Large Animal Anesthesia Research Articles

Effects of intravenous lignocaine on anaesthetic parameters in cattle under dexmedetomidine-butorphanol-ketaminemidazolam- isofluraneanaesthesia

The present study was conducted for clinical evaluation of a multimodal anaesthetic protocol using butorphanol-dexmedetomidine-midazolam-ketamine-isoflurane and lignocaine continuous rate infusion (CRI) in six cross-bred female cattle. Preanaesthetics used were butorphanol and dexmedetomidine which were administered intravenously at dose rates of 0.05 mg/kg and 1 μg/ kg body weight, respectively. Ketamine and midazolam were intravenously administered at dose rates of 4.0 and 0.2 mg/kg body weight respectively, to induce anaesthesia. Isoflurane was used to maintain anaesthesia after endotracheal intubation, at a concentration of 1.05 ± 0.97 per cent concentration in 100 per cent oxygen using a large animal anaesthesia machine. Simultaneously, intravenous lignocaine was administered at a bolus dose of 2 mg/kg body weight followed by a CRI of 3 mg/kg body weight/hour using a volumetric infusion pump. Isoflurane sparing effect of intravenous lignocaine reduced the required concentration of isoflurane for maintenance. The third plane of surgical anaesthesia was maintained and various surgical procedures were done. Recovery was smooth. Other than the mild regurgitation of ruminal fluid in an animal, no anaesthetic complications were noticed.

Analysis of teaching methods in anaesthesia in the undergraduate curriculum of four veterinary universities

ObjectiveTo design a holistic audit tool to assess the effectiveness of anaesthesia teaching strategies, and thereby to study veterinary undergraduate teaching methods in different geographical areas. Study designQualitative study using interviews of university staff and students to identify common themes and differences in teaching veterinary anaesthesia. MethodsAn audit was performed using an audit tool in four veterinary universities (École Nationale Vétérinaire d'Alfort, France; Royal Veterinary College, UK; University of Buenos Aires, Argentina; and Alma mater studiorum - Università di Bologna, Italy). First, an open-question interview of anaesthesia head of service (60–90 minutes) identified the pedagogical strategies in order to conceive a subsequent semi-directive interview formulated as a SWOT analysis (Strength/Weaknesses/Opportunity/Threats). Second, the SWOT reflection was conducted by a second staff member and focussed on: 1) general organization; 2) topics for pre-rotation teaching; 3) teaching methods for clinical rotation; and 4) assessment methods. Qualitative analysis of the interview responses was performed with semi-structured interviews. Finally, the students evaluated their teaching through a students’ questionnaire generated from the output of both interviews. ResultsA group of nine lecturers and 106 students participated in the study at four different sites. Preclinical teaching ranged from 13 to 24 hours (median 15 hours). Clinical teaching ranged from 4 to 80 hours (median 60 hours). Overall, all faculties perceived time as a limitation and attempted to design strategies to achieve the curriculum expectations and optimize teaching using more time-efficient exercises. Large animal anaesthesia teaching was found to be a common area of weakness. Internal feedback was delivered to each university, whereas generalized results were shared globally. ConclusionsThis preliminary study proved the generalizability of the protocol used. Recruiting a larger pool of universities would help to identify and promote efficient teaching strategies and innovations for training competent new graduates in an ever-expanding curriculum.

Evaluation of Sevoflurane Anesthesia in Donkeys (Equus asinus) Premedicated With Xylazine and Induced With Thiopental

Sevoflurane is a volatile anesthetic agent that has become popular in the field of large animal anesthesia. The aim of this study was to evaluate the use of sevoflurane in adult healthy donkeys. Six male, adult, healthy donkeys were premedicated with xylazine (1 mg/kg IV), induced with thiopental (5 mg/kg IV), and then maintained for 90 minutes with sevoflurane in 100% oxygen at a flow rate of 6 L/min with spontaneous breathing. Rectal temperature (RT), respiratory rate, heart rate (HR), oxygen hemoglobin saturation (OHS), and mean arterial blood pressure (MBP) were measured before and 20 minutes after the administration of xylazine, 10 minutes after the injection of thiopental, and then continuously every 10 minutes until recovery. Times for various signs of recovery, total duration of recovery, and quality of recovery were recorded. Jugular blood samples were collected from each donkey and complete blood counts and venous blood gases including concentrations of oxygen (PO2) and carbon dioxide (PCO2) were measured. In addition, the concentrations of sodium, potassium, calcium, lactate, bicarbonate, and glucose in venous blood were measured. Results showed that during the anesthesia maintained with sevoflurane, there was a significant decrease in HR, MBP, RT, red blood corpuscles, hematocrit, total white blood cells, neutrophils, and lymphocytes, whereas the levels of OHS and glucose significantly increased. The concentrations of PO2, PCO2, and lactate in venous blood significantly increased, whereas the pH significantly decreased. The levels of calcium significantly decreased immediately following the recovery. Sternal recumbency and standing occurred 15.8 ± 2.6 minutes and 28.2 ± 2.2 minutes, respectively, after turning off the vaporizer. Overall, the quality of recovery was good and relatively quick. It was concluded that sevoflurane appears to provide safe and effective anesthesia in donkeys, with relatively rapid induction and recovery.

The Modification and Performance of a Large Animal Anesthesia Machine (Tafonius®) in Order to Deliver Xenon to a Horse.

Xenon, due to its interesting anesthetic properties, could improve the quality of anesthesia protocols in horses despite its high price. This study aimed to modify and test an anesthesia machine capable of delivering xenon to a horse. An equine anesthesia machine (Tafonius, Vetronic Services Ltd., UK) was modified by including a T-connector in the valve block to introduce xenon, so that the xenon was pushed into the machine cylinder by the expired gases. A xenon analyzer was connected to the expiratory limb of the patient circuit. The operation of the machine was modeled and experimentally tested for denitrogenation, wash-in, and maintenance phases. The system was considered to consist of two compartments, one being the horse's lungs, the other being the machine cylinder and circuit. A 15-year-old, 514-kg, healthy gelding horse was anesthetized for 70 min using acepromazine, romifidine, morphine, diazepam, and ketamine. Anesthesia was maintained with xenon and oxygen, co-administered with lidocaine. Ventilation was controlled. Cardiorespiratory variables, expired fraction of xenon (FeXe), blood gases were measured and xenon was detected in plasma. Recovery was unassisted and recorded. FeXe remained around 65%, using a xenon total volume of 250 L. Five additional boli of ketamine were required to maintain anesthesia. PaO2 was 45 ± 1 mmHg. The recovery was calm. Xenon was detected in blood during the entire administration time. This pilot study describes how to deliver xenon to a horse. Although many technical problems were encountered, their correction could guide future endeavors to study the use of xenon in horses.

Threshold valves to create positive end-expiratory pressure (PEEP) in conventional large animal anaesthesia ventilators and circuits

Threshold valves to create positive end-expiratory pressure (PEEP) in conventional large animal anaesthesia ventilators and circuits

A novel flow partition device for spirometry during large animal anaesthesia

ObjectiveWe describe and test a novel device for large animal anaesthesia monitoring that uses standard human medicine spirometry sensors. Study designIn-vitro study. MethodsThe device consists of two adapters that enable the flow to be split evenly into four tubes in parallel, each tube containing a D-lite sensor. The performance of this flow partitioning device (FPD) over a range of flows from 100 to 700 L minute−1 was determined and the pressure versus flow relation, resistance and dead space was compared with a Horse-lite (Moens 2010). ResultsEquipped with four D-lite sensors, and a flow of 700 L minute−1 the pressure drop of the FPD was 13.5 cmH2O, resistance 1.17 cmH2O second L−1 and volume (potential dead space) 182 mL, compared to 2.8 cmH2O, 0.24 cmH2O second L−1 and 54 mL respectively for the Horse-lite. The predicted value of the flow partition of ¼ could be confirmed. Limits of agreement were found to be 4.2% in inspiratory direction and 7.1% in expiratory direction. Conclusions and clinical relevanceThe FPD is an affordable device that extends the specification of any commercially available human spirometry sensors to large animal applications. However, an increase in total resistance and dead space has to be taken into account. Therefore, the new device could be useful during equine anaesthesia.

In vitro and in vivo evaluation of a new large animal spirometry device using mainstream CO2 flow sensors

A spirometry device equipped with mainstream CO2 flow sensor is not available for large animal anaesthesia. To measure the resistance of a new large animal spirometry device and assess its agreement with reference methods for volume measurements. In vitro experiment and crossover study using anaesthetised horses. A flow partitioning device (FPD) equipped with 4 human CO2 flow sensors was tested. Pressure differences were measured across the whole FPD and across each sensor separately using air flows (range: 90-720 l/min). One sensor was connected to a spirometry monitor for in vitro volume (3, 5 and 7 l) measurements. These measurements were compared with a reference method. Five anaesthetised horses were used for tidal volume (VT) measurements using the FPD and a horse-lite sensor (reference method). Bland-Altman analysis, ANOVA and linear regression analysis were used for data analysis. Pressure differences across each sensor were similar suggesting equal flow partitioning. The resistance of the device increased with flow (range: 0.3-1.5 cmH2 O s/l) and was higher than that of the horse-lite. The limits of agreement for volume measurements were within -1 and 2% in vitro and -12 and 0% in vivo. Nine of 147 VT measurements in horses were outside of the ± 10% limits of acceptance but most of these erroneous measurements occurred with VTs lower than 4 l. The determined correction factor for volume measurements was 3.97 ± 0.03. The limits of agreement for volume measurements by the new device were within ± 10% using clinically relevant range of volumes. The new spirometry device can be recommended for measurement of VT in adult Warmblood horses.

Clinicophysiological and haemodynamic effects of fentanyl with dexmedetomidine in halothane and isoflurane anaesthetized buffaloes

The clinical, physiological, haemodynamic and anaesthetic effects of halothane and isoflurane in buffaloes premedicated with dexmedetomidine and fentanyl, were studied. Clinically healthy male buffaloes (6) were used. All the animals received 2 treatments randomly at weekly interval in groups H (halothane) and I (isoflurane). In both groups sedation was accomplished by fentanyl (5 μg/kg body wt) and dexmedetomidine (5 μg/kg body wt) intravenously. Induction of anaesthesia was achieved by 5% thiopental sodium in both groups. Maintenance of anaesthesia was done by halothane in group H and by isoflurane in group I respectively in 100% oxygen through a large animal anaesthesia machine. The different treatments were evaluated on the basis of clinical, physiological, haematological, biochemical and haemodynamic parameters. It is concluded that dexmedetomidine-fentanyl-thiopental and isoflurane provided better clinical, physiological and haemodynamic stability than dexmedetomidine-fentanyl-thiopental and halothane in buffaloes.

Clinicophysiological and haemodynamic effects of fentanyl with xylazine, medetomidine and dexmedetomidine in isoflurane-anaesthetised water buffaloes (<i>Bubalus bubalis</i>)

The present study was undertaken to investigate the sedative, analgesic and clinical effects of xylazine, medetomidine and dexmedetomidine with fentanyl as pre-anaesthetics in water buffaloes and to compare the dose-sparing effect of xylazine, medetomidine and dexmedetomidine on thiopental for induction and isoflurane for maintenance of anaesthesia in water buffaloes. Six male water buffaloes randomly received intravenous fentanyl (5.0 µg/kg body weight) and xylazine (0.05 mg/kg body weight), fentanyl (5.0 µg/kg body weight) and medetomidine (2.5 µg/kg body weight), fentanyl (5.0 µg/kg body weight) and dexmedetomidine (5.0 µg/kg body weight) at weekly intervals in groups I1, I2 and I3, respectively. After 15 min, the animals were restrained in right lateral recumbency and anaesthesia was induced by 5% thiopental sodium administered intravenously. The intubated animal was connected to the large animal anaesthesia machine and isoflurane in 100% oxygen (5 L/min) was insufflated for 60 min. The treatments were compared by clinicophysiological, haematobiochemical and haemodynamic parameters. Fentanyl-medetomidine and fentanyl-dexmedetomidine produced more cardiovascular depression during the pre-anaesthetic period but less depression of cardio-respiratory dynamics in the post induction and maintenance period. Quicker recovery was recorded in I2 and I3 groups. A lower dose of thiopental was required in group I3 (4.33 mg/kg ± 0.66 mg/kg) than in groups I2 (4.41 mg/kg ± 0.98 mg/kg) and I1 (4.83 mg/kg ± 0.79 mg/kg). The dose of isoflurane was less in group I3 (45.50 mL ± 5.45 mL) than in group I1 and I2 (48.66 mL ± 5.10 mL and 48.00 mL ± 6.38 mL). Better anaesthesia was recorded with fentanyl-dexmedetomidine-thiopental-isoflurane (group I3) than with fentanyl-medetomidine-thiopental-isoflurane (group I2) and fentanyl-xylazine-thiopental-isoflurane (group I1). Fentanyl-medetomidine and fentanyl-dexmedetomidine were better pre-anaesthetic agents in comparison to fentanyl-xylazine for thiopental and isoflurane anaesthesia. Fentanyl-dexmedetomidine-thiopental-isoflurane and fentanyl-medetomidine-thiopental-isoflurane produced effective surgical anaesthesia and were found to be safe, as cardio-pulmonary functions were well preserved during maintenance anaesthesia with no deleterious effect on vital organ functions in water buffaloes.

In vitro validation of a Pitot‐based flow meter for the measurement of respiratory volume and flow in large animal anaesthesia

ObjectiveTo remodel and validate commercially available monitors and their Pitot tube‐based flow sensors for use in large animals, using in vitro techniques. Study designProspective, in vitro experiment. MethodsBoth the original and the remodelled sensor were studied with a reference flow generator. Measurements were taken of the static flow‐pressure relationship and linearity of the flow signal. Sensor airway resistance was calculated. Following recalibration of the host monitor, volumes ranging from 1 to 7 L were generated by a calibration syringe, and bias and precision of spirometric volume was determined. Where manual recalibration was not available, a conversion factor for volume measurement was determined. The influence of gas composition mixture and peak flow on the conversion factor was studied. ResultsBoth the original and the remodelled sensor showed similar static flow–pressure relationships and linearity of the flow signal. Mean bias (%) of displayed values compared with the reference volume of 3, 5 and 7 L varied between −0.4% and +2.4%, and this was significantly smaller than that for 1 L (4.8% to +5.0%). Conversion factors for 3, 5 and 7 L were very similar (mean 6.00 ± 0.2, range 5.91–6.06) and were not significantly influenced by the gas mixture used. Increasing peak flow caused a small decrease in the conversion factor. Volume measurement error and conversion factors for inspiration and expiration were close to identity. ConclusionThe combination of the host monitor with the remodelled flow sensor allowed accurate in vitro measurement of flows and volumes in a range expected during large animal anaesthesia. Clinical relevanceThis combination has potential as a reliable spirometric monitor for use during large animal anaesthesia.

Clinical use of atracurium in large animal species

Predictable duration and unique method of elimination make atracurium a suitable muscle relaxant for large animals. This abstract presents experience with clinical use of atracurium in large animal anesthesia from 1989 to 2001. Anesthesia records for large animals were reviewed for use of atracurium. Species of animal, nature of the surgical procedure, maintenance anesthetic, method of atracurium administration, antagonism of atracurium, and recovery experience were noted. Of the 264 animals that received atracurium, 248 were horses. Other species included cattle, pigs, llama, and one lion. Surgical procedures most likely to be associated with atracurium use were laparotomy (63) and ophthalmologic (56), orthopedic (44), and reproductive (35) procedures. Majority of maintenance anesthesia was isoflurane in oxygen, 21 animals received halothane, and six received desflurane. Relaxation was evaluated using train-of-four or 50 Hz tetanic stimulus to the superficial peroneal nerve or the facial nerve, and subsequent muscle response was observed. Atracurium was given by single IV bolus dose, by infusion, or a combination of techniques. Initial bolus of atracurium was 0.1–0.2 mg kg−1. Repeat bolus doses and dose interval varied. Mean infusion duration was 77 minutes Infusion rate varied, but was 0.2 mg kg−1 hour−1 for orthopedic and ophthalmologic procedures. Edrophonium (0.5 mg kg−1) given IV over 1 minute, was used to antagonize atracurium in 173 cases. No cardiovascular effects were noted. Recovery to standing was reported as smooth for 158 animals, fair for 33, and rough for 24. A total of 40 recoveries did not have a detailed description. Eight horses were recovered in a support sling. Nine horses were euthanized prior to recovery. In conclusion, atracurium is a useful, safe adjunct to large animal anesthesia, especially when the surgical conditions specifically require relaxation.

A simple method of providing intermittent positive-pressure ventilation to etorphine-immobilized elephants (Loxodonta africana) in the field.

Five African elephants (Loxodonta africana) were immobilized with etorphine in Waza National Park, Cameroon, for the purpose of deploying radio/satellite tracking collars. A portable ventilator constructed from two high-flow demand valves and the Y-piece of a large animal anesthesia circuit was used to provide intermittent positive-pressure ventilation with 100% oxygen. Oxygenation status improved dramatically in all five elephants. In one hypoxemic elephant, arterial PaO2 increased from 40 to 366 mm Hg. The results of this study demonstrate that both oxygenation and ventilation can be readily controlled in etorphine-immobilized elephants even under remote field conditions.

Airflow and device effects on aerosol delivery for large animals.

Aerosol delivery of medications has recently gained acceptance in large animal veterinary medicine. However, delivery of therapeutic aerosols currently relies on equipment modified from human use and delivery of medical aerosols may be adversely affected by the equipment design. In this study, we demonstrate the effect of typical large animal inspiratory flow rates on aerosol delivery characteristics. A benchtop system was assembled to simulate aerosol delivery to large animals. Phasic airflow was generated using a large animal anesthesia machine set to deliver 6 bpm (7 L/breath) at 100, 150 and 180 L/min mean inspiratory airflow. Aerosol from a DeVilbis ultrasonic nebulizer was delivered to a simulated facemask using standard 22 mm tubing and fittings. Total mass, delivery efficiency and mass median aerosol diameter (MMAD) was measured with and without an inspiratory one-way valve on the facemask. Delivered aerosol mass ranged from 0.26 to 0.08 g/min and delivery efficiency ranged from 30 to 6%. Both parameters were significantly reduced by both increasing flow rates and the presence of a one-way valve between the nebulizer and the facemask. Average MMAD was 0.7 microm and was not affected by any experimental variable. These results demonstrate that current aerosol equipment used on large animals has a substantial adverse effect on aerosol delivery. Elimination of one-way valves between the aerosol source and the patient is expected to improve delivery of the aerosol in these patients.

Large Animal Anesthesia

Large Animal Anesthesia