Total intravenous anesthesia with Ketofol in rabbits: a comparison of the effects of constant rate infusion of midazolam, fentanyl or dexmedetomidine.

BACKGROUND: When inhalant anesthetic equipment is not available or during upper airway surgery, intravenous infusion of one or more drugs are commonly used to induce and/or maintain general anesthesia. Total intravenous anesthesia (TIVA) does not require endotracheal intubation, which may be more difficult to achieve in rabbits. A range of different injectable drug combinations have been used as continuous infusion rate in animals. Recently, a combination of ketamine and propofol (ketofol) has been used for TIVA in both human patients and animals. The purpose of this prospective, blinded, randomized, crossover study was to evaluate anesthetic and cardiopulmonary effects of ketofol total intravenous anesthesia (TIVA) in combination with constant rate infusion (CRI) of midazolam, fentanyl or dexmedetomidine in eight New Zealand White rabbits. Following IV induction with ketofol and endotracheal intubation, anesthesia was maintained with ketofol infusion in combination with CRIs of midazolam (loading dose [LD]: 0.3 mg/kg; CRI: 0.3 mg/kg/hr; KPM), fentanyl (LD: 6 µg/kg; CRI: 6 µg/kg/hr; KPF) or dexmedetomidine (LD: 3 µg/kg; CRI: 3 µg/kg/hr; KPD). Rabbits in the control treatment (KPS) were administered the same volume of saline for LD and CRI. Ketofol infusion rate (initially 0.6 mg kg- 1 minute- 1 [0.3 mg kg- 1 minute- 1 of each drug]) was adjusted to suppress the pedal withdrawal reflex. Ketofol dose and physiologic variables were recorded every 5 min. RESULTS: Ketofol induction doses were 14.9 ± 1.8 (KPM), 15.0 ± 1.9 (KPF), 15.5 ± 2.4 (KPD) and 14.7 ± 3.4 (KPS) mg kg- 1 and did not differ among treatments (p > 0.05). Ketofol infusion rate decreased significantly in rabbits in treatments KPM and KPD as compared with saline. Ketofol maintenance dose in rabbits in treatments KPM (1.0 ± 0.1 mg/kg/min) and KPD (1.0 ± 0.1 mg/kg/min) was significantly lower as compared to KPS (1.3 ± 0.1 mg/kg/min) treatment (p < 0.05). Ketofol maintenance dose did not differ significantly between treatments KPF (1.1 ± 0.3 mg/kg/min) and KPS (1.3 ± 0.1 mg/kg/min). Cardiovascular variables remained at clinically acceptable values but ketofol infusion in combination with fentanyl CRI was associated with severe respiratory depression. CONCLUSIONS: At the studied doses, CRIs of midazolam and dexmedetomidine, but not fentanyl, produced ketofol-sparing effect in rabbits. Mechanical ventilation should be considered during ketofol anesthesia, particularly when fentanyl CRI is used.

Influence of fentanyl, medetomidine-fentanyl or acepromazine-fentanyl premedication on oesophageal and rectal temperature in dogs under anaesthesia.

OBJECTIVE: To compare changes in oesophageal (T-Oeso) and rectal (T-Rec) temperature in dogs during general anaesthesia and premedicated with fentanyl, medetomidine-fentanyl or acepromazine-fentanyl. STUDY DESIGN: Prospective, randomized, blind clinical study. ANIMALS: A total of 120 healthy dogs, aged 2-10 years and weighing 5-20 kg. METHODS: Dogs were randomly allocated to one of three groups. Animals of F group were premedicated with fentanyl (0.01 mg kg-1), MF group with medetomidine (0.005 mg kg-1) and fentanyl (0.01 mg kg-1) and AF group with acepromazine (0.01 mg kg-1) and fentanyl (0.01 mg kg-1). Anaesthesia was induced with propofol and maintained with isoflurane in oxygen-air mixture. Fentanyl was administered continuously (0.01 mg kg-1 hour-1). The T-Oeso, T-Rec and ambient temperatures were recorded after induction (T0) and subsequently at 10 minute intervals for 60 minutes (T10-T60). Data were analysed using anova or their non-parametric equivalents (p < 0.05). RESULTS: Median T-Oeso was significantly higher in MF group between T0-T20 compared with other groups. Median T-Oeso significantly decreased in F group from 38.0 °C (T0) to 37.4 °C (T30), 37.1 °C (T40), 36.9 °C (T50) and 36.6 °C (T60), in MF group from 38.3 °C (T0) to 37.7 °C (T30), 37.5 °C (T40), 37.2 °C (T50) and 37.1 °C (T60) and in AF group from 37.7 °C (T0) to 37.3 °C (T40), 37.2 °C (T50) and 37.1 °C (T60). The T-Rec significantly decreased in F group from 38.0 °C (T0) to 37.4 °C (T40), 37.2 °C (T50) and 36.9 °C (T60), in MF group from 38.3 °C (T0) to 37.5 °C (T50) and 37.4 °C (T60) and in AF group from 38.2 °C (T0) to 37.6 °C (T40), 37.5 °C (T50) and 37.4 °C (T60). CONCLUSIONS AND CLINICAL RELEVANCE: Premedication with fentanyl, medetomidine-fentanyl or acepromazine-fentanyl in the doses used decreased the T-Oeso and T-Rec. The T-Oeso at the beginning of anaesthesia was higher after premedication with medetomidine-fentanyl. However, this difference was not clinically significant.

TILETAMINE-ZOLAZEPAM-XYLAZINE ANESTHESIA IN EX SITU BLACK-HANDED SPIDER MONKEYS (ATELES GEOFFROYI SSP.).

Black-handed spider monkeys (Ateles geoffroyi ssp.) are endangered in Mexico. Safe anesthetic protocols are important for in situ and ex situ conservation problems. Such protocols are scarce in the literature; nor have safety and physiologic responses been reported. High doses and volume are a counter side for field immobilizations. We tested an anesthetic protocol with a combination of tiletamine-zolazepam (5 mg/kg) plus xylazine (1 mg/kg) in 14 black-handed spider monkeys under human care from two facilities in Mexico. Physiological parameters such as HR, RR, T, SPO2, systolic arterial pressure (), diastolic arterial pressure (DAP), and median arterial pressure (MAP) were obtained. HR and RR decreased over time, but T increased significantly during the anesthetic time for the whole group; RR and T decreased for juveniles only. Variation between individuals was observed for HR, RR, and DAP. Volume reduction of drugs was achieved compared to previously reported anesthesia protocols. Induction time was fast (6.2 ± 10.4 min) and no tail prehension was seen. Recovery was prolonged (mean and SD). Physiologic parameters remained stable throughout. The protocol proved to be safe for the chemical immobilization of black-handed spider monkeys.

Neurodevelopmental Outcomes after Premedication with Atropine/Propofol vs Atropine/Atracurium/Sufentanil for Neonatal Intubation: 2-Year Follow-Up of a Randomized Clinical Trial.

This study followed 173 newborn infants in the PREmedication Trial for Tracheal Intubation of the NEOnate multicenter, double-blind, randomized controlled trial of atropine-propofol vs atropine-atracurium-sufentanil for premedication before nonemergency intubation. At 2 years of corrected age, there was no significant difference between the groups in death or risk of neurodevelopmental delay assessed with the Ages and Stages Questionnaire. Trial registration Clinicaltrials.gov: NCT01490580.

Safety and Efficacy of the Combination of Propofol and Ketamine for Procedural Sedation/Anesthesia in the Pediatric Population: A Systematic Review and Meta-analysis.

BACKGROUND: Drugs such as propofol and ketamine are used alone or in combination to provide sedation for medical procedures in children. The purpose of this systematic review was to compare the safety and effectiveness of propofol and ketamine to other drug regimens. METHODS: We searched Medline, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), Cochrane Database of Systematic Reviews (CDSR), Web of Science, and the grey literature (meta-Register of Controlled Trials, ClinicalTrials.gov, and Google Scholar) for randomized controlled studies comparing intravenous propofol and ketamine to any other single or combination drug regimen administered to children undergoing diagnostic or therapeutic procedures. Meta-analyses were performed for primary (hemodynamic and respiratory adverse events) and secondary outcomes using RevMan 5.3. We assessed the risk of bias and the certainty (quality) evidence for all outcomes using Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology. RESULTS: Twenty-nine studies were included for analysis. Based on low-to-moderate quality evidence, we concluded that the use of propofol and ketamine may result in a slight-to-small reduction in the risk of hypotension, bradycardia, and apnea, and a slight increase in the risk of tachycardia, hypertension, and other respiratory adverse events, such as cough or laryngospasm. The ratio of propofol to ketamine and comparator drug regimen subgroups effects were important for desaturation and some secondary outcomes. CONCLUSIONS: The use of propofol and ketamine had a minimal effect on the incidence of adverse events and other secondary outcomes. Large-scale studies are required to more accurately estimate adverse event rates and the effects of propofol and ketamine on patient-important outcomes.

Effects of isoflurane and sevoflurane alone and in combination with butorphanol or medetomidine on the bispectral index in chickens.

BACKGROUND: The bispectral index (BIS) is an anaesthesia monitoring technique able to assess the level of central nervous system depression in humans and various animal species. In birds, it has been validated in chickens undergoing isoflurane anaesthesia. The aim of this study was to evaluate in an avian species the influence of isoflurane and sevoflurane on BIS, each at different minimum anaesthetic concentrations (MAC) multiples, alone or combined with butorphanol or medetomidine. Ten chickens (5 males and 5 females) underwent general anaesthesia with isoflurane or sevoflurane alone, and combined with either intramuscular administration of butorphanol (1 mg/kg) or medetomidine (0.1 mg/kg), in a prospective and cross-over study (i.e., 6 treatments per animal). BIS measurements were compared to heart rate (HR), non-invasive blood pressure (NIBP) and to a visual analogue scale (VAS) of anaesthesia depth. RESULTS: HR was significantly increased, and both NIBP and VAS were significantly reduced, with higher gas concentrations. NIBP (but not HR or VAS) was additionally affected by the type of gas, being lower at higher concentrations of sevoflurane. Butorphanol had no additional effect, but medetomidine led to differences in HR, NIBP, and in particular a reduction in VAS. With respect to deeper level of hypnosis at higher concentrations and the absence of difference between gases, BIS measurements correlated with all other measures (except with HR, where no significant relationship was found) The difference in BIS before (BISpre) and after stimulation (BISpost) did not remain constant, but increased with increasing MAC multiples, indicating that the BISpost is not suppressed proportionately to the suppression of the BISpre values due to gas concentration. Furthermore, neither butorphanol nor medetomidine affected the BIS. CONCLUSIONS: The difference of degree of central nervous system depression monitored by BIS compared with neuromuscular reflexes monitored by VAS, indicate that BIS records a level of anaesthetic depth different from the one deducted from VAS monitoring alone. BIS provided complementary information such as that medetomidine suppressed spinal reflexes without deepening the hypnotic state. As a consequence, it is concluded that BIS improves the assessment of the level of hypnosis in chickens, improving anaesthesia monitoring and anaesthesia quality in this species.

Comparison of anesthetic effects of tiletamine-zolazepam-medetomidine or ketamine-medetomidine in captive Amur leopard cats (Prionailurus bengalensis euptailurus).

OBJECTIVE: To evaluate the effects and utility of tiletamine-zolazepam-medetomidine (TZM) and ketamine-medetomidine (KM) for anesthesia of Amur leopard cats (Prionailurus bengalensis euptailurus). STUDY DESIGN: Prospective, randomized experimental trial. ANIMALS: A total of six female (3.70 ± 0.49 kg) and six male (5.03 ± 0.44 kg; mean ± standard deviation) Amur leopard cats aged 2-6 years. METHODS: Each animal was administered four protocols separated by ≥3 weeks. Each protocol included medetomidine (0.05 mg kg-1) combined with tiletamine-zolazepam (1 mg kg-1; protocol MTZLO); tiletamine-zolazepam (2 mg kg-1; protocol MTZHI); ketamine (2 mg kg-1; protocol MKLO); or ketamine (4 mg kg-1; MKHI) administered intramuscularly. At time 0 (onset of lateral recumbency) and 30 minutes, heart rate (HR), respiratory rate (fR), rectal temperature, noninvasive mean arterial pressure (MAP) and hemoglobin oxygen saturation (SpO2) were recorded. Times to onset of lateral recumbency, duration of anesthesia and time to standing were recorded. RESULTS: Overall, animals were anesthetized with all protocols within 10 minutes, anesthesia was maintained ≥57 minutes, and recovery (time from the first head lift to standing) was completed within 5 minutes. During anesthesia with all protocols, HR, fR, rectal temperature, SpO2 and MAP were 99-125 beats minute-1, 33-44 breaths minute-1, 37.6-39.4 °C, 90-95% and 152-177 mmHg, respectively. No adverse event was observed. CONCLUSIONS AND CLINICAL RELEVANCE: TZM and KM at various dosages resulted in rapid onset of anesthesia, duration of >57 minutes and rapid recovery without administration of an antagonist. Accordingly, all these combinations are useful for anesthetizing Amur leopard cats and for performing simple procedures. However, the low doses of the anesthetic agents are recommended because there was no difference in duration of anesthesia between the dose rates studied.

Evaluation of anaesthetic and cardiorespiratory effects after intramuscular administration of alfaxalone alone, alfaxalone-ketamine and alfaxalone-butorphanol-medetomidine in common marmosets (Callithrix jacchus).

BACKGROUND: Anaesthesia is often required in common marmosets undergoing various procedures. The aim of this study was to evaluate anaesthetic and cardiopulmonary effects of alfaxalone, alfaxalone-ketamine and alfaxalone-butorphanol-medetomidine in common marmosets. METHODS: The following treatments were repeatedly administered to seven female common marmosets: Treatment A, alfaxalone (12 mg kg-1 ) alone; treatment AK, alfaxalone (1 mg animal-1 ) plus ketamine (2.5 mg animal-1 ); treatment AMB, alfaxalone (4 mg kg-1 ), medetomidine (50 µg kg-1 ) plus butorphanol (0.3 mg kg-1 ); and treatment AMB-Ati, AMB with atipamezole at 45 minutes. RESULTS AND CONCLUSIONS: Marmosets became laterally recumbent and unresponsive for approximately 30 minutes in A and AK and for approximately 60 minutes in AMB. The animals showed rapid recovery following atipamezole injection in AMB-Ati. The decrease in heart rate and SpO2 was significantly greater in AMB compared to A and AK. Oxygen supplementation, anaesthetic monitors and atipamezole should be available especially when AMB is administered.

Short-term outcomes of combined neuraxial and general anaesthesia versus general anaesthesia alone for elective open abdominal aortic aneurysm repair: retrospective population-based cohort study†.

BACKGROUND: Use of neuraxial anaesthesia for open abdominal aortic aneurysm repair is postulated to reduce mortality and morbidity. This study aimed to determine the 90-day outcomes after elective open abdominal aortic aneurysm repair in patients receiving combined general and neuraxial anaesthesia vs general anaesthesia alone. METHODS: A retrospective population-based cohort study was conducted from 2003 to 2016. All patients ≥40 yr old undergoing open abdominal aortic aneurysm repair were included. The propensity score was used to construct inverse probability of treatment weighted regression models to assess differences in 90-day outcomes. RESULTS: A total of 10 447 elective open abdominal aortic aneurysm repairs were identified; 9003 (86%) patients received combined general and neuraxial anaesthesia and 1444 (14%) received general anaesthesia alone. Combined anaesthesia was associated with significantly lower hazards for all-cause mortality (hazard ratio [HR]=0.47; 95% confidence interval [CI], 0.37-0.61) and major adverse cardiovascular events (HR=0.72; 95% CI, 0.60-0.86). Combined patients were at lower odds for acute kidney injury (odds ratio [OR]=0.66; 95% CI, 0.49-0.89), respiratory failure (OR=0.41; 95% CI, 0.36-0.47), and limb complications (OR=0.30; 95% CI, 0.25-0.37), with higher odds of being discharged home (OR=1.32; 95% CI, 1.15-1.51). Combined anaesthesia was also associated with significant mechanical ventilation and ICU and hospital length of stay benefits. CONCLUSIONS: Combined general and neuraxial anaesthesia in elective open abdominal aortic aneurysm repair is associated with reduced 90-day mortality and morbidity. Neuraxial anaesthesia should be considered as a routine adjunct to general anaesthesia for elective open abdominal aortic aneurysm repair.

Different Reactions of Zebra Finches and Bengalese Finches to a Three-Component Mixture of Anesthetics.

Kawai et al. (2011) recently introduced a mixture of three anesthetic agents (here called MMB) that has an effect similar to ketamine/xylazine in mice, which might allow more effective reaction to changes in the animal condition, as an antagonist is available, and which can be used without license for handling narcotic drugs. Using Kawai's study as a baseline, we tested whether this anesthesia and its antagonist can also be used in avian studies. In the present study, we used two species, the zebra finch and the Bengalese finch, of the avian family Estrildidae. In zebra finches, anesthesia effects similar to the use of ketamine/xylazine and to those obtained in mice can be reached by the use of MMB if a higher dose is applied. MMB leads to more variable anesthesia, but has the advantage of a longer time window of deep anesthesia. An antagonist to one component of MMB reduced the awaking time, but was not as effective as in mice. For Bengalese finches, MMB cannot be generally recommended because of difficult handling and high mortality rate when used without antagonist, but could be used for perfusions instead of pentobarbital.

Total injectable anesthesia of dogs and cats for remote location veterinary sterilization clinic.

BACKGROUND: Sterilization clinics often occur in remote places where anesthesia machines and compressed oxygen are unavailable. This study describes the use of total injectable anesthesia in dogs and cats presented for sterilization in a remote location. RESULTS: A total of 100 animals were sterilized; 26 female cats (CF), 22 male cats (CM), 28 female dogs (DF), and 24 male dogs (DM). CF were anesthetized with dexmedetomidine (20 mcg/kg), ketamine (8 mg/kg) and hydromorphone (0.1 mg/kg) IM. CM were anesthetized with dexmedetomidine (15 mcg/kg), ketamine (5 mg/kg) and hydromorphone (0.1 mg/kg) IM. Insufficient anesthesia in cats was treated with alfaxalone (1 mg/kg) IM. All cats were administered meloxicam at 0.3 mg/kg SQ. DF were anesthetized with dexmedetomidine (15 mcg/kg), ketamine (7-10 mg/kg) and hydromorphone (0.1 mg/kg) IM. DM were anesthetized with dexmedetomidine (15 mcg/kg), ketamine (5 mg/kg) and hydromorphone (0.1 mg/kg) IM. All dogs had IV catheter and endotracheal tube placed. If SpO2 < 91%, ventilation was assisted with an Ambu bag. Insufficient anesthesia in dogs was treated with alfaxalone (1 mg/kg) IV. All dogs were administered meloxicam at 0.2 mg/kg SQ. Following surgery, atipamezole (0.05-0.1 mg/kg) IM was administered to any patient that did not have voluntary movement. All patients survived and were discharged. Less than 25% of cats and male dogs required supplemental anesthesia. Fifty seven percent of female dogs required supplemental anesthesia. More than 89% of patients (in any group) required atipamezole administration. One cat recovered with agitation and hyperthermia (41.1C/ 106F). Some dogs required ventilatory assistance to remain normoxemic while anesthetized. CONCLUSION: Total injectable anesthesia can be accomplished for remote location sterilization clinics with minimal morbidity.

Lidocaine Reduces Sevoflurane Consumption and Improves Recovery Profile in Children Undergoing Major Spine Surgery.

BACKGROUND Intravenous lidocaine administered during surgery improves postoperative outcomes; however, few studies have evaluated the relationship between intravenous lidocaine and volatile anesthetics requirements. This study assessed the effects of lidocaine treatment on sevoflurane consumption and postoperative consciousness disorders in children undergoing major spine surgery. MATERIAL AND METHODS Patients were randomly divided into 2 treatment groups: lidocaine and placebo (control). The lidocaine group received lidocaine as a bolus of 1.5 mg/kg over 30 min, followed by a continuous infusion at 1 mg/kg/h to 6 h after surgery. The following data were assessed: end-tidal sevoflurane concentration required to maintain a bispectral index BIS between 40 and 60, intraoperative blood pressure, heart rate, demand for fentanyl, and consciousness level assessed after surgery using the Richmond Agitation-Sedation Scale. Any treatment-related adverse events were recorded. RESULTS Compared to the control group, lidocaine treatment reduced by 15% the end-tidal sevoflurane concentration required to maintain the intraoperative hemodynamic stability and appropriate level of anesthesia (P=0.0003). There were no intergroup differences in total dose of fentanyl used, average mean arterial pressure, or heart rate measured intraoperatively. The postoperative level of patient consciousness did not differ during the first 6 h between groups. After 9 h, more patients in the control group were still sleepy (P=0.032), and there were fewer perioperative complications in the lidocaine group. CONCLUSIONS Lidocaine treatment decreases sevoflurane consumption and improves recovery profiles in children undergoing major spine surgery.

Efficacy of Eutectic Mixture of Local Anesthetics on Pain Control During Extracorporeal Shock Wave Lithotripsy: A Systematic Review and Meta-Analysis.

BACKGROUND The efficacy of a eutectic mixture of local anesthetics (EMLA) for pain control in extracorporeal shock wave lithotripsy is unclear. The aim of this study was to assess the effect of EMLA cream on pain control during extracorporeal shock wave lithotripsy. MATERIAL AND METHODS We searched Medline, EMBASE, and the Cochrane Central Register of Controlled Trials to identify relevant randomized controlled trials that compared the pain control efficacies of EMLA vs. placebo. Study eligibility criteria, participants, and interventions: Randomized controlled trials that compared the effect of EMLA with placebo cream for patients underwent extracorporeal shock wave lithotripsy. Study appraisal and synthesis methods: Two review authors extracted data independently using a designed data extraction form and risk of bias by Cochrane Collaboration's tool. RESULTS Nine studies, including 10 randomized controlled trials with 1167 patients, were eligible. The EMLA group experienced less pain (mean difference, -0.47; 95% confidence interval, -0.78 to -0.16; p=0.003) and shorter duration of lithotripsy (mean difference, -1.70, 95% confidence interval: -2.31 to -1.10, p<0.0001) than the placebo group. There were no significant differences in the number of patients who needed extra intravenous medication (p=0.610), number of patients with insufficient extracorporeal shock wave lithotripsy pain control (p=0.530), and number of patients with opioid adverse effects (p=0.320). Limitations: Long interval between the studies, different kinds of lithotripters. CONCLUSIONS EMLA can reduce pain during the ESWL procedure.

Influence of Topical Anesthesia on Superficial Sensitivity: A Double-Blind, Randomized, Placebo-Controlled Study on 48 Healthy Subjects.

BACKGROUND: Topical anesthetics are used in noninvasive transdermal anesthesia to decrease the superficial pain sensation threshold during dermatologic surgery. Combined pain relief and sensitivity loss can avoid discomfort during the surgery. OBJECTIVE: The aim of this placebo-controlled study was to compare the efficacy of 3 commonly used topical agents by collating loss of sensitivity over time. MATERIALS AND METHODS: Three topical anesthetic creams, a topical anti-inflammatory cream, and a moisturizing cream were applied on the left volar forearm of each of the 48 healthy Caucasian participants. Sensitivity was assessed with the dynamic 2-point discrimination and the Semmes-Weinstein test at 0, 60, 90, 120, 150, and 180 minutes after cream application. RESULTS: After 180 minutes, benzocaine showed a significantly lower 2-point discrimination reduction than lidocaine alone and a lidocaine and prilocaine mixture. Sensory threshold measurements by the Semmes-Weinstein test after 60 minutes revealed a significantly higher effect with lidocaine alone and with the lidocaine and prilocaine mixture than with benzocaine. CONCLUSION: The authors found a stronger skin sensitivity reduction by the eutectic lidocaine and prilocaine mixture and lidocaine alone compared with benzocaine. We suggest increased discomfort reduction in topical anesthetic supported dermatologic surgery by the eutectic mixture and lidocaine alone.

Anesthetic effects of ketamine-medetomidine-hydromorphone in dogs during high-quality, high-volume surgical sterilization program under field conditions.

OBJECTIVE: To describe the anesthetic and adverse effects of an injectable anesthetic protocol in dogs as part of a high-volume sterilization program under field conditions in Belize. STUDY DESIGN: Prospective, observational, field study. ANIMALS: A total of 23 female and eight male dogs (14.2 ± 7.7 kg; age ≥ 8 weeks). METHODS: Using a volume per kg-based dose chart, dogs were administered ketamine (4.5 mg kg-1), medetomidine (0.04 mg kg-1) and hydromorphone (0.09 mg kg-1) intramuscularly. After induction of anesthesia, an endotracheal tube was inserted and dogs were allowed spontaneous breathing in room air. Monitoring included peripheral oxygen saturation (SpO2), mean arterial pressure (MAP), heart rate (HR), respiratory rate, rectal temperature and end-tidal carbon dioxide (Pe'CO2). Meloxicam (0.2 mg kg-1) was administered subcutaneously after surgery. Data were analyzed with linear models and chi-square tests (p < 0.05). RESULTS: Onset of lateral recumbency (3.4 ± 2 minutes) was rapid. Desaturation (SpO2 < 90%) was observed at least once in 64.5% of dogs and was more frequent in large dogs (p = 0.019). Hypercapnia (Pe'CO2 ≥ 50 mmHg; 6.7 kPa) was observed in 48.4% of dogs. MAP was 111 ± 19 mmHg, mean ± standard deviation. Hypertension (MAP ≥ 120 mmHg), bradycardia (HR ≤ 60 beats minute-1) and tachycardia (HR ≥ 140 beats minute-1) were observed in 45.2%, 16.1% and 3.3% of dogs, respectively. Hypotension and hypothermia were not observed. Sex was not significantly associated with any complication. Return of swallowing reflex and time to standing were 71 ± 23 and 152 ± 50 minutes after injection, respectively. Return of swallowing was significantly longer in large dogs. CONCLUSIONS AND CLINICAL RELEVANCE: At the doses used, ketamine-medetomidine-hydromorphone was effective in dogs for high-volume sterilization. In this field setting, adverse effects included hypoventilation, hypoxemia and prolonged recovery.

Dose and cardiopulmonary effects of propofol alone or with midazolam for induction of anesthesia in critically ill dogs.

OBJECTIVE: To determine the dose and cardiopulmonary effects of propofol alone or with midazolam for induction of anesthesia in American Society of Anesthesiologists status ≥III dogs requiring emergency abdominal surgery. STUDY DESIGN: Prospective, randomized, blinded, clinical trial. ANIMALS: A total of 19 client-owned dogs. METHODS: Dogs were sedated with fentanyl (2 µg kg-1) intravenously (IV) for instrumentation for measurement of heart rate, arterial blood pressure, cardiac index, systemic vascular resistance index, arterial blood gases, respiratory rate and rectal temperature. After additional IV fentanyl (3 µg kg-1), the quality of sedation was scored and cardiopulmonary variables recorded. Induction of anesthesia was with IV propofol (1 mg kg-1) and saline (0.06 mL kg-1; group PS; nine dogs) or midazolam (0.3 mg kg-1; group PM; 10 dogs), with additional propofol (0.25 mg kg-1) IV every 6 seconds until endotracheal intubation. Induction/intubation quality was scored, and anesthesia was maintained with isoflurane. Variables were recorded for 5 minutes with the dog in lateral recumbency, breathing spontaneously, and then in dorsal recumbency with mechanical ventilation for the next 15 minutes. A general linear mixed model was used with post hoc analysis for multiple comparisons between groups (p < 0.05). RESULTS: There were no differences in group demographics, temperature and cardiopulmonary variables between groups or within groups before or after induction. The propofol doses for induction of anesthesia were significantly different between groups, 1.9 ± 0.5 and 1.1 ± 0.5 mg kg-1 for groups PS and PM, respectively, and the induction/intubation score was significantly better for group PM. CONCLUSIONS AND CLINICAL RELEVANCE: Midazolam co-induction reduced the propofol induction dose and improved the quality of induction in critically ill dogs without an improvement in cardiopulmonary variables, when compared with a higher dose of propofol alone.

Evaluation of xylazine-alfaxalone anesthesia for field castration in donkey foals.

OBJECTIVE: To evaluate the anesthetic and cardiopulmonary effects of xylazine-alfaxalone anesthesia in donkey foals undergoing field castration. STUDY DESIGN: Prospective clinical study. ANIMALS: A group of seven standard donkeys aged [median (range)] 12 (10-26) weeks, weighing 47.3 (37.3-68.2) kg. METHODS: Donkeys were anesthetized with xylazine (1 mg kg-1) intravenously (IV) followed 3 minutes later by alfaxalone (1 mg kg-1) IV. Additional doses of xylazine (0.5 mg kg-1) and alfaxalone (0.5 mg kg-1) IV were administered as needed to maintain surgical anesthesia. Intranasal oxygen was supplemented at 3 L minute-1. Heart rate (HR), respiratory rate (fR) and mean arterial pressure (MAP) by oscillometry were recorded before drug administration and every 5 minutes after induction of anesthesia. Peripheral oxygen saturation (SpO2) was recorded every 5 minutes after induction. Time to recumbency after alfaxalone administration, time to anesthetic re-dose, time to first movement, sternal and standing after last anesthetic dose and surgery time were recorded. Induction and recovery quality were scored (1, very poor; 5, excellent). RESULTS: Median (range) induction score was 5 (1-5), and recovery score 4 (1-5). Overall, two donkeys were assigned a score of 1 (excitement) during induction or recovery. HR and MAP during the procedure did not differ from baseline. fR was decreased at 5 and 10 minutes but was not considered clinically significant. SpO2 was <90% at one time point in two animals. CONCLUSIONS AND CLINICAL RELEVANCE: Xylazine-alfaxalone anesthesia resulted in adequate conditions for castration in 12 week old donkeys. While the majority of inductions and recoveries were good to excellent, significant excitement occurred in two animals and may limit the utility of this protocol for larger donkeys. Hypoxemia occurred despite intranasal oxygen supplementation.

Sedative effects of two doses of alfaxalone in combination with methadone and a low dose of dexmedetomidine in healthy Beagles.

OBJECTIVE: To evaluate the sedative effects of two doses of alfaxalone when added to a combination of dexmedetomidine and methadone injected intramuscularly (IM) in healthy Beagles. STUDY DESIGN: Randomized, blinded, crossover, experimental study. ANIMALS: A group of six adult Beagles. METHODS: Dogs were sedated on three different occasions with IM dexmedetomidine (3 µg kg-1) and methadone (0.3 mg kg-1) combined with two doses of alfaxalone (0.5 and 1 mg kg-1; A0.5 and A1, respectively) or saline (A0). Quality of sedation, response to tail clamping and rectal temperature were recorded at baseline, 5, 15, 25, 35 and 45 minutes. Pulse and respiratory rates, oxygen saturation of haemoglobin (SpO2) and noninvasive blood pressure (NIBP) were recorded every 5 minutes. Onset of sedation and duration of recumbency, response to venous catheterization and recovery quality were assessed. Physiological variables (analysis of variance) were analysed between treatments and within treatments compared with baseline (Student t test). Nonparametric data were analysed using Friedman and Cochran's Q tests. Significance was p < 0.05. RESULTS: Sedation scores were significantly higher when alfaxalone was co-administered (area under the curve; p = 0.024, A0.5; p = 0.019, A1), with no differences between doses. Onset of sedation was similar, but duration of recumbency was longer in A0.5 than in A0 [median (minimum-maximum), 43 (35-54) versus 30 (20-47) minutes, p = 0.018], but not in A1. Response to venous catheterization and tail clamping, and quality of recovery (acceptable) presented no differences between treatments. A decrease in all physiological variables (compared with baseline) was observed, except for NIBP, with no differences between treatments. All dogs required oxygen supplementation due to reduced SpO2. CONCLUSIONS AND CLINICAL RELEVANCE: Adding alfaxalone to methadone and dexmedetomidine enhanced sedation and duration of recumbency. Although cardiopulmonary depression was limited, oxygen supplementation is advisable.

Effects of ketamine or midazolam continuous rate infusions on alfaxalone total intravenous anaesthesia requirements and recovery quality in healthy dogs: a randomized clinical trial.

OBJECTIVE: To determine the alfaxalone dose reduction during total intravenous anaesthesia (TIVA) when combined with ketamine or midazolam constant rate infusions and to assess recovery quality in healthy dogs. STUDY DESIGN: Prospective, blinded clinical study. ANIMALS: A group of 33 healthy, client-owned dogs subjected to dental procedures. METHODS: After premedication with intramuscular acepromazine 0.05 mg kg-1 and methadone 0.3 mg kg-1, anaesthetic induction started with intravenous alfaxalone 0.5 mg kg-1 followed by either lactated Ringer's solution (0.04 mL kg-1, group A), ketamine (2 mg kg-1, group AK) or midazolam (0.2 mg kg-1, group AM) and completed with alfaxalone until endotracheal intubation was achieved. Anaesthesia was maintained with alfaxalone (6 mg kg-1 hour-1), adjusted (±20%) every 5 minutes to maintain a suitable level of anaesthesia. Ketamine (0.6 mg kg-1 hour-1) or midazolam (0.4 mg kg-1 hour-1) were employed for anaesthetic maintenance in groups AK and AM, respectively. Physiological variables were monitored during anaesthesia. Times from alfaxalone discontinuation to extubation, sternal recumbency and standing position were calculated. Recovery quality and incidence of adverse events were recorded. Groups were compared using parametric analysis of variance and nonparametric (Kruskal-Wallis, Chi-square, Fisher's exact) tests as appropriate, p < 0.05. RESULTS: Midazolam significantly reduced alfaxalone induction and maintenance doses (46%; p = 0.034 and 32%, p = 0.012, respectively), whereas ketamine only reduced the alfaxalone induction dose (30%; p = 0.010). Recovery quality was unacceptable in nine dogs in group A, three dogs in group AK and three dogs in group AM. CONCLUSIONS AND CLINICAL RELEVANCE: Midazolam, but not ketamine, reduced the alfaxalone infusion rate, and both co-adjuvant drugs reduced the alfaxalone induction dose. Alfaxalone TIVA allowed anaesthetic maintenance for dental procedures in dogs, but the quality of anaesthetic recovery remained unacceptable irrespective of its combination with ketamine or midazolam.

Effects of constant rate infusions of dexmedetomidine, remifentanil and their combination on minimum alveolar concentration of sevoflurane in dogs.

OBJECTIVE: To evaluate the effects of constant rate infusions (CRIs) of dexmedetomidine and remifentanil alone and their combination on minimum alveolar concentration (MAC) of sevoflurane in dogs. STUDY DESIGN: Randomized crossover experimental study. ANIMALS: A total of six (three males, three females) healthy, adult neutered Beagle dogs weighing 12.6 ± 1.4 kg. METHODS: Anesthesia was induced with sevoflurane in oxygen until endotracheal intubation was possible and anesthesia maintained with sevoflurane using positive-pressure ventilation. Each dog was anesthetized five times and was administered each of the following treatments: saline (1 mL kg-1 hour-1) or dexmedetomidine at 0.1, 0.5, 1.0 or 5.0 µg kg-1 loading dose intravenously over 10 minutes followed by CRI at 0.1, 0.5, 1.0 or 5.0 µg kg-1 hour-1, respectively. Following 60 minutes of CRI, sevoflurane MAC was determined in duplicate using an electrical stimulus (50 V, 50 Hz, 10 ms). Then, CRI of successively increasing doses of remifentanil (0.15, 0.60 and 2.40 µg kg-1 minute-1) was added to each treatment. MAC was also determined after 30 minutes equilibration at each remifentanil dose. Isobolographic analysis determined interaction from the predicted doses required for a 50% MAC reduction (ED50) with remifentanil, dexmedetomidine and remifentanil combined with dexmedetomidine, with the exception of dexmedetomidine 5.0 µg kg-1 hour-1, obtained using log-linear regression analysis. RESULTS: The sevoflurane MAC decreased dose-dependently with increasing infusion rates of dexmedetomidine and remifentanil. Remifentanil ED50 values were lower when combined with dexmedetomidine than those obtained during saline-remifentanil. Synergistic interactions between dexmedetomidine and remifentanil for MAC reduction occurred with dexmedetomidine at 0.5 and 1.0 µg kg-1 hour-1. CONCLUSIONS AND CLINICAL RELEVANCE: Combined CRIs of dexmedetomidine and remifentanil synergistically resulted in sevoflurane MAC reduction. The combination of dexmedetomidine and remifentanil effectively reduced the requirement of sevoflurane during anesthesia in dogs.