Adrian M Wong

Respiratory complications are a major cause of post-anaesthetic mortality in dogs. Its
pathophysiology is poorly understood due to the limitations of traditional monitoring
technologies. The thesis aimed to i) develop an electrode belt that accommodates dogs of
different breeds and thoracic conformations, and ii) to quantify respiratory changes using
electrical impedance tomography (EIT) via the constructed belt in the post-anaesthetic period
in dogs.

In the first study, a canine-specific 32-electrode belt was developed. Its performance was
assessed in 18 dogs. In the second study, EIT data was collected via the constructed belt in 8
dogs in the post-anaesthetic period after neutering. The EIT data collected included global
variables: tidal impedance variation (TIV), minute TIV (MTIV) and end-expiratory lung
impedance (EELI), which describes lung volumes; and regional variables: centre of
ventilation, region of interests and silent spaces, which describes ventilation distribution.
These variables were statistically and descriptively compared at time points from the end of
anaesthesia to 15 minutes post-extubation.

In the first study, the constructed belt obtained optimal signals in 15/18 (83 %) of dogs of
varying breeds and thoracic conformations. Reasons of failure included computer issue and
failed signal acquisition from thick hair coat. The second study showed an overall
improvement in respiratory function in 7/8 (87.5 %) of dogs based on an increase in MTIV
and EELI at 15 minutes post-extubation. Inter-individual variations were observed, with
many showed temporary improvement in respiratory function at the time of extubation with
subsequent deterioration. The study was limited by the small sample size and lack of preanaesthetic baseline. It is unknown if respiratory function were normalised by 15 minutes
post-extubation.

The use of EIT via the constructed belt provided insight of the mechanisms and timings of
post-anaesthetic pulmonary complications. The need for vigilant, individualised monitoring
during recovery is highlighted.

Objective
To explore the influence of acepromazine on the cardiovascular effects of dobutamine in isoflurane-anaesthetised horses premedicated with romifidine.

Study design
Prospective randomised clinical trial.

Animals
A total of 18 horses undergoing elective arthroscopy were enrolled, of which 12 horses requiring dobutamine were included.

Methods
orses were randomised to receive acepromazine 0.02 mg kg-1 (Group A+) intravenously (IV) or none (Group A-), 35 minutes before anaesthesia. Horses received xylazine 0.2 mg kg-1 concurrently to facilitate IV access. Horses were premedicated with romifidine 0.08 mg kg-1, induced with ketamine 2.2 mg kg-1 and diazepam 0.08 mg kg-1 IV, and maintained with isoflurane in oxygen. Dobutamine infusion was commenced when mean arterial pressure (MAP) was < 60 mmHg. Cardiovascular data were collected prior to dobutamine, and at a target MAP of ≥ 70 mmHg. Dobutamine start time from induction, duration and dose to reach target MAP were compared using Mann-Whitney U test. Cardiovascular variables were compared using repeated measures ANOVA and post-hoc Fisher’s least significant difference test.

Results
Cardiac index (CI) and its percentage change was significantly higher at target MAP in group A+ [42.8 (17.0–68.7) %] than in A- [-4.05 (-21.2–13.0) %] (p = 0.003). Group A+ required significantly earlier dobutamine [20 (18–25) minutes] than group A- [36 (27–60) minutes] (p = 0.02). Group A+ required significantly higher dobutamine dose [1.5 (1–2.5) μg kg-1 minute-1] to reach target MAP than group A- [0.5 (0.5–1) μg kg-1 minute-1] (p = 0.009). No significant difference in infusion duration to reach target MAP was found between groups.

Conclusion and clinical relevance
Dobutamine significantly increased MAP and CI following pre-anaesthetic acepromazine sedation, in isoflurane-anaesthetised horses premedicated with romifidine. Without acepromazine, dobutamine increased MAP but not CI. Interactions between acepromazine, romifidine and dobutamine on the cardiovascular system should be considered.

The applicability of electrical impedance tomography (EIT) in birds is unknown. This study aimed to evaluate the use of EIT in anaesthetised chickens in four recumbency positions. Four adult Hyline chickens were anaesthetised with isoflurane in oxygen, and intubated endotracheally for computed tomography (CT). A rubber belt was placed around the coelom caudal to the shoulder joint. A chicken-specific finite element (FE) model, which is essential to generate anatomically accurate functional EIT images for analysis, was constructed based on the CT images obtained at the belt level. Ten additional chickens were anaesthetised with the same protocol. An EIT electrode belt was placed at the same location. The chickens were breathing spontaneously and positioned in dorsal, ventral, right and left lateral recumbency in a randomised order. For each recumbency, raw EIT data were collected over 2 min after 13 min of stabilisation. The data were reconstructed into functional EIT images. EIT variables including tidal impedance variation (TIV), centre of ventilation right to left (CoVRL) and ventral to dorsal (CoVVD), right to left (RL) ratio, impedance change (ΔZ) and eight regional impedance changes including the dorsal, central-dorsal, central-ventral and ventral regions of the right and left regions were analysed. Four breathing patterns (BrP) were observed and categorised based on the expiratory curve. A linear mixed model was used to compare EIT variables between recumbencies. Fisher's exact test was used to compare the frequencies of breathing patterns for each recumbency. The ΔZ observed was synchronous to ventilation, and represented tidal volume of the cranial air sacs as confirmed by CT. Significant differences were found in CoVVD and regional impedance changes between dorsal and ventral recumbencies (P < 0.05), and in CoVRL, RL ratio and regional impedance changes between right and left recumbencies (P < 0.05), which suggested a tendency for the distribution of ventilation to shift towards non-dependent air sacs. No differences were found for TIV and respiratory rate between recumbencies. Recumbency had a significant effect on the frequencies of each of the four BrPs (P = 0.001). EIT can monitor the magnitude and distribution of ventilation of the cranial air sacs in different recumbencies in anaesthetised chickens.

Endotracheal tube breakage during extubation is a rare complication previously reported in domestic animals, but not in zoo animals. A 9-year-old, male lion was anaesthetised to investigate lethargy and inappetence. Following anaesthesia, the lion was transported to its night quarter, a dedicated enclosed area for recovery. The lion was secured within the night quarter, with all personnel separated from the lion by a metal mesh fence. The lion was positioned adjacent to the fence, allowing distant monitoring and access for extubation through the fence. The silicone endotracheal tube broke during extubation. No immediate signs of airway obstruction were observed. The lion was re-anaesthetised within the night quarter with intramuscular medetomidine and tiletamine/zolazepam administered using a pole syringe. Radiographs confirmed the presence of the broken distal endotracheal tube in the oesophagus, which was then manually retrieved with a mouth gag in place. The lion subsequently recovered with no complications.

PICO question
In dogs with osteoarthritis how effective is treatment with tramadol in reducing the severity of the clinical signs associated with pain when compared to no treatment?
 
Clinical bottom line
Category of research question
Treatment
The number and type of study designs reviewed
Two papers were critically reviewed. There was one randomised crossover controlled trial and one non-randomised controlled trial
Strength of evidence
Strong
Outcomes reported
Budsberg et al. (2018) found no significant differences in the objective gait analyses (vertical ground reaction forces, and peak vertical force) between baseline and end of treatment, between tramadol and placebo. Similarly, there was no significant difference in the proportion of dogs with positive response based on the subjective Canine Brief Pain Inventory questionnaire (CBPI) between tramadol and placebo. The positive control of carprofen yielded significant differences to both placebo and tramadol in all outcomes measured.
Malek et al. (2012) found no significant differences in the objective outcomes measured (gait analyses, and total daily activity) between tramadol and placebo. There were significant improvements in the subjective CBPI (total score, pain severity and pain interference score) between the baseline and end of treatment, within the tramadol group. However, there was no significant difference in the percentage change of the total score, pain severity or pain interference score between all treatment groups including tramadol and placebo
Conclusion
In dogs with osteoarthritis, the use of tramadol alone did not demonstrate any significant analgesic effects
 
How to apply this evidence in practice
The application of evidence into practice should take into account multiple factors, not limited to: individual clinical expertise, patient’s circumstances and owners’ values, country, location or clinic where you work, the individual case in front of you, the availability of therapies and resources.
Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.
 

A 2-year-old male neutered domestic short hair cat presented following trauma with bilateral pneumothorax. Thoracocentesis was performed and thoracostomy tubes were placed bilaterally. Manual suction of the chest was performed at least hourly for the initial 12 hours of treatment with eventual resolution of the left-sided pneumothorax. The right-sided pneumothorax was persistent. Autologous blood patching with 2 mL/kg of blood was performed 13 hours after presentation and the pneumothorax resolved. A diaphragmatic hernia was subsequently diagnosed and surgical correction performed. The patient was discharged after 7 days in hospital. Autologous blood patching appears to be well-tolerated, effective, and safe to perform in cats. It should be considered as a treatment for continuous pneumothorax in cats, particularly those of traumatic origin.

AIMS
To compare the effect of oxygen supplementation using flow-by or a face mask on the partial pressure of arterial oxygen (PaO2) in sedated dogs.

METHODS
Twenty healthy dogs weighing >15 kg, of mixed sex and breed, were enrolled in a randomised cross-over study. Each dog was sedated with I/M 0.015 mg/kg medetomidine and 0.5 mg/kg methadone. Twenty minutes later dogs were exposed to two 5-minute treatment periods of oxygen supplementation separated by a 15-minute washout period during which dogs were allowed to breathe room air. During the treatment periods, oxygen was delivered at a flow rate of 3 L/minute either through a face mask (face mask oxygenation), or via a tube held 2 cm from the dog’s nares (flow-by oxygenation). The order in which the treatments were administered was randomised. Arterial blood was collected for blood gas analysis and rectal temperature measured at four times: prior to commencing treatments, after each treatment, and at the end of the 15 minutes washout period between treatments.

RESULTS
The mean PaO2 in arterial samples taken from the dogs after face mask oxygen supplementation was 371.3 (SE 13.74) mmHg which was higher than in samples taken after they received flow-by oxygen supplementation (182.2 (SE 6.741) mmHg; p<0.001). The mean PaO2 in samples taken after receiving either form of oxygen supplementation was higher than in samples taken after the dogs had been breathing room air (82.43 (SE 2.143) mmHg; p<0.001). There was no association between sex, age, weight or breed of dogs and blood gas parameters or rectal temperature (p>0.05).

CONCLUSIONS
Oxygen supplementation delivered using a face mask was more effective at increasing PaO2 than flow-by oxygen supplementation. Flow-by oxygen supplementation at a distance of 2 cm from the nose may be a suitable alternative when the use of a face mask is not tolerated by the patient.