Pj Murison

Assessment of the influence of surgical technique on postoperative pain and wound tenderness in cats following ovariohysterectomy

Elective ovariohysterectomy was performed on 66 cats. Surgical approach was flank (group F) or midline (group M) allocated by block randomisation. Pre-anaesthetic medication was acepromazine (0.1 mg/kg) via intramuscular injection. Anaesthesia was induced with intravenous thiopentone, and maintained with halothane in 100% oxygen. Carprofen (4 mg/kg) was administered by the subcutaneous route immediately after induction of anaesthesia. Postoperative pain and wound tenderness were assessed at 1, 3, 6, 9, 11–12 and 20–24 h after the end of surgery, and the assessment outcome marked on visual analogue scales (VAS). Intervention analgesia (if pain VAS was >40 mm) was pethidine 4 mg/kg via intramuscular injection. Area under the curve (AUC) for VAS for pain and VAS for wound tenderness for each cat were calculated. AUC for wound tenderness was significantly greater for group F (P=0.007). There was no significant difference for AUC for pain between the groups. In conclusion, wounds after flank ovariohysterectomy are significantly more tender than after midline ovariohysterectomy in the cat. This indicates that interactive methods, including wound palpation, must be used to assess postoperative pain and the findings should be appropriately weighted in the overall assessment.

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 [PECO2] 3.7 [0.8] kPa) and the propofol group (PR 147 [16] bpm, DBP 77 [12] mmHg, RR 32 [8] breaths/minute, PECO2 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.

Fentanyl or midazolam for co-induction of anaesthesia with propofol in dogs

OBJECTIVE Propofol may cause adverse effects (e.g. apnoea, hypotension) at induction of anaesthesia. Co-induction of anaesthesia may reduce propofol requirements. The effect of fentanyl or midazolam on propofol dose requirements and cardiorespiratory parameters was studied. STUDY DESIGN Randomized, controlled, blinded clinical study. ANIMALS Sixty-six client owned dogs (35 male, 31 female, ASA I-II, age 6-120 months, body mass 4.7-48.0 kg) were selected. METHODS Pre-medication with acepromazine (0.025 mg kg(-1)) and morphine (0.25 mg kg(-1)) was administered by intramuscular injection. After 30 minutes group fentanyl-propofol (FP) received fentanyl (2 microg kg(-1)), group midazolam-propofol (MP) midazolam (0.2 mg kg(-1)) injected over 30 seconds via a cephalic catheter and in a third group, control-propofol (CP), the IV catheter was flushed with an equivalent volume of heparinized saline. Anaesthesia was induced 2 minutes later, with propofol (4 mg kg(-1)minute(-1)) administered to effect. After endotracheal intubation anaesthesia was maintained with a standardized anaesthetic protocol. Pulse rate, respiratory rate (RR) and mean arterial pressure (MAP) were recorded before the co-induction agent, before induction, and 0, 2 and 5 minutes after intubation. Apnoea >or=30 seconds was recorded and treated. Sedation after pre-medication, activity after the co-induction agent, quality of anaesthetic induction and endotracheal intubation were scored. RESULTS Propofol dose requirement was significantly reduced in FP [2.90 mg kg(-1)(0.57)] compared to CP [3.51 mg kg(-1) (0.74)] and MP [3.58 mg kg(-1)(0.49)]. Mean pulse rate was higher in MP than in CP or FP (p = 0.003). No statistically significant difference was found between groups in mean RR, MAP or incidence of apnoea. Activity score was significantly higher (i.e. more excited) (p = 0.0001), and quality of induction score was significantly poorer (p = 0.0001) in MP compared to CP or FP. Intubation score was similar in all groups. CONCLUSIONS AND CLINICAL RELEVANCE Fentanyl decreased propofol requirement but did not significantly alter cardiovascular parameters. Midazolam did not reduce propofol requirements and caused excitement in some animals.

Morphine administration in horses anaesthetized for upper respiratory tract surgery

OBJECTIVE To determine the effect of morphine administration on commonly monitored cardio-respiratory variables and recovery quality in horses undergoing anaesthesia and surgery. STUDY DESIGN Prospective, randomized clinical study. ANIMALS Thirty-eight thoroughbred horses, 32 geldings and six mares, 3-13 years old, weighing 411-600 kg. MATERIALS AND METHODS A standard anaesthetic technique was used. Twenty minutes after induction of anaesthesia horses received 0.1 mg kg-1 (0.1 m) or 0.2 mg kg-1 (0.2 m) morphine by intravenous injection. A control group did not receive morphine. Heart rate, respiratory rate (fr), mean arterial pressure (MAP) and blood gases were measured before morphine administration and every 10 minutes thereafter. Horses were positioned for 35 minutes in right lateral recumbency for tension palatoplasty by cautery and were then moved into dorsal recumbency for additional intraluminal surgery comprising one or more of aryepiglottic fold resection, sub-epiglottal mucosal resection, ventriculectomy and cordectomy. A subjective recovery score from 0 (worst) to 5 (best) was assigned by a single observer who was unaware of treatment group. Two-way repeated measures anova, one-way anova, Kruskal-Wallis test, Mann-Whitney test, Pearson and Spearman correlation coefficients, and chi-squared tests were used to analyse the data where appropriate. RESULTS Arterial partial pressure of oxygen (PaO2) decreased significantly over time and was significantly lower in horses that received morphine. One horse in the control group and two horses in each of the morphine groups had a PaO2 <13 kPa. No other significant cardiopulmonary effects were detected. Recovery scores [median (range)] were higher in morphine recipients: 4 (2-5) in 0.1 m, 4 (3-5) in 0.2 m compared with 3 (2-4) in the control group. CONCLUSIONS AND CLINICAL RELEVANCE The lower PaO2 in morphine recipients did not appear to be of clinical significance in healthy horses because the number of horses with a low PaO2 was similar between groups. The quality of recovery was significantly better in morphine recipients. These results indicate that morphine may be considered for use in clinical cases although further work is required to assess the analgesic properties of the drug in this species.

A comparison of ketamine-midazolam and ketamine-medetomidine combinations for induction of anaesthesia in rabbits.

OBJECTIVE To compare ketamine-midazolam (KMZ) and ketamine-medetomidine (KMT) anaesthesia in rabbits using anaesthetic induction, maintenance and recovery data. STUDY DESIGN Randomized, prospective, blinded clinical trial. ANIMALS Fifty rabbits (25 male, 25 female) of different breeds undergoing ovariohysterectomy or castration. Rabbits were 12.7 +/- 9.8 months old with body mass 2.24 +/- 0.61 kg. STUDY DESIGN Randomized, prospective, blinded clinical trial. METHODS Ketamine (15 mg kg(-1)) and midazolam (3 mg kg(-1)) or medetomidine (0.25 mg kg(-1)) were administered by intramuscular (IM) injection. Ten minutes after IM injection, blind intubation of the trachea was attempted. The time taken, the number of attempts and a subjective score of the ease of intubation were recorded. Isoflurane (range 0-3.6%) in 100% oxygen was delivered via a Jackson Rees modification of an Ayres T-piece non-rebreathing system. Carprofen (3 mg kg(-1)) and dextrose saline (5 mL kg(-1) hour(-1)) were administered intravenously (IV). During surgery heart rate (HR), respiratory rate (RR) and arterial oxygen saturation of haemoglobin (SpO(2)) were monitored. Times to extubation and first head lift were recorded. Group KMT received atipamezole (0.5 mg kg(-1)) IM 30 minutes after discontinuation of isoflurane. Activity was scored at 30, 60 and 120 minutes after volatile agent discontinuation. Mean time to loss of righting reflex (LRR), body mass, RR and vaporizer setting were compared using a two-tailed t-test. Median values for all other data were compared using a Mann-Whitney test. RESULTS Mean time to LRR (+/-SD) was significantly shorter with KMT (1.64 +/- 0.55 minutes) compared with KMZ (2.28 +/- 0.66 minutes). Intubation was not possible in seven rabbits (three with KMT, four with KMZ) and three with KMT developed laryngospasm. Mean HR, SpO(2) and vaporizer settings were all significantly lower in group KMT. CONCLUSION AND CLINICAL RELEVANCE KMT has a faster onset of action and a greater isoflurane-sparing effect when compared with KMZ. Rabbits with KMT were more prone to laryngospasm and had significantly lower HR.

Prevention and treatment of perioperative hypothermia in animals under 5 kg bodyweight

HYPOTHERMIA resulting from anaesthesia is common in the perioperative period and may increase the risk of cardiac arrhythmias and other complications. Very small animals are especially at risk of developing hypothermia because of their larger surface area to volume ratio compared with heavier animals. If the bodyweight of an animal is abnormally low, heat loss may also be increased due to less body fat insulation. The risk of hypothermia can be reduced by a variety of methods and many devices are available to provide warmth for anaesthetised animals. This article discusses why temperature loss is important, and how its effects can be minimised.

Comparison of direct and Doppler arterial blood pressure measurements in rabbits during isoflurane anaesthesia

OBJECTIVE To measure the level of agreement between Doppler measured (DOP) arterial blood pressure (ABP) in the forelimb and directly measured (DIR) auricular systolic ABP (SAP) and mean ABP (MAP) in isoflurane-anaesthetized rabbits. STUDY DESIGN Prospective clinical study. ANIMALS Data were analysed from 17 of 24 healthy rabbits, weighing 1.3-2.8 kg. METHODS Rabbits were anaesthetized for neutering using a standardized protocol. A 26G catheter placed in an auricular artery was connected via heparinised saline filled non-compliant tubing (regularly flushed) to a calibrated pressure transducer (zeroed level with the thoracic inlet) to obtain DIR ABP. A cuff was placed proximal to the carpus (approximately level with the thoracic inlet) and a Doppler transducer sited over the dorsal carpal branch of the radial artery to obtain DOP ABP. Simultaneous DIR and DOP ABP recordings were made every 5-10 minutes during anaesthesia. Agreement was assessed as described by Bland JM & Altman (2007). RESULTS Mean ± SD cuff width: limb circumference ratio was 0.50 ± 0.04. Mean between-method differences ± SD, DIR SAP- DOP and DIR MAP- DOP, were +1 ± 8 and -13 ± 8 mmHg respectively. The 95% limits of agreement between DIR SAP and DOP and between DIR MAP and DOP were -14 to +17 and -28 to +2 mmHg respectively. Differences between DIR SAP and DOP were ≤ 10 mmHg 85% of the time. Defining hypotension as either DIR SAP < 80 mmHg or DIR MAP < 60 mmHg, and taking DOP ABP of <80 mmHg to indicate hypotension, sensitivity and specificity were 92% and 67% respectively. CONCLUSIONS Good agreement was found between DIR SAP and DOP. Doppler measurements below 80 mmHg are a reliable indicator of arterial hypotension. CLINICAL RELEVANCE DOP is acceptable for monitoring ABP in isoflurane-anaesthetized rabbits and is useful for detection of hypotension.

Effect of propofol and alfaxalone on pain after ovariohysterectomy in cats

ALTHOUGH many anaesthetics do not have analgesic properties, induction and maintenance anaesthetic agents may influence postoperative analgesic requirements ([Slingsby and others 1998][1]). Propofol, a substituted phenol, is a commonly used anaesthetic in current veterinary practice. The steroid

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.

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.