Matthew McMillan

Immersion and branchial/transcutaneous irrigation anaesthesia with alfaxalone in a Mexican axolotl

INTRODUCTION Immersion anaesthetic techniques are commonly used in amphibian species. Alfaxalone has been reported as an immersion anaesthetic in fish but not amphibians. CASE HISTORY AND EXAMINATION A Mexican 56 g axolotl was presented with a 3-day history of anorexia. Anaesthesia was required for the surgical retrieval of two gastric foreign bodies. Prior to anaesthesia, on visual inspection the axolotl was bright and active. Branchial and gular respiratory movements occurred at approximately 24 respirations minute(-1) and heart rate was approximately 52 beats minute(-1) . MANAGEMENT The axolotl was exposed to increasing concentrations (up to 5 mg L(-1) ) of alfaxalone (Alfaxan; Vetóquinol, UK) in a water bath. After becoming sedated the axolotl was removed from the water bath. Anaesthesia was induced and maintained with alfaxalone (5 mg L(-1) ) via continuous irrigation of the gills (branchial) and skin (cutaneous) with additional 30 μL drops of alfaxalone (10 mg mL(-1) ) administered branchially as required. Endoscopy and surgery were performed to remove two gastric foreign bodies. Branchial and gular respiratory movements persisted at what was considered an appropriate anaesthetic depth. Anaesthetic depth could be rapidly deepened by branchial irrigation of alfaxalone solutions and lightened by irrigation using fresh water. Anaesthesia lasted approximately 1 hour and recovery was rapid (within 15 minutes). Recovery was assisted through branchial and cutaneous irrigation with fresh water. FOLLOW-UP No obvious adverse effects of anaesthesia were observed immediately post-anaesthesia or, according to the owner, in the following week. Conclusions  Axolotls can be anaesthetized using alfaxalone administered via immersion and branchial/transcutaneous irrigation offering an alternative technique for anaesthetising axolotls for clinical and research purposes.

Assessment of the variation in American Society of Anaesthesiologists Physical Status Classification assignment in small animal anaesthesia

OBJECTIVE To evaluate the interobserver variability in the assignment of the American Society of Anesthesiologists Physical Status Classification (ASA-PSC) to compromised small animal patients amongst a group of veterinary anaesthetists. STUDY DESIGN Anonymous internet survey. ANIMALS Hypothetical case presentations. METHODS Sixteen hypothetical small animal cases with differing degrees of physiological or patho-physiological compromise were presented as part of an internet survey. Respondents were asked to assign a single ASA-PSC to each case and also to answer a number of demographic questions. ASA-PSC scores were considered separately and then grouped as scores of I-II and III-V. Agreement was analysed using the modified kappa statistic for multiple observers. Data were then sorted into various demographic groups for further analysis. RESULTS There were 144 respondents of which 60 (~42%) were anaesthesia diplomates, 24 (~17%) were post-residency (nondiploma holders), 24 (~17%) were current anaesthesia residents, 21 (~15%) were general practitioners, 12 (~8%) were veterinary nurses or technicians, and 3 (~2%) were interns. Although there was a majority agreement (>50% in a single category) in 15 of the 16 cases, ASA-PSC were spread over at least three ASA-PS classifications for every case. Overall agreement was considered only fair (κ = 0.24, mean ± SD agreement 46 ± 7%). When comparing grouped data (ASA-PSC I-II versus III-V) overall agreement remained fair (κ = 0.36, mean ± SD agreement 69 ± 19%). There was no difference in ASA-PSC assignment between any of the demographic groups investigated. CONCLUSIONS AND CLINICAL RELEVANCE This study suggests major discrepancies can occur between observers given identical information when using the ASA-PSC to categorise health status in compromised small animal patients. The significant potential for interobserver variability in classification allocation should be borne in mind when the ASA-PSC is used for clinical, scientific and statistical purposes.

Checklists in veterinary anaesthesia: why bother?

ANAESTHESIA underpins modern veterinary medicine by enabling invasive diagnostic, surgical and medical interventions to be carried out in a humane way (Taylor 2014). As veterinary interventions continue to advance and public awareness of pain and safety increases, anaesthesia will become even more pivotal to our profession. Despite this, little is known about the quality and safety of the anaesthesia that we, as a profession, provide to our patients. In general terms, anaesthesia should be concerned with keeping animals safe and maintaining welfare during procedures by identifying, minimising and managing risks and by ensuring that pain is recognised and treated as appropriate. However, anaesthesia can often be viewed as a means to an end; a necessary step performed merely to facilitate the performance of another procedure. With this mindset, it is easy to undertake anaesthesia with little care and attention, cutting corners in the name of efficiency and economy or in the belief that certain tasks are not always necessary. We often consider the biggest threat to the anaesthetised patient to be adverse effects of drugs. These drugs, by definition, are potent depressors of the central nervous system and therefore affect cardiovascular, respiratory, neurological and metabolic function. Such effects are often exacerbated and more pronounced in sick patients. Derangement in one, several or all of these physiological systems has the potential to cause harm to the patient and could lead to death. We do what we can to recognise, reduce and manage these complications, but our efforts have their limitations and it would therefore appear, superficially at least, that death due to the administration of anaesthetic drugs is an inevitable, inherent component of anaesthesia that we can do little about. So, case by case and day by day, we accept this ‘risk of anaesthesia’ in the light of the vast array …

Pitfalls and common errors of anaesthetic monitoring devices. Part 1: Pulse oximetry

Abstract Pulse oximetry is the most commonly used piece of monitoring equipment in general practice. It gives non-invasive objective information on oxygenation and pulse rate and subjective information on pulse quality. Like all electronic anaesthetic monitoring devices pulses oximeters can be used to improve the safety of anaesthesia; however, over-reliance on their use has a number of pitfalls. Foremost is the potential for erroneous measurement. Poor pulse quality, light interference, movement, pigmented tissue can all effect the accuracy and reliability of pulse oximetry. Understanding how the pulse oximeter works and how to assess signal quality is vital if pulse oximeters are to be used in an appropriate fashion. This allows the anaesthetist to ensure that the readings being given and recorded are realistic, which in turn helps decision making and ensures timely intervention.

Endotracheal tube placement during computed tomography of brachycephalic dogs alters upper airway dimensional measurements

Computed tomography (CT) is used to document upper airway lesions in dogs with brachycephalic obstructive airway syndrome. The presence of an endotracheal tube during CT scanning is often required for general anesthesia. We hypothesized that the endotracheal tube placement would change the soft tissue dimensions of the upper airway. The aims of this prospective, method comparison study were to evaluate the reliability of the previously reported upper airway CT measurements with endotracheal tube placement, and to propose measurements that are minimally affected by the endotracheal tube. Twenty brachycephalic dogs were included in this study. Each dog underwent head/neck CT with an endotracheal tube, followed by a second scan without the endotracheal tube. Ten measurements of the soft palate, nasopharynx, and trachea were performed. Tracheal dimension was significantly larger with the endotracheal tube compared to without, whereas the soft palate cross-sectional area was significantly smaller with the endotracheal tube than without the endotracheal tube. The influence of the endotracheal tube on the caudal nasopharynx cross-sectional (transverse-sectional) area varied with a mean proportional absolute difference of 35%. Rostral soft palate thickness, tracheal perimeter, and cross-sectional area of the rostral nasopharynx were the measurements least affected by the endotracheal tube (intraclass correlation coefficient = 0.964, 0.967, and 0.951, respectively). Therefore, we proposed that these three measurements may be most useful for future brachycephalic obstructive airway syndrome studies that require CT scanning of intubated animals. However, with endotracheal tube placement, measurements of soft palate length, caudal nasopharyngeal cross-sectional area, and trachea height and width may not be reliable.

Pitfalls and common errors of anaesthetic monitoring devices part 3: Capnography

Abstract In order to use an electronic monitoring device safely and effectively it is important to know how the equipment generates the numbers that we record on our anaesthetic records. This way, we can be more confident that the data realistically represent the physiology of our patient. Understanding the common pitfalls and errors that each piece of monitoring is prone to can help us recognise when to intervene rather than putting a number down to a quirk of the monitor. This third article in the series explores the capnograph.

Systems analysis of voluntary reported anaesthetic safety incidents occurring in a university teaching hospital

OBJECTIVE To identify factors contributing to the development of anaesthetic safety incidents. STUDY DESIGN Prospective, descriptive, voluntary reporting audit of safety incidents with subsequent systems analysis. ANIMALS All animals anaesthetized in a multispecies veterinary teaching hospital from November 2014 to October 2016. METHODS Peri-anaesthetic incidents that risked or caused unnecessary harm to an animal were reported by anaesthetists alongside animal morbidity and mortality data. A modified systems analysis framework was used to identify contributing factors from the following categories: Animal and Owner, Task and Technology, Individual, Team, Work Environmental, and Organizational and Management. The outcome was graded using a simple descriptive scale. Data were analysed using Pearsons Chi-Square test for association and univariable and multivariable logistic regression analysis. RESULTS Totally, 3379 anaesthetics were performed during the audit period. Of these, 174 incident reports were analysed, 163 of which impacted safe veterinary care and 26 incidents were considered to have had major or catastrophic outcomes. Incident outcome was believed to have been limited by anaesthetist intervention in 104 (63.8%) cases. Various factors were identified as: Individual in 123 (70.7%), Team in 108 (62.1%), Organizational and Management in 94 (54.0%), Task and Technology in 80 (46.0%), Work Environmental in 53 (30.5%) and Animal and Owner in 36 (20.7%) incidents. Individual factors were rarely seen in isolation. Significant associations were identified between Experience and Supervision, X2 (1, n=174)=54177, p=0.001, Failure to follow a standard operating procedure and Task Management, X2 (2, n=174)=11318, p=0.001, and Staffing and Poor Scheduling, X2 (1, n=174)=36742, p=0.001. Animal Condition [odds ratio (OR)=16210, 95% confidence interval (CI)=5573-47147)] and anaesthetist Decision Making (OR=3437, 95% CI=1184-9974) were risk factors for catastrophic and major outcomes. CONCLUSIONS AND CLINICAL RELEVANCE Individual factors contribute to many safety incidents but tend to occur concurrently with other factors. Anaesthetist intervention limits the consequences of incidents for most animals.

Transient millwheel heart murmur and cardiorespiratory alterations in a dachshund during hemilaminectomy

A four-year-old dachshund was admitted for progressive para-paresis. The dog had no signs of cardiovascular disease, and cardiac auscultation was unremarkable. The dog was anaesthetised for MRI and subsequently hemilaminectomy. During surgery, drops in blood pressure and end-tidal carbon dioxide were observed concurrent to surgical site haemorrhage. At this time, a rumbling/churning ‘millwheel’-type cardiac murmur was detected via an oesophageal stethoscope. Other anomalies, such as arrhythmias and tachypnoea, were also observed. The planned surgery was shortened and the dog made a full uneventful recovery. The heart murmur audible externally immediately after recovery, disappeared over the following 12 hours. The events reported are compatible with the occurrence of a venous air embolism (VAE). Review of the literature indicates that subclinical VAE might be more frequent than usually believed, as precursor signs might be tenuous and non-evocative of VAE. Awareness of this potentially life-threatening complication should be raised.