Post-anesthetic CPS and EQUUS-FAP scores in surgical and non-surgical equine patients: an observational study.

Background: Equine pain scoring may be affected by the residual effect of anesthetic drugs. Objectives: To compare pain scores in the hours immediately following anesthetic recovery to baseline pre-anesthetic scores in equine patients undergoing surgical and non-surgical procedures. Study design: Clinical observational study. Methods: Fifty adult horses undergoing anesthesia for surgical or non-surgical procedures were enrolled. Horses underwent pain scoring using the Composite Pain Score (CPS) and Equine Utrecht University Scale for Facial Assessment of Pain (EQUUS-FAP) prior to anesthesia (T0) and following anesthetic recovery to standing, every hour for 5 h (T1-T5). Data were analyzed using a generalized linear mixed effects model. A post-hoc Dunnett's test for multiple comparisons was performed for variables where an effect was detected. Results: Mean (95% confidence interval) CPS scores for T0-T5 were 1.6 (1.2-2.0), 6.8 (6.0-7.6), 5.1 (4.3-5.9), 4.3 (3.4-5.2), 3.7 (2.8-4.6), and 2.8 (2.0-3.6) and EQUUS-FAP scores were 0.6 (0.3-0.9), 3.0 (2.5-3.5), 1.9 (1.6-2.2), 1.1 (0.8-1.4), 0.6 (0.4-0.8), and 0.7 (0.4-1.0), respectively. For the CPS, scores greater than 5, and for the EQUUS-FAP scores greater than 3, are consistent with minor pain. There was no effect of type of procedure (surgical vs non-surgical) on CPS or EQUUS-FAP scores. There was an effect of time with CPS scores significantly greater than baseline at T1-T5 and EQUUS-FAP scores significantly greater than baseline at T1 and T2. Main limitations: Discomfort caused by hoisting was not quantified and it was difficult to ascertain if this affected the results. Conclusions: Post-anesthetic pain scores may be influenced by the residual effect of anesthetic agents for as long as 5 h and 2 h for the CPS and EQUUS-FAP, respectively.

The effect of adding a heated humidified breathing circuit on body temperature in healthy anesthetized dogs.

OBJECTIVE: To compare the effect of a circulating warm water blanket (WWB) in combination with a heated humidified breathing circuit (HHBC) heated to 45 °C on rectal temperature (RT) in dogs undergoing general anesthesia for elective ovariohysterectomies. ANIMALS: 29 healthy dogs. PROCEDURES: Dogs in the experimental group (n = 8) and dogs in the control group (21) were connected to an HHBC and a conventional rebreathing circuit, respectively. All dogs were placed on a WWB in the operating room (OR). The RT was recorded at baseline, premedication, induction, transfer to OR, every 15 minutes during maintenance of anesthesia, and extubation. Incidence of hypothermia (RT < 37 °C) at extubation was recorded. Data were analyzed using unpaired t tests, the Fisher exact test, and mixed-effect ANOVA. Statistical significance was defined as P < .05. RESULTS: There was no difference in RT during baseline, premedication, induction, and transfer to OR. The overall RT was higher for the HHBC group during anesthesia (P = .005) and at extubation (37.7 ± 0.6 °C) compared with the control group (36.6 ± 1.0 °C; P = .006). The incidence of hypothermia at extubation was 12.5% for the HHBC group and 66.7% for the control group (P = .014). CLINICAL RELEVANCE: The combination of HHBC and WWB can reduce the incidence of postanesthetic hypothermia in dogs. Use of an HHBC should be considered in veterinary patients.

Anesthesia for the dog with heartworm disease: a brief, practical review.

Dogs with heartworm disease may present for procedures that require anesthesia. This article is a brief, practical review of anesthetic techniques for dogs with heartworm. Dogs with heartworm, such as in a shelter that undergo spay and neuter procedures, may be safely anesthetized prior to heartworm treatment. The dog presenting with caval syndrome may require emergent anesthesia for extraction of the heartworms; anesthetic drugs and potential adverse effects are discussed. The anesthetic agents that have been used are discussed.

Antinociceptive effects of bupivacaine injected within the internal abdominis rectus sheath in standing healthy horses.

OBJECTIVE: To evaluate a regional anesthetic technique for blocking the abdominal midline in horses. STUDY DESIGN: Anatomical description and prospective, crossover, placebo-controlled, blinded study. ANIMALS: Adult horses; two cadavers, six healthy animals. METHODS: In stage 1, 0.5% methylene blue with 0.25% bupivacaine (0.5 mL kg-1) was injected using ultrasonography into the internal rectus abdominis sheath (RAS) of two cadavers with a one-point or two-point technique. The dye spread was described after the dissection of the abdomens. In stage 2, each horse was injected with 1 mL kg-1 of 0.9% NaCl (treatment PT) or 0.2% bupivacaine (treatment BT) using a two-point technique. The abdominal midline mechanical nociceptive threshold (MNT) was measured with a 1 mm blunted probe tip and results analyzed with mixed-effect anova. Signs of pelvic limb weakness were recorded. RESULTS: The cadaver dissections showed staining of the ventral branches from the eleventh thoracic (T11) to the second lumbar (L2) nerve with the one-point technique and T9-L2 with the two-point technique. Baseline MNTs were, mean ± standard deviation, 12.6 ± 1.6 N and 12.4 ± 2.4 N in treatments PT and BT, respectively. MNT increased to 18.9 ± 5.8 N (p = 0.010) at 30 minutes, and MNT was between 9.4 ± 2.0 and 15.3 ± 3.4 N from 1 to 8 hours (p > 0.521) in treatment PT. MNTs in treatment BT were 21.1 ± 5.9 to 25.0 ± 0.1 N from 30 minutes to 8 hours (p < 0.001). MNTs after the RAS injections were higher in treatment BT than PT (p = 0.007). No pelvic limb weakness was observed. CONCLUSIONS AND CLINICAL RELEVANCE: Antinociception of at least 8 hours without pelvic limb weakness was observed in the abdominal midline in standing horses after the RAS block. Further investigations are necessary to evaluate suitability for ventral celiotomies.

Retrospective assessment of general anesthesia-related challenges, morbidity, and death in snakes: 139 cases (2000-2022).

OBJECTIVE: To summarize the anesthetic events of snakes seen at a large university hospital, identify challenges with record keeping, and assess patient and anesthesia-related morbidity and death. SAMPLE: 139 anesthetic events were performed; only 106 cases had detailed anesthetic reports available for further analyses. PROCEDURES: Medical records of snakes that underwent general anesthesia between October 2000 and January 2022 were retrospectively reviewed. Only cases with complete anesthesia records were used to assess anesthetic parameters. Collected data included general patient details, diagnoses, procedures, premedication, induction, maintenance, monitoring, and recovery. RESULTS: A thorough review of the records identified issues or scenarios that resulted in poor record management as well as highlighted the most frequently used anesthetics in snakes. For premedication this was alfaxalone, butorphanol, and hydromorphone, whereas isoflurane, alfaxalone, or propofol were the most common with induction. Lastly, with maintenance, isoflurane was the most popular choice. Of the 139 cases performed, 127 animals recovered, 8 were euthanatized due to poor prognosis, and 4 failed to recover. All snakes that failed to recover had preexisting disease identified pre-, peri-, or postoperatively at necropsy. CLINICAL RELEVANCE: General anesthesia can be reliably and safely undertaken in snakes without severe preexisting disease. Efforts should be directed at identifying preexisting disease and maintaining and completing anesthesia records, and we recommend an auditing system to identify and correct issues as they arise.

Development of the Auburn Induction Scale for evaluating induction quality in dogs.

OBJECTIVE: To develop and begin establishing evidence for validity of an instrument to assess the quality of induction in dogs. STUDY DESIGN: Cross-sectional survey and video scoring. ANIMALS AND POPULATION: A total of 51 veterinary anesthesia personnel, four board-certified anesthesiologists and videos of induction of anesthesia in 18 dogs. METHODS: In Part 1, an online survey was sent to veterinary anesthesia personnel to solicit expressions and words that they associate with induction of anesthesia. These expressions were evaluated by four anesthesiologists to create a composite scale (Auburn Induction Scale). In Part 2, 18 videos were reviewed by the same four anesthesiologists on two separate occasions. The videos were scored using the Auburn Induction Scale, a simple descriptive scale (SDS) and a visual analog scale (VAS). Intra-rater and inter-rater reliability was measured using an intraclass correlation coefficient (ICC). Significance was set at p < 0.05. RESULTS: The survey yielded 51 responses that were condensed into 133 expressions. The four anesthesiologists created 18 items incorporating the 133 expressions. The mean ± standard deviation intra-rater reliability ICC was 0.81 ± 0.08 for the Auburn Induction Scale, 0.71 ± 0.02 for the SDS and 0.71 ± 0.08 for the VAS for all raters. The mean ± standard deviation inter-rater reliability ICC was 0.69 ± 0.04 for the Auburn Induction Scale, 0.61 ± 0.05 for the SDS and 0.60 ± 0.06 for the VAS. CONCLUSIONS AND CLINICAL RELEVANCE: In a research setting, widespread use of this scale may be helpful in increasing the accuracy of data and improving agreement between studies assessing induction of anesthesia in dogs. The results of this study have yielded a composite scale that is more reliable between and among raters than a unidimensional scale.

Comparison of hydromorphone and butorphanol for management of pain in equine patients undergoing elective arthroscopy: a randomized clinical trial.

OBJECTIVE: To compare the effects of hydromorphone and butorphanol in horses undergoing arthroscopy and describe the pharmacokinetics of hydromorphone in anesthetized horses. STUDY DESIGN: Randomized controlled clinical trial. ANIMALS: A total of 40 adult horses admitted for elective arthroscopy. METHODS: Horses were randomly assigned to be administered intravenous hydromorphone (0.04 mg kg-1; group TxH; n = 19) or butorphanol (0.02 mg kg-1; group TxB; n = 21) prior to surgery as part of a standardized anesthetic protocol. Pain was scored by two observers unaware of group assignment using the Equine Utrecht University Scale for Facial Assessment of Pain (EQUUS-FAP) and a composite pain scale (CPS) prior to surgery (baseline), 2 hours (P2) and 4 hours (P4) following recovery from anesthesia. Blood samples were collected at various time points for determination of plasma hydromorphone concentration using liquid chromatography-tandem mass spectrometry. Data were analyzed with a mixed-effect model. RESULTS: Median (range) baseline EQUUS-FAP was 1.2 (0.0-4.0) with no effect of group, time points or interaction. Baseline CPS was similar between groups. Group TxH baseline CPS was 2.5 (0.0-10.0), increased at P2 [4.5 (0-10.0); p = 0.046] and returned to baseline values at P4 [3.0 (0.0-11.0)]. Group TxB baseline CPS was 2.0 (0.0-8.0), increased at P2 [3.5 (0.0-11.0); p = 0.009] and P4 [5.0 (0.0-11.0); p < 0.001]. Pharmacokinetic terminal half-life was 774 ± 82.3 minutes, area under the curve was 1362 ± 314 ng minutes mL-1, clearance was 30.7 ± 7.23 mL minute-1 kg-1 and volume of distribution at steady state was 884 ± 740 mL kg-1. CONCLUSIONS: Hydromorphone, but not butorphanol, decreased CPS back to baseline at P4 after recovery. CLINICAL RELEVANCE: Hydromorphone may provide superior postoperative analgesia compared with butorphanol in horses undergoing arthroscopy.

The effect of a ketamine constant rate infusion on cardiovascular variables in sheep anesthetized at the minimum alveolar concentration of sevoflurane that blunts adrenergic responses.

OBJECTIVE: To evaluate the effect of a constant rate infusion of ketamine on cardiac index (CI) in sheep, as estimated using noninvasive cardiac output (NICO) monitoring by partial carbon dioxide rebreathing, when anesthetized with sevoflurane at the previously determined minimum alveolar concentration that blunts adrenergic responses (MACBAR). ANIMALS: 12 healthy Dorset-crossbred adult sheep. PROCEDURES: Sheep were anesthetized 2 times in a balanced placebo-controlled crossover design. Anesthesia was induced with sevoflurane delivered via a tight-fitting face mask and maintained at MACBAR. Following induction, sheep received either ketamine (1.5 mg/kg IV, followed by a constant rate infusion of 1.5 mg/kg/h) or an equivalent volume of saline (0.9% NaCl) solution (placebo). After an 8-day washout period, each sheep received the alternate treatment. NICO measurements were performed in triplicate 20 minutes after treatment administration and were converted to CI. Blood samples were collected prior to the start of NICO measurements for analysis of ketamine plasma concentrations. The paired t test was used to compare CI values between groups and the ketamine plasma concentrations with those achieved during the previous study. RESULTS: Mean ± SD CI of the ketamine and placebo treatments were 2.69 ± 0.65 and 2.57 ± 0.53 L/min/m2, respectively. No significant difference was found between the 2 treatments. Mean ketamine plasma concentration achieved prior to the NICO measurement was 1.37 ± 0.58 µg/mL, with no significant difference observed between the current and prior study. CLINICAL RELEVANCE: Ketamine, at the dose administered, did not significantly increase the CI in sheep when determined by partial carbon dioxide rebreathing.

The pharmacokinetics of a fentanyl matrix patch applied at three different anatomical locations in horses.

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.

Influence of doxapram and intermittent 10% carbon dioxide inspiration on cardiovascular and laryngeal functions in anesthetized dogs.

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 < .001 compared to I-CO2 ), and persisted during the other stimulations (both p < .001). An intermittent tachycardic effect of up to 79% increase in HR was observed with doxapram. The HR following H-DOX was higher than L-DOX and I-CO2 (both p < .016). Neither hypertension nor tachycardia was observed with I-CO2 . The iNGGA increased with all treatments (p < .001). The iNGGA was greater with H-DOX than L-DOX and I-CO2 (both p < .007). All treatments received higher scores (all p < .001) with acceptable inter- and intra-observers Krippendorff's alphas. CONCLUSION: All treatments were effective respiratory stimulants in anesthetized dogs; however, doxapram caused hypertension and tachycardia. CLINICAL SIGNIFICANCE: Carbon dioxide inhalation might improve arytenoid motion without cardiovascular effects in dogs during clinical airway examinations.

Physiologic and blood gas effects of xylazine-ketamine versus xylazine-tiletamine-zolazepam immobilization of white-tailed deer before and after oxygen supplementation: a preliminary study.

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 < 0.05. RESULTS: When breathing air, PaO2 was < 80 mmHg (10.7 kPa) in six and seven deer with XK and XTZ, respectively, and of these, PaO2 was < 60 mmHg (8.0 kPa) in three and five deer, respectively. With oxygen supplementation, PaO2 increased to 128 ± 4 and 140 ± 5 mmHg (17.1 ± 0.5 and 18.7 ± 0.7 kPa), mean ± standard error, with XK and XTZ, respectively (p < 0.001). PaO2 was not significantly different between treatments at either time point. HR decreased during oxygen supplementation in both treatments (p < 0.001). Lactate was significantly lower (p = 0.047) with XTZ than with XK (2.2 ± 0.6 versus 3.5 ± 0.6 mmol L-1) and decreased (p < 0.001) with oxygen supplementation (4.1 ± 0.6 versus 1.6 ± 0.6 mmol L-1). PaCO2 increased in XTZ during oxygen breathing. 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.

Pharmacokinetics and pharmacodynamics of methadone administered intravenously and intramuscularly to isoflurane-anesthetized chickens.

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.

Arterial oxygenation in anesthetized horses placed in a 5-degree reverse Trendelenburg position.

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 < .05. Overall, PaO2 increased in all groups; however no significant difference was found between recumbencies (dorsal, right and left lateral) and RT versus H in changes over time for PaO2 (p = .064 and p = .070, respectively), Cdyn (p = .721 and p = .672, respectively), F-shunt (p = .055 and p = .054, respectively), or VD/VT (p = .616 and p = .064, respectively). In healthy anesthetized horses, 5-degree RT did not affect changes in PaO2 as compared to H position.

Pharmacokinetics and pharmacodynamics of meperidine after intramuscular and subcutaneous administration in horses.

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.

A retrospective evaluation of the effect of perianesthetic hydromorphone administration on the incidence of postanesthetic signs of colic 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.

Comparison of endoscopic endotracheal intubation and the v-gel supraglottic airway device for spontaneously ventilating New Zealand white rabbits undergoing ovariohysterectomy.

BACKGROUND: Due to the technical difficulties with endotracheal intubation of rabbits, a prospective, randomised, controlled study was performed to compare a rabbit-specific supraglottic airway device (SGAD), the v-gel, with endoscopic endotracheal intubation (EEI) in spontaneously breathing rabbits undergoing ovariohysterectomy. METHODS: Fourteen adult female New Zealand white rabbits were randomly allocated to one of two groups based on the method of airway establishment: EEI or v-gel SGAD. Anaesthesia was induced with ketamine and xylazine and maintained using isoflurane in 100 per cent oxygen. Comparisons were made between groups based on placement time of endotracheal tube/SGAD, number of attempts and adjustments, the necessity to increase isoflurane concentrations to maintain a surgical plane of anaesthesia, arterial blood gas values, gross laryngeal evaluation, and laryngotracheal histopathology. RESULTS: Both techniques resulted in elevated arterial pCO2 levels, but the v-gel was associated with more elevated pCO2 in comparison with EEI (P=0.045). Airway trauma was histologically present but clinically negligible in both groups, with no statistically significant differences observed between techniques (P>0.05). Placement time of the v-gel was significantly faster (P=0.003) and required less technical skill than EEI, but was more easily displaced when changing the animal's position (P=0.004). CONCLUSION: The v-gel is a practical alternative to EEI for securing the airway of healthy spontaneously ventilating rabbits, provided a capnograph is utilised to ensure continuous placement. Both airway techniques appear safe and effective with few complications, as long as intermittent positive pressure ventilation can be employed to correct hypercapnia.

Effect of Meperidine on Equine Blood Histamine, Tryptase, and Immunoglobulin-E Concentrations.

Objectives: To evaluate changes in immunological parameters following subcutaneous (SC) and intramuscular (IM) administration of meperidine in horses through quantitative analysis of plasma tryptase, histamine, and IgE levels. Methods: Six adult horses were enrolled in a prospective randomized crossover design. Horses were administered one treatment per day, with a seven day washout period: (a) meperidine 1 mg/kg IM, saline 6 mL SC; (b) saline 6 mL IM, meperidine 1 mg/kg SC; (c) saline 6 mL SC, saline 6 mL IM. Blood samples were obtained for plasmatic histamine (baseline, 5, 10, 15, 30, and 60 min) via LC-MS/MS and plasmatic tryptase (baseline, 15, 30, 60, 120, and 240 min) quantification with enzyme-linked immunoabsorbent assays. Serum immunoglobulin E (IgE) concentrations prior to any meperidine treatment and 7-14 days following the first meperidine treatment were evaluated with enzyme-linked immunoabsorbent assays. Histamine and tryptase concentrations were evaluated with a mixed-effect analysis of variance. The levels of IgE at baseline (before the administration of the first dose of meperidine) were compared with the IgE values at 60 min following the second meperidine administration with the Paired t test. Biopsies of localized injection site reactions from subcutaneous meperidine administration were collected from two horses. Results: No statistically significant elevations from baseline in histamine (p = 0.595), tryptase (p = 0.836), or IgE (p = 0.844) were found in any of the horses in this study. There were no differences between treatment groups. Administration of SC meperidine caused a localized vasculitis and thrombosis with regional edema and hemorrhage. Conclusion: No evidence of anaphylactoid or anaphylactic type reactions occurred following IM or SC meperidine administration.

Determination of the minimum alveolar concentration of sevoflurane that blunts adrenergic responses and the effect of a constant rate infusion of ketamine in sheep.

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.

The pharmacokinetics and pharmacodynamics of intravenous hydromorphone in horses.

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.

Agreement among anesthesiologists regarding postoperative pain assessment in dogs.

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 < 0.0001, R2 = 0.93; VAS versus GPS, p < 0.0001, R2 = 0.59; and NRS versus GPS, p < 0.0001, R2 = 0.61) and apart (VAS versus NRS, p < 0.0001, R2 = 0.68; VAS versus GPS, p < 0.0001, R2 = 0.40; and NRS versus GPS, p < 0.0001, R2 = 0.47). Posture, appearance, vocalization, stiffness, interaction between the animal and a person and response to palpation were identified as important variables for assessing pain. Intra-observer reliability produced average ICC values of 0.90 for VAS, 0.89 for NRS and 0.85 for GPS. Interobserver reliability produced average ICC values when scores were assigned together (VAS: 0.93, NRS: 0.93 and GPS: 0.93) and when done separately (VAS: 0.91, NRS: 0.93 and GPS: 0.95). 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.