Anesthesia update - Incorporating methadone into companion animal anesthesia and analgesic protocols: A narrative review.

Opioid analgesics are routinely used during the perioperative period, to provide analgesia and reduce anesthetics doses required to maintain a surgical plane of anesthesia in companion animals. Acting on receptors in the brain, spinal cord, and peripheral nervous system, opioids provide reliable and consistent analgesia; however, they are not without adverse effects. Methadone, a mu agonist opioid analgesic, was recently licensed for veterinary use in Canada. In addition to its action on opioid receptors, methadone contributes to analgesia through other pathways, including inhibition of N-methyl-D-aspartate (NMDA) receptors. It has physiologic effects similar to other mu opioid agents, but fewer adverse gastrointestinal effects. This review discusses methadone's mechanism of action, pharmacologic characteristics, and clinical effects in dogs and cats. Current recommendations for using methadone in companion animals are also provided.

Le point sur l'anesthésie ­ Intégration de la méthadone dans les protocoles d'anesthésie et d'analgésie des animaux de compagnie : une revue descriptive. Les analgésiques opioïdes sont couramment utilisés pendant la période peropératoire, afin de fournir une analgésie et réduire les doses d'anesthésiques nécessaires pour maintenir un plan d'anesthésie chirurgical chez les animaux de compagnie. Agissant sur les récepteurs du cerveau, de la moelle épinière et du système nerveux périphérique, les opioïdes fournissent une analgésie fiable et constante; cependant, ils ne sont pas sans effets indésirables. La méthadone, un analgésique opioïde agoniste mu, a récemment été homologuée pour un usage vétérinaire au Canada. En plus de son action sur les récepteurs opioïdes, la méthadone contribue à l'analgésie par d'autres voies, notamment l'inhibition des récepteurs N-méthyl-D-aspartate (NMDA). Elle a des effets physiologiques similaires à ceux d'autres agents opioïdes mu, mais moins d'effets gastrointestinaux indésirables. Cette revue discute du mécanisme d'action de la méthadone, de ses caractéristiques pharmacologiques et de ses effets cliniques chez les chiens et les chats. Les recommandations actuelles concernant l'utilisation de la méthadone chez les animaux de compagnie sont également fournies.(Traduit par Dr Serge Messier).

Sedative effects of an intramuscular or intranasal combination of sufentanil and midazolam in New Zealand White rabbits.

OBJECTIVE: To evaluate the sedative effects of a combination of sufentanil and midazolam administered intramuscularly (IM) or intranasally (IN) prior to induction of anesthesia with propofol in New Zealand White rabbits. STUDY DESIGN: Prospective, randomized, crossover, experimental study. ANIMALS: A total of 11 adult New Zealand White rabbits. METHODS: Sufentanil (0.5 µg kg-1) and midazolam (2 mg kg-1) were administered to rabbits via IM or IN route. The righting reflex was assessed, and sedation was scored. Heart rate, respiratory rate (fR) and temperature were recorded prior to treatment administration and after loss of the righting reflex. RESULTS: Measured variables remained within normal physiologic ranges for all rabbits. The only statistically significant change was for fR, which was significantly lower after sedation for both routes. The time to loss of righting reflex was 14.8 ± 6.5 and 12.5 ± 7.4 minutes and sedation scores were 6 (4-8) and 7 (6-8) for IM and IN routes, respectively, with no difference between treatments. No adverse effects were observed during the experimental period. CONCLUSIONS AND CLINICAL RELEVANCE: Sufentanil combined with midazolam administered either IM or IN resulted in moderate to deep sedation in New Zealand White rabbits at the dose rates studied.

Randomized Trial Comparing Instructor-Delivered Feedback with Self-Assessment Using Video during Basic Skills Training.

Feedback has been shown to be one of the most powerful and effective influences on student achievement; however, the optimal method for providing feedback to trainees during veterinary skills training has yet to be determined. A prospective mixed-methods study was undertaken to evaluate student perceptions and performance outcomes with self-assessment using video- or instructor-delivered feedback during skills training using a model. Forty participants naïve to intravenous (IV) catheter placement were randomly assigned either to self-assessment using video or to instructor-directed feedback. A questionnaire probing participants' perceptions of their knowledge level and confidence in their skills was completed before and after the training, and an interview was done at study completion. Final skill performance was recorded using video capture to permit blind evaluations using a standard assessment tool. A quantitative evaluation of the performance and questionnaire scores, as well as a qualitative assessment of the interviews, was performed. Questionnaire scores were significantly higher in the post-study questionnaire for 12 of the 14 questions in both groups. Students assigned to the instructor-directed group had significantly higher scores than students in the self-directed group on the skill performance (p < .05). Self-reported confidence in knowledge and skill related to the IV catheterization technique improved with both self-directed feedback using video and instructor-directed feedback. Skill performance, however, was superior following instructor-directed feedback. Participants expressed positive experiences associated with use of the models for skills training, the value of the learning materials including the video, and guidance during learning.

Comparison of fentanyl and hydromorphone constant rate infusions for pain management in dogs in an intensive care unit.

OBJECTIVE: To compare the efficacy and quality of analgesia provided by constant rate infusions (CRIs) of hydromorphone and fentanyl in dogs in the intensive care unit (ICU). STUDY DESIGN: Prospective, randomized, blinded, clinical trial. ANIMALS: A total of 29 client-owned dogs. METHODS: Dogs prescribed a µ-opioid agonist infusion for postsurgical or medical pain were randomized to be administered either hydromorphone (0.025 or 0.05 mg kg-1 bolus, followed by a 0.03 mg kg-1 hour-1 infusion) or fentanyl (2.5 or 5 µg kg-1 bolus, followed by a 3 µg kg-1 hour-1 infusion). The technical staff and clinicians were blinded as to which drug was administered. Pain scores, using the Colorado State University Canine Acute Pain Scale, sedation scores and nausea scores were assigned at regular intervals and compared between groups. Dose escalation and de-escalation of the study drug were performed according to set protocols. Adverse clinical signs and all other medications administered were recorded and compared between groups. The study drug was discontinued if the animal remained painful despite dose escalations, or if adverse effects were noted. RESULTS: The pain scores were of low magnitude and were not significantly different between groups. The use of concurrent analgesia, sedation/anxiolytic medications and antacid/antiemetic medications was not different between groups. Sedation and nausea scores were not statistically different between groups. CONCLUSIONS AND CLINICAL RELEVANCE: Hydromorphone and fentanyl CRIs appear to be equally effective for adequate pain relief in dogs, with no significant differences in adverse effects. Therefore, either drug may be chosen for control of postsurgical or medical pain in an ICU setting.

The Impact of Distraction on Laparoscopic Skills in Veterinary Medical Students.

OBJECTIVE: To investigate the impact of distraction on the performance of a simulator-based laparoscopic task in veterinary students. STUDY DESIGN: Prospective, randomized trial. SAMPLE POPULATION: Years 1-4 veterinary students (n=41). METHODS: Participants repeated a simulated laparoscopic peg transfer task to eliminate any learning effects and were subsequently randomized to receive either a cognitive (double-digit addition questions, n=21) or sensory distraction (dogs barking and anesthesia monitor alerts, n=20). The laparoscopic task scores were compared between baseline and in the presence and absence of each distraction. The number of addition questions attempted, and the number of questions answered correctly in 1 minute were compared between baseline and during a concurrent laparoscopic task. RESULTS: Baseline laparoscopic task scores were not significantly different between groups (P=.09). Laparoscopic task scores were significantly lower than baseline when performed with the cognitive distraction (P<.001) and significantly higher than baseline when performed with the sensory distraction (P=.005). Participants undergoing cognitive distraction attempted significantly fewer addition questions (P<.001) and answered significantly fewer addition questions correctly (P<.001) when a concurrent laparoscopic task was performed. CONCLUSION: Cognitive distraction had a negative impact on the performance of a laparoscopic task in this cohort of veterinary students, whereas sensory distraction had a positive effect.

Investigation of the use of three electroencephalographic electrodes for long-term electroencephalographic recording in awake and sedated dogs.

OBJECTIVE: To compare electroencephalography (EEG) artifact associated with use of the subdermal wire electrode (SWE), gold cup electrode (GCE), and subdermal needle electrode (SNE) over an 8-hour period in sedated and awake dogs. ANIMALS: 6 healthy dogs. PROCEDURES: 8 EEG channels were recorded during 20-minute video-EEG recording sessions (intermittently at 0.5, 2, 4, 6, and 8 hours) with and without chlorpromazine sedation. Nonphysiologic artifacts were identified. Duration of artifact was summed for each channel. Number of unaffected channels (NUC) was determined. RESULTS: NUC was significantly affected by electrode type and sedation over time; median for SWE (2.80 channels; 95% confidence interval [CI], 0.84 to 5.70 channels) was significantly different from medians for GCE (7.87 channels; 95% CI, 7.44 to 7.94 channels) and SNE (7.60 channels; 95% CI, 6.61 to 7.89 channels). After 4 hours, NUC decreased in awake dogs, regardless of electrode type. In awake dogs, duration of artifact differed significantly between SWE and GCE or SNE; medians at 8 hours were 61.55 seconds (95% CI, 21.81 to 173.65 seconds), 1.33 seconds (95% CI, 0.47 to 3.75 seconds), and 21.01 seconds (95% CI, 6.85 to 64.42 seconds), respectively. CONCLUSIONS AND CLINICAL RELEVANCE: The SWE had a significant duration of artifact during recording periods > 2 hours, compared with results for the GCE and SNE, in awake dogs. The GCE, SNE, and sedation resulted in significantly more channels unaffected by artifact. For longer recordings, caution should be exercised in selecting EEG electrodes and sedation state, although differences among electrodes may not be clinically relevant.

Cardiopulmonary effects of an intravenous infusion of fentanyl in cats during isoflurane anesthesia and with concurrent acepromazine or dexmedetomidine administration during anesthetic recovery.

OBJECTIVE: To determine the cardiopulmonary effects of IV administration of fentanyl to cats anesthetized with isoflurane and during anesthetic recovery with concurrent administration of acepromazine or dexmedetomidine. ANIMALS: 6 healthy adult cats. PROCEDURES: Cats received an IV bolus (5 µg/kg) followed by an IV infusion (5 µg/kg/h) of fentanyl for 120 minutes during isoflurane anesthesia and for 30 minutes after discontinuing isoflurane. Cats were randomly assigned in a crossover study to receive acepromazine (0.05 mg/kg) or dexmedetomidine (2.5 µg/kg), IV, when isoflurane was discontinued. Cardiopulmonary data were obtained during anesthesia and for 30 minutes during the anesthetic recovery period. RESULTS: The administration of fentanyl during isoflurane anesthesia resulted in a transient increase in arterial blood pressure, mean pulmonary artery pressure, and oxygen delivery. Compared with values during isoflurane anesthesia, administration of dexmedetomidine during anesthetic recovery resulted in significant decreases in cardiac index, stroke index, and oxygen delivery and significant increases in arterial, central venous, and mean pulmonary artery pressures; systemic vascular resistance index; and oxygen extraction ratio. Administration of acepromazine resulted in increases in heart rate, cardiac index, oxygen uptake, and oxygen extraction ratio. Oxygen extraction ratio did not differ between acepromazine and dexmedetomidine. CONCLUSIONS AND CLINICAL RELEVANCE: Fentanyl transiently improved indices of cardiopulmonary performance when administered to healthy cats anesthetized with isoflurane. The cardiovascular effects of acepromazine and dexmedetomidine in healthy cats receiving fentanyl during recovery from isoflurane anesthesia differed, but measured cardiopulmonary parameters remained within acceptable limits.

Cardiopulmonary effects and recovery characteristics associated with 2 sedative protocols for assisted ventilation in healthy neonatal foals.

Neonatal foals may require prolonged sedation to permit ventilatory support in the first few days of life. The objective of this study was to evaluate and compare the cardiopulmonary effects and clinical recovery characteristics of 2 sedative/analgesia protocols in healthy foals receiving assisted ventilation. Foals were randomized to receive dexmedetomidine, butorphanol, and propofol (DBP) or midazolam, butorphanol, and propofol (MBP) during a 24-hour period. Infusion rates of dexmedetomidine, midazolam, and propofol were adjusted and propofol boluses administered according to set protocols to maintain optimal sedation and muscle relaxation. Ventilatory support variables were adjusted to preset targets. Physiologic variables were recorded, cardiac output (CO) measured (thermodilution), and arterial and mixed venous blood collected for gas analysis at intervals up to 24 hours. Foals in group DBP received dexmedetomidine [2.4 ± 0.5 µg/kg body weight (BW) per hour], butorphanol (13 µg/kg BW per hour), and propofol (6.97 ± 0.86 mg/kg BW per hour), whereas foals in group MBP received midazolam (0.14 ± 0.04 mg/kg BW per hour), butorphanol (13 µg/kg BW per hour), and propofol (5.98 ± 1.33 mg/kg BW per hour). Foals in the DBP group received significantly more propofol boluses (9.0 ± 3.0) than those in the MBP group (4.0 ± 2.0). Although physiologic variables remained within acceptable limits, heart rate (HR), mean arterial pressure (MAP), and cardiac index (CI) were lower in foals in the DBP group than in the MBP group. Times to sternal recumbency, standing, and nursing were significantly shorter in the DBP than MBP group. We found that MBP and DBP protocols are suitable to assist ventilatory support in neonatal foals, although MBP results in a prolonged recovery compared to DBP.

Les poulains nouveau-nés peuvent nécessiter une sédation prolongée pour permettre une assistance ventilatoire au cours des premiers jours de vie. L'objectif de cette étude était d'évaluer et de comparer les effets cardio-pulmonaires et les caractéristiques de récupération clinique de deux protocoles sédatifs/analgésiques chez des poulains sains recevant une ventilation assistée. Les poulains ont été randomisés pour recevoir de la dexmédétomidine, du butorphanol et du propofol (DBP) ou du midazolam, du butorphanol et du propofol (MBP) pendant une période de 24 heures. Les débits de perfusion de dexmédétomidine, de midazolam et de propofol ont été ajustés et des bolus de propofol ont été administrés selon des protocoles définis pour maintenir une sédation et une relaxation musculaire optimales. Les variables d'assistance ventilatoire ont été ajustées à des cibles prédéfinies. Les variables physiologiques ont été enregistrées, le débit cardiaque (CO) mesuré (thermodilution) et le sang artériel et veineux mixte prélevé pour analyse des gaz à des intervalles allant jusqu'à 24 h. Les poulains du groupe DBP ont reçu de la dexmédétomidine [2,4 ± 0,5 µg/kg de poids corporel (PC) par heure], du butorphanol (13 µg/kg de PC par heure) et du propofol (6,97 ± 0,86 mg/kg de PC par heure), tandis que les poulains du groupe MBP ont reçu du midazolam (0,14 ± 0,04 mg/kg de PC par heure), du butorphanol (13 µg/kg de PC par heure) et du propofol (5,98 ± 1,33 mg/kg de PC par heure). Les poulains du groupe DBP ont reçu significativement plus de bolus de propofol (9,0 ± 3,0) que ceux du groupe MBP (4,0 ± 2,0). Bien que les variables physiologiques soient restées dans des limites acceptables, la fréquence cardiaque (FC), la pression artérielle moyenne (MAP) et l'index cardiaque (IC) étaient plus faibles chez les poulains du groupe DBP que dans le groupe MBP. Les temps de décubitus sternal, de station debout et d'allaitement étaient significativement plus courts dans le groupe DBP que dans le groupe MBP. Nous avons constaté que les protocoles MBP et DBP sont adaptés pour assister l'assistance ventilatoire chez les poulains nouveau-nés, bien que le MBP entraîne une récupération prolongée par rapport au DBP.(Traduit par Docteur Serge Messier).

Effects of hypercapnia, hypocapnia, and hyperoxemia on brain morphometrics determined by use of T1-weighted magnetic resonance imaging in isoflurane-anesthetized dogs.

OBJECTIVE: To evaluate the effects of various combinations of PaCO2 and PaO2 values on brain morphometrics. ANIMALS: 6 healthy adult dogs. PROCEDURES: A modified Latin square design for randomization was used. Dogs were anesthetized with propofol (6 to 8 mg/kg, IV), and anesthesia was maintained with isoflurane (1.7%) and atracurium (0.2 mg/kg, IV, q 30 min). Three targeted values of PaCO2 (20, 40, and 80 mm Hg) and 2 values of PaO2 (100 and 500 mm Hg) were achieved in each dog, yielding 6 combinations during a single magnetic resonance (MR) imaging session. When the endpoints were reached, dogs were given at least 5 minutes for physiologic variables to stabilize before T1-weighted MR images were obtained. Total brain volume (TBV) and lateral ventricular volume (LVV) were calculated from manually drawn contours of areas of interest by use of a software program, with each dog serving as its own control animal. Three blinded investigators subjectively evaluated the lateral ventricular size (LVS) and the cerebral sulci width (CSW). Brain morphometric values were compared among the target blood gas states. RESULTS: No significant differences in TBV were found among target states. The LVV was significantly greater during hypocapnia, compared with hypercapnia at the same PaO2 value. With regard to the subjective evaluations, there were no significant differences among evaluators or among combinations of PaO2 and PaCO2 values. CONCLUSIONS AND CLINICAL RELEVANCE: The changes observed in LVV during hypocapnia and hypercapnia may serve as a potential confounding factor when neuromorphometric evaluations are performed in anesthetized dogs.

Effects of hypercapnia, hypocapnia, and hyperoxemia on blood oxygenation level-dependent signal intensity determined by use of susceptibility-weighted magnetic resonance imaging in isoflurane-anesthetized dogs.

OBJECTIVE: To assess the effects of alterations in PaCO(2) and PaO(2) on blood oxygenation level-dependent (BOLD) signal intensity determined by use of susceptibility-weighted magnetic resonance imaging in brains of isoflurane-anesthetized dogs. ANIMALS: 6 healthy dogs. PROCEDURES: In each dog, anesthesia was induced with propofol (6 to 8 mg/kg, IV) and maintained with isoflurane (1.7%) and atracurium (0.2 mg/kg, IV, q 30 min). During 1 magnetic resonance imaging session in each dog, targeted values of PaCO(2) (20, 40, or 80 mm Hg) and PaO(2) (100 or 500 mm Hg) were combined to establish 6 experimental conditions, including a control condition (PaCO(2), 40 mm Hg; PaO(2), 100 mm Hg). Dogs were randomly assigned to different sequences of conditions. Each condition was established for a period of >or= 5 minutes before susceptibility-weighted imaging was performed. Signal intensity was measured in 6 regions of interest in the brain, and data were analyzed by use of an ANCOVA and post hoc Tukey-Kramer adjustments. RESULTS: Compared with control condition findings, BOLD signal intensity did not differ significantly in any region of interest. However, signal intensities in the thalamus and diencephalic gray matter decreased significantly during both hypocapnic conditions, compared with all other conditions except for the control condition. CONCLUSIONS AND CLINICAL RELEVANCE: In isoflurane-anesthetized dogs, certain regions of gray matter appeared to have greater cerebrovascular responses to changes in PaCO(2) and PaO(2) than did others. Both PaO(2) and PaCO(2) should be controlled during magnetic resonance imaging procedures that involve BOLD signaling and taken into account when interpreting findings.

High-flow nasal cannula oxygen therapy in acute hypoxemic respiratory failure in 22 dogs requiring oxygen support escalation.

OBJECTIVE: To determine the effect of high-flow nasal cannula (HFNC) oxygen therapy on cardiorespiratory variables and outcome in dogs with acute hypoxemic respiratory failure. DESIGN: Prospective, sequential clinical trial. SETTING: University veterinary teaching hospital. ANIMALS: Twenty-two client-owned dogs that failed to respond to traditional oxygen support. INTERVENTIONS: Initiation of HFNC therapy after traditional oxygen supplementation failed to increase Spo2 > 96% and Pao2 > 75 mm Hg or improve respiratory rate/effort. MEASUREMENTS AND MAIN RESULTS: Physiological variables, blood gas analyses, and dyspnea/sedation/tolerance scores were collected prior to HFNC initiation (on traditional oxygen support [time 0 or T0]), and subsequently during HFNC oxygen administration at time 30 minutes, 60 minutes, and 7 ± 1 hours. Relative to T0, use of HFNC resulted in a decreased respiratory rate at 1 hour (P = 0.022) and 7 hours (P = 0.012), a decrease in dyspnea score at all times (P < 0.01), and an increase in Spo2 at all times (P < 0.01). There was no difference in arterial/venous Pco2 relative to T0, although Paco2 was correlated with flow rate. Based on respiratory assessment, 60% of dogs responded to HFNC use by 30 minutes, and 45% ultimately responded to HFNC use and survived. No clinical air-leak syndromes were observed. CONCLUSIONS: HFNC use improved oxygenation and work of breathing relative to traditional oxygen therapies, without impairing ventilation. HFNC use appears to be a beneficial oxygen support modality to bridge the gap between standard oxygen supplementation and mechanical ventilation.

Preliminary evaluation of the use of high-flow nasal cannula oxygen therapy during recovery from general anesthesia in dogs with obstructive upper airway breathing.

BACKGROUND: Brachycephalic airway syndrome can pose a risk of complicated recovery from anesthesia as a result of irritation to the excess pharyngeal andlaryngeal tissue present in affected dogs. High-flow nasal cannula (HFNC) oxygen therapy is a respiratory support modality that offers provision of continuous positive airway pressure via high gas flow rates. The HFNC system actively warms and humidifies inspired gases, which improves comfort and facilitates tolerance of the high flow rates in people and dogs. HFNC oxygen therapy was applied to brachycephalic dogs that developed increased work of breathing or hypoxemia in the recovery phase of anesthesia to determine if this device would be tolerable and effective for relief of upper respiratory difficulty. KEY FINDINGS: The HFNC nasal prong interface is well suited to the brachycephalic facial structure. The application of HFNC was found to reduce dyspnea scores in patients with signs of upper airway obstruction after general anesthesia. Aerophagia and changes in PCO2 were noted. SIGNIFICANCE: Application of HFNC in the recovery period may result in improved airflow during times of somnolent obstructive breathing, not unlike the use of continuous positive airway pressure therapy in sleep-disordered breathing in people.

Cardiopulmonary effects of diazepam-ketamine-isoflurane or xylazine-ketamine-isoflurane during abdominal surgery in foals.

OBJECTIVE: To evaluate cardiopulmonary effects of anesthetic induction with diazepam and ketamine or xylazine and ketamine, with subsequent maintenance of anesthesia with isoflurane, in foals undergoing abdominal surgery. ANIMALS: 17 pony foals. PROCEDURES: Foals underwent laparotomy at 7 to 15 days of age and laparoscopy 7 to 10 days later. Foals were randomly assigned to receive diazepam, ketamine, and isoflurane (D/K/Iso; n = 8) or xylazine, ketamine, and isoflurane (X/K/Iso; 9) for both procedures. RESULTS: During anesthesia for laparotomy, cardiac index, and mean arterial blood pressure ranged from 110 to 180 mL/kg/min and 57 to 81 mm Hg, respectively, in the D/K/Iso group and 98 to 171 mL/kg/min and 50 to 66 mm Hg, respectively, in the X/K/Iso group. Cardiac index, heart rate, and arterial blood pressures were significantly higher in the D/K/Iso group, compared with the X/K/Iso group. During anesthesia for laparoscopy, cardiac index and mean arterial blood pressure ranged from 85 to 165 mL/kg/min and 67 to 83 mm Hg, respectively, in the D/K/Iso group, and 98 to 171 mL/kg/min and 48 to 67 mm Hg, respectively, in the X/K/Iso group. Heart rates and arterial blood pressures were significantly higher in the D/K/Iso group, compared with the X/K/Iso group. There were no significant differences between groups during either experimental period for percentage end-tidal isoflurane, arterial blood gas partial pressures, or pH values. CONCLUSIONS AND CLINICAL RELEVANCE: Anesthesia of foals for abdominal surgery with D/K/Iso was associated with less hemodynamic depression than with X/K/Iso.

The cardiopulmonary effects of anesthetic induction with isoflurane, ketamine-diazepam or propofol-diazepam in the hypovolemic dog.

OBJECTIVE: To evaluate and compare the cardiopulmonary effects of induction of anesthesia with isoflurane (Iso), ketamine-diazepam (KD), or propofol-diazepam (PD) in hypovolemic dogs. Study design Prospective randomized cross-over trial. ANIMALS: Six healthy intact, mixed breed, female dogs weighing 20.7 +/- 4.2 kg and aged 22 +/- 2 months. Methods Dogs had 30 mL kg(-1) of blood removed at a rate of 1.5 mL kg(-1) minute(-1) under isoflurane anesthesia. Following a 30-minute recovery period, anesthesia was reinduced. Dogs were assigned to one of three treatments: isoflurane via facemask using 0.5% incremental increases in the delivered concentration every 30 seconds, 1.25 mg kg(-1) ketamine and 0.0625 mg kg(-1) diazepam intravenously (IV) with doses repeated every 30 seconds as required, and 2 mg kg(-1) propofol and 0.2 mg kg(-1) diazepam IV followed by 1 mg kg(-1) propofol increments IV every 30 seconds as required. Following endotracheal intubation all dogs received 1.7% end-tidal isoflurane in oxygen. Cardiopulmonary variables were recorded at baseline (before induction) and at 5 or 10 minute intervals following endotracheal intubation. RESULTS: Induction time was longer in Iso (4.98 +/- 0.47 minutes) compared to KD (3.10 +/- 0.47 minutes) or PD (3.22 +/- 0.45 minutes). To produce anesthesia, KD received 4.9 +/- 2.3 mg kg(-1) ketamine and 0.24 +/- 0.1 mg kg(-1) diazepam, while PD received 2.2 +/- 0.4 mg kg(-1) propofol and 0.2 mg kg(-1) diazepam. End-tidal isoflurane concentration immediately following intubation was 1.7 +/- 0.4% in Iso. Arterial blood pressure and heart rate were significantly higher in KD and PD compared to Iso and in KD compared to PD. Arterial carbon dioxide partial pressure was significantly higher in PD compared to KD and Iso immediately after induction. CONCLUSIONS AND CLINICAL RELEVANCE: In hypovolemic dogs, KD or PD, as used in this study to induce anesthesia, resulted in less hemodynamic depression compared to isoflurane.

Comparison of high flow nasal cannula oxygen administration to traditional nasal cannula oxygen therapy in healthy dogs.

OBJECTIVE: To determine the feasibility, degree of respiratory support, and safety of high flow nasal cannula (HFNC) oxygen therapy in sedated and awake healthy dogs, when compared to traditional nasal cannula (TNC) oxygen administration. DESIGN: Randomized experimental crossover study. SETTING: University research facility. ANIMALS: Eight healthy dogs. INTERVENTIONS: Variable flow rates (L/kg/min) were assessed, TNC: 0.1, 0.2, and 0.4 and HFNC: 0.4, 1.0, 2.0, and 2.5. HFNC was assessed in sedated and awake dogs. MEASUREMENTS: Variables measured included: inspiratory/expiratory airway pressures, fraction of inspired oxygen (FiO2 ), end-tidal oxygen (ETO2 ), end-tidal carbon dioxide (ETCO2 ), partial pressure of oxygen (PaO2 ), partial pressure of carbon dioxide (PaCO2 ), temperature, heart/respiratory rate, arterial blood pressure, and pulse oximetry. Sedation status, complications, and predefined tolerance and respiratory scores were recorded. MAIN RESULTS: Using HFNC, continuous positive airway pressure (CPAP) was achieved at 1 and 2 L/kg/min. CPAP was not higher at 2.5 than 2 L/kg/min, with worse tolerance scores. Expiratory airway pressures were increased when sedated (P = 0.006). FiO2 at 0.4 L/kg/min for both methods was 72%. FiO2 with TNC 0.1 L/kg/min was 27% and not different from room air. The FiO2 at all HFNC flow rates ≥1 L/kg/min was 95%. PaO2 for HFNC 0.4 L/kg/min was lower than at other flow rates (P = 0.005). The only noted complication was aerophagia. PaCO2 was increased with sedation and use of HFNC when compared to baseline (P = 0.006; P < 0.01). CONCLUSIONS: Use of HFNC in dogs is feasible and safe, provides predictable oxygen support and provides CPAP, but may cause a mild increase in PaCO2 . Flow rates of 1-2 L/kg/min are recommended. If using TNC, flow rates above 0.1 L/kg/min may attain higher FiO2 .

Sedative and cardiopulmonary effects of medetomidine hydrochloride and xylazine hydrochloride and their reversal with atipamezole hydrochloride in calves.

OBJECTIVE: To assess the sedative and cardiopulmonary effects of medetomidine and xylazine and their reversal with atipamezole in calves. ANIMALS: 25 calves. PROCEDURES: A 2-phase (7-day interval) study was performed. Sedative characteristics (phase I) and cardiopulmonary effects (phase II) of medetomidine hydrochloride and xylazine hydrochloride administration followed by atipamezole hydrochloride administration were evaluated. In both phases, calves were randomly allocated to receive 1 of 4 treatments IV: medetomidine (0.03 mg/kg) followed by atipamezole (0.1 mg/kg; n = 6), xylazine (0.3 mg/kg) followed by atipamezole (0.04 mg/kg; 7), medetomidine (0.03 mg/kg) followed by saline (0.9% NaCl; 6) solution (10 mL), and xylazine (0.3 mg/kg) followed by saline solution (10 mL; 6). Atipamezole or saline solution was administered 20 minutes after the first injection. Cardiopulmonary variables were recorded at intervals for 35 minutes after medetomidine or xylazine administration. RESULTS: At the doses evaluated, xylazine and medetomidine induced a similar degree of sedation in calves; however, the duration of medetomidine-associated sedation was longer. Compared with pretreatment values, heart rate, cardiac index, and PaO(2) decreased, whereas central venous pressure, PaCO(2), and pulmonary artery pressures increased with medetomidine or xylazine. Systemic arterial blood pressures and vascular resistance increased with medetomidine and decreased with xylazine. Atipamezole reversed the sedative and most of the cardiopulmonary effects of both drugs. CONCLUSIONS AND CLINICAL RELEVANCE: At these doses, xylazine and medetomidine induced similar degrees of sedation and cardiopulmonary depression in calves, although medetomidine administration resulted in increases in systemic arterial blood pressures. Atipamezole effectively reversed medetomidine- and xylazine-associated sedative and cardiopulmonary effects in calves.

Cardiopulmonary effects of anesthetic induction with thiopental, propofol, or a combination of ketamine hydrochloride and diazepam in dogs sedated with a combination of medetomidine and hydromorphone.

OBJECTIVE: To evaluate the cardiopulmonary effects of anesthetic induction with thiopental, propofol, or ketamine hydrochloride and diazepam in dogs sedated with medetomidine and hydromorphone. ANIMALS: 6 healthy adult dogs. PROCEDURES: Dogs received 3 induction regimens in a randomized crossover study. Twenty minutes after sedation with medetomidine (10 microg/kg, IV) and hydromorphone (0.05 mg/kg, IV), anesthesia was induced with ketamine-diazepam, propofol, or thiopental and then maintained with isoflurane in oxygen. Measurements were obtained prior to sedation (baseline), 10 minutes after administration of preanesthetic medications, after induction before receiving oxygen, and after the start of isoflurane-oxygen administration. RESULTS: Doses required for induction were 1.25 mg of ketamine/kg with 0.0625 mg of diazepam/kg, 1 mg of propofol/kg, and 2.5 mg of thiopental/kg. After administration of preanesthetic medications, heart rate (HR), cardiac index, and PaO(2) values were significantly lower and mean arterial blood pressure, central venous pressure, and PaCO(2) values were significantly higher than baseline values for all regimens. After induction of anesthesia, compared with postsedation values, HR was greater for ketamine-diazepam and thiopental regimens, whereas PaCO(2) tension was greater and stroke index values were lower for all regimens. After induction, PaO(2) values were significantly lower and HR and cardiac index values significantly higher for the ketamine-diazepam regimen, compared with values for the propofol and thiopental regimens. CONCLUSIONS AND CLINICAL RELEVANCE: Medetomidine and hydromorphone caused dramatic hemodynamic alterations, and at the doses used, the 3 induction regimens did not induce important additional cardiovascular alterations. However, administration of supplemental oxygen is recommended.

Effects of a peripheral alpha2 adrenergic-receptor antagonist on the hemodynamic changes induced by medetomidine administration in conscious dogs.

OBJECTIVE: To evaluate the effects of administration of a peripheral alpha(2)-adrenergic receptor antagonist (L-659,066), with and without concurrent administration of glycopyrrolate, on cardiopulmonary effects of medetomidine administration in dogs. ANIMALS: 6 healthy adult dogs. PROCEDURES: Dogs received saline (0.9% NaCl) solution (saline group), L-659,066 (group L), or L-659,066 with glycopyrrolate (group LG). These pretreatments were followed 10 minutes later by administration of medetomidine in a randomized crossover study. Hemodynamic measurements and arterial and mixed-venous blood samples for blood gas analysis were obtained prior to pretreatment, 5 minutes after pretreatment, and after medetomidine administration at intervals up to 60 minutes. RESULTS: After pretreatment in the L and LG groups, heart rate, cardiac index, and partial pressure of oxygen in mixed-venous blood (PvO2) values were higher than those in the saline group. After medetomidine administration, heart rate, cardiac index, and PvO2 were higher and systemic vascular resistance, mean arterial blood pressure, and central venous pressure were lower in the L and LG groups than in the saline group. When the L and LG groups were compared, heart rate was greater at 5 minutes after medetomidine administration, mean arterial blood pressure was greater at 5 and 15 minutes after medetomidine administration, and central venous pressure was lower during the 60-minute period after medetomidine administration in the LG group. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of L-659,066 prior to administration of medetomidine reduced medetomidine-induced cardiovascular changes in healthy dogs. No advantage was detected with concurrent administration of L-659,066 and glycopyrrolate.

Cardiopulmonary effects of administration of a combination solution of xylazine, guaifenesin, and ketamine or inhaled isoflurane in mechanically ventilated calves.

OBJECTIVE: To compare the cardiopulmonary effects of administration of a solution of xylazine, guaifenesin, and ketamine (XGK) or inhaled isoflurane in mechanically ventilated calves undergoing surgery. ANIMALS: 13 male calves 2 to 26 days of age. Procedures-In calves in the XGK group, anesthesia was induced (0.5 mL/kg) and maintained (2.5 mL/kg/h) with a combination solution of xylazine (0.1 mg/mL), guaifenesin (50 mg/mL), and ketamine (1.0 mg/mL). For calves in the isoflurane group, anesthesia was induced and maintained with isoflurane in oxygen. The rates of XGK infusion and isoflurane administration were adjusted to achieve suitable anesthetic depth. All calves received 100% oxygen and were mechanically ventilated to maintain end-tidal carbon dioxide concentrations from 35 to 40 mm Hg and underwent laparoscopic bladder surgery through an abdominal approach. Cardiopulmonary variables were measured before induction and at intervals up to 90 minutes after anesthetic induction. RESULTS: The quality of induction was excellent in all calves. The XGK requirements were 0.57 +/- 0.18 mL/kg and 2.70 +/- 0.40 mL/kg/h to induce and maintain anesthesia, respectively. Heart rate was significantly lower than baseline throughout the anesthetic period in the XGK group. Systolic arterial blood pressure was significantly higher in the XGK group, compared with the isoflurane group, from 5 to 90 minutes. Cardiac index was lower than baseline in both groups. Differences between groups in cardiac index and arterial blood gas values were not significant. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of XGK resulted in excellent anesthetic induction and maintenance with cardiopulmonary alterations similar to those associated with isoflurane in mechanically ventilated calves.

Factors associated with simulator-assessed laparoscopic surgical skills of veterinary students.

OBJECTIVE To determine whether simulator-assessed laparoscopic skills of veterinary students were associated with training level and prior experience performing nonlaparoscopic veterinary surgery and other activities requiring hand-eye coordination and manual dexterity. DESIGN Experiment. SAMPLE 145 students without any prior laparoscopic surgical or fundamentals of laparoscopic surgery (FLS) simulator experience in years 1 (n = 39), 2 (34), 3 (39), and 4 (33) at a veterinary college. PROCEDURES A questionnaire was used to collect data from participants regarding experience performing veterinary surgery, playing video games, and participating in other activities. Participants performed a peg transfer, pattern cutting, and ligature loop-placement task on an FLS simulator, and FLS scores were assigned by an observer. Scores were compared among academic years, and correlations between amounts of veterinary surgical experience and FLS scores were assessed. A general linear model was used to identify predictors of FLS scores. RESULTS Participants were predominantly female (75%), right-hand dominant (92%), and between 20 and 29 years of age (98%). No significant differences were identified among academic years in FLS scores for individual tasks or total FLS score. Scores were not significantly associated with prior surgical or video game experience. Participants reporting no handicraft experience had significantly lower total FLS scores and FLS scores for task 2 than did participants reporting a lot of handicraft experience. CONCLUSIONS AND CLINICAL RELEVANCE Prior veterinary surgical and video game experience had no influence on FLS scores in this group of veterinary students, suggesting that proficiency of veterinary students in FLS may require specific training.