Influence of body weight, age, and sex on cerebrospinal fluid peak flow velocity in dogs without neurological disorders.

BACKGROUND: Changes in the brain can affect the flow velocity of cerebrospinal fluid (CSF). In humans, the flow velocity of CSF is not only altered by disease but also by age and sex. Such influences are not known in dogs. HYPOTHESIS: Peak flow velocity of CSF in dogs is associated with body weight, age, and sex. ANIMALS: Peak flow velocity of CSF was measured in 32 client-owned dogs of different breeds, age, and sex. METHODS: Peak flow velocity of CSF was determined by phase-contrast magnetic resonance imaging (PC-MRI) at the mesencephalic aqueduct, foramen magnum (FM), and second cervical vertebral body (C2). Dogs were grouped according to body weight, age, and sex. Flow velocity of CSF was compared between groups using linear regression models. RESULTS: Dogs with body weight >20 kg had higher CSF peak velocity compared with dogs <10 kg within the ventral and dorsal subarachnoid space (SAS) at the FM (P = .02 and P = .01, respectively), as well as in the ventral and dorsal SAS at C2 (P = .005 and P = .005, respectively). Dogs ≤2 years of age had significantly higher CSF peak flow velocity at the ventral SAS of the FM (P = .05). Females had significantly lower CSF peak flow velocity within the ventral SAS of FM (P = .04). CONCLUSION: Body weight, age, and sex influence CSF peak flow velocity in dogs. These factors need to be considered in dogs when CSF flow is quantitatively assessed.

Enantiospecific pharmacokinetics of intravenous dexmedetomidine in beagles.

The goal of this study was to investigate the pharmacokinetic (PK) behaviour of dexmedetomidine in dogs administered as a pure enantiomer versus as part of a racemic mixture. Eight unmedicated intact purpose-bread beagles were included. Two intravenous treatments of either medetomidine or dexmedetomidine were administered at 10- to 14-day intervals. Atipamezole or saline solution was administered intramuscularly 45 min later. Venous blood samples were collected into EDTA collection tubes, and the quantification of dexmedetomidine and levomedetomidine was performed by chiral LC-MS/MS. All dogs appeared sedated after each treatment without complication. Plasma concentrations of levomedetomidine were measured only in the racemic group and were 51.4% (51.4%-56.1%) lower than dexmedetomidine. Non-compartmental analysis (NCA) was performed for both drugs, while dexmedetomidine data were further described using a population pharmacokinetic approach. A standard two-compartment mammillary model with linear elimination with combined additive and multiplicative error model for residual unexplained variability was established for dexmedetomidine. An exponential model was finally retained to describe inter-individual variability on parameters of clearance (Cl1 ) and central and peripheral volumes of distribution (V1 , V2 ). No effect of occurrence, levomedetomidine or atipamezole could be observed on dexmedetomidine PK parameters. Dexmedetomidine did not undergo significantly different PK when administered alone or as part of the racemic mixture in otherwise unmedicated dogs.

A Survey on the Use of Spirometry in Small Animal Anaesthesia and Critical Care.

The objective was to document the use of spirometry and ventilation settings in small animal anaesthesia and intensive care through a descriptive, open, online, anonymous survey. The survey was advertised on social media and via email. Participation was voluntary. The google forms platform was used. It consisted of eight sections in English: demographic information, use of spirometry in spontaneously ventilating/mechanically ventilated dogs, need for spirometry, equipment available and calibration status, ventilation modes, spirometry displays, compliance (CRS) and resistance (RRS) of the respiratory system. Simple descriptive analyses were applied. There were 128 respondents. Respondents used spirometry more in ventilated dogs than during spontaneous breathing. Over 3/4 of the respondents considered spirometry essential in "selected" (43%) or "most" cases (33%). Multiple devices and technologies were used. The majority of the respondents were not directly involved in or informed about the calibration of their equipment. Of all displays, pressure-volume loops were the most common. Values of CRS and RRS were specifically monitored in more than 50% of cases by 44% of the respondents only. A variety of ventilation modes was used. Intensivists tend to use smaller VT than anaesthetists. More information on reference intervals of CRS and RRS and technical background on spirometers is required.

Neuronal current imaging: An experimental method to investigate electrical currents in dogs with idiopathic epilepsy.

BACKGROUND: The diagnosis of idiopathic epilepsy (IE) in dogs is based on exclusion of other potential causes of seizures. Recently, a novel magnetic resonance imaging (MRI) sequence that utilizes a variant of the rotary saturation approach has been suggested to detect weak transient magnetic field oscillations generated by neuronal currents in humans with epilepsy. HYPOTHESIS/OBJECTIVES: Effects on the magnetic field evoked by intrinsic epileptic activity can be detected by MRI in the canine brain. As proof-of-concept, the novel MRI sequence to detect neuronal currents was applied in dogs. ANIMALS: Twelve dogs with IE and 5 control dogs without a history of epileptic seizures were examined. METHODS: Prospective case-control study as proof-of-concept. All dogs underwent a clinical neurological examination, scalp electroencephalography, cerebrospinal fluid analysis, and MRI. The MRI examination included a spin-locking (SL) experiment applying a low-power on-resonance radiofrequency pulse in a predefined frequency domain in the range of oscillations generated by the epileptogenic tissue. RESULTS: In 11 of 12 dogs with IE, rotary saturation effects were detected by the MRI sequence. Four of 5 control dogs did not show rotary saturation effects. One control dog with a diagnosis of neuronal ceroid lipofuscinosis had SL-related effects, but did not have epileptic seizures clinically. CONCLUSIONS AND CLINICAL IMPORTANCE: The proposed MRI method detected neuronal currents in dogs with epileptic seizures and represents a potential new line of research to investigate neuronal currents possibly related to IE in dogs.

A Systematic Review of the Methods of Assessment of Gastro-Oesophageal Reflux in Anaesthetized Dogs.

We reviewed the definitions and methods of assessment of gastro-oesophageal reflux (GOR) in anaesthetized dogs. Three databases were used. Titles and abstracts were screened by two of the authors independently. A total of 22 studies was included in the analysis. The definition of GOR implied the presence of fluids not reaching the mouth or nose in the oesophagus in all studies. Most studies considered a change in pH using oesophageal pH meters as the sole method of assessment. Calibration of the pH probe was inconsistently reported. The position of the tip of the oesophageal probe was inconsistent and not always precisely described. The correct positioning in the intended location was verified in a limited number of studies. Some studies considered that GOR had happened for changes in pH below 4.0 or above 7.5 while others considered that GOR had happened when the pH dropped below 4.0 only. Some studies stated that the pH change had to be sustained for a minimum period of time (20 or 30 s) whereas others did not mention any duration. The variability of definitions and methods of assessment of GOR in anaesthetized dogs precludes meaningful comparison of the findings. Re-evaluation and uniformization of the methods appear necessary.

Investigation of selected respiratory effects of (dex)medetomidine in healthy Beagles.

OBJECTIVE: To investigate the effects of sedative doses of intravenous (IV) medetomidine (MED) or dexmedetomidine (DEX) on selected respiratory variables in dogs. STUDY DESIGN: Randomized, blinded, crossover study. ANIMALS: A total of eight healthy adult research Beagles. METHODS: Dogs breathing room air had an electrical impedance tomography belt placed around the chest and were maintained in right lateral recumbency. Respiratory rate (fR) in movements minute-1 (mpm) and changes in thoracic impedance (ΔZ) in arbitrary units (AU) were recorded for 120 seconds before (T0) and exactly 10 minutes (T10) after the administration of IV DEX (10 µg kg-1) or MED (20 µg kg-1), with a minimum washout period of 10 days between treatments. Minute ΔZ (ΔZ˙) was calculated by multiplying median ΔZ with fR. Data are presented as median (interquartile range). Significance for an overall effect of drugs (DEX versus MED) or treatment (T0 versus T10) was quantified with a two-way analysis of variance for repeated measures, followed by, when appropriate, Wilcoxon's signed rank test for each factor. RESULTS: Overall, fR decreased from 26 (22-29) mpm at T0 to 13 (10-21) mpm at T10 (p = 0.003) and ΔZ increased from 1.133 (0.856-1.599) AU at T0 to 1.650 (1.273-2.813) AU at T10 (p = 0.007), but ΔZ˙ did not change [30.375 (23.411-32.445) AU minute-1 at T0 and 30.581 (22.487-35.091) AU minute-1 at T10]. There was no difference between DEX and MED. Most dogs developed a peculiar breathing pattern characterized by clusters of breaths followed by short periods of apnoea. CONCLUSIONS AND CLINICAL RELEVANCE: Both drugs caused a change in breathing pattern, reduction in fR and increase in ΔZ but did not affect ΔZ˙. It is likely that (dex)medetomidine resulted in reduction in fR and increase in tidal volume without impacting minute volume.

Effect of Medetomidine, Dexmedetomidine, and Their Reversal with Atipamezole on the Nociceptive Withdrawal Reflex in Beagles.

The objectives were: (1) to compare the antinociceptive activity of dexmedetomidine and medetomidine, and (2) to investigate its modulation by atipamezole. This prospective, randomized, blinded experimental trial was carried out on eight beagles. During the first session, dogs received either medetomidine (MED) (0.02 mg kg-1 intravenously (IV)] or dexmedetomidine (DEX) [0.01 mg kg-1 IV), followed by either atipamezole (ATI) (0.1 mg kg-1) or an equivalent volume of saline (SAL) administered intramuscularly 45 min later. The opposite treatments were administered in a second session 10-14 days later. The nociceptive withdrawal reflex (NWR) threshold was determined using a continuous tracking approach. Sedation was scored (0 to 21) every 10 min. Both drugs (MED and DEX) increased the NWR thresholds significantly up to 5.0 (3.7-5.9) and 4.4 (3.9-4.8) times the baseline (p = 0.547), at seven (3-11) and six (4-9) minutes (p = 0.938), respectively. Sedation scores were not different between MED and DEX during the first 45 min (15 (12-17), p = 0.67). Atipamezole antagonized sedation within 25 (15-25) minutes (p = 0.008) and antinociception within five (3-6) minutes (p = 0.008). Following atipamezole, additional analgesics may be needed to maintain pain relief.

Anaesthetic and Perioperative Management of 14 Male New Zealand White Rabbits for Calvarial Bone Surgery.

Calvarial bone surgery on rabbits is frequently performed. This report aims to document a simple and practical anaesthetic and perioperative management for this procedure. Fourteen male New Zealand white rabbits were included in the study. Subcutaneous (SC) dexmedetomidine, ketamine and buprenorphine ± isoflurane vaporized in oxygen administered through a supraglottic airway device (V-gel®) provided clinically suitable anaesthesia. Supplemental oxygen was administered throughout recovery. Monitoring was clinical and instrumental (pulse-oximetry, capnography, invasive blood pressure, temperature, arterial blood gas analysis). Lidocaine was infiltrated at the surgical site and meloxicam was injected subcutaneously as perioperative analgesia. After surgery, pain was assessed five times daily (composite behavioural pain scale and grimace scale). Postoperative analgesia included SC meloxicam once daily for four days and buprenorphine every 8 h for three days (unless both pain scores were at the lowest possible levels). Rescue analgesia (buprenorphine) was administered in case of the score > 3/8 in the composite pain scale, >4/10 on the grimace scale or if determined necessary by the caregivers. Airway management with a V-gel® was possible but resulted in respiratory obstruction during the surgery in two cases. Hypoventilation was observed in all rabbits. All rabbits experienced pain after the procedure. Monitoring, pain assessments and administration of postoperative analgesia were recommended for 48 h.

Do the Manual or Computer-Controlled Flowmeters Generate Similar Isoflurane Concentrations in Tafonius?

Introduction: Tafonius is an anesthesia machine with computer-controlled monitor and ventilator. We compared the isoflurane fluctuations in the circuit with manual (MF) or computer-driven (CF) flowmeters, investigated the origin of the differences and assessed whether isoflurane concentration time course followed a one-compartment model. Material and Methods: A calibrated TEC-3 isoflurane vaporizer was used. Gas composition and flows were measured using a multiparametric monitor and a digital flowmeter. Measurements included: (1) Effects of various FiO2 with MF/CF on the isoflurane fraction changes in the breathing system during mechanical ventilation of a lung model; wash-in kinetic was fitted to a compartmental model; (2) Gas outflow at the common gas outlet (CGO) with MF/CF at different FiO2; (3) Isoflurane output of the vaporizer at various dial settings with MF/CF set at different flows without and with reduction of the CGO diameter. Results: (1) The 3% targeted isoflurane concentration was not reached; additional time was required to reach specific concentrations with CF (lowest FiO2, longer time). The exponential course fitted a two-compartment model; (2) Set and measured flows were identical with MF. With CF at 0.21 FiO2, flow was intermittently 7.6 L min-1 or zero (mean total: 38% of the set flow); with CF at 1.00 FiO2, flow was 10.6 L min-1 or zero (mean: 4-5.3 L min-1); with 0.21 < FiO2 < 1.00, combined flow was intermittent (maximum output: 15.6 L min-1); (3) With MF, isoflurane output was matching dial setting at 5 L min-1 but was lower at higher flows; with CF generating intermittent flows, isoflurane output was fluctuating. With the 4 mm diameter CGO, isoflurane concentration was close to dial setting with both MF and CF. With a 14 G CGO, isoflurane concentration was lower than dial setting with MF, higher with CF. Conclusions and Clinical Relevance: Using MF or CF led to different isoflurane fraction time course in Tafonius. Flows were lower than set with CF; the TEC-3 did not compensate for high/intermittent flows and pressures; the CGO diameter influenced isoflurane output.

Heart Transplantation With Donation After Circulatory Death.

Heart transplantation remains the preferred option for improving quality of life and survival for patients suffering from end-stage heart failure. Unfortunately, insufficient supply of cardiac grafts has become an obstacle. Increasing organ availability with donation after circulatory death (DCD) may be a promising option to overcome the organ shortage. Unlike conventional donation after brain death, DCD organs undergo a period of warm, global ischemia between circulatory arrest and graft procurement, which raises concerns for graft quality. Nonetheless, the potential of DCD heart transplantation is being reconsidered, after reports of more than 70 cases in Australia and the United Kingdom over the past 3 years. Ensuring optimal patient outcomes and generalized adoption of DCD in heart transplantation, however, requires further development of clinical protocols, which in turn require a better understanding of cardiac ischemia-reperfusion injury and the various possibilities to limit its adverse effects. Thus, we aim to provide an overview of the knowledge obtained with preclinical studies in animal models of DCD heart transplantation, to facilitate and promote the most effective and efficient advancement in preclinical research. A literature search of the PubMed database was performed to identify all relevant preclinical studies in DCD heart transplantation. Specific aspects relevant for DCD heart transplantation were analyzed, including animal models, graft procurement and storage conditions, cardioprotective approaches, and graft evaluation strategies. Several potential therapeutic strategies for optimizing graft quality are identified, and recommendations for further preclinical research are provided.

Development and Implementation of a Perianesthetic Safety Checklist in a Veterinary University Small Animal Teaching Hospital.

INTRODUCTION: The use of a surgical safety checklist is recommended by the World Health Organization and is associated with advantages: improved communication and reduced complications and mortality. Adapting checklists to the environment in which they are used improves their efficiency, but their implementation can be challenging. The aim of this study was to develop and implement a perianesthetic safety checklist for a small animal hospital. MATERIALS AND METHODS: A panel of eight anesthesia diplomates and seven residents and doctoral students were gathered. The Delphi method was used to generate a checklist. The checklist was presented individually to each user by the primary investigator and introduced into the clinical routine over a 5-week period. An interdisciplinary meeting was then held, and the checklist was modified further. Six months after introduction, the use of the checklist was directly observed during 69 anesthetic cases and a survey was sent to the users. A second implementation was organized after formally presenting the checklist to the staff, designating the anesthesia clinical lead as the person responsible for printing and controlling use of the checklist. A second evaluation was performed 3 months later (64 anesthetic cases). RESULTS: Using the Delphi process led to the creation of a checklist consisting of three parts: "sign in" (before induction of anesthesia), "time out" (before the beginning of the procedure), "sign out" (at the end of the procedure). At the first assessment, the checklist was printed and used in 32% of cases and not printed in 41% of cases. Response rate of the survey was fair (19/32 surveys): 14/19 users thought the checklist contributed to improving communication; 15/19 reported improved safety and better management of the animals; 9/19 users avoided mistakes (77% would have omitted the administration of antimicrobial prophylaxis); 10/19 thought it was time consuming. At the second assessment, the checklist was used in 45% of cases (printed but not used in 55%). The use of the sign-out section of the checklist was significantly improved. CONCLUSION AND CLINICAL RELEVANCE: This study illustrates an innovative use of the Delphi method to create a safety checklist. Challenges associated with implementation are reported.

Effect of predosing versus slow administration of propofol on the dose required for anaesthetic induction and on physiologic variables in healthy dogs.

OBJECTIVE: To investigate the effects of the timing of propofol administration on the dose required for induction of anaesthesia and commonly measured physiological effects. STUDY DESIGN: Randomized, investigator-blinded clinical study. ANIMALS: A group of 32 healthy dogs aged 6-144 months and weighing 3.5-47.2 kg. METHODS: Premedication was intramuscular acepromazine (0.025 mg kg-1) and methadone (0.25 mg kg-1). After 30 minutes, one of three treatments was administered to the dogs: propofol (0.5 mg kg-1; group PP), an equivalent volume of saline (group CP) or a propofol infusion (1.3 mg kg-1 minute-1; group SI). Two minutes later, a propofol infusion (4 mg kg-1 minute-1) was started in PP and CP, whereas the propofol infusion was continued in SI. At this stage an investigator, blinded to the group assignments, entered the room and decided when each animal was ready for intubation and stopped the propofol infusion. After intubation, management of anaesthesia was standardized. Pulse rate (PR), respiratory rate (fR) and mean arterial pressure (MAP) were recorded before induction, 2 minutes later and 0, 2 and 5 minutes after intubation. Apnoea >30 seconds was recorded and managed. Sedation, quality of induction and endotracheal intubation were scored using simple descriptive scales. Data are presented as mean±standard deviation. RESULTS: Propofol dose requirement was lower in SI (3.5±1.2 mg kg-1) compared with PP and CP (5.0±0.9 and 4.8±0.6 mg kg-1; p=0.002 and 0.012), respectively. No statistically significant differences were found among groups for PR, fR, MAP or incidence of apnoea. Sedation score and quality of induction were similar among groups. CONCLUSIONS: Slow administration of propofol reduced the anaesthetic induction dose required compared with predosing and control groups. Effects on PR, fR, MAP and apnoea were similar among groups. CLINICAL RELEVANCE: Slower injection of propofol reduces the dose required for induction of anaesthesia.

Suspected bilateral phrenic nerve damage following a mediastinal mass removal in a 17-week-old pug.

The anesthetic management of a pediatric pug for removal of a mediastinal mass is described. During recovery from anesthesia, the dog's respiratory pattern was compatible with bilateral diaphragmatic paralysis. Incidence, complications, possible treatments of phrenic nerve injury, problems of long-term mechanical ventilation, and alternative case management are discussed.

Lésion bilatérale suspectée du nerf phrénique après l'ablation d'une masse médiastinale chez un Pug âgé de 17 semaines. Nous décrivons la gestion anesthésique d'un Pug pédiatrique présenté pour l'ablation d'une masse médiastinale. Durant le réveil après l'anesthésie, le profil respiratoire du chien était compatible avec la paralysie diaphragmatique bilatérale. L'incidence, les complications et les traitements possibles d'une blessure du nerf phrénique, les problèmes de la ventilation mécanique à long terme et les solutions pour la gestion du cas sont discutés.(Traduit par Isabelle Vallières).

Comparison of medetomidine-morphine and medetomidine-methadone for sedation, isoflurane requirement and postoperative analgesia in dogs undergoing laparoscopy.

OBJECTIVE: To compare the effects of intravenous (IV) medetomidine-morphine and medetomidine-methadone on preoperative sedation, isoflurane requirements and postoperative analgesia in dogs undergoing laparoscopic surgery. STUDY DESIGN: Randomized, crossover trial. ANIMALS: Twelve adult Beagle dogs weighing 15.1 ± 4.1 kg. METHODS: Dogs were administered medetomidine (2.5 µg kg-1) IV 5 minutes before either methadone (MET) or morphine (MOR) (0.3 mg kg-1) IV. Anaesthesia was induced with propofol, maintained with isoflurane in oxygen, and depth was clinically assessed and adjusted by an anaesthetist blinded to the treatment. Animals underwent laparoscopic abdominal biopsies. Sedation and nausea scores, pulse rate (PR), respiratory rate (fR), noninvasive systolic arterial blood pressure (SAP), rectal temperature (RT) and pain scores were recorded before drug administration, 5 minutes after medetomidine injection and 10 minutes after opioid administration. Propofol dose, PR, fR, SAP, oesophageal temperature (TOES), end-tidal carbon dioxide and end-tidal isoflurane concentration (Fe'Iso) were recorded intraoperatively. Pain scores, PR, fR, SAP and RT were recorded 10 minutes after extubation, every hour for 6 hours, then at 8, 18 and 24 hours. The experiment was repeated with the other drug 1 month later. RESULTS: Nine dogs completed the study. After opioid administration and intraoperatively, PR, but not SAP, was significantly lower in MET. Fe'Iso was significantly lower in MET. Temperature decreased in both treatments. Pain scores were significantly higher in MOR at 3 hours after extubation, but not at other time points. Two dogs required rescue analgesia; one with both treatments and one in MOR. CONCLUSION AND CLINICAL RELEVANCE: At the dose used, sedation produced by both drugs when combined with medetomidine was equivalent, while volatile anaesthetic requirements and PR perioperatively were lower with methadone. Postoperative analgesia was deemed to be adequate for laparoscopy with either protocol, although methadone provided better analgesia 3 hours after surgery.

Surgical Treatment of Cor Triatriatum Sinister in a Cat Under Cardiopulmonary Bypass.

OBJECTIVE: To report the surgical repair of cor triatriatum sinister (CTS) incorporating heart-beating cardiopulmonary bypass (CPB) in a cat. STUDY DESIGN: Clinical case report. ANIMAL: Fourteen-month-old, 5.9-kg male castrated Maine Coon cat. MATERIALS AND METHODS: The cat had a 3 month history of inappetance, weight loss, and recurrent pulmonary edema. CTS with severe systolic pulmonary arterial (SPA) hypertension (124 mm Hg) was diagnosed by 2D echocardiography, color flow and continuous wave Doppler modes, and left atrial and pulmonary angiography. Surgery was performed through a left intercostal thoracotomy. CPB was initiated and the heart was kept beating. The left atrial appendage was opened and the intra-atrial membrane was excised. RESULTS: After 48 hours, the cat was doing well. Reduced SPA pressure (52 mm Hg) with decreased right heart enlargement was observed on ultrasound examination and the cat was discharged 6 days after surgery with oral antibiotics for 10 days, aspirin, and furosemide. Four months after surgery, the cat presented with increased activity and weight gain and was completely asymptomatic. Transthoracic echocardiography showed a marked improvement of all echo-Doppler variables with disappearance of SPA hypertension (24 mm Hg). Four years after surgery, the cat was still doing well with no recurrence of clinical signs despite the lack of medical treatment. CONCLUSION: CTS in the cat may be successfully treated by surgery facilitated by use of CPB leading to early and long-term substantial improvement in clinical status and cardiac function. CTS can safely be repaired under CPB in cats.