A comparison of two ketamine doses for field anaesthesia in horses undergoing castration.

BACKGROUND: Ketamine at 2.2 mg/kg given i.v. is often used to induce anaesthesia for surgical procedures in horses under field conditions. Commonly, additional doses are needed to complete the surgery. We hypothesised that surgical conditions would be improved when 5 mg/kg of ketamine was used to induce anaesthesia, while induction and recovery qualities would not differ from those when 2.2 mg/kg ketamine was used. OBJECTIVE: To compare the anaesthetic effects of two ketamine doses (5 and 2.2 mg/kg) during field anaesthesia for castration of horses. STUDY DESIGN: Prospective, randomised, blinded, clinical study. METHOD: Seventy-seven client-owned Icelandic horses presented for castration under field conditions were studied. Pre-anaesthetic medication was xylazine (0.7 mg/kg) butorphanol (25 µg/kg) and acepromazine (50 µg/kg) injected i.v. Anaesthesia was induced with either 2.2 mg/kg (K2.2) or 5 mg/kg (K5) i.v. of ketamine mixed with diazepam (30 µg/kg). The quality of induction, surgical conditions and recovery were compared using subjective and objective measures, and the number of additional ketamine doses recorded. RESULTS: Ketamine 5 mg/kg provided better surgical conditions and a more rapid induction. Recovery quality was subjectively better in K2.2. Five horses in K2.2 and two in K5 required additional ketamine doses. MAIN LIMITATIONS: While the pre-anaesthetic sedation and benzodiazepine doses were consistent among horses, the level of sedation and muscle relaxation achieved differed. CONCLUSION: A ketamine dose of 5 mg/kg can be used to improve the quality of field anaesthesia for castration in Icelandic horses. Although recovery quality is subjectively better when using 2.2 mg/kg, no adverse events were observed during recovery with either dose The Summary is available in Portuguese - see Supporting Information.

Intra-breath arterial oxygen oscillations detected by a fast oxygen sensor in an animal model of acute respiratory distress syndrome.

BACKGROUND: There is considerable interest in oxygen partial pressure (Po2) monitoring in physiology, and in tracking Po2 changes dynamically when it varies rapidly. For example, arterial Po2 ([Formula: see text]) can vary within the respiratory cycle in cyclical atelectasis (CA), where [Formula: see text] is thought to increase and decrease during inspiration and expiration, respectively. A sensor that detects these [Formula: see text] oscillations could become a useful diagnostic tool of CA during acute respiratory distress syndrome (ARDS). METHODS: We developed a fibreoptic Po2 sensor (<200 µm diameter), suitable for human use, that has a fast response time, and can measure Po2 continuously in blood. By altering the inspired fraction of oxygen ([Formula: see text]) from 21 to 100% in four healthy animal models, we determined the linearity of the sensor's signal over a wide range of [Formula: see text] values in vivo. We also hypothesized that the sensor could measure rapid intra-breath [Formula: see text] oscillations in a large animal model of ARDS. RESULTS: In the healthy animal models, [Formula: see text] responses to changes in [Formula: see text] were in agreement with conventional intermittent blood-gas analysis (n=39) for a wide range of [Formula: see text] values, from 10 to 73 kPa. In the animal lavage model of CA, the sensor detected [Formula: see text] oscillations, also at clinically relevant [Formula: see text] levels close to 9 kPa. CONCLUSIONS: We conclude that these fibreoptic [Formula: see text] sensors have the potential to become a diagnostic tool for CA in ARDS.

Laryngeal transplantation in minipigs: early immunological outcomes.

Despite recent tissue-engineering advances, there is no effective way of replacing all the functions of the larynx in those requiring laryngectomy. A recent clinical transplant was a success. Using quantitative immunofluorescence targeted at immunologically relevant molecules, we have studied the early (48 h and 1 week) immunological responses within larynxes transplantated between seven pairs of National Institutes of Health (NIH) minipigs fully homozygous at the major histocompatibility complex (MHC) locus. There were only small changes in expression of some molecules (relative to interindividual variation) and these were clearest in samples from the subglottic region, where the areas of co-expression of CD25(+) CD45RC(-) CD8(-) and of CD163(+) CD172(+) MHC-II(-) increased at 1 week after transplant. In one case, infiltration by recipient T cells was analysed by T cell receptor (TCR) Vß spectratype analysis; this suggested that changes in the T cell repertoire occur in the donor subglottis mucosal tissues from day 0 to day 7, but that the donor and recipient mucosal Vß repertoires remain distinct. The observed lack of strong immunological responses to the trauma of surgery and ischaemia provides encouraging evidence to support clinical trials of laryngeal transplantation, and a basis on which to interpret future studies involving mismatches.

Laryngeal transplantation in minipigs: vascular, myologic and functional outcomes.

There is no effective way of replacing all the functions of the larynx in those requiring laryngectomy. Regenerative medicine offers promise, but cannot presently deliver implants with functioning neuromuscular units. A single well-documented laryngeal transplant in man was a qualified success, but more information is required before clinical trials may be proposed. We studied the early response of the larynx to laryngeal transplantation between 17 pairs of NIH minipigs full matched at the MHC2 locus. Following iterative technical improvements, pigs had good swallowing and a patent airway at 1 week. No significant changes in mucosal blood flux were observed compared with pre-operative measurements. Changes in muscle morphology and fibre phenotype were observed in transplant muscles retrieved after 7 days: the levels of fast and slow myosin heavy chain (MyHC) protein were reduced and embryonic MyHC was up regulated consistent with denervation induced atrophy. At 1 week laryngeal transplantation can result in good swallowing, and is not associated with clinical evidence of ischemia-reperfusion injury in MHC-matched pigs.

Postoperative analgesic efficacy of meloxicam compared to tolfenamic acid in cats undergoing orthopaedic surgery.

OBJECTIVES: To investigate the efficacy of meloxicam or tolfenamic acid administered preoperatively and postoperatively (five days in total) to cats undergoing surgical fracture repair. METHODS: Eighty-eight otherwise healthy cats were matched according to fracture site and then randomly allocated to one of two groups, receiving 0·2 mg/kg meloxicam by subcutaneous injection (group M) or 1·5 to 3 mg/kg tolfenamic acid orally (group T) before anaesthesia. Analgesia was continued with 0.05 mg/kg oral meloxicam once daily or 1·5 to 3 mg/kg oral tolfenamic acid twice daily for four days postoperatively. Pain was assessed by a blinded observer using visual analogue scales and a functional limb score. The drug administrator assessed feed intake and palatability of the treatment. RESULTS: Data from 66 cats were analysed. Visual analogue scale pain scores and functional limb scores decreased over time in both groups but were not significantly different between treatments. Feed intake was similar in both groups. Meloxicam was significantly more palatable than tolfenamic acid on all treatment days. CLINICAL SIGNIFICANCE: Meloxicam and tolfenamic acid demonstrated comparable analgesia, without clinically observable side effects. Meloxicam may be associated with superior compliance in clinical practice due to the higher palatability and once daily treatment resulting in better ease of administration.

Induction of anaesthesia with alfaxalone or propofol before isoflurane maintenance in cats.

Thirty-nine healthy cats that were presented for ovariohysterectomy received intramuscular acepromazine (0.05 mg/kg) and subcutaneous meloxicam (0.3 mg/kg) as preanaesthetic medication. They were then randomly assigned to receive either propofol or alfaxalone by intravenous injection for induction of anaesthesia, administered to effect until tracheal intubation was possible. Anaesthesia was maintained with isoflurane in oxygen. Cardiorespiratory variables were measured before induction and every five minutes throughout anaesthesia. The recovery times and quality of recovery were also recorded. Data relating to one cat were omitted because it was found to be pregnant. The mean (sd) induction doses were 4.7 (1.2) mg/kg for alfaxalone and 7.5 (2.0) mg/kg for propofol. Postinduction apnoea was not observed. There were no significant differences in cardiorespiratory variables between the alfaxalone group (mean pulse rate [PR] 155 [18]) bpm, Doppler arterial blood pressure [DBP] 73 [6] mmHg, respiratory rate [RR] 31 [8] breaths/minute, end-tidal carbon dioxide partial pressure [PECO(2)] 3.7 [0.8] kPa) and the propofol group (PR 147 [16] bpm, DBP 77 [12] mmHg, RR 32 [8] breaths/minute, PECO(2) 3.7 [0.5] kPa). Recovery times were very similar and the quality of recovery was considered fair or good in most cats in both groups. The induction of anaesthesia, the cardiorespiratory variables and the recovery were clinically acceptable and similar after induction with either alfaxalone or propofol.

Induction of anaesthesia with either midazolam or propofol in rabbits premedicated with fentanyl/fluanisone.

Fifty-four rabbits that were to be neutered were premedicated with 0.1 ml/kg fentanyl/fluanisone and then randomly allocated to be anaesthetised with either midazolam or propofol. Anaesthesia was then maintained with isoflurane. The ease of orotracheal intubation, the rabbits' cardiorespiratory variables, and the speed and quality of recovery from anaesthesia were assessed by the same anaesthetist who was unaware of the induction agent used. Hypotension was common in both groups. The mean (sd) respiratory rates were 30 (12) breaths per minute in the midazolam group and 43 (15) breaths per minute in the propofol group. The mean (sd) time to first head lift was 36 (21) minutes in the midazolam group and 14 (11) minutes in the propofol group, and the mean (sd) times to the return of the righting reflex were 35 (19) minutes and 15 (eight) minutes, respectively. The quality of recovery was better in the propofol group than in the midazolam group.

Development of perioperative care for pigs undergoing laryngeal transplantation: a case series.

Pigs are ideal animal models for airway surgical research, facilitating the successful translation of science into clinical practice. Despite their ubiquitous use, there is a paucity of information on the perioperative care of pigs, especially for major procedures. In a series of experiments to investigate laryngeal transplantation, we combined veterinary and medical experience to develop protocols for perioperative management of pigs, including high dependency care. Novel airway management methods were developed. A pain scoring system was used to direct analgesia use. Fluid balance and electrolytes were monitored closely. Recent animals received a central venous line via the femoral vein two days prior to transplantation to facilitate blood sampling and drug delivery. Intensive monitoring and airway management were required to ensure a successful outcome. Methods for optimal perioperative care are proposed. These results will help future groups wishing to use pigs in airway research, will reduce numbers of animals used and improve animal welfare.

The effects of nitrous oxide on recovery from isoflurane anaesthesia in dogs.

OBJECTIVES: To assess rate and quality of recovery from anaesthesia where isoflurane was delivered in oxygen or oxygen/nitrous oxide. METHODS: Dogs anaesthetised with propofol were randomly allocated to receive isoflurane maintenance in either 100 per cent oxygen (group 1) or 66 per cent nitrous oxide (N(2)O)/34 per cent oxygen (group 2). Time from end of anaesthesia to achieving sternal recumbency was recorded. Incidence of adverse behaviours (vocalisation, uncontrolled head movement and restlessness) were assessed. Recovery quality was recorded on a visual analogue scale (VAS) (anchored at 0 with "best possible" recovery and "did not recover" at 100 mm). Age, weight, gender, anaesthetic duration, mean vaporiser setting, VAS scores, recovery times, postoperative temperature and behavioural scores were compared (chi-squared test, Mann-Whitney U test or t-test as appropriate, significance P< or =0.05). RESULTS: Objective data from 54 dogs were analysed, only VAS data where the observer was unaware of treatment group were used (n=33). Recovery was faster in group 2 dogs (median 10 min [range 4 to 31] compared with 14 minutes [3 to 43] in group 1, P=0.049) with less restlessness (0 [0 to 4] compared with 2 [0 to 4] in group 1, P=0.013) and uncontrolled head movement (0 [0 to 4] compared with 1 [0 to 3] in group 1, P<0.001). However, VAS scores were not statistically different between groups (group 1: mean 39.4 mm [s.d. 24.0)]; group 2: 30.1 mm [25.9]; P=0.303). CLINICAL SIGNIFICANCE: Addition of N(2)O to isoflurane anaesthesia results in a lower incidence of adverse behaviour (for example restlessness) and marginally faster recovery.

Recovery characteristics following maintenance of anaesthesia with sevoflurane or isoflurane in dogs premedicated with acepromazine.

A standard anaesthetic protocol was used to anaesthetise 40 dogs for intravenous urography and a retrograde urethrogram or vaginourethrogram. The dogs were allocated by blocked randomisation to receive either isoflurane or sevoflurane for maintenance of anaesthesia after they had been premedicated with acepromazine and pethidine, and anaesthesia induced with propofol. An observer who was unaware of which agent had been used assessed ataxia 30 and 60 minutes after discontinuation of administration of the anaesthetic and assigned an overall recovery score. No complications occurred during anaesthesia of either group of dogs. The scores for ataxia were significantly lower after 60 minutes than after 30 minutes, but there was no significant difference between the groups. The quality of recovery was significantly better in the dogs that received sevoflurane than in those that received isoflurane, but the recovery times were similar.

Dystocia in a Rothschild giraffe leading to a caesarean section.

A 9-year-old female Rothschild giraffe (Giraffa camelopardalis rothschildi), weighing approximately 900 kg, at Longleat Safari Park, Wiltshire, UK was presented with dystocia in September 2005. This paper details the surgical and anaesthetic procedures carried out performing a caesarean section to remove a dead male calf and the successful recovery of the giraffe.

Early immunological changes associated with laryngeal transplantation in a major histocompatibility complex-matched pig model.

Laryngeal transplantation is an increasingly viable proposition for patients with irreversible diseases of the larynx. One human transplant has been performed successfully, but many questions remain before routine transplantation can begin. In order to measure the immunological changes in mismatched transplants, it is first necessary to know the immediate combined effects of ischaemia-reperfusion injury (IRI) plus the added insult of major surgery in a fully matched setting. We measured the changes in immunologically active mucosal cells following 3 h of cold ischaemia and 8 h of in situ reperfusion in a major histocompatibility complex (MHC)-matched minipig model (n = 4). Biopsies were prepared for quantitative, multiple-colour immunofluorescence histology. The number of immunologically active cells was significantly altered above (supraglottis) and below (subglottis) the vocal cords following transplantation and reperfusion (P < 0.05, P < 0.001, respectively). However, the direction of the change differed between the two subsites: cell numbers decreased post-transplant in the supraglottis and increased in the subglottis. Despite the statistical evidence for IRI, these changes were less than the large normal inter- and intrapig variation in cell counts. Therefore, the significance of IRI in exacerbating loss of function or rejection of a laryngeal allograft is open to question. Longer-term studies are required.