Anaesthetic management and complications of transvascular patent ductus arteriosus occlusion in dogs.

OBJECTIVE: To retrospectively analyse the anaesthetic management, complications and haemodynamic changes in a cohort of dogs undergoing transvascular patent ductus arteriosus (PDA) occlusion in a tertiary referral centre (from January 2017 to August 2018). STUDY DESIGN: Retrospective study. ANIMALS: A total of 49 client-owned dogs. METHODS: Anaesthetic records of dogs with PDA that underwent transvascular occlusion of the ductus were reviewed. Anaesthetic complications evaluated included tachycardia [heart rate (HR) > 160 beats minute-1], bradycardia (HR < 50 beats minute-1), hypertension [systolic arterial pressure (SAP) > 150 mmHg], hypotension [mean arterial pressure (MAP) < 60 mmHg], hypothermia (<37 °C) and the presence of arrhythmias. Cardiovascular variables [HR and invasive SAP, MAP and diastolic arterial pressure (DAP)] at the time of occlusion device deployment (time 0) were compared with variables at 5 and 10 minutes after deployment. Descriptive statistics, Shapiro-Wilk test and repeated measures analysis of variance followed by a Dunnett's post hoc test were used to analyse the data (p < 0.05). RESULTS: Crossbreed dogs were the most commonly represented followed by the Cavalier King Charles Spaniel. The median age was 8 (2-108) months, and female dogs were over-represented (65.3%). The most common American Society of Anesthesiologists score was III. Mean duration of anaesthesia was 96 ± 26 minutes and mean surgery time was 58 ± 21 minutes. Acepromazine with methadone was the most commonly used premedication combination (77.6%). Propofol was the most common induction agent (73.5%). General anaesthesia was maintained with isoflurane in oxygen in all dogs. Complications included hypotension (63%), hypothermia (34%), bradycardia (28%), arrhythmias (16%), hypertension (16%) and haemorrhage (2%). MAP and DAP increased significantly 10 minutes after device deployment compared with time 0. CONCLUSIONS: and clinical relevance: Hypotension was the most common complication reported in dogs undergoing transvascular PDA occlusion. No major adverse events were documented.

Appraisal of the 'penumbra effect' using lingual pulse oximetry in anaesthetized dogs and cats.

OBJECTIVE: Factors described as contributors to the 'penumbra effect' in relation to pulse oximetry include optical shunting, circulatory anastomoses and probe parallelity. This study aimed to clarify the main underlying mechanism involved. STUDY DESIGN: Prospective clinical trial. ANIMALS: A total of 30 dogs and 15 cats (client-owned). METHODS: In anaesthetized dogs and cats, a pulse oximeter probe was placed on the tongue to measure haemoglobin oxygen saturation (SpO2) and perfusion index. In 15 dogs, the probe was positioned at the root (baseline) of the tongue, then at 0.5 and 1 cm rostral to it, to investigate the effect of circulatory anastomoses on SpO2 values. In cats (which do not have lingual arteriovenous anastomoses), the probe was positioned at the root and apex of the tongue. To assess the effect of probe parallelity on SpO2 values in dogs, two lines were drawn parallel to the planes of the light-emitting diode and the detector surfaces and the intersection angle calculated using ImageMeter Pro, Google Play. In a further 15 dogs, the probe was placed at the tongue edge (0% optical shunt), with 50% optical shunt, then with the 50% optical shunt shielded. Data were analysed using Friedman's test, Student t test and Pearson's correlation coefficient (p < 0.05). RESULTS: In dogs, SpO2 values were significantly higher at 1.0 cm than at baseline (p < 0.0001). In cats, there were no significant differences in SpO2 values at each location. There was no significant difference in SpO2 between 0% and 50% optical shunt in dogs. SpO2 had a moderate negative correlation with tongue thickness and negligible correlation with intersection angle. CONCLUSIONS AND CLINICAL RELEVANCE: Circulatory anastomoses are probably responsible for observed changes in SpO2 as the probe is placed towards an extremity, rather than optical shunting or probe parallelity.

One-lung ventilation with use of a double lumen tube in two dogs; when right might be wrong.

One-lung ventilation (OLV) is an anaesthetic technique utilised for improved visualisation and access of the surgical field during thoracoscopy. The authors present two cases that underwent OLV with use of a double lumen tube (DLT). The first case was intubated with endoscopic guidance for bronchial port intubation of the right mainstem bronchus. This dog experienced prolonged periods of intraoperative hypoxemia. Upon case review, it was suspected intubation of the mainstem bronchus resulted in occlusion of the right cranial lung lobe. In the second case, the DLT was placed bronchoscopically into the left mainstem bronchus with the aid of computed tomography (CT). Excellent intraoperative oxygenation was achieved. When DLTs are used in dogs, their anatomical differences from humans make them susceptible to additional lung occlusion and pulmonary shunting. Computed tomography is recommended as a fundamental addition to bronchoscopy for correct tube placement.

Completeness of handwritten preanaesthetic records at two veterinary referral institutions.

OBJECTIVE: To retrospectively analyse handwritten preanaesthetic records for completeness at two veterinary referral institutions: a university veterinary teaching hospital and a private veterinary referral hospital. To evaluate if emergency records were less complete compared with non-emergency records. Animal or Animal Population Two hundred and fifty preanaesthetic records at each referral institution. MATERIALS AND METHODS: Handwritten preanaesthetic records were analysed for completeness. Data was described as complete or incomplete. In order to be classified as complete information had to be present, legible and correct. Sections of the preanaesthetic record analysed included the date, anaesthetist, clinician, presenting problem, procedure, time food withheld, temperature, pulse rate (PR), respiratory rate (fR), American Society of Anesthesiologists-Physical Status Classification (ASA-PSC), premedication drug name, premedication drug dose, premedication route of administration, premedication time, effect of premedication, induction drug name, induction drug dose, induction time, induction quality, maintenance anaesthetic agent, endotracheal tube (ET) diameter, anaesthetic breathing system and monitoring equipment. RESULTS: At both referral institutions 250 records were analysed. Completeness of data was generally poor, however, several differences did exist. Completion rates were generally higher at the university veterinary teaching hospital. A mix of structured and unstructured (requiring free text) data fields were poorly complete. Emergency records were significantly less complete with respect to: Time food withheld (p = 0.006) and Temperature (p = 0.0275). CONCLUSIONS: Differences observed may be due to anaesthetic record design, anaesthetic caseload, case discussion, education or quality assurance programmes. Clinical relevance Increased emphasis on education and implementation of quality assurance programmes should be considered in order to improve completeness of preanaesthetic records.

Opioid-free anaesthesia in three dogs.

Opioid-free anaesthesia (OFA) is a relatively new and growing field in human medicine. There are multiple motivations behind this emerging practice with the recognition of several serious potential opioid-related adverse effects including opioid induced hyperalgesia, opioid tolerance and immunomodulatory effects of opioids. Opioids have long been the mainstay of veterinary anaesthesia and pain management practice. The feasibility of OFA in veterinary patients is presented here. A case series of three dogs that underwent OFA for canine ovariohysterectomy is reported. The authors conclude OFA is possible in veterinary medicine; however the move away from the familiar effects of opioids perioperatively is challenging. Gaining experience with these types of protocols for standard procedures in healthy animals, such as neutering, will provide the anaesthetist with the building blocks for more invasive surgeries.

The effect of user experience and inflation technique on endotracheal tube cuff pressure using a feline airway simulator.

OBJECTIVE: The effect of user experience and inflation technique on endotracheal tube cuff pressure using a feline airway simulator. STUDY DESIGN: Prospective, experimental clinical study. METHODS: Participants included veterinary students at the beginning (group S1) and end (group S2) of their 2-week anaesthesia rotation and veterinary anaesthetists (group A). The feline airway simulator was designed to simulate an average size feline trachea, intubated with a 4.5 mm low-pressure, high-volume cuffed endotracheal tube, connected to a Bain breathing system with oxygen flow of 2 L minute-1. Participants inflated the on-endotracheal tube cuff by pilot balloon palpation and by instilling the minimum occlusive volume (MOV) required for loss of airway leaks during manual ventilation. Intracuff pressures were measured by manometers obscured to participants and ideally were 20-30 cm H2O. Student t, Fisher exact, and Chi-squared tests were used where appropriate to analyse data (p < 0.05). RESULTS: Participants were 12 students and eight anaesthetists. Measured intracuff pressures for palpation and MOV, respectively, were 19 ± 12 and 29 ± 19 cm H2O for group S1, 10 ± 5 and 20 ± 11 cm H2O for group S2 and 13 ± 6 and 29 ± 18 cm H2O for group A. All groups performed poorly at achieving intracuff pressures within the ideal range. There was no significant difference in intracuff pressures between techniques. Students administered lower (p = 0.02) intracuff pressures using palpation after their training. CONCLUSIONS AND CLINICAL RELEVANCE: When using palpation and MOV for cuff inflation operators rarely achieved optimal intracuff pressures. Experience had no effect on this skill and, as such, a cuff manometer is recommended.

A comparison of low dose tiletamine-zolazepam or acepromazine combined with methadone for pre-anaesthetic medication in cats.

OBJECTIVE: To compare the level of sedation, cardiorespiratory changes, and quality of recovery in cats receiving methadone plus either low dose tiletamine-zolazepam or acepromazine for premedication prior to general anaesthesia for neutering. STUDY DESIGN: Prospective, randomized, blinded clinical study. ANIMALS: Twenty cats 0.54 ± 0.12 years-old (mean ± SD), weighing 3.17 ± 0.65 kg (10 male and 10 female). METHODS: Cats were allocated randomly to receive intramuscularly either 0.03 mg kg(-1) acepromazine (ACE) or 3 mg kg(-1) tiletamine-zolazepam (TZ), both regimens combined with 0.2 mg kg(-1) methadone for premedication. Sedation was assessed 25 minutes after premedication using a visual analogue scale (VAS) and a simple descriptive scale (SDS). Anaesthesia was induced with alfaxalone and maintained with isoflurane. Physiological parameters were recorded at 1, 3 and 5 minutes post-endotracheal intubation. Recovery from cessation of isoflurane was timed and quality assessed using a SDS and a VAS. Data was analysed with Mann-Whitney U-test, students t-test, anova or ordinal logistic regression as relevant. Significance was taken as p < 0.05. RESULTS: Sedation was more pronounced in TZ than ACE as indicated by higher VAS (67 ± 21 versus 13 ± 5) and SDS scores [4 (1-4) versus 1 (0-1)]. Following sedation, Heart (HR) and respiratory (fR ) rates did not differ between groups. After anaesthetic induction, at times 1, 3 and 5 HR, systolic arterial pressure and end tidal carbon dioxide were significantly higher and fR was significantly lower in TZ than ACE. Recovery quality was similar between groups. In both groups, times to extubation, head lift and sternal recumbency were similar, but time (minutes) until standing was significantly longer in TZ (31 ± 16) than ACE (18 ± 11). CONCLUSION AND CLINICAL RELEVANCE: Low dose tiletamine-zolazepam combined with methadone provided superior sedation to ACE. Recovery quality was similar, although time to standing was longer.

Cardiovascular effects of intravenous gadolinium administration to anaesthetized dogs undergoing magnetic resonance imaging.

OBJECTIVE: To assess changes in heart rate and arterial blood pressure following intravenous (IV) gadolinium-based contrast media administration to sevoflurane-anaesthetized dogs undergoing magnetic resonance imaging (MRI). STUDY DESIGN: Prospective clinical study. ANIMALS: Fifty client-owned dogs (31 male, 19 female; aged 6-156 months; weighing 4.2-45.4 kg; ASA 2-3). METHODS: Heart rate and oscillometric blood pressures (systolic, mean and diastolic) were recorded at 10 minutes, 5 minutes and immediately pre-administration of IV gadolinium contrast medium (time 0), then at 1, 2, 3, 5 and 10 minutes post-gadolinium administration. Repeated measures anova was used to compare cardiovascular variables pre and post-gadolinium administration. Significance was set at p < 0.05. RESULTS: There were no significant changes in cardiovascular variables following the IV administration of gadolinium. CONCLUSIONS AND CLINICAL RELEVANCE: Administration IV of gadolinium-based contrast media was not associated with adverse cardiovascular effects in these sevoflurane-anaesthetized dogs undergoing MRI.

A comparison of the effects of two different doses of ketamine used for co-induction of anaesthesia with a target-controlled infusion of propofol in dogs.

OBJECTIVE: To assess the cardiorespiratory and hypnotic-sparing effects of ketamine co-induction with target-controlled infusion of propofol in dogs. STUDY DESIGN: Prospective, randomized, blinded clinical study. ANIMALS: Ninety healthy dogs (ASA grades I/II). Mean body mass 30.5 +/- SD 8.6 kg and mean age 4.2 +/- 2.6 years. METHODS: All dogs received pre-anaesthetic medication with acepromazine (0.03 mg kg(-1)) and morphine (0.2 mg kg(-1)) administered intramuscularly 30 minutes prior to induction of anaesthesia. Heart rate and respiratory rate were recorded prior to pre-medication. Animals were allocated into three different groups: Group 1 (control) received 0.9% NaCl, group 2, 0.25 mg kg(-1) ketamine and group 3, 0.5 mg kg(-1) ketamine, intravenously 1 minute prior to induction of anaesthesia, which was accomplished using a propofol target-controlled infusion system. The target propofol concentration was gradually increased until endotracheal intubation was possible and the target concentration at intubation was recorded. Heart rate, respiratory rate and noninvasive blood pressure were recorded immediately prior to induction, at successful intubation and at 3 and 5 minutes post-intubation. The quality of induction was graded according to the amount of muscle twitching and paddling observed. Data were analysed using a combination of chi-squared tests, Fisher's exact tests, Kruskal-Wallis, and anova with significance assumed at p < 0.05. RESULTS: There were no significant differences between groups in the blood propofol targets required to achieve endotracheal intubation, nor with respect to heart rate, noninvasive blood pressure or quality of induction. Compared with the other groups, the incidence of post-induction apnoea was significantly higher in group 3, but despite this dogs in this group had higher respiratory rates overall. CONCLUSIONS AND CLINICAL RELEVANCE: Under the conditions of this study, ketamine does not seem to be a useful agent for co-induction of anaesthesia with propofol in dogs.