Minimum infusion rate of alfaxalone for total intravenous anaesthesia after sedation with acepromazine or medetomidine in cats undergoing ovariohysterectomy.

OBJECTIVE: To determine the induction doses, then minimum infusion rates of alfaxalone for total intravenous anaesthesia (TIVA), and subsequent, cardiopulmonary effects, recovery characteristics and alfaxalone plasma concentrations in cats undergoing ovariohysterectomy after premedication with butorphanol-acepromazine or butorphanol-medetomidine. STUDY DESIGN: Prospective randomized blinded clinical study. ANIMALS: Twenty-eight healthy cats. METHODS: Cats undergoing ovariohysterectomy were assigned into two groups: together with butorphanol [0.2 mg kg(-1) intramuscularly (IM)], group AA (n = 14) received acepromazine (0.1 mg kg(-1) IM) and group MA (n = 14) medetomidine (20 µg kg(-1) IM). Anaesthesia was induced with alfaxalone to effect [0.2 mg kg(-1) intravenously (IV) every 20 seconds], initially maintained with 8 mg kg(-1)  hour(-1) alfaxalone IV and infusion adjusted (±0.5 mg kg(-1)  hour(-1) ) every five  minutes according to alterations in heart rate (HR), respiratory rate (fR ), Doppler blood pressure (DBP) and presence of palpebral reflex. Additional alfaxalone boli were administered IV if cats moved/swallowed (0.5 mg kg(-1) ) or if fR >40 breaths minute(-1) (0.25 mg kg(-1) ). Venous blood samples were obtained to determine plasma alfaxalone concentrations. Meloxicam (0.2 mg kg(-1) IV) was administered postoperatively. Data were analysed using linear mixed models, Chi-squared, Fishers exact and t-tests. RESULTS: Alfaxalone anaesthesia induction dose (mean ± SD), was lower in group MA (1.87 ± 0.5; group AA: 2.57 ± 0.41 mg kg(-1) ). No cats became apnoeic. Intraoperative bolus requirements and TIVA rates (group AA: 11.62 ± 1.37, group MA: 10.76 ± 0.96 mg kg(-1)  hour(-1) ) did not differ significantly between groups. Plasma concentrations ranged between 0.69 and 10.76 µg mL(-1) . In group MA, fR , end-tidal carbon dioxide, temperature and DBP were significantly higher and HR lower. CONCLUSION AND CLINICAL RELEVANCE: Alfaxalone TIVA in cats after medetomidine or acepromazine sedation provided suitable anaesthesia with no need for ventilatory support. After these premedications, the authors recommend initial alfaxalone TIVA rates of 10 mg kg(-1)  hour(-1) .

The Advanced Locking Plate System (ALPS): a retrospective evaluation in 71 small animal patients.

OBJECTIVE: To evaluate use of the Advanced Locking Plate System (ALPS) in dogs and cats and report outcome. STUDY DESIGN: Retrospective case series. ANIMALS: Dogs (n = 29) and cats (n = 42). METHODS: The medical records (April 2007-April 2010) of dogs and cats treated with ALPS were reviewed evaluated. Data retrieved included signalment, indication for surgery, complications, and outcome. RESULTS: ALPS was used for 54 fractures, 12 tarsal or carpal ligament injuries and in 6 cases, to prevent or treat fractures during total hip replacement. Complications needing revision surgery occurred in 4 cases (5.5%): fixation failure was identified in 3 (2 fracture-fixations, 1 pancarpal arthrodesis), and a fracture occurred through a screw hole. The most common complication after tarsal arthrodesis was suture dehiscence. All cases had healed by study end. CONCLUSIONS: ALPS offers a reliable alternative for fracture treatment and some other orthopedic conditions in small animals.

Effect of contrast medium injection duration on peak enhancement and time to peak enhancement of canine pulmonary arteries.

Our goal was to investigate the effect of contrast medium injection duration on pulmonary artery peak enhancement and time to peak enhancement. Fourteen dogs were allocated into one of seven predefined weight categories, each category contained two dogs. Dogs in each weight category were assigned to group A or B. Animals in each group received a different contrast medium injection protocol. In group A, a fixed injection rate of 5 ml/s was used. In group B, the contrast injection rate was calculated as follows: flow rate= contrast volume/scan duration + 10s. Time to peak enhancement and peak enhancement of the main left and right pulmonary arteries were measured on single-level, dynamic CT images for a fixed time of 30s. Rank correlation (Spearman's) coefficients between injection duration and time to peak enhancement and between body weight and peak enhancement were calculated. For group A, there was a significant negative correlation between peak enhancement and weight (r = -0.94; P = 0.005), while for group B, there was no significant correlation (r = -0.64 and P = 0.18). There was a significant correlation between time to peak enhancement and injection duration in both groups (group A: r = 0.99; P = 0.006 and group B: r = 0.85; P = 0.02). In conclusion, injection duration is a key feature in a CT angiography injection protocol. A protocol with an injection duration adjusted to the scan duration seems to be particularly suitable for veterinary applications where a population with great weight variability is studied.

A study of cardiovascular function under controlled and spontaneous ventilation in isoflurane-medetomidine anaesthetized horses.

OBJECTIVE: To determine, in mildly hypercapnic horses under isoflurane-medetomidine balanced anaesthesia, whether there is a difference in cardiovascular function between spontaneous ventilation (SV) and intermittent positive pressure ventilation (IPPV). STUDY DESIGN: Prospective randomized clinical study. ANIMALS: Sixty horses, undergoing elective surgical procedures under general anaesthesia: ASA classification I or II. METHODS: Horses were sedated with medetomidine and anaesthesia was induced with ketamine and diazepam. Anaesthesia was maintained with isoflurane and a constant rate infusion of medetomidine. Horses were assigned to either SV or IPPV for the duration of anaesthesia. Horses in group IPPV were maintained mildly hypercapnic (arterial partial pressure of carbon dioxide (PaCO(2)) 50-60 mmHg, 6.7-8 kPa). Mean arterial blood pressure (MAP) was maintained above 70 mmHg by an infusion of dobutamine administered to effect. Heart rate (HR), respiratory rate (f(R)), arterial blood pressure and inspiratory and expiratory gases were monitored continuously. A bolus of ketamine was administered when horses showed nystagmus. Cardiac output was measured using lithium dilution. Arterial blood-gas analysis was performed regularly. Recovery time was noted and recovery quality scored. RESULTS: There were no differences between groups concerning age, weight, body position during anaesthesia and anaesthetic duration. Respiratory rate was significantly higher in group IPPV. Significantly more horses in group IPPV received supplemental ketamine. There were no other significant differences between groups. All horses recovered from anaesthesia without complications. CONCLUSIONS: There was no difference in cardiovascular function in horses undergoing elective surgery during isoflurane-medetomidine anaesthesia with SV in comparison with IPPV, provided the horses are maintained slightly hypercapnic. CLINICAL RELEVANCE: In horses with health status ASA I and II, cardiovascular function under general anaesthesia is equal with or without IPPV if the PaCO(2) is maintained at 50-60 mmHg.

A clinical comparison of two anaesthetic protocols using lidocaine or medetomidine in horses.

OBJECTIVE: To compare the effects of two balanced anaesthetic protocols on end-tidal isoflurane (Fe'ISO), cardiopulmonary performance and quality of recovery in horses. DESIGN: Prospective blinded randomized clinical study. ANIMALS: Sixty-nine client-owned horses, American Society of Anesthesiologists category I and II, undergoing elective surgery. METHODS: The horses were premedicated with acepromazine (0.03 mg kg(-1)) IM 30-60 minutes before induction of anaesthesia and were randomly assigned to one of two treatments: in group L (37 horses) xylazine (1 mg kg(-1)) and in group M (31 horses) medetomidine (7 microg kg(-1)) was administered IV for sedation. Anaesthesia was induced 5 minutes later with ketamine (2.2 mg kg(-1)) and diazepam (0.02 mg kg(-1)) IV and maintained with isoflurane in oxygen/air (initial FIO2 0.40-0.50) and a constant rate infusion (CRI) of either lidocaine (2 mg kg(-1)/15 minutes loading dose followed by 50 microg kg(-1) minute(-1)) (group L) or medetomidine (3.5 microg kg(-1) hour(-1)) (group M). If horses showed movement or nystagmus, additional thiopental or ketamine was administered. Heart rate, mean arterial pressure (MAP), Fe'ISO and arterial blood gases were measured. Cardiac output was measured with the lithium dilution method in 10 (group L) and 11 (group M) horses every 45 minutes. Recovery was scored. RESULTS: Heart rate and the cardiac index (CI) were significantly higher in group L with changes over time. In group M, MAP was significantly higher during the first 50 minutes. Group L needed more additional ketamine and thiopental to maintain a surgical plane of anaesthesia and Fe'ISO was significantly higher from 70 minutes. Recovery was longer in group M and of better quality. The significance level was set at p < 0.05. CONCLUSIONS AND CLINICAL RELEVANCE: In group M, maintenance of stable anaesthetic depth was easier and lower Fe'ISO was required to maintain a surgical plane of anaesthesia. Recoveries were longer but of better quality. The CI was higher in group L but cardiovascular function was generally well maintained in both groups.

Total intravenous anaesthesia in horses using medetomidine and propofol.

OBJECTIVE: To examine the clinical suitability of medetomidine-propofol infusions for total intravenous anaesthesia in horses. ANIMALS: Fifty client-owned horses of mixed breed, age [mean +/- SD (range)] 6.6 +/- 4.4 (0.04-18) years, mass 478 +/- 168.3 (80-700) kg presented for a range of operations requiring general anaesthesia. MATERIALS AND METHODS: Pre-anaesthetic medication was intravenous (IV) medetomidine 7 mug kg(-1). Anaesthesia was induced with IV ketamine (2 mg kg(-1)) and diazepam (0.02 mg kg(-1)). After endotracheal intubation, O2 was delivered (FiO2 > 0.85). Positive pressure ventilation was initiated if breath-holding in excess of 1 minute occurred. Anaesthesia was maintained with a constant rate medetomidine infusion (3.5 microg kg(-1) hour(-1)) and propofol infused IV to effect (initial dose 0.1 mg kg(-1) minute(-1)). Heart (HR) respiratory (fr) and propofol administration rates, and systemic arterial blood pressures were recorded at 5-minute intervals. Arterial blood gas (O2 and CO2) tensions and pH values were recorded every 15 minutes. Ten minutes after ending medetomidine-propofol infusion, medetomidine (2 microg kg(-1); IV) was given. Cardiopulmonary data were analysed using descriptive statistical techniques. RESULTS: Thirty-three orthopaedic, seven integumentary and 10 elective abdominal operations were performed. Cardiopulmonary data, presented as range of mean individual (and absolute individual minimum and maximum values) were: HR: 28.0-39.2 (16-88) beats minute(-1); mean arterial blood pressure: 74.0-132.5 (42-189) mmHg; PaO2: 22.1-42.9 (4.9-67.8) kPa; [166-322 (37-508) mmHg], PaCO2: 6.7-8.1 (4.2-11.8) kPa [50-61 (32-88) mmHg] and pH 7.35-7.39 (7.15-7.48). Positive pressure ventilation was required in 23 horses. In three horses, HR values below 20 beats minute(-1) were treated with 20 microg kg(-1) atropine (IV). Mean propofol infusion rates were 98-108 microg kg(-1) minute(-1). During anaesthesia, movement occurring in 14 horses was controlled with thiopental. Duration of anaesthesia was 111.6 +/- 41.4 (46-225) minutes. Recovery in all horses was uneventful and completed within 42.2 +/- 19.8 (12-98) minutes. CONCLUSIONS AND CLINICAL RELEVANCE: Medetomidine-propofol infusion produces adequate conditions for a range of surgical procedures. Cardiovascular function was adequate, as no pressor agents were required. Positive pressure ventilation was required in 23 horses.