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Background Matrix fentanyl patches have not been investigated in horses and may represent an effective means of providing analgesia over an extended time period without venous catheterisation. Objectives To describe the pharmacokinetics of a matrix transdermal fentanyl patch in horses. Study design Randomised experiment, Latin-square design. Methods Six adult horses were given each of three treatments with a 96-hour washout. For each treatment, two 100 µg/h matrix fentanyl patches were applied to the inguinal region (TXA), metacarpus (TXM) or ventral tail base (TXT) for 72 hours. Blood samples for fentanyl analysis were obtained and heart rate (HR), respiratory rate (RR) and rectal temperature (RT) were measured at various time points for 96 hours. Fentanyl plasma concentrations were measured with LC-MS/MS for pharmacokinetic analysis. A mixed-effects model was used to analyse pharmacodynamic variables. Results The time to maximum plasma concentration, maximum plasma concentration and area under the curve extrapolated to infinity were 10 ± 3.79, 14.3 ± 5.13 and 10.3 ± 4.8 hours; 2.07 ± 0.74, 1.55 ± 0.53 and 2.07 ± 0.72 ng/mL; and 46.6 ± 9.3, 44.6 ± 6.0 and 46.2 ± 7.68 ng hours/mL for TXA, TXM and TXT respectively. There was no significant difference among groups. There was no significant change from baseline or among treatment groups with regard to HR, RR or RT (P > .1 for all). Main limitations There was no intravenous treatment group for determination of bioavailability. Conclusions Fentanyl was rapidly absorbed and persisted in the plasma for up to 96 hours. No adverse effects of treatment on HR, RR or RT were observed. Further controlled prospective studies are needed to determine what plasma concentration, if any, of fentanyl achieves an analgesic effect in horses when administered via a transdermal patch system.

Low arterial oxygen is a common complication in anesthetized horses and placing the animal in reverse Trendelenburg (RT) position may treat hypoxemia. The objective of this study was to assess the arterial partial pressure of oxygen (PaO2) in horses placed in a 5-degree RT compared to horizontal (H) position. Client-owned healthy horses (n = 60) undergoing elective surgeries were enrolled in a randomized controlled clinical study. Horses were sedated with butorphanol, an α2-adrenoceptor agonist, ± acepromazine and induced with ketamine combined with a benzodiazepine, propofol, or guaifenesin. Anesthesia was maintained with isoflurane in oxygen with mechanical ventilation. Each group (RT and H) included 30 horses, 10 in each recumbency (dorsal, right and left lateral). Arterial blood gas analyses (aBG) were performed following arterial catheter placement then hourly. Time first-to-last aBG, changes in PaO2, dynamic compliance (Cdyn), estimated pulmonary shunt fraction (F-shunt), and alveolar dead space to tidal volume ratio (VD/VT) were evaluated with a 2-way analysis of variance. Statistical significance was set at p

OBJECTIVE To determine the pharmacokinetics and pharmacodynamics of methadone after IV or IM administration to isoflurane-anesthetized chickens. ANIMALS 6 healthy adult Hy-Line hens. PROCEDURES In a randomized crossover-design study, methadone (6 mg/kg) was administered IV and IM to isoflurane-anesthetized chickens with a 1-week washout period between experiments. Blood samples were collected immediately before and at predetermined time points up to 480 minutes after methadone administration. Plasma concentrations were determined by liquid chromatography–mass spectrometry, and appropriate compartmental models were fit to the plasma concentration-versus-time data. Cardiorespiratory variables were compared between treatments and over time with mixed-effect repeated-measures analysis. RESULTS A 3-compartment model best described the changes in plasma methadone concentration after IV or IM administration. Estimated typical values for volumes of distribution were 692 mL/kg for the central compartment and 2,439 and 2,293 mL/kg for the first and second peripheral compartments, respectively, with metabolic clearance of 23.3 mL/kg/min and first and second distributional clearances of 556.4 and 51.8 mL/kg/min, respectively. Typical bioavailability after IM administration was 79%. Elimination half-life was 177 minutes, and maximum plasma concentration after IM administration was 950 ng/mL. Heart rate was mildly decreased at most time points beginning 5 minutes after IV or IM drug administration. CONCLUSIONS AND CLINICAL RELEVANCE Disposition of methadone in isoflurane-anesthetized chickens was characterized by a large volume of distribution and moderate clearance, with high bioavailability after IM administration. Additional studies are warranted to assess pharmacokinetics and pharmacodynamics of methadone in awake chickens.

Objective To describe the pharmacokinetics and pharmacodynamics of meperidine after IM and subcutaneous administration in horses. Study design prospective, randomized, blinded, crossover trial. Animals Six adult horses weighing 494 ± 33 kg. Methods Treatments included meperidine 1 mg/kg IM with saline 6 mL subcutaneously, meperidine 1 mg/kg subcutaneously with saline 6 mL IM, and saline 6 mL subcutaneously and 6 mL IM, with a 7-day washout between treatments. Plasma meperidine concentrations and pharmacodynamic values (thermal and mechanical thresholds, physiological variables, fecal production) were collected at various time points for 24 hours. Accelerometry data were obtained for 8 hours to measure locomotor activity. Data were analyzed with a mixed effects model, and α was set at .05. Results Meperidine terminal half-life (T1/2 ), maximal plasma concentrations, and time to maximal concentration were 186 ± 59 and 164 ± 56 minutes, 265.7 ± 47.2 and 243.1 ± 80.1 ng/mL at 17 ± 6, and 24 ± 13 minutes for IM at subcutaneous administration, respectively. No effect of treatment or time was observed on thermal or mechanical thresholds, heart rate, respiratory rate, locomotor activity, frequency of defecations, or fecal weight (P > .2 for all). Conclusion Maximum meperidine concentrations were achieved quickly with a short T1/2 in both treatment groups. Neither IM nor subcutaneous meperidine influenced thermal or mechanical threshold or physiological variables. Clinical significance The short half-life and lack of detectable antinociceptive effect do not support IM or subcutaneous administration meperidine at 1 mg/kg for analgesia in horses.

Objective To describe the incidence of postanesthetic signs of colic (PASC) in horses and determine if perianesthetic administration of hydromorphone was associated with an increased risk of PASC. Study design Retrospective, cohort study. Animals A total of 409 horses. Methods Anesthesia and clinical records of horses admitted for various procedures from July 2018 to September 2019 were reviewed. Signs of colic and interventions were recorded up to 48 hours after anesthesia. A binomial logistic regression model was used to evaluate the association between the type of surgery, administration of hydromorphone, the duration of anesthesia and the incidence of PASC. Results Overall, 25 (6.1%) horses developed PASC within 48 hours of general anesthesia. Of 60 horses that underwent colic surgery, 16 (26.7%) developed PASC. Of 349 horses that underwent noncolic procedures, nine (2.6%) developed PASC. Thus, the incidence of PASC was higher in horses that underwent colic surgery than in horses that underwent noncolic procedures [odds ratio (OR) = 13.74 (5.73–32.95)]. No effect of hydromorphone on the incidence of PASC was identified [OR = 1.61 (0.71–3.62)]. Longer procedures (>2 hours) were identified as an independent risk factor for PASC [OR = 4.13 (1.52–11.22)]. Conclusions No association between hydromorphone and an increase in the incidence of PASC was identified. Anesthesia for colic surgery and duration of anesthesia were associated with an increased risk of PASC. Clinical relevance Hydromorphone did not increase the incidence of PASC in this population.

Minimizing sympathetic stimulation under anesthesia prevents activation of the neuroendocrine stress response. The minimum alveolar concentration blunting adrenergic responses in 50% of the population when exposed to a noxious stimulus is defined as MAC-BAR. The purpose of this study was to determine the MAC-BAR of sevoflurane (MAC-BARsevo) in sheep and the MAC-BAR sparing effects of ketamine. Thirteen healthy Dorset-cross adult ewes, 4 ± 1 year old and weighing 74 ± 9 kg, were enrolled in a randomized blinded crossover study design. Ewes were anesthetized twice for MAC-BARsevo determination. After face mask induction with sevoflurane, sheep received intravenous ketamine at 1.5 mg/kg and a constant rate infusion of 1.5 mg/kg/h or an equivalent volume of saline (placebo). After 8 day washout, the other treatment was administered. A bracketing technique was used for MAC-BARsevo determination and values were collected in duplicate. The mechanical stimulus (sponge forceps) was applied at the coronary band for 1 min and blood was collected for ketamine plasma concentrations. The MAC-BARsevo values of each treatment were compared using a paired t-test. Mean MAC-BARsevo of the ketamine and placebo were 2.73 ± 0.23% and 2.77 ± 0.31%, respectively and no significant difference was found (p = .638). Average ketamine plasma concentrations was 1.54 ± 0.18 μg/mL maintained through the study. Ketamine at 1.5 mg/kg, followed by 1.5 mg/kg/h, did not decrease the MAC-BARsevo in sheep. Further studies to determine the effect of higher doses of ketamine on inhalational anesthetic agents and their potential adverse effects are warranted.

Local anesthetics are the only class of drugs that can block transduction and transmission of nociception. Physical properties, mechanism of action, and pharmacokinetics of this class of drugs are reviewed in this article. The clinical use, such intravenous administration of lidocaine, and local and systemic toxic effects are covered. A review of current studies published in the human and veterinary literature on lidocaine patches (Lidoderm) and liposomal bupivacaine (Experal and Nocita) are discussed.

Objective Describe the pharmacokinetics and pharmacodynamics of intravenous hydromorphone in healthy horses. Study design Masked, randomized, cross-over, Latin square design. Animals A group of eight healthy adult horses Methods Horses were administered each of four treatments with an 8 day washout. Treatments groups included intravenous hydromorphone 0.02 mg kg–1 (LD), 0.04 mg kg–1 (MD), 0.08 mg kg–1 (HD) and saline (P). Blood samples for hydromorphone analysis were obtained for 24 hours after treatment. Plasma hydromorphone was quantified and pharmacokinetic parameters were determined using non-compartmental analysis. Pharmacodynamic data collected for 24 hours after treatment included thermal nociceptive threshold, heart rate (HR), respiratory rate (fR) and rectal temperature, and analyzed using mixed-effects linear models. Results Mean (± standard deviation) hydromorphone terminal half-life (t1/2), systemic clearance and apparent volume of distribution at steady state (Vdss) were 18.1 ± 18.6, 34.0 ± 12.8, and 41.3 ± 32.5 minutes, 66.6 ± 5.3, 550.0 ± 76.4, and 92.7 ± 13.9 mL kg–1 minute–1, and 1118 ± 369, 1460 ± 325 and 2242 ± 950 mL kg–1 for treatments LD, MD and HD, respectively. Thermal threshold increased significantly compared to baseline for all treatments for up to 12 hours. HR was elevated above baseline in treatments LD, MD and HD, extending to 30, 15 and 105 minutes after treatment, respectively. Respiratory rate was elevated above baseline in treatments MD and HD from 30 to 195 minutes and from 45 to 480 minutes after treatment, respectively. Temperature was elevated above baseline in treatment HD until 255 minutes after treatment. Conclusions Hydromorphone exhibited a short t1/2, rapid clearance and large Vdss in horses. It also provided a dose-dependent increase in thermal threshold with associated increases in HR, fR and rectal temperature. Clinical relevance Hydromorphone 0.04 mg kg–1 provided clinically relevant thermal antinociception with minimal adverse effects.

OBJECTIVE To compare the effects of two doses of doxapram intravenous injection and carbon dioxide inhalation on the cardiovascular and laryngeal functions of anesthetized hounds. STUDY DESIGN Experimental study. ANIMALS Six healthy adult dogs. METHODS In a Latin-square design, the mean arterial blood pressure (MABP) and heart rate (HR) were recorded continuously. The inspiratory normalized glottic gap areas (iNGGA) were measured before and after each stimulation with 0.55 mg/kg of doxapram (L-DOX), 2.2 mg/kg of doxapram (H-DOX), or 90 s of inhalation of 10% carbon dioxide in oxygen (I-CO2 ). The stimulations were tested in duplicate or triplicate. Video clips of the laryngeal movement were scored by board-certified surgeons masked to the treatment. RESULTS The MABP increased with L-DOX and H-DOX up to 81% (both p

Made available in DSpace on 2021-06-25T15:01:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-03-01 Respiratory depression from isoflurane seems to be greater in birds than in mammals. Isoflurane respiratory anesthetic index (AI) has only been evaluated in ducks (Anas platyrhynchos), which indeed showed a lower AI compared to mammals, but the isoflurane AI for other avian species is not known. The aim of this study was to evaluate the isoflurane AI in chickens (Gallus gallus domesticus). Six adult hens were anesthetized with isoflurane for determination of the minimum anesthetic concentration (MAC) using the bracketing method. During a second anesthetic event, the isoflurane AI was determined by progressively increasing the expired fraction of isoflurane by 0.5 times MAC until apnea was achieved (ETiso-apnea). The isoflurane AI was considered the ratio between the ETiso-apnea and the MAC. Heart rate, systolic arterial pressure, respiratory rate, and end-tidal carbon dioxide were continuously monitored throughout both anesthetic events. Data were analyzed using a mixed-effect model with Greenhouse-Geisser correction, followed by Tukey's test. The MAC for isoflurane was 1.18% +/- 0.09% (mean +/- SD). The ETiso-apnea was 3.31% +/- 0.34% and the isoflurane AI was 2.80 +/- 0.26. In chickens, isoflurane AI is similar to that measured in mammals, which is in contrast with published data in other avian species. Sao Paulo State Univ, Sch Agr & Vet Sci, Dept Vet Clin & Surg, Via Acesso Prof Paulo Donato Castelane S-N, BR-14884900 Jaboticabal, SP, Brazil Univ Georgia, Coll Vet Med, Dept Large Anim Med, Athens, GA 30602 USA Auburn Univ, Coll Vet Med, Dept Clin Sci, 1010 Wire Rd, Auburn, AL 36849 USA Ross Univ, Dept Clin Sci, Sch Vet Med, POB 334, Bassetere, St Kitts & Nevi Sao Paulo State Univ, Sch Agr & Vet Sci, Dept Vet Clin & Surg, Via Acesso Prof Paulo Donato Castelane S-N, BR-14884900 Jaboticabal, SP, Brazil

Objective To apply the critical incident technique (CIT) methodology to a series of perianesthetic cardiac arrest events at a university teaching hospital to describe the factors that contributed to cardiac arrest. Study design CIT qualitative analysis of a case series. Animals A group of 16 dogs and cats that suffered a perioperative cardiac arrest between November 2013 and November 2016. Methods If an arrest occurred, the event was discussed among the anesthesiologists. The discussion included a description of the case, a description of the sequence of events leading up to the arrest and a discussion of what could have been done to affect the outcome. A written description of the case and the event including animal signalment and a timeline of events was provided by the supervising anesthesiologist following discussion among the anesthesiologists. Only dogs or cats were included. After the data collection period, information from the medical record was collected. A qualitative document analysis was performed on the summaries provided about each case by the supervising anesthesiologist, the medical record and any supporting documents. Each case was then classified into one or more of the following: animal, human, equipment, drug and procedural factors for cardiac arrest. Results The most common factor was animal (n = 14), followed by human (n = 12), procedural (n = 4), drugs (n = 1) and equipment (n = 1). The majority (n = 11) of animals had multiple factors identified. Conclusions and clinical relevance Cardiac arrests during anesthesia at a referral teaching hospital were primarily a result of animal and human factors. Arrests because of procedural, drug and equipment factors were uncommon. Most animals experienced more than one factor and two animals arrested after a change in recumbency. Future work should focus on root cause analysis and interventions designed to minimize all factors, particularly human ones.

Buprenorphine is a partial μ agonist opioid used for analgesia in dogs. An extended-release formulation (ER-buprenorphine) has been shown to provide effective analgesia for 72 hr in rats and mice. Six healthy mongrel dogs were enrolled in a randomized, blinded crossover design to describe and compare the pharmacokinetics and pharmacodynamics of ER-buprenorphine administered subcutaneous at 0.2 mg/kg (ER-B) and commercially available buprenorphine for injection intravenously at 0.02 mg/kg (IV-B). After drug administration, serial blood samples were collected to measure plasma buprenorphine concentrations using liquid chromatography/mass spectrometry detection. Heart rate, respiratory rate, body temperature, sedation score, and thermal threshold latency were recorded throughout the study. Median (range) terminal half-life, time to maximum concentration, and maximum plasma concentration of ER-buprenorphine were 12.74 hr (10.43-18.84 hr), 8 hr (4-36 hr), and 5.00 ng/ml (4.29-10.98 ng/ml), respectively. Mild bradycardia, hypothermia, and inappetence were noted in both groups. Thermal threshold latency was significantly prolonged compared to baseline up to 12 hr and up to 72 hr in IV-B and ER-B, respectively. These results showed that ER-buprenorphine administered at a dose of 0.2 mg/kg resulted in prolonged and sustained plasma concentrations and antinociceptive effects up to 72 hr after drug administration.

OBJECTIVE To assess agreement between a point-of-care glucometer (POCG) and a laboratory chemistry analyzer for blood glucose measurements in goats. DESIGN Prospective study. SETTING University teaching hospital. ANIMALS Eighteen healthy adult goats. INVESTIGATIONS Whole blood samples were obtained via jugular venipuncture prior to premedication with xylazine and butorphanol (T0), following premedication (T20), and after 1 hour of inhalant anesthesia (T60). Each sample was tested with a POCG and a laboratory analyzer (HITA). Agreement was assessed using concordance correlation coefficients and calculation of bias and 95% limits of agreement. MEASUREMENTS AND MAIN RESULTS Mean blood glucose concentration at T0 was 3.9 ± 0.6 mmol/L (70 ± 10 mg/dL; POCG) and 2.9 ± 0.4 mmol/dL (53 ± 8 mg/dL; HITA). Glucose concentrations at T20 were 6.7 ± 2.4 mmol/L (121 ± 43 mg/dL) and 5.4 ± 2.1 mmol/L (97 ± 37 mg/dL) and at T60 were 5.7 ± 1.7 mmol/L (102 ± 31 mg/dL) and 4.7 ± 1.3 mmol/L (85 ± 24 mg/dL) when measured with the POCG and HITA, respectively. The POCG overestimated blood glucose compared to the HITA. The bias ± SD was 1.08 ± 0.53 mmol/L (19.4 ± 9.5 mg/dL) (95% LOA 0.04 to 2.11 mmol/L [0.7 to 38.0 mg/dL]) and the concordance correlation coefficient was 0.82. After correcting the results of the POCG using a mixed-effects linear model, the bias was 0.0 ± 0.38 mmol/L (0.0 ± 6.8 mg/dL) (95% LOA ± 0.74 mmol/L [± 13.4 mg/dL]) and the concordance correlation coefficient was 0.98. CONCLUSIONS The POCG overestimated blood glucose concentrations in goats, compared to the HITA, but when the POCG concentrations were corrected, the agreement was excellent.

OBJECTIVE To compare analgesic and gastrointestinal effects of lidocaine and buprenorphine administered to rabbits undergoing ovariohysterectomy. ANIMALS Fourteen 12-month-old female New Zealand White rabbits. PROCEDURES Rabbits were assigned to 2 treatment groups (7 rabbits/group). One group received buprenorphine (0.06 mg/kg, IV, q 8 h for 2 days), and the other received lidocaine (continuous rate infusion [CRI] at 100 μg/kg/min for 2 days). Variables, including food and water consumption, fecal output, glucose and cortisol concentrations, and behaviors while in exercise pens, were recorded. RESULTS Rabbits receiving a lidocaine CRI had significantly higher gastrointestinal motility, food intake, and fecal output and significantly lower glucose concentrations, compared with results for rabbits receiving buprenorphine. Rabbits receiving lidocaine also had a higher number of normal behaviors (eg, sprawling, traveling, and frolicking) after surgery, compared with behaviors such as crouching and sitting that were seen more commonly in rabbits receiving buprenorphine. Both groups had significant weight loss after surgery. Pain scores did not differ significantly between treatment groups. Significant decreases in heart rate and respiratory rate were observed on the day of surgery, compared with values before and after surgery. Rabbits in the lidocaine group had significantly overall lower heart rates than did rabbits in the buprenorphine group. CONCLUSIONS AND CLINICAL RELEVANCE A CRI of lidocaine to rabbits provided better postoperative outcomes with respect to fecal output, food intake, and glucose concentrations. Thus, lidocaine appeared to be a suitable alternative to buprenorphine for alleviating postoperative pain with minimal risk of anorexia and gastrointestinal ileus.

Objective To compare oxygenation and ventilation in white-tailed deer (Odocoileus virginianus) anesthetized with two treatments with and without oxygen supplementation. Study design Randomized, blinded, crossover study. Animals A total of eight healthy adult white-tailed deer weighing 49–62 kg. Methods Each deer was anesthetized twice intramuscularly: 1) treatment XK, xylazine (2 mg kg–1) and ketamine (6 mg kg–1) and 2) treatment XTZ, xylazine (2 mg kg–1) and tiletamine–zolazepam (4 mg kg–1). With the deer in sternal position, arterial and venous blood was collected before and at 30 minutes during administration of oxygen at 1 L minute–1 through a face mask. PaO2 and heart rate (HR) were compared using two-way repeated measures anova . pH, PaCO2 and lactate concentration were analyzed using mixed-effects linear models, p Results When breathing air, PaO2 was Conclusions and clinical relevance Treatments XK and XTZ resulted in hypoxemia, which responded to oxygen supplementation. Both treatments are suitable for immobilization of white-tailed deer under the study circumstances.

Green tea and its catechins have been shown to ameliorate high fat diet-induced oxidative stress and hyperlipidemia. However, low bioavailability of catechins limits their therapeutic potential. Lemon juice (LJ) has been suggested to enhance the bioavailability of catechins in vitro. This study investigated the antioxidative and hypolipidemic efficacy of a single dose of green tea extract (GTE) or GTE plus LJ (GTE + LJ) in high-fat diet fed pigs. Sixteen pigs ingested a single dose of GTE (190 mg/kg/day) or GTE + LJ (0.75 mL/kg/day) mixed with low-fat (LF, 5% fat) or high-fat (HF, 22% fat) diets and blood samples were collected for 24 h. Plasma catechin level peaked at two hours, and gradually returned to baseline after six hours following the intake. The addition of LJ significantly increased plasma catechin level. The diet containing GTE did not lower plasma cholesterol and triacylglycerol (TG) concentrations, superoxide dismutase (SOD) and catalase activity, or malondialdehyde concentration in 24 h in HF-fed pigs. Addition of a single dose of LJ, however, significantly decreased plasma TG level in LF groups but did not cause further changes on any other markers compared to the GTE alone. Our findings indicate limited effect of a single meal containing GTE on plasma antioxidant enzymes, lipid profile, and lipid peroxidation in pigs and no significant synergistic/additive action of adding LJ to GTE within 24 h in pigs. A study with a longer treatment period is warranted to further understand the potential role of GTE in reducing HF diet-induced oxidative stress and the possible synergistic role of LJ.

Objective To compare the pharmacokinetics and pharmacodynamics of hydromorphone in horses after intravenous (IV) and intramuscular (IM) administration. Study design Randomized, masked, crossover design. Animals A total of six adult horses weighing [mean ± standard deviation (SD))] 447 ± 61 kg. Methods Horses were administered three treatments with a 7 day washout. Treatments were hydromorphone 0.04 mg kg⁻1 IV with saline administered IM (H-IV), hydromorphone 0.04 mg kg⁻1 IM with saline IV (H-IM), or saline IV and IM (P). Blood was collected for hydromorphone plasma concentration at multiple time points for 24 hours after treatments. Pharmacodynamic data were collected for 24 hours after treatments. Variables included thermal nociceptive threshold, heart rate (HR), respiratory frequency (fR), rectal temperature, and fecal weight. Data were analyzed using mixed-effects linear models. A p value of less than 0.05 was considered statistically significant. Results The mean ± SD hydromorphone terminal half-life (t1/2), clearance and volume of distribution of H-IV were 19 ± 8 minutes, 79 ± 12.9 mL minute⁻1 kg⁻1 and 1125 ± 309 mL kg⁻1. The t1/2 was 26.7 ± 9.25 minutes for H-IM. Area under the curve was 518 ± 87.5 and 1128 ± 810 minute ng mL⁻1 for H-IV and H-IM, respectively. The IM bioavailability was 217%. The overall thermal thresholds for both H-IV and H-IM were significantly greater than P (p Conclusions and clinical relevance IM hydromorphone has high bioavailability and provides a similar degree of antinociception to IV administration. IM hydromorphone in horses provides a similar degree and duration of antinociception to IV administration.

OBJECTIVE To determine the minimum alveolar concentration that blunts adrenergic responses (MACBAR) for isoflurane and evaluate effects of fentanyl on isoflurane MACBAR in sheep. ANIMALS 13 healthy adult Dorset-cross adult ewes. PROCEDURES In a crossover design, each ewe was anesthetized 2 times for determination of isoflurane MACBAR. Anesthesia was induced with propofol administered IV. Sheep initially received fentanyl (5 μg/kg, IV, followed by a constant rate infusion of 5 μg/kg/h) or an equivalent volume of saline (0.9% NaCl) solution (control treatment). After a washout period of at least 8 days, the other treatment was administered. For MACBAR determination, a mechanical nociceptive stimulus (ie, sponge forceps) was applied at the coronary band for 1 minute. The MACBAR values of the 2 treatments were compared by means of a paired t test. During MACBAR determination, blood samples were collected for measurement of plasma fentanyl concentration. RESULTS Mean ± SD isoflurane MACBAR of the fentanyl and control treatments was 1.70 ± 0.28% and 1.79 ± 0.35%, respectively; no significant difference was found between the 2 treatments. Plasma concentration of fentanyl reached a median steady-state concentration of 1.69 ng/mL (interquartile range [25th to 75th percentile], 1.47 to 1.79 ng/mL), which was maintained throughout the study. CONCLUSIONS AND CLINICAL RELEVANCE Administration of fentanyl at 5 μg/kg, IV, followed by a constant rate infusion of the drug at 5 μg/kg/h did not decrease isoflurane MACBAR. Further studies to determine the effect of higher doses of fentanyl on inhalation anesthetic agents and their potential adverse effects are warranted. (Am J Vet Res 2016;77:119–126)

The purpose of this study is to evaluate the accuracy of an oscillometric blood pressure monitor in anesthetized pigs. Invasive blood pressure (IBP) and noninvasive blood pressure (NIBP) measurements were taken using a DRE Waveline Pro multiparameter monitor at four different time points in 17 pigs undergoing injectable anesthesia. NIBP measurements were taken on both the thoracic and pelvic limbs. Bland Altman analysis was used to assess agreement between methods and a linear mixed-effects model was used to evaluate the effect of cuff position and blood pressure on bias. Invasive systolic arterial pressure (SAP) ranged between 112 and 161 mmHg (mean ± SD: 138.8 ± 13.3; median: 139.5). Invasive diastolic arterial pressure (DAP) ranged between 60 and 104 mmHg (mean ± SD: 86.0 ± 9.1; median: 87.0). Invasive mean arterial pressure (MAP) ranged between 79 and 121 mmHg (mean ± SD: 103.2 ± 9.3; median 103.0). Only the diastolic and mean measurements obtained from the pelvic limb met criteria outlined by the American College of Internal Medicine for required accuracy of NIBP monitors. Bias was significantly higher in the thoracic limb in comparison to the pelvic limb and was significantly higher at blood pressures above median. In general, NIBP measurements underestimated IBP measurements. In conclusion, the use of the DRE Waveline Pro to assess NIBP in anesthetized pigs may be useful in monitoring trends in mean and diastolic blood pressure and is most accurate when used on the pelvic limb.

To determine the levels of agreement among first- and second-year veterinary students and experienced anesthesiologists in assessing postoperative pain in dogs from video-recordings.Cross-sectional study.Twenty-seven veterinary students, five anesthesiologists and 13 canine clinical patients.Prior to their enrolment in a core anesthesia course, veterinary students volunteered to watch 13 90 second videos of dogs. Dogs were hospitalized in an intensive care unit after a variety of surgical procedures. Students were asked to score the level of the dogs' pain using the Dynamic Interactive Visual Analog Scale and the Short Form of the Glasgow Composite-Measure Pain Scale. The same videotapes were scored by five board-certified anesthesiologists. The differences and agreement between the ratings of anesthesiologists and students, and first- and second-year students were determined with Mann-Whitney U-tests and Fleiss' or Cohen's kappa, respectively.Pain scores assigned by students and anesthesiologists differed significantly (p0.01). Students assigned higher pain scores to dogs that were given low pain scores by anesthesiologists, and lower pain scores to dogs deemed to be in more pain by anesthesiologists. On average, students assigned higher scores on both scales.Veterinary students early in their training assigned pain scores to dogs that differed from scores assigned by experienced anesthesiologists.

Minimum alveolar concentration (MAC) is a reliable measurement of the potency of inhaled anesthetic agents. The determination of MAC in different species has followed a fairly consistent methodology. In people, MAC is determined with the up-and-down method, whereas in animal the bracketing technique is commonly used. The objectives of this study were to determine the MAC value of isoflurane in dogs and cats using the up-and-down method and to determine the MAC value of isoflurane at extubation (MACex). General anesthesia was induced in 13 dogs and 5 cats with 5% isoflurane in oxygen. An initial end-tidal isoflurane concentration of 1.3% was used for the first dog and of 1.6% for the first cat and maintained constant for ≥20min. A noxious stimulus in the form of Carmalt forceps was applied to the base of the tail for no more than one minute or until movement was noticed. After stimulation, the response was recorded as positive (movement) or negative (no movement) and the animal was recovered. The end-tidal isoflurane concentration of the following animal was increased or decreased by 0.1% if the response of the previous animal to the stimulus was negative or positive, respectively. Isoflurane MAC values in dogs were 1.27% and 1.23%. Isoflurane MAC value in cats was 1.58%. MACex value was 0.45% in dogs and in cats. The up-and-down method for MAC determination achieved similar results when compared to MAC values of isoflurane in dogs and cats reported in the literature using the bracketing technique.

Objective To compare the effect of propofol and ketamine/diazepam for induction following premedication on intraocular pressure (IOP) in healthy dogs. Study design Prospective, quasi-experimental, unmasked, longitudinal. Animals A total of 61 client-owned dogs. Methods Dogs were anesthetized twice with a 4 week washout period. Premedication with dexmedetomidine (5 μg kg–1) and hydromorphone (0.1 mg kg–1) intramuscularly was followed by either propofol (4 mg kg–1) or ketamine (5 mg kg–1) and diazepam (0.25 mg kg–1) intravenously for induction and inhaled isoflurane for maintenance. IOP was measured by applanation tonometry using TonoPen-XL before premedication and after 5, 10, 20 and 30 minutes. IOP was measured again immediately after induction and after 3, 5, 10, 15, 20, 30 and 40 minutes. Data were analyzed using one- or two-way repeated measures ANOVA. Results No difference was found between right and left IOP (p = 0.45), and data from both the eyes of each dog were averaged and considered as one set of data. Following premedication, IOP was significantly lower at all time points than at baseline when animals were grouped together, mean difference –1.6 ± 0.2 mmHg (p Conclusions and clinical relevance Sedation with hydromorphone and dexmedetomidine significantly decreased IOP in normal dogs and may be an appropriate choice for dogs that cannot tolerate acute increases in IOP. However, IOP increased significantly after both induction protocols, abolishing the effect of premedication.

Objective To establish evidence for the validity and reliability of three commonly used pain scales in dogs when assessed by video by specialists in anesthesia. Study design Mixed-method test–retest observational study. Subjects A group of six American College of Veterinary Anesthesia and Analgesia board-certified specialists and 31 postoperative dogs. Methods The evaluators scored 31 dogs using a visual analogue scale (VAS), numeric rating scale (NRS), and Glasgow pain scale (GPS). The evaluators individually scored the dogs using all three scales together and subsequently, at 3 month intervals, using each of the scales apart. Then, all evaluators in one room reviewed 23 of the videos. A camera was positioned for video and audio recording of discussion about the videos. Intra- and interobserver reliability was determined using a two-way random model intra-class correlation coefficient (ICC). Results Linear regression indicated a strong correlation among all scales when assigned together (VAS versus NRS, p Conclusions and clinical relevance The preferred use of the VAS and NRS over the use of the GPS should be cautiously considered for research applications when experts are observers. Revisions of the GPS to clarify descriptors and remove or modify items that may not be associated with pain in dogs should be considered.

The purpose of this study was to determine if dexmedetomidine administered IV prior to euthanasia in sheep affected the speed or quality of euthanasia. Twenty clinically healthy Dorset-cross adult ewes between 1 and 3years of age were enrolled in a randomized blinded experimental trial. The subjects were randomly assigned to receive dexmedetomidine 5μg/kg IV or an equivalent volume of saline. Five minutes later, euthanasia was accomplished with a pentobarbital/phenytoin overdose given IV. The time to apnea, asystole, cessation of audible heartbeat, and absence of corneal reflex were recorded by two blinded investigators. If any muscle spasms, contractions, vocalization, and/or dysrhythmias were noted, the time was recorded and type of ECG abnormality was described. An overall score of the euthanasia event was assigned using a numeric rating scale (NRS) after the animal was declared dead. The time to loss of corneal reflex was significantly longer in sheep given dexmedetomidine compared with those who received saline (P=0.03). Although vocalization was observed only in some animals premedicated with dexmedetomidine, no significance was found for this event and no other significant differences between groups were noted. Dexmedetomidine at 5μg/kg IV 5min prior to injection of pentobarbital/phenytoin for euthanasia did not substantially affect the progress of euthanasia. Dexmedetomidine may be given to sedate sheep prior to euthanasia without concern for it adversely affecting the progress of euthanasia, however vocalization may occur.

OBJECTIVE To compare the doses of propofol required to induce general anesthesia in dogs premedicated with acepromazine maleate or trazodone hydrochloride and compare the effects of these premedicants on cardiovascular variables in dogs anesthetized for orthopedic surgery. DESIGN Prospective, randomized study. ANIMALS 30 systemically healthy client-owned dogs. PROCEDURES 15 dogs received acepromazine (0.01 to 0.03 mg/kg [0.005 to 0.014 mg/lb], IM) 30 minutes before anesthetic induction and 15 received trazodone (5 mg/kg [2.27 mg/lb] for patients > 10 kg or 7 mg/kg [3.18 mg/lb] for patients ≤ 10 kg, PO) 2 hours before induction. Both groups received morphine sulfate (1 mg/kg [0.45 mg/lb], IM) 30 minutes before induction. Anesthesia was induced with propofol (4 to 6 mg/kg [1.82 to 2.73 mg/lb], IV, to effect) and maintained with isoflurane or sevoflurane in oxygen. Bupivacaine (0.5 mg/kg [0.227 mg/lb]) and morphine (0.1 mg/kg [0.045 mg/lb]) were administered epidurally. Dogs underwent tibial plateau leveling osteotomy (n = 22) or tibial tuberosity advancement (8) and were monitored throughout anesthesia. Propofol induction doses and cardiovascular variables (heart rate and systemic, mean, and diastolic arterial blood pressures) were compared between groups. RESULTS The mean dose of propofol required for anesthetic induction and all cardiovascular variables evaluated did not differ between groups. Intraoperative hypotension developed in 6 and 5 dogs of the acepromazine and trazodone groups, respectively; bradycardia requiring intervention developed in 3 dogs/group. One dog that received trazodone had priapism 24 hours later and was treated successfully. No other adverse effects were reported. CONCLUSIONS AND CLINICAL RELEVANCE At the described dosages, cardiovascular effects of trazodone were similar to those of acepromazine in healthy dogs undergoing anesthesia for orthopedic surgery.

Monitoring blood pressure under general anesthesia in animals is important to prevent hypotension and poor tissue perfusion. Thirteen sheep were enrolled to evaluate the accuracy of the petMAP, a portable non-invasive blood pressure (NIBP) monitor. Animals were anesthetized with midazolam, fentanyl, ketamine, propofol and maintained with isoflurane in oxygen for ovariectomy. Invasive and non-invasive (petMAP) blood pressure measurements were recorded simultaneously every 5 minutes. Agreement between IBP and NIBP was assessed by evaluation of bias and 95% limits of agreement (LOA) using the Bland-Altman method and correlation coefficient. None of the measurements met the criteria for good agreement between invasive and non-invasive readings established by the Association for the Advancement of Medical Instrumentation. Systolic blood pressure readings obtained at the left thoracic limb site and mean blood pressure at the right pelvic limb site met the bias and LOA criteria established by the American College of Veterinary Internal Medicine.

To determine the impact of intraoperative anesthetic variables on the length of hospitalization, cost of care and mortality in dogs.Retrospective, observational study.A total of 235 dogs undergoing general anesthesia.Medical records of dogs undergoing general anesthesia between 2007 and 2014 at the University of Georgia Veterinary Teaching Hospital were reviewed. Data collected included demographic data, American Society of Anesthesiologists (ASA) physical status, type and duration of anesthesia, hemodynamic variables, temperature, ventilation, fluid therapy and adjunctive drugs administered. Outcome variables were length of hospitalization in the intensive care unit (ICU), hospital charges and survival to discharge.The only factor significantly associated with duration of ICU care was higher ASA status (p0.0001). Factors associated with increased cost of hospitalization were ICU duration (p0.0001), anesthesia duration (p0.0001), hemorrhage amount (p0.0001), colloid use (p=0.0081), increased age (p=0.0253), increased weight (p = 0.0293) and presence of hypertension (p=0.0179). Overall mortality rate was 5.1%. The only factors negatively associated with survival were the administration of colloids (p0.0008) and ASA status (p=0.0314).Several intrinsic patient factors and intraoperative hemodynamic variables were significantly associated with postoperative morbidity and mortality in dogs. These factors might have prognostic value in conjunction with preoperative risk assessment, and patient outcome may be improved by stricter intraoperative control of these variables.

Objective—To compare the efficacy of preoperative administration of buprenorphine (via oral transmucosal [OTM] and IV routes) for postoperative analgesia in dogs undergoing ovariohysterectomy. Design—Prospective, randomized, blinded study. Animals—18 dogs undergoing routine ovariohysterectomy. Procedures—Dogs were allocated to 3 groups (6 dogs/group) and were assigned to receive buprenorphine (20 μg/kg [9.09 μg/lb], IV; a low dose [20 μg/kg] via OTM administration [LOTM]; or a high dose [120 μg/kg [54.54 μg/lb] via OTM administration [HOTM]) immediately before anesthetic induction with propofol and maintenance with isoflurane for ovariohysterectomy. Postoperative pain was assessed by use of a dynamic interactive pain scale. Dogs were provided rescue analgesia when postoperative pain exceeded a predetermined threshold. Blood samples were collected, and liquid chromatography-electrospray ionization-tandem mass spectrometry was used to determine plasma concentrations of buprenorphine and its metabolites. Data were analyzed with an ANOVA. Results—Body weight, surgical duration, propofol dose, isoflurane concentration, and cardiorespiratory variables did not differ significantly among treatment groups. Number of dogs requiring rescue analgesia did not differ significantly for the HOTM (1/6), IV (3/6), and LOTM (5/6) treatments. Similarly, mean ± SEM duration of analgesia did not differ significantly for the HOTM (20.3 ± 3.7 hours), IV (16.0 ± 3.8 hours), and LOTM (7.3 ± 3.3 hours) treatments. Plasma buprenorphine concentration was ≤ 0.60 ng/mL in 7 of 9 dogs requiring rescue analgesia. Conclusions and Clinical Relevance—Buprenorphine (HOTM) given immediately before anesthetic induction can be an alternative for postoperative pain management in dogs undergoing ovariohysterectomy.

Endotracheal intubation has been associated with several complications in cats. The v-gel supraglottic airway device (SGAD) has been developed to adapt to the unique oropharynx of the cat and to overcome these complications. Thirty-three cats were randomly assigned to receive an endotracheal tube (ETT group) or a v-gel SGAD (v-gel group) after induction of general anaesthesia. Third year veterinary students without previous clinical experience placed these devices under direct supervision of an anaesthesiologist. Amount of propofol, number of attempts, time required to secure the airway, leakage around the device, signs of upper airway discomfort and food consumption were compared between the two groups. The v-gel group required less propofol (P=0.03), less time (P0.01) and fewer attempts (P0.01) to secure the cats' airway. The incidence of leakage was lower for the v-gel group immediately after placement of the device (P0.01) and 60 minutes after induction of general anaesthesia (P=0.04). Cats that received the v-gel SGAD presented a lower incidence of upper airway discomfort immediately after the device was removed (P=0.03) and recorded a higher food consumption score (P=0.03). The v-gel SGAD is a feasible way to secure the airway of healthy cats when performed by inexperienced personnel.

The objectives of this study were to determine if Doppler (DOP) blood pressure measurements more closely estimate either invasive systolic or invasive mean arterial blood pressures (ISAP or IMAP, respectively) in small dogs under general anesthesia and to assess the ability of DOP to detect anesthesia-related hypotension in small dogs. Blood pressure measurements (n = 203) were obtained from 10 client-owned dogs. DOP, ISAP, and IMAP were recorded simultaneously, and the data were categorized into two groups: hypotensive (ISAP

Objective—To compare the cardiorespiratory effects of IM administration of dexmedetomidine-buprenorphine (DB) and dexmedetomidine-buprenorphine-ketamine (DBK) in dogs with subsequent reversal with atipamezole. Design—Prospective, randomized crossover study. Animals—5 healthy dogs. Procedures—Dogs were instrumented for cardiac output (CO) measurement and received DB (15 μg of dexmedetomidine/kg [6.8 μg/lb] and 40 μg of buprenorphine/kg [18.2 μg/lb]) or DBK (DB plus 3 mg of ketamine/kg [1.36 mg/lb]) in randomized order while breathing room air. Atipamezole (150 μg/kg [68.2 μg/lb], IM) was administered 1 hour later. Hemodynamic data were collected in the conscious dogs and then at 5, 10, 15, 20, 30, 45, and 60 minutes after drug administration. Lactate concentration was measured in mixed venous blood samples. Oxygen delivery (Do2) and oxygen consumption (o2) were calculated. Results—Heart rate (HR), CO, and Do2 decreased after DB and DBK administration. The o2 did not change in the DB group but decreased in the DBK group. The HR was higher in the DBK group than in the DB group throughout the study, but the CO, Do2, and o2 values were similar for the 2 groups. Blood lactate concentrations remained low (< 1 mmol/L) throughout the study. Arterial hypoxemia and hypercapnea occurred in both groups. Mean arterial blood pressure and pulmonary artery wedge pressure were markedly increased in both groups, but to a greater extent in the DBK group. After atipamezole administration, HR, CO, and Do2 returned to the baseline values. Conclusions and Clinical Relevance—Adding ketamine to the DB combination allowed dogs to maintain a higher HR and delayed the onset of sinus arrhythmias but failed to provide a significantly higher CO because of a reduction in stroke volume.

Objective To determine if lactate concentrations in jugular venous and auricular arterial blood differ in anesthetized sheep. Study design Prospective, controlled experimental study. Animals Twelve healthy adult ewes, 4–7 years and weighing 62–77 kg. Methods Jugular venous blood was collected before anesthesia (PreO v ) for measurement of lactate concentration, packed cell volume and total protein. Ewes were administered a standard anesthesia protocol. Jugular venous (IntraO v ) and auricular arterial (IntraO a ) blood samples were obtained 40 minutes after induction of anesthesia, and again in recovery (PostO v and PostO a ). An additional blood sample was drawn 6 weeks post-operatively from non-fasted sheep (NF_Lact). Lactate concentrations were compared among PreO v , IntraO v and IntraO a , PostO v and PostO a , and between PreO v and NF_Lact with paired t-test and repeated measure analyses of variance ( anova ) with PreO v as a covariate ( p = 0.05). Results IntraO v lactate concentration had decreased from PreO v There were significant differences between arterial and venous IntraO and PostO lactate concentrations. There was no significant difference between IntraO and PostO, or PreO v and NF_Lact. Conclusions and clinical relevance Lactate concentrations were significantly lower in anesthetized sheep compared to non-anesthetized sheep. Lactate concentrations in venous blood were higher than in arterial blood. Therefore, anesthetic status and sampling site should be considered when interpreting lactate concentrations, and the sampling site should be consistent for repeated measurements.

Objective—To compare the efficacy and cardiorespiratory effects of dexmedetomidine-ketamine in combination with butorphanol, hydromorphone, or buprenorphine with or without reversal by atipamezole in cats undergoing castration. Design—Prospective, randomized, split-plot, blinded study. Animals—30 healthy male cats. Procedures—Cats were assigned to receive dexmedetomidine (25 μg/kg [11.4 μg/lb]) and ketamine (3 mg/kg [1.4 mg/lb]) with butorphanol (0.2 mg/kg [0.09 mg/lb]; DKBut; n = 10), hydromorphone (0.05 mg/kg [0.023 mg/lb]; DKH; 10), or buprenorphine (30 μg/kg [13.6 μg/lb]; DKBup; 10). Drugs were administered as a single IM injection. Supplemental isoflurane was administered to cats if the level of anesthesia was inadequate for surgery. At the conclusion of surgery, half the cats (5 cats in each treatment group) received atipamezole (250 μg/kg [113.6 μg/lb], IM) and the remainder received saline (0.9% NaCl) solution IM. All cats received meloxicam (0.2 mg/kg, SC) immediately prior to the conclusion of surgery. Results—All drug combinations induced lateral recumbency, and intubation was achievable in 13 of 30 (43%) cats at 10 minutes after injection. Supplemental isoflurane was needed for the surgery in 1 of 10 of the DKBut-, 2 of 10 of the DKH-, and 7 of 10 of the DKBup-treated cats. Cats that received atipamezole had a significantly shorter recovery time. Conclusions and Clinical Relevance—DKBut and DKH combinations were suitable injectable anesthetic protocols for castration in cats commencing at 10 minutes after injection, but cats receiving DKBup may require additional time or anesthetics for adequate anesthesia.

Objective—To compare efficacy and cardiorespiratory effects of dexmedetomidine and ketamine in combination with butorphanol, hydromorphone, or buprenorphine (with or without reversal by atipamezole) in dogs undergoing castration. Design—Prospective, randomized, split-plot, blinded study. Animals—30 healthy client-owned sexually intact male dogs. Procedures—Dogs (n = 10 dogs/group) were assigned to receive dexmedetomidine (15 μg/kg [6.82 μg/lb]) and ketamine (3 mg/kg [1.36 mg/lb]) with butorphanol (0.2 mg/kg [0.09 mg/lb]; DKBut), the same dosages of dexmedetomidine and ketamine with hydromorphone (0.05 mg/kg [0.023 mg/lb]; DKH), or the same dosages of dexmedetomidine and ketamine with buprenorphine (40 μg/kg [18.18 μg/lb]; DKBup). All drugs were administered as a single IM injection for induction and maintenance of anesthesia for castration. At conclusion of the surgery, 5 dogs in each treatment group received atipamezole (150 μg/kg [68.18 μg/lb], IM), and the remainder received saline (0.9% NaCl) solution IM. Cardiorespiratory variables and quality of anesthesia were assessed. Supplemental isoflurane was administered to the dogs when anesthesia was considered inadequate during surgery. Results—All drug combinations rapidly induced anesthesia. Dogs were intubated within 10 minutes after injection. Supplemental isoflurane was needed during surgery in 1, 3, and 4 dogs in the DKBup, DKBut, and DKH groups, respectively. Dogs that received atipamezole had a significantly shorter recovery time. Some dogs in each group had bradycardia and hypoxemia with hypertension. Conclusions and Clinical Relevance—DKBup was the most suitable injectable anesthetic combination used. Recovery was shortened by IM administration of atipamezole. There were minimal adverse effects in all groups.