an elevated arterial pH and bicarbonate concentration despite artificial ventilation. In ruminal fluid, the pH significantly decreased and no significant changes in electrolytes occurred. Kidney function tests revealed no significant changes in any of the animals. However, fractional excretion of water and phosphate was slightly increased. One animal showed severe complications due to hypokalaemia.ConclusionInvasive surgery under long-term anaesthesia in sheep is possible without great imbalances of arterial pH and electrolytes. Nevertheless, potassium concentrations should be monitored carefully, as a deficiency can lead to life-threatening complications. The operated sheep tended not to develop metabolic acidosis and the mean kidney function could be maintained within the physiological range throughout anaesthesia. However, slight elevations in renal fractional water and phosphate excretion could suggest an early tubular reabsorption dysfunction. In ruminal fluid, acidification occurred, though no significant changes were observed in l- and d-lactate levels or in electrolyte concentrations. To our knowledge, the role of the rumen in storing fluids and balancing electrolytes in the blood has not yet been documented during anaesthesia. However, the importance of the rumen for fluid equilibrium in sheep indicates the necessity for routine monitoring and further research.

Role of Renal Sympathetic Nerve Activity in Volatile Anesthesia's Effect on Renal Excretory Function.

Regulation of fluid balance is pivotal during surgery and anesthesia and affects patient morbidity, mortality, and hospital length of stay. Retention of sodium and water is known to occur during surgery but the mechanisms are poorly defined. In this study, we explore how the volatile anesthetic sevoflurane influences renal function by affecting renal sympathetic nerve activity (RSNA). Our results demonstrate that sevoflurane induces renal sodium and water retention during pediatric anesthesia in association with elevated plasma concentration of renin but not arginine–vasopressin. The mechanisms are further explored in conscious and anesthetized ewes where we show that RSNA is increased by sevoflurane compared with when conscious. This is accompanied by renal sodium and water retention and decreased renal blood flow (RBF). Finally, we demonstrate that renal denervation normalizes renal excretory function and improves RBF during sevoflurane anesthesia in sheep. Taken together, this study describes a novel role of the renal sympathetic nerves in regulating renal function and blood flow during sevoflurane anesthesia.

Effect of phentolamine mesylate on regression of lidocaine–epinephrine epidural anaesthesia in sheep

ObjectiveTo determine the impact of epidural phentolamine on the duration of anaesthesia following epidural injection of lidocaine–epinephrine. Study designBlinded randomized experimental study. AnimalsA group of 12 adult ewes weighing 25.7 ± 2.3 kg and aged 8–9 months. MethodsAll sheep were administered epidural lidocaine (approximately 4 mg kg–1) and epinephrine (5 μg mL–1). Of these, six sheep were randomized into three epidural treatments, separated by 1 week, administered 30 minutes after lidocaine–epinephrine: SAL: normal saline, PHE1: phentolamine (1 mg) and PHE2: phentolamine (2 mg). The other six sheep were administered only epidural lidocaine–epinephrine: treatment LIDEP. Each injection was corrected to 5 mL using 0.9% saline. Noxious stimuli were pinpricks with a hypodermic needle and skin pinch with haemostatic forceps to determine the onset and duration of sensory and motor block. Heart rate, noninvasive mean arterial pressure (MAP), respiratory rate and rectal temperature were recorded. ResultsThe onset times were not different among treatments. Duration of sensory block was significantly shorter in SAL (57.5 ± 6.2 minutes), PHE1 (60.7 ± 9.0 minutes) and PHE2 (62.0 ± 6.7 minutes) than in LIDEP (81.7 ± 13.4 minutes) (p < 0.05). Duration of motor blockade was significantly shorter in PHE1 (59.4 ± 5.4 minutes) and PHE2 (54.3 ± 4.0 minutes) than in SAL (84.8 ± 7.0 minutes) and LIDEP (91.5 ± 18.2 minutes) (p < 0.01). MAP in PHE2 was decreased at 10 minutes after administration of phentolamine (p < 0.05). Conclusion and clinical relevanceEpidural administration of 5 mL normal saline after epidural injection of lidocaine–epinephrine reduced the duration of sensory but not motor block in sheep. Epidural administration of phentolamine diluted to the final volume of 5 mL diminished both the duration of sensory and motor block in sheep administered epidural lidocaine–epinephrine.

Renal perfusion, oxygenation, and sympathetic nerve activity during volatile or intravenous general anaesthesia in sheep

BackgroundGlobal and intra-renal perfusion and oxygenation may be affected by the choice of anaesthetic. We compared the effects of isoflurane with those of propofol and fentanyl on renal blood flow (RBF) and intra-renal perfusion and oxygenation, and assessed how these were associated with renal sympathetic nerve activity (RSNA). MethodsA renal artery flow probe and laser Doppler and oxygen-sensing probes were surgically implanted in the renal medulla and cortex in 20 Merino ewes. RSNA was measured in 12 additional ewes. We compared the effects of volatile or i.v. anaesthesia on global RBF, renal oxygen delivery (RDO2), intra-renal perfusion, and RSNA with the non-anaesthetised state on postoperative day 3 as control reference. ResultsCompared with a non-anaesthetised state, volatile anaesthesia reduced global RBF [–76 (82–68)%], RDO2 [−76 (83–71)%], and cortical [–68 (74–54)%] and medullary [–76 (84–72)%] perfusion. I.V. anaesthesia reduced RBF [–55 (67–38)%], RDO2 [–55 (65–44)%], and cortical [–27 (45–6)%] and medullary [–35 (48–30)%] perfusion, but to a lesser extent than volatile anaesthesia. Renal PO2 was not influenced by anaesthesia, whilst RSNA was elevated during volatile, but not during i.v. anaesthesia. ConclusionsVolatile and i.v. general anaesthesia markedly reduced global RBF, RDO2, and regional kidney perfusion. These effects were greater with volatile anaesthesia, and were paralleled by an increase in RSNA. Our findings suggest a neurogenic modulatory effect of anaesthetics on renal perfusion and oxygenation.

A comparative study among using of Ketamine, Tramadol, and Paracetamol in three injectable anesthetic protocols for induction of general anesthesia in sheep

A comparative study among using of Ketamine, Tramadol, and Paracetamol in three injectable anesthetic protocols for induction of general anesthesia in sheep

Clinical and haematological changes upon administration of Xylazine-Ketamine and Xylazine-Thiopentoneanaesthetic combinations in ewes

The study was done to evaluate the effect of Xylazine-Ketamine and Xylazine- Thiopentone combinations for general anaesthesia in sheep. Six healthy sheep were divided into two groups: Group XK (n = 3), anaesthetized with Xylazine-Ketamine and Group XT (n = 3), anaesthetized with xylazine-thiopentone. Anaesthesia was induced using 1.1 mg/kg xylazine with 10 mg/kg ketamine or 20 mg/kg thiopentone as a single intravenous injection. Induction, duration and recovery from anaesthesia were monitored. Respiratory rate, heart rate and rectal temperature were recorded 15 min before and 5 min after induction, and 15 and 30 min and 24 hours after recovery. Packed Cell Volume (PCV) (%), Haemoglobin (Hb) (g/dL), Total Leucocyte Count (TLC) (millions per cubic millimetre) and Total Erythrocyte Count (TEC; Thousands per cubic millimetre) were measured before anaesthesia, one hour after induction and 24 hours after recovery. Heart rate increased significantly in both XT and XK groups and returned to control value 24 hours after recovery. Respiration rate decreased at 15 min after induction, then highly increased at 30 min and then returned to control value 24 hours after recovery in XK group. Rectal temperature decreased significantly in both groups. Hb, TLC, and TEC decreased, but PCV increased significantly in both groups. The mean time of induction of anaesthesia was less in XT group (0.2 ± 0.0 min) than in group XK (2.7 ± 0.1 min). The duration of anaesthesia and its recovery was less in Group XK than in Group XT. A combination of Xylazine-Ketamine and Xylazine-Thiopentone can be used to induce short term anaesthesia in sheep with negligible effects on clinical and haematological parameters.Bangl. vet. 2017. Vol. 34, No. 1, 9-19

Ameliorating the adverse cardiorespiratory effects of chemical immobilization by inducing general anaesthesia in sheep and goats: implications for physiological studies of large wild mammals.

Chemical immobilization is necessary for the physiological study of large wild animals. However, the immobilizing drugs can adversely affect the cardiovascular and respiratory systems, yielding data that do not accurately represent the normal, resting state. We hypothesize that these adverse effects can be ameliorated by reversing the immobilizing agent while holding the animal under general anaesthesia. We used habituated sheep Ovis aries (N = 5, 46.9 ± 5.3kg body mass, mean ± SEM) and goats Capra hircus (N = 4, 27.7 ± 2.8kg) as ungulate models for large wild animals, and measured their cardiorespiratory function under three conditions: (1) mild sedation (midazolam), as a proxy for the normal resting state, (2) immobilization (etorphine and azaperone), and (3) general anaesthesia (propofol) followed by etorphine antagonism (naltrexone). Cardiac output for both sheep and goats remained unchanged across the three conditions (overall means of 6.2 ± 0.9 and 3.3 ± 0.3L min-1, respectively). For both sheep and goats, systemic and pulmonary mean arterial pressures were significantly altered from initial midazolam levels when administered etorphine + azaperone, but those arterial pressures were restored upon transition to propofol anaesthesia and antagonism of the etorphine. Under etorphine + azaperone, minute ventilation decreased in the sheep, though this decrease was corrected under propofol, while the minute ventilation in the goats remained unchanged throughout. Under etorphine + azaperone, both sheep and goats displayed arterial blood hypoxia and hypercapnia (relative to midazolam levels), which failed to completely recover under propofol, indicating that more time might be needed for the blood gases to be adequately restored. Nonetheless, many of the confounding cardiorespiratory effects of etorphine were ameliorated when it was antagonized with naltrexone while the animal was held under propofol, indicating that this procedure can largely restore the cardiovascular and respiratory systems closer to a normal, resting state.

Cardiovascular effects and intraoperative pharmacokinetics of tramadol in sheep undergoing spinal surgery

ObjectiveTo evaluate the pharmacokinetics of two doses of tramadol during isoflurane anaesthesia in sheep and their ability to prevent the cardiovascular response induced by surgical stimulation. Study designProspective randomized controlled study. AnimalsA total of 12 healthy sheep (mean weight, 47.5±7.9 kg) undergoing lumbar transpedicular intervertebral disk nucleotomy. MethodsSheep were sedated with medetomidine, anaesthesia was induced with propofol and maintained with isoflurane at 1.5 vol.%. Baseline heart rate and blood pressure were measured and sheep were randomly assigned an intravenous injection of tramadol (4 or 6 mg kg−1). Fentanyl was injected as rescue analgesic if cardiovascular parameters were increased more than 20% compared to baseline. If those variables were below 20% of baseline, the concentration of isoflurane was gradually decreased until parameters returned to the original value. Blood collections were performed at pre-assigned times, and concentrations of tramadol and O-desmethyltramadol (M1) assessed by high-performance liquid chromatography. ResultsTime from premedication to anaesthesia induction, anaesthesia time, propofol dose and intraoperative body temperature were similar between doses. Cardiovascular variables remained between ±20% of baseline value, and no statistical difference was observed between treatments. Regardless of the dose of tramadol administered, arterial blood pressure was statistically higher than baseline 10 minutes after tramadol administration, but it gradually returned to previous values. A two-compartment model and a non-compartment model described the pharmacokinetics of tramadol and M1, respectively. Plasma concentrations of tramadol rapidly decreased in the first 2 hours for both doses with an elimination half-life of more than 40 minutes. The M1 maximum concentration was similar for both doses, and it was detected in plasma after 35 minutes. Conclusions and clinical relevanceBoth doses of tramadol provided adequate cardiovascular stability during spinal surgery in sheep. The pharmacokinetic variables may be used to plan the dosage regime during general anaesthesia.

Effects of eight vehicles on transdermal lidocaine penetration in sheep skinin vitro

This study investigated the effects of vehicles on penetration and retention of lidocaine applied to sheep skin in vitro. Thoracic skin from two sheep was clipped of wool and stored at -20 °C, until used. Skin samples were defrosted and mounted in Franz-type diffusion cells, and then one of the following formulations, each saturated with lidocaine, was added: sodium lauryl sulphate (SLS) 0.5% in water, SLS 1% in water, dimethyl sulphoxide (DMSO) 50% in water (wt/wt), DMSO 100%, isopropyl myristate 100% (IPM), water alone, diethylene glycol monoethyl ether (DGME) 50% in water (wt/wt) and DGME 100%. The penetration of lidocaine in each skin sample was measured over 8 h. Significantly greater lidocaine skin concentrations and flux (J(SS)) were achieved with the nonaqueous vehicles, DMSO 100% (P < 0.00001 and P < 0.01, respectively), followed by DGME 100% and IPM (P < 0.00001 and P < 0.01, respectively). The lag time (t(lag)) for lidocaine penetration in the DMSO 100% vehicle was significantly shorter (P < 0.01) compared with all other vehicles except water. Improved transdermal penetration of lidocaine in the DMSO 100% vehicle was likely due to skin barrier disruption, as determined by differences in pre- and post-treatment transepidermal water loss (TEWL). This study has shown that nonaqueous vehicles enhanced penetration of lidocaine in sheep skin to a greater extent than aqueous vehicles, which has implications for topically applied local anaesthesia in sheep.

A comparison of two different ketamine and diazepam combinations with an alphaxalone and medetomidine combination for induction of anaesthesia in sheep

AIMS: To investigate the perceived adverse effects of a particular batch of ketamine during induction of anaesthesia in sheep and to assess if any adverse effects would make intubation more difficult for the veterinary students. METHODS: Thirty adult sheep (mean bodyweight 74.5 (SD 9.4) kg) were randomly assigned to one of six groups of five sheep. Sheep in Groups A and B received I/V 0.5 mg/kg diazepam and 10 mg/kg ketamine (Ketamine Injection; Parnell Laboratories NZ Ltd, of the suspect batch); those in Groups C and D received I/V 0.5 mg/kg diazepam and 10 mg/kg ketamine (Ketalar; Hospira NZ Ltd.), and those in Groups E and F received I/V 2 μg/kg medetomidine and 2 mg/kg alphaxalone. In Groups A, C and E, intubation was by an experienced anaesthetist, and in Groups B, D and F intubation was by a veterinary student. Time from injection to successful intubation, the ease of intubation, saturation of haemoglobin with oxygen (SpO2) and partial pressure of oxygen in arterial blood (PaO2) were measured before the sheep were connected to an anaesthetic machine and allowed to breath oxygen. Times to extubation, holding its head up and standing, maximum and minimum heart rates, respiratory rates, maximal end tidal CO2, and the quality of recovery were then recorded. RESULTS: There were no measurable differences in outcomes between sheep in Groups A and B compared with C and D. Time to intubation was slightly shorter for the experienced anaesthetist than the student, but the difference was not significant. The sheep in Groups E and F took less time to recover than those in Groups A−D (p<0.05), but there were no significant differences between the groups in either the ease of induction or quality of recovery. Most sheep in Groups E and F showed minor excitatory effects, mainly at induction, which did not interfere with induction. Respiratory rates were lower in Groups E and F than Groups A−D (p<0.01), but SpO2 was higher in Groups E and F than A and B (p<0.05). CONCLUSIONS: The clinical impression that the batch of Parnell ketamine produced unexpected effects was shown to be incorrect. All the combinations produced anaesthesia that allowed intubation by the veterinary student. CLINICAL RELEVANCE: All the drug combinations produced satisfactory anaesthesia in sheep, but the alphaxaloneand medetomidine combination resulted in faster recovery.

Effects of an intravenous bolus of alfaxalone versus propofol on intraocular pressure in sheep

The objective of this prospective study was to determine the effects of a single intravenous bolus of alfaxalone in 2-hydroxypropyl-β-cyclodextrin and propofol on the intraocular pressure (IOP) in sheep. Ten...

Lidocaine containing high concentrations of a vasoconstrictor: is it safe for infiltration anesthesia?

For economical and practical reasons, flank laparotomy performed on cattle is done while the animal is standing. To prolong the duration of surgical anesthesia with local anesthetic drugs, vasoconstrictors are commonly added to delay absorption and reduce the systemic toxicity. The purpose of this study was to examine the effects of lidocaine containing either 80 μg ml-1 norepinephrine or 12.5 μg ml-1 epinephrine on tissue integrity following flank inverted L infiltration anesthesia in sheep.

The effects on cardio-respiratory and acid-base variables of the anaesthetic alfaxalone in a 2-hydroxypropyl-β-cyclodextrin (HPCD) formulation in sheep

The objective of this study was to determine the pharmacodynamic effects in sheep of the anaesthetic alfaxalone in a 2-hydroxypropyl-β-cyclodextrin formulation. Seven Ripollesa sheep, weighing 43.0±6.6 kg, were used in the study. Twenty-four hours after instrumentation, the sheep were anesthetised with alfaxalone (2 mg/kg bodyweight IV) in cyclodextrin. Heart rate, arterial blood pressure, respiratory rate and arterial blood gases were recorded. Alfaxalone administration resulted in minimal cardio-respiratory depression. Time to standing from anaesthesia was 22.0±10.6 min. Apnoea was not observed in any of the sheep. Significant differences from baseline were not observed in respiratory rate or arterial blood pressure. Heart rate increased significantly (P<0.05) immediately after administration, returning to control values at 20 min. The calculated haemoglobin saturation (SO2) decreased significantly during the first 15 min after alfaxalone administration. The arterial pH decreased significantly during the first 30 min of the study, although no significant differences from basal values were observed in the arterial partial pressure of carbon dioxide (PaCO2). The results showed that alfaxalone in 2-hydroxypropyl-β-cyclodextrin administered as an IV bolus at 2 mg/kg produced minimal adverse effects and an uneventful recovery from anaesthesia in sheep.