Medetomidine continuous rate intravenous infusion in horses in which surgical anaesthesia is maintained with isoflurane and intravenous infusions of lidocaine and ketamine

ObjectiveTo evaluate medetomidine as a continuous rate infusion (CRI) in horses in which anaesthesia is maintained with isoflurane and CRIs of ketamine and lidocaine.Study designProspective, randomized, blinded clinical trial.AnimalsForty horses undergoing elective surgery.MethodsAfter sedation and induction, anaesthesia was maintained with isoflurane. Mechanical ventilation was employed. All horses received lidocaine (1.5 mg kg^?1 initially, then 2 mg kg^?1 hour^?1) and ketamine (2 mg kg^?1 hour^?1), both CRIs reducing to 1.5 mg kg^?1 hour^?1 after 50 minutes. Horses in group MILK received a medetomidine CRI of 3.6 μg kg^?1 hour^?1, reducing after 50 minutes to 2.75 μg kg^?1 hour^?1, and horses in group ILK an equal volume of saline. Mean arterial pressure (MAP) was maintained above 70 mmHg using dobutamine. End-tidal concentration of isoflurane (FE′ISO) was adjusted as necessary to maintain surgical anaesthesia. Group ILK received medetomidine (3 μg kg^?1) at the end of the procedure. Recovery was evaluated. Differences between groups were analysed using Mann-Whitney, Chi-Square and anova tests as relevant. Significance was taken as p < 0.05.ResultsFE′ISO required to maintain surgical anaesthesia in group MILK decreased with time, becoming significantly less than that in group ILK by 45 minutes. After 60 minutes, median (IQR) FE′ISO in MILK was 0.65 (0.4–1.0) %, and in ILK was 1 (0.62–1.2) %. Physiological parameters did not differ between groups, but group MILK required less dobutamine to support MAP. Total recovery times were similar and recovery quality good in both groups.Conclusion and clinical relevanceA CRI of medetomidine given to horses which were also receiving CRIs of lidocaine and ketamine reduced the concentration of isoflurane necessary to maintain satisfactory anaesthesia for surgery, and reduced the dobutamine required to maintain MAP. No further sedation was required to provide a calm recovery.     

Comparison of analgesic efficacy of epidural methadone or ropivacaine/methadone with or without pre‐operative oral tepoxalin in dogs undergoing tuberositas tibiae advancement surgery

ObjectiveTo investigate the clinical efficacy of four analgesia protocols in dogs undergoing tibial tuberosity advancement (TTA).Study designProspective, randomized, blinded study.AnimalsThirty-two client owned dogs undergoing TTA-surgery.MethodsDogs (n= 8 per treatment) received an oral placebo (PM and PRM) or tepoxalin (10 mg kg^?1) tablet (TM and TRM) once daily for 1 week before surgery. Epidural methadone (0.1 mg kg^?1) (PM and TM) or the epidural combination methadone (0.1 mg kg^?1)/ropivacaine 0.75% (1.65 mg kg^?1) (PRM and TRM) was administered after induction of anaesthesia. Intra-operative fentanyl requirements (2 μg kg^?1 IV) and end-tidal isoflurane concentration after 60 minutes of anaesthesia (Fe′ISO₆₀) were recorded. Post-operative analgesia was evaluated hourly from 1 to 8 and at 20 hours post-extubation with a visual analogue scale (VAS) and the University of Melbourne Pain Scale (UMPS). If VAS > 50 and/or UMPS > 10, rescue methadone (0.1 mg kg^?1) was administered IV. Analgesic duration (time from epidural until post-operative rescue analgesia) and time to standing were recorded. Normally distributed variables were analysed with an F-test (α = 0.05) or t-test for pairwise inter-treatment comparisons (Bonferonni adjusted α = 0.0083). Non-normally distributed data were analysed with the Kruskall–Wallis test (α = 0.05 or Bonferonni adjusted α = 0.005 for inter-treatment comparison of post-operative pain scores).ResultsMore intra-operative analgesia interventions were required in PM [2 (0–11)] [median (range)] and TM [2 (1–2)] compared to PRM (0) and TRM (0). Fe′ISO₆₀ was significantly lower in (PRM + TRM) compared to (PM + TM). Analgesic duration was shorter in PM (459 ± 276 minutes) (mean ± SD) and TM (318 ± 152 minutes) compared to TRM (853 ± 288 minutes), but not to PRM (554 ± 234 minutes). Times to standing were longer in the ropivacaine treatments compared to TM.Conclusions and clinical relevanceInclusion of epidural ropivacaine resulted in reduction of Fe′ISO₆₀, avoidance of intra-operative fentanyl administration, a longer duration of post-operative analgesia (in TRM) and a delay in time to standing compared to TM.     

The isoflurane sparing effect of a medetomidine constant rate infusion in horses

This clinical study analysed the anaesthetic sparing effect of a medetomidine constant rate infusion (CRI) during isoflurane anaesthesia in horses. Forty healthy horses undergoing different types of orthopaedic and soft tissue surgeries were studied in a randomized trial. Orthopaedic surgeries were primarily arthroscopies and splint bone extractions. Soft tissue surgeries were principally castrations with one ovariectomy. All horses received 0.03 mg kg^?1 acepromazine IM 1 hour prior to sedation. Group A (11 orthopaedic and nine soft tissue surgeries), was sedated with 1.1 mg kg^?1 xylazine IV, group B (13 orthopaedic and seven soft tissue surgeries) with 7 µg kg^?1 medetomidine IV. Anaesthesia was induced in both groups with 2.2 mg kg^?1 ketamine and diazepam 0.02 mg kg^?1 IV. Maintenance of anaesthesia was with isoflurane (ISO) in 100% oxygen, depth of anaesthesia was always adjusted by the first author. Group B received an additional CRI of 3.5 µg kg^?1 hour^?1 medetomidine. Respiratory rate (RR), heart rate (HR), mean arterial blood pressure (MAP), Fe ′ISO and Fe ′CO₂ were monitored with a methane insensitive monitor (Cardiocap 5, Ohmeda, Anandic, Diessenhofen) and noted every 5 minutes. Arterial blood was withdrawn for gas analysis (PaO₂, PaCO₂) 5 minutes after the induction of anaesthesia and every 30 minutes thereafter. Dobutamine (DOB) was given as a CRI to maintain mean arterial blood pressure above 70 mm Hg. Data were averaged over time (sum of measurements/number of measurements) and tested for differences between groups by unpaired t‐tests. There were no significant differences between the groups in terms of body mass (group A, 508 ± 73.7 kg; group B, 529.25 ± 78.4 kg) or duration of anaesthesia (group A, 125.5 ± 36 minutes; group B, 121.5 ± 48.4 minutes). The mean Fe ′ISO required to maintain a surgical plane of anaesthesia was significantly higher in group A (1.33 ± 0.13%) than in group B (1.07 ± 0.19%; p = 2.78 × 10^?5). Heart rate was different between the two groups (group A, 42.2 ± 8.3; group B, 32.6 ± 3.5; p = 8.8 × 10^?5). Dobutamine requirements were higher in group A (group A, 0.72 ± 0.24 μg kg^?1 minute^?1; group B, 0.53 ± 0.23 μg kg^?1 minute^?1; p = 0.023). Respiratory rate, Fe ′CO₂, PaO₂, PaCO₂ were not different between the groups. Adjustment of anaesthetic depth subjectively was easier with the medetomidine infusion and isoflurane (group B) than with isoflurane as a sole agent (group A). In group A 12 horses and in group B five horses showed purposeful movements on 27 (A) and 12 (B) occasions. They were given thiopental (group A, 0.0114 mg kg^?1 minute^?1; group B, 0.0023 mg kg^?1 minute^?1). In group A, a further 17 horses were given ketamine to deepen anaesthesia (52 occasions, 0.00426 mg kg^?1 minute^?1) whereas in group B only nine horses needed ketamine (34 occasions, 0.00179 mg kg^?1 minute^?1). An infusion of 3.5 µg kg^?1 MED during ISO anaesthesia resulted in a significantly reduced ISO requirement.     

A comparison of extradural and intravenous methadone on intraoperative isoflurane and postoperative analgesia requirements in dogs

Objective To compare the effects of intravenous (IV) and extradural (ED) methadone on end‐tidal isoflurane concentration (Fe ′ISO) and postoperative analgesic requirements in dogs undergoing femoro‐tibial joint surgery. Study Design Randomized, blinded, clinical study. Animals Twenty‐four healthy client‐owned dogs undergoing surgical repair of ruptured cruciate ligaments. Methods Dogs were randomly assigned to two groups of 12 animals and received either ED or IV methadone (0.3 mg kg^?1 diluted with saline to 0.2 mL kg^?1). Pre‐anaesthetic medication was IV acepromazine (0.05 mg kg^?1). Anaesthesia was induced with propofol and maintained initially with an Fe ′ISO of 1.0% delivered in oxygen. Methadone was injected with the dogs in sternal recumbency; the observer was unaware of the administration route. At 10 minutes (stimulation 1) and 20 minutes (stimulation 2) after methadone administration pelvic limb reflexes were tested by digit‐clamping. The time at skin incision (stimulation 3), joint‐capsule incision (stimulation 4), tibial tuberosity drilling (stimulation 5), fabellar suturing (stimulation 6) and extracapsular tightening (stimulation 7) were noted. Changes in heart rate (HR) and respiratory rate and arterial blood pressure associated with surgery were recorded along with the corresponding Fe ′ISO. After 20 minutes of anaesthesia, Fe ′ISO was decreased to the minimum required to maintain stable anaesthesia. Immediately after tracheal extubation, 1, 2, 3 and 6 hours postoperatively and on the morning after surgery, the degree of pain present was assessed using a numerical rating scale. The HR, respiratory rates and blood pressure were also recorded at these times. Serum cortisol and blood glucose concentrations were measured before pre‐anaesthetic medication and at each postoperative pain scoring interval except at 1 and 2 hours. Ketoprofen (2 mg kg^?1), carprofen (4 mg kg^?1) or meloxicam (0.2 mg kg^?1) were given by subcutaneous injection whenever pain scoring indicated moderate discomfort was present. Results Controlled ventilation was required in six dogs which stopped breathing after IV methadone. The median Fe ′ISO at stimulus 5 was 1.0% in the IV and 0.83% in the ED group. At stimulus 6, Fe ′ISO was 1.0% in the IV and 0.8% in the ED group; the difference was statistically significant (p ≤ 0.05). There was no significant difference in the duration of postoperative analgesia associated with administration route. Conclusions Extradural methadone significantly reduces the isoflurane requirement compared with IV methadone during femoro‐tibial joint surgery in dogs. Clinical relevance Extradural methadone provides safe and effective pain relief in dogs undergoing cruciate ligament repair.     

Clinical evaluation of ketamine and lidocaine intravenous infusions to reduce isoflurane requirements in horses under general anaesthesia

ObjectiveTo compare isoflurane alone or in combination with systemic ketamine and lidocaine for general anaesthesia in horses.Study designProspective, randomized, blinded clinical trial.AnimalsForty horses (ASA I-III) undergoing elective surgery.MethodsHorses were assigned to receive isoflurane anaesthesia alone (ISO) or with ketamine and lidocaine (LKI). After receiving romifidine, diazepam, and ketamine, the isoflurane end-tidal concentration was set at 1.3% and subsequently adjusted by the anaesthetist (unaware of treatments) to maintain a light plane of surgical anaesthesia. Animals in the LKI group received lidocaine (1.5 mg kg⁻¹ over 10 minutes, followed by 40 μg kg⁻¹ minute⁻¹) and ketamine (60 μg kg⁻¹ minute⁻¹), both reduced to 65% of the initial dose after 50 minutes, and stopped 15 minutes before the end of anaesthesia. Standard clinical cardiovascular and respiratory parameters were monitored. Recovery quality was scored from one (very good) to five (very poor). Differences between ISO and LKI groups were analysed with a two-sample t-test for parametric data or a Fischer's exact test for proportions (p < 0.05 for significance). Results are mean ± SD.ResultsHeart rate was lower (p = 0.001) for LKI (29 ± 4) than for ISO (34 ± 6). End-tidal concentrations of isoflurane (ISO: 1.57% ± 0.22; LKI: 0.97% ± 0.33), the number of horses requiring thiopental (ISO: 10; LKI: 2) or dobutamine (ISO:8; LKI:3), and dobutamine infusion rates (ISO:0.26 ± 0.09; LKI:0.18 ± 0.06 μg kg⁻¹ minute⁻¹) were significantly lower in LKI compared to the ISO group (p < 0.001). No other significant differences were found, including recovery scores.Conclusions and clinical relevanceThese results support the use of lidocaine and ketamine to improve anaesthetic and cardiovascular stability during isoflurane anaesthesia lasting up to 2 hours in mechanically ventilated horses, with comparable quality of recovery.     

Clinical comparison of two regimens of lidocaine infusion in horses undergoing laparotomy for colic

ObjectiveTo compare, in horses undergoing laparotomy for colic, the effects of administering or not administering a loading intravenous (IV) bolus of lidocaine prior to its constant rate infusion (CRI). Effects investigated during isoflurane anaesthesia were end-tidal isoflurane concentration (Fe’ISO), cardiovascular function, anaesthetic stability and the quality of recovery.Study designProspective, randomized clinical study.AnimalsThirty-six client-owned horses.MethodsHorses were assigned randomly to receive lidocaine as a CRI (50 μg kg⁻¹ minute⁻¹) either preceded (LB) or not preceded (L) by a loading dose (1.5 mg kg⁻¹ IV over 15 minutes). Lidocaine infusion (LInf) was started (T0) within 20 minutes after induction of general anaesthesia and discontinued approximately 30 minutes before the end of surgery. Anaesthetic depth, Fe’ISO, intra-operative physiological parameters and quality of recovery were assessed or measured. Data were analysed using one-way anova, t-test, Fisher test, Wilcoxon and Kruskal–Wallis tests as appropriate (p < 0.05).ResultsMean ± SD Fe’ISO was 1.21 ± 0.08% in group LB and 1.23 ± 0.06% in group L. Heart rate was significantly higher in group L than in group LB at times T5-T15, T25, T35 and T95. No difference was found between groups in other measured physiological values, nor in any measure taken to improve these parameters. Recovery phase was comparable and satisfactory in all but one full term pregnant horse in group L which fractured a femur during recovery.ConclusionPreloading with a lidocaine bolus prior to a CRI of lidocaine did not influence isoflurane requirements, cardiopulmonary effects (other than a reduction in heart rate at some time points) or recovery compared to no preloading bolus.Clinical relevanceA loading dose of lidocaine prior to CRI does not confer any advantage in horses undergoing laparotomy for colic.     

Comparison of isoflurane inhalation anaesthesia, injection anaesthesia and high volume caudal epidural anaesthesia for umbilical surgery in calves; metabolic, endocrine and cardiopulmonary effects

ObjectiveTo compare three anaesthetic protocols for umbilical surgery in calves regarding adequacy of analgesia, and cardiopulmonary and hormonal responses.Study designProspective, randomised experimental study.AnimalsThirty healthy German Holstein calves (7 female, 23 male) aged 45.9 ± 6.4 days.MethodsAll calves underwent umbilical surgery in dorsal recumbency. The anaesthetic protocols were as follows: group INH (n = 10), induction 0.1 mg kg^?1 xylazine IM and 2.0 mg kg^?1 ketamine IV, maintenance isoflurane in oxygen; Group INJ (n = 10), induction 0.2 mg kg^?1 xylazine IM and 5.0 mg kg^?1 ketamine IV, maintenance 2.5 mg kg^?1 ketamine IV every 15 minutes or as required; group EPI (n = 10), high volume caudal epidural anaesthesia with 0.2 mg kg^?1 xylazine diluted to 0.6 mL kg^?1 with procaine 2%. All calves received peri-umbilical infiltration of procaine and pre-operative IV flunixin (2.2 mg kg^?1). Cardiopulmonary variables were measured at preset intervals for up to 2 hours after surgery. The endocrine stress response was determined. Intra-operative nociception was assessed using a VAS scale. Data were compared between groups using appropriate statistical tests. A value of p < 0.05 was considered significant.ResultsAll three protocols provided adequate anaesthesia for surgery although, as judged by the VAS scale, intra-operative response was greatest with INJ. Lowest mean cortisol levels during surgery occurred in EPI. Heart rate and cardiac output did not differ between groups, but mean arterial blood pressure, systemic vascular resistance, and partial pressure of carbon dioxide were higher and arterial pH lower in groups INH and INJ than in Group EPI. Group INJ became hypoxaemic and had a significantly greater vascular shunt than did the other groups.Conclusion and clinical relevanceGroups INH and EPI both proved acceptable protocols for calves undergoing umbilical surgery, whilst INJ resulted in variable anti-nociception and in hypoxaemia. High volume caudal epidural anaesthesia provides a practical inexpensive method of anaesthesia for umbilical surgery.     

Alfaxalone or ketamine‐medetomidine in cats undergoing ovariohysterectomy: a comparison of intra‐operative parameters and post‐operative pain

ObjectiveTo compare post-operative pain in cats after alfaxalone or ketamine- medetomidine anaesthesia for ovariohysterectomy (OHE) and physiologic parameters during and after surgery.Study designProspective ‘blinded’ randomized clinical study.AnimalsTwenty-one healthy cats.MethodsCats were assigned randomly into two groups: Group A, anaesthesia was induced and maintained with alfaxalone [5 mg kg^?1 intravenously (IV) followed by boli (2 mg kg^?1 IV); Group MK, induction with ketamine (5 mg kg^?1 IV) after medetomidine (30 μg kg^?1 intramuscularly (IM)], and maintenance with ketamine (2 mg kg^?1 IV). Meloxicam (0.2 mg kg^?1 IV) was administered after surgery. Basic physiological data were collected. At time T = -2, 0, 0.5, 1, 2, 4, 6, 8, 12, 16, 20, and 24 hours post-operatively pain was assessed by three methods, a composite pain scale (CPS; 0–24 points), a visual analogue scale (VAS 0–100 mm), and a mechanical wound threshold (MWT) device. Butorphanol (0.2 mg kg^?1 IM) was administered if CPS was scored =13. Data were analyzed using a general linear model, Kruskal–Wallis analyses, Bonferroni-Dunn test, unpaired t-test and Fisher's exact test as relevant. Significance was set at p < 0.05.ResultsVASs were significantly higher at 0.5, 1, 2, 4, and 20 hours in group A; MWT values were significantly higher at 8 and 12 hours in group MK. Post-operative MWT decreased significantly compared to baseline in both groups. There was no difference in CPS at any time point. Five cats required rescue analgesia (four in A; one in MK).Conclusion and clinical relevanceAnaesthesia with ketamine-medetomidine was found to provide better post-surgical analgesia than alfaxalone in cats undergoing OHE; however, primary hyperalgesia developed in both groups. Alfaxalone is suitable for induction and maintenance of anaesthesia in cats undergoing OHE, but administration of additional sedative and analgesic drugs is highly recommended.     

Effects of detomidine or romifidine during maintenance and recovery from isoflurane anaesthesia in horses

ObjectiveTo evaluate the effects of detomidine or romifidine on cardiovascular function, isoflurane requirements and recovery quality in horses undergoing isoflurane anaesthesia.Study designProspective, randomized, blinded, clinical study.AnimalsA total of 63 healthy horses undergoing elective surgery during general anaesthesia.MethodsHorses were randomly allocated to three groups of 21 animals each. In group R, horses were given romifidine intravenously (IV) for premedication (80 μg kg^–1), maintenance (40 μg kg^–1 hour^–1) and before recovery (20 μg kg^–1). In group D2.5, horses were given detomidine IV for premedication (15 μg kg^–1), maintenance (5 μg kg^–1 hour^–1) and before recovery (2.5 μg kg^–1). In group D5, horses were given the same doses of detomidine IV for premedication and maintenance but 5 μg kg^–1 prior to recovery. Premedication was combined with morphine IV (0.1 mg kg^–1) in all groups. Cardiovascular and blood gas variables, expired fraction of isoflurane (Fe′Iso), dobutamine or ketamine requirements, recovery times, recovery events scores (from sternal to standing position) and visual analogue scale (VAS) were compared between groups using either anova followed by Tukey, Kruskal-Wallis followed by Bonferroni or chi-square tests, as appropriate (p < 0.05).ResultsNo significant differences were observed between groups for Fe′Iso, dobutamine or ketamine requirements and recovery times. Cardiovascular and blood gas measurements remained within physiological ranges for all groups. Group D5 horses had significantly worse scores for balance and coordination (p = 0.002), overall impression (p = 0.021) and final score (p = 0.008) than group R horses and significantly worse mean scores for VAS than the other groups (p = 0.002).Conclusions and clinical relevanceDetomidine or romifidine constant rate infusion provided similar conditions for maintenance of anaesthesia. Higher doses of detomidine at the end of anaesthesia might decrease the recovery quality.     

The influence of a continuous rate infusion of dexmedetomidine on the nociceptive withdrawal reflex and temporal summation during isoflurane anaesthesia in dogs

ObjectiveTo examine the influence of a low dose dexmedetomidine infusion on the nociceptive withdrawal reflex and temporal summation in dogs during isoflurane anaesthesia.Study designProspective experimental blinded cross-over study.AnimalsEight healthy mixed breed dogs, body weight Mean ± SD 26.5 ± 8.4 kg and age 25 ± 16 months.MethodsAnaesthesia was induced with propofol and maintained with isoflurane (Fe′ISO 1.3%) delivered in oxygen and air. After stabilization, baseline recordings (time 0) were obtained, then a dexmedetomidine bolus (1 μg kg^?1 IV) followed by a continuous rate infusion (1 μg kg^?1 hour^?1) or saline placebo were administered. At times 10, 30 and 60 minutes after the initial bolus, electrical stimulations of increasing intensity were applied over the lateral plantar digital nerve, and administered both as single and as repeated stimuli. The resulting reflex responses were recorded using electromyography. Data were analysed using a multivariable linear regression model and a Kruskal Wallis test for single stimulation data, and repeated measures anova and paired t-test for repeated stimulation data.ResultsThe AUC for the stimulus-response curves after single stimulation were similar for both treatments at time 0. At times 10, 30 and 60 the AUCs for the stimulus-response curves were significantly lower with dexmedetomidine treatment than with placebo. Temporal summation was evident in both treatments at times 0, 10, 30 and 60 starting from a stimulation intensity of 10 mA. The magnitude of temporal summation was smaller in dexmedetomidine than in placebo treated dogs at time 10, 30 and 60, but not at time 0.ConclusionsDuring isoflurane anaesthesia, low dose dexmedetomidine suppresses the nociceptive reflex responses after single and repeated electrical stimulation.Clinical relevanceThis experimental study confirms previous reports on its peri-operative efficacy under clinical conditions, and further indicates that dexmedetomidine might reduce the risk of post-operative chronic pain development.     

A clinical study on the effect in horses during medetomidine-isoflurane anaesthesia, of butorphanol constant rate infusion on isoflurane requirements, on cardiopulmonary function and on recovery characteristics

ObjectiveTo test if the addition of butorphanol by constant rate infusion (CRI) to medetomidine–isoflurane anaesthesia reduced isoflurane requirements, and influenced cardiopulmonary function and/or recovery characteristics.Study designProspective blinded randomised clinical trial.Animals61 horses undergoing elective surgery.MethodsHorses were sedated with intravenous (IV) medetomidine (7 μg kg^?1); anaesthesia was induced with IV ketamine (2.2 mg kg^?1) and diazepam (0.02 mg kg^?1) and maintained with isoflurane and a CRI of medetomidine (3.5 μg kg^?1 hour^?1). Group MB (n = 31) received butorphanol CRI (25 μg kg^?1 IV bolus then 25 μg kg^?1 hour^?1); Group M (n = 30) an equal volume of saline. Artificial ventilation maintained end-tidal CO₂ in the normal range. Horses received lactated Ringer’s solution 5 mL kg^?1 hour^?1, dobutamine <1.25 μg kg^?1 minute^?1 and colloids if required. Inspired and exhaled gases, heart rate and mean arterial blood pressure (MAP) were monitored continuously; pH and arterial blood gases were measured every 30 minutes. Recovery was timed and scored. Data were analyzed using two way repeated measures anova, independent t-tests or Mann–Whitney Rank Sum test (p < 0.05).ResultsThere was no difference between groups with respect to anaesthesia duration, end-tidal isoflurane (MB: mean 1.06 ± SD 0.11, M: 1.05 ± 0.1%), MAP (MB: 88 ± 9, M: 87 ± 7 mmHg), heart rate (MB: 33 ± 6, M: 35 ± 8 beats minute^?1), pH, PaO₂ (MB: 19.2 ± 6.6, M: 18.2 ± 6.6 kPa) or PaCO_2. Recovery times and quality did not differ between groups, but the time to extubation was significantly longer in group MB (26.9 ± 10.9 minutes) than in group M (20.4 ± 9.4 minutes).Conclusion and clinical relevanceButorphanol CRI at the dose used does not decrease isoflurane requirements in horses anaesthetised with medetomidine–isoflurane and has no influence on cardiopulmonary function or recovery.     

Cardiopulmonary and isoflurane‐sparing effects of epidural or intravenous infusion of dexmedetomidine in cats undergoing surgery with epidural lidocaine

ObjectiveTo compare the cardiorespiratory, anesthetic-sparing effects and quality of anesthetic recovery after epidural and constant rate intravenous (IV) infusion of dexmedetomidine (DEX) in cats given a low dose of epidural lidocaine under propofol-isoflurane anesthesia and submitted to elective ovariohysterectomy.Study designRandomized, blinded clinical trial.AnimalsTwenty-one adult female cats (mean body weight: 3.1 ± 0.4 kg).MethodsCats received DEX (4 μg kg^?1, IM). Fifteen minutes later, anesthesia was induced with propofol and maintained with isoflurane. Cats were divided into three groups. In GI cats received epidural lidocaine (1 mg kg^?1, n = 7), in GII cats were given epidural lidocaine (1 mg kg^?1) + DEX (4 μg kg^?1, n = 7), and in GIII cats were given epidural lidocaine (1 mg kg^?1) + IV constant rate infusion (CRI) of DEX (0.25 μg kg^?1 minute^?1, n = 7). Variables evaluated included heart rate (HR), respiratory rate (f_R), systemic arterial pressures, rectal temperature (RT), end-tidal CO₂, end-tidal isoflurane concentration (e′ISO), arterial blood gases, and muscle tone. Anesthetic recovery was compared among groups by evaluation of times to recovery, HR, f_R, RT, and degree of analgesia. A paired t-test was used to evaluate pre-medication variables and blood gases within groups. anova was used to compare parametric data, whereas Friedman test was used to compare muscle relaxation.ResultsEpidural and CRI of DEX reduced HR during anesthesia maintenance. Mean ± SD e′ISO ranged from 0.86 ± 0.28% to 1.91 ± 0.63% in GI, from 0.70 ± 0.12% to 0.97 ± 0.20% in GII, and from 0.69 ± 0.12% to 1.17 ± 0.25% in GIII. Cats in GII and GIII had longer recovery periods than in GI.Conclusions and clinical relevanceEpidural and CRI of DEX significantly decreased isoflurane consumption and resulted in recovery of better quality and longer duration, despite bradycardia, without changes in systemic blood pressure.     

Sedative and analgesic effects of buprenorphine,combined with either acepromazine or dexmedetomidine,for premedication prior to elective surgery in cats and dogs

ObjectiveTo evaluate the sedative and analgesic effects of intramuscular buprenorphine with either dexmedetomidine or acepromazine, administered as premedication to cats and dogs undergoing elective surgery.Study designProspective, randomized, blinded clinical study.AnimalsForty dogs and 48 cats.MethodsAnimals were assigned to one of four groups, according to anaesthetic premedication and induction agent: buprenorphine 20 μg kg^?1 with either dexmedetomidine (dex) 250 μg m^?2 or acepromazine (acp) 0.03 mg kg^?1, followed by alfaxalone (ALF) or propofol (PRO). Meloxicam was administered preoperatively to all animals and anaesthesia was always maintained using isoflurane. Physiological measures and assessments of pain, sedation and mechanical nociceptive threshold (MNT) were made before and after premedication, intraoperatively, and for up to 24 hours after premedication. Data were analyzed with one-way, two-way and mixed between-within subjects anova, Kruskall–Wallis analyses and Chi squared tests. Results were deemed significant if p ≤ 0.05, except where multiple comparisons were performed (p ≤ 0.005).ResultsCats premedicated with dex were more sedated than cats premedicated with acp (p < 0.001) and ALF doses were lower in dex cats (1.2 ± 1.0 mg kg^?1) than acp cats (2.5 ± 1.9 mg kg^?1) (p = 0.041). There were no differences in sedation in dogs however PRO doses were lower in dex dogs (1.5 ± 0.8 mg kg^?1) compared to acp dogs (3.3 ± 1.1 mg kg^?1) (p < 0.001). There were no differences between groups with respect to pain scores or MNT for cats or dogs.ConclusionChoice of dex or acp, when given with buprenorphine, caused minor, clinically detectable, differences in various characteristics of anaesthesia, but not in the level of analgesia.Clinical relevanceA combination of buprenorphine with either acp or dex, followed by either PRO or ALF, and then isoflurane, accompanied by an NSAID, was suitable for anaesthesia in dogs and cats undergoing elective surgery. Choice of sedative agent may influence dose of anaesthetic induction agent.     

Dose-dependent effects of isoflurane and dobutamine on cardiovascular function in dogs with experimental mitral regurgitation

Objective

To investigate the dose-dependent effects of isoflurane and dobutamine on haemodynamics in dogs with experimentally induced mitral valve insufficiency (MI).

Evaluation of chemical restraint,isoflurane anesthesia and methadone or tramadol as preventive analgesia in spotted pacas (Cuniculus paca) subjected to laparoscopy

ObjectiveTo evaluate the efficacy and cardiopulmonary effects of ketamine–midazolam for chemical restraint, isoflurane anesthesia and tramadol or methadone as preventive analgesia in spotted pacas subjected to laparoscopy.Study designProspective placebo-controlled blinded trial.AnimalsA total of eight captive female Cuniculus paca weighing 9.3 ± 0.9 kg.MethodsAnimals were anesthetized on three occasions with 15 day intervals. Manually restrained animals were administered midazolam (0.5 mg kg^–1) and ketamine (25 mg kg^–1) intramuscularly. Anesthesia was induced and maintained with isoflurane 30 minutes later. Tramadol (5 mg kg^–1), methadone (0.5 mg kg^–1) or saline (0.05 mL kg^–1) were administered intramuscularly 15 minutes prior to laparoscopy. Heart rate (HR), respiratory rate, mean arterial pressure (MAP), peripheral oxygen saturation (SpO₂), end-tidal CO₂ partial pressure (Pe′CO₂), end-tidal concentration of isoflurane (Fe′Iso), pH, PaO₂, PaCO₂, bicarbonate (HCO₃^?), anion gap (AG) and base excess (BE) were monitored after chemical restraint, anesthesia induction and at different laparoscopy stages. Postoperative pain was assessed by visual analog scale (VAS) for 24 hours. Variables were compared using anova or Friedman test (p < 0.05).ResultsChemical restraint was effective in 92% of animals. Isoflurane anesthesia was effective; however, HR, MAP, pH and AG decreased, whereas Pe′CO₂, PaO₂, PaCO₂, HCO₃^? and BE increased. MAP was stable with tramadol and methadone treatments; HR, Fe′Iso and postoperative VAS decreased. VAS was lower for a longer time with methadone treatment; SpO₂ and AG decreased, whereas Pe′CO₂, PaCO₂ and HCO₃^? increased.Conclusions and clinical relevanceKetamine–midazolam provided satisfactory restraint. Isoflurane anesthesia for laparoscopy was effective but resulted in hypotension and respiratory acidosis. Tramadol and methadone reduced isoflurane requirements, provided postoperative analgesia and caused hypercapnia, with methadone causing severe respiratory depression. Thus, the anesthetic protocol is adequate for laparoscopy in Cuniculus paca; however, methadone should be avoided.     

Effects of vatinoxan in dogs premedicated with medetomidine and butorphanol followed by sevoflurane anaesthesia: a randomized clinical study

ObjectiveTo investigate effects of vatinoxan in dogs, when administered as intravenous (IV) premedication with medetomidine and butorphanol before anaesthesia for surgical castration.Study designA randomized, controlled, blinded, clinical trial.AnimalsA total of 28 client-owned dogs.MethodsDogs were premedicated with medetomidine (0.125 mg m^?2) and butorphanol (0.2 mg kg^?1) (group MB; n = 14), or medetomidine (0.25 mg m^?2), butorphanol (0.2 mg kg^?1) and vatinoxan (5 mg m^?2) (group MB-VATI; n = 14). Anaesthesia was induced 15 minutes later with propofol and maintained with sevoflurane in oxygen (targeting 1.3%). Before surgical incision, lidocaine (2 mg kg^?1) was injected intratesticularly. At the end of the procedure, meloxicam (0.2 mg kg^?1) was administered IV. The level of sedation, the qualities of induction, intubation and recovery, and Glasgow Composite Pain Scale short form (GCPS-SF) were assessed. Heart rate (HR), respiratory rate (f_R), mean arterial pressure (MAP), end-tidal concentration of sevoflurane (Fe′Sevo) and carbon dioxide (Pe′CO₂) were recorded. Blood samples were collected at 10 and 30 minutes after premedication for plasma medetomidine and butorphanol concentrations.ResultsAt the beginning of surgery, HR was 61 ± 16 and 93 ± 23 beats minute^?1 (p = 0.001), and MAP was 78 ± 7 and 56 ± 7 mmHg (p = 0.001) in MB and MB-VATI groups, respectively. No differences were detected in f_R, Pe′CO₂, Fe′Sevo, the level of sedation, the qualities of induction, intubation and recovery, or in GCPS-SF. Plasma medetomidine concentrations were higher in group MB-VATI than in MB at 10 minutes (p = 0.002) and 30 minutes (p = 0.0001). Plasma butorphanol concentrations were not different between groups.Conclusions and clinical relevanceIn group MB, HR was significantly lower than in group MB-VATI. Hypotension detected in group MB-VATI during sevoflurane anaesthesia was clinically the most significant difference between groups.     

Comparison of bupivacaine femoral and sciatic nerve block versus bupivacaine and morphine epidural for stifle surgery in dogs

ObjectiveTo evaluate the efficacy of combined femoral and sciatic nerve blocks as an alternative to epidural anesthesia and analgesia in dogs undergoing stifle surgery under general anesthesia.Study designProspective, blinded, randomized, clinical comparison.AnimalsTwenty dogs weighing 37 ± 11 (mean ± SD) kg, aged 3 (1–8) [median (minimum–maximum)] years undergoing elective unilateral tibial-plateau leveling osteotomy.MethodsDogs were assigned randomly to receive either epidural anesthesia (bupivacaine 0.5%, 0.5 mg kg^?1 + morphine 0.1%, 0.1 mg kg^?1, in 0.2 mL kg^?1; EPID) or femoral and sciatic nerve blocks (Bupivacaine 0.5%, 0.1 mL kg^?1, was administered at each site; F + S) guided by electrolocation. All patients received a standard general anesthesia technique. Pain and sedation were scored (on scales of 0–10 and 0–3, respectively) pre-operatively, at extubation, and at 1, 4 and then every 4 hours thereafter up to 24 hours. Postoperatively, hydromorphone was administered to any patient with a pain score of >5 or whenever the blinded caregiver determined that more hydromorphone was necessary. Intraoperative heart rate (HR), mean arterial pressure (MAP), end tidal isoflurane (FE′ISO), body temperature, post-operative pain scores, time to first hydromorphone dose after surgery, time to first feeding, time to first drinking, time to first urination, time to first ambulation (walk on a lead) and cumulative dose of hydromorphone were recorded.ResultsIntra-operatively, FE′ISO and MAP were significantly lower in the EPID group (p = 0.05 and p = 0.04, respectively). Postoperatively, the cumulative hydromorphone consumption (p = 0.04) and the incidence of urinary retention (p = 0.03) were higher in the EPID group.Conclusion and clinical relevance F + S is a practical alternative to EPID that produces less urine retention and reduces opioid consumption in the 24 hours after surgery. EPID might be associated with a lower isoflurane requirement and lower systemic blood pressure.     

Evaluation of the isoflurane‐sparing effects of fentanyl,lidocaine, ketamine,dexmedetomidine, or the combination lidocaine‐ketamine‐dexmedetomidine during ovariohysterectomy in dogs

ObjectiveTo evaluate the isoflurane‐sparing effects of an intravenous (IV) constant rate infusion (CRI) of fentanyl, lidocaine, ketamine, dexmedetomidine, or lidocaine‐ketamine‐dexmedetomidine (LKD) in dogs undergoing ovariohysterectomy.Study designRandomized, prospective, blinded, clinical study.AnimalsFifty four dogs.MethodsAnesthesia was induced with propofol and maintained with isoflurane with one of the following IV treatments: butorphanol/saline (butorphanol 0.4 mg kg^?1, saline 0.9% CRI, CONTROL/BUT); fentanyl (5 μg kg^?1, 10 μg kg^?1 hour^?1, FENT); ketamine (1 mg kg^?1, 40 μg kg^?1 minute^?1, KET), lidocaine (2 mg kg^?1, 100 μg kg^?1 minute^?1, LIDO); dexmedetomidine (1 μg kg^?1, 3 μg kg^?1 hour^?1, DEX); or a LKD combination. Positive pressure ventilation maintained eucapnia. An anesthetist unaware of treatment and end‐tidal isoflurane concentration (Fe′Iso) adjusted vaporizer settings to maintain surgical anesthetic depth. Cardiopulmonary variables and Fe′Iso concentrations were monitored. Data were analyzed using anova (p < 0.05).ResultsAt most time points, heart rate (HR) was lower in FENT than in other groups, except for DEX and LKD. Mean arterial blood pressure (MAP) was lower in FENT and CONTROL/BUT than in DEX. Overall mean ± SD Fe′Iso and % reduced isoflurane requirements were 1.01 ± 0.31/41.6% (range, 0.75 ± 0.31/56.6% to 1.12 ± 0.80/35.3%, FENT), 1.37 ± 0.19/20.8% (1.23 ± 0.14/28.9% to 1.51 ± 0.22/12.7%, KET), 1.34 ± 0.19/22.5% (1.24 ± 0.19/28.3% to 1.44 ± 0.21/16.8%, LIDO), 1.30 ± 0.28/24.8% (1.16 ± 0.18/32.9% to 1.43 ± 0.32/17.3%, DEX), 0.95 ± 0.19/54.9% (0.7 ± 0.16/59.5% to 1.12 ± 0.16/35.3%, LKD) and 1.73 ± 0.18/0.0% (1.64 ± 0.21 to 1.82 ± 0.14, CONTROL/BUT) during surgery. FENT and LKD significantly reduced Fe′Iso.Conclusions and clinical relevanceAt the doses administered, FENT and LKD had greater isoflurane‐sparing effect than LIDO, KET or CONTROL/BUT, but not at all times. Low HR during FENT may limit improvement in MAP expected with reduced Fe′Iso.