The cardiopulmonary effects of romifidine in dogs with and without prior or concurrent administration of glycopyrrolate

Objective To determine the electrocardiographic and cardiopulmonary effects of romifidine with and without prior or concurrent administration of glycopyrrolate. Study design Randomized crossover experimental study. Animals Six (three male, three female) cross‐bred dogs weighing 23 ± 2.4 kg. Methods Baseline cardiopulmonary measurements were obtained in conscious dogs and one of five treatments was administered. Glycopyrrolate (G) 0.01 mg kg^?1, or saline (S) 0.5 mL, were administered IM as premedication (Gp or Sp), or G was administered concurrently (Gc) with romifidine (RO). Treatments were as follows T1, Sp + RO 40 µg kg^?1; T2, Gp + RO (40 µg kg^?1); T3, Sp + RO 120 µg kg^?1; T4, Gp + RO (120 µg kg^?1); T5, Sp + Gc + RO (120 µg kg^?1). Romifidine or RO + Gc was administered subcutaneously 20 minutes after premedication (time 0), and further measurements were taken 10, 20, 30, 60 and 90 minutes after RO. The main treatment effect was evaluated using two‐way anova for repeated measures, followed by one‐way anova and a post‐hoc least squares difference test with a modified Bonferroni correction (p < 0.02). A Student's t‐test was used to compare the effect of romifidine at 20 and 60 minutes versus baseline values (p < 0.05). Results Both low‐ and high‐dose RO (T1, T3) significantly decreased heart rate (HR), respiratory rate (RR), cardiac index (CI) and stroke volume index, and increased arterial blood pressure (SAP), systemic vascular resistance (SVR), pulmonary arterial occlusion pressure (PAOP) and central venous pressure. High‐dose RO produced greater increases in SVR and SAP measurements. Neither dose of RO produced an alteration in blood gas values or the alveolar to arterial oxygen gradient. Glycopyrrolate significantly increased HR and CI from 10 to 90 minutes between T1/T2 and T3/T4. Increases in SAP were dose related with significant differences between T1/T3 and T2/T4 at 90 and 10 minutes, respectively, and were highest in animals receiving Gp or Gc. High‐dose RO groups (T3, T4) had higher values for SVR than low‐dose RO groups (T1, T2), unrelated to G administration. There was an increase in PAOP in all treatments. The oxygen extraction ratio was increased with all treatments: larger increases were observed in T1, T3 and T4 compared with only minimal changes in T2. Concurrent G administration was associated with an increased frequency of high‐grade second‐degree atrioventricular heart block with variable conduction at 10 and 20 minutes. Conclusions Romifidine produced effects consistent with other selective α₂‐adrenoreceptor agonists. Glycopyrrolate offset the decrease in HR and partially offset the decrease in CI associated with RO administration. Glycopyrrolate premedication produced an initial tachycardia and added to the increase in SAP associated with RO. Concurrent G administration was associated with a higher frequency of dysrhythmias and is not recommended. Despite the decrease in RR, RO sedation did not alter blood gas values. Clinical relevance It appears likely that G administration prior to or concurrent with RO produces an increase in myocardial workload and oxygen demand suggesting that this combination should not be used in dogs with cardiomyopathy or heart failure. The improvement in oxygen extraction ratio with T2 suggests that G may be beneficial with lower doses of RO, nevertheless, the use of G and RO in cardiovascularly compromised patients is not advised.     

The echocardiographic effects of romifidine in dogs with and without prior or concurrent administration of glycopyrrolate

Objective To determine the cardiopulmonary response to romifidine (RO) in the dog with or without prior or concurrent administration of glycopyrrolate. Study Design Randomized, cross‐over experimental study. Animals Six (three male, three female) cross‐bred dogs weighing 23 ± 2.4 kg. Methods Two‐dimensional guided M‐mode echocardiography was performed in conscious dogs simultaneously with measurement of systolic arterial blood pressure (SBP) and heart rate (HR). Dimensions of the left ventricle (LVID), interventricular septum (IVS), and left ventricular free wall (LVFW) were obtained in systole (S) and diastole (D). Amplitude of motion (Amp) of the IVS and LVFW were also measured. From these, measures of wall stress (WS) and fractional shortening (FS) of the left ventricle were derived. Baseline echocardiographic measurements were recorded, following which one of the five treatments was administered. Glycopyrrolate (G) 0.01 mg kg^?1, or saline (S) 0.5 mL, was administered IM as pre‐medication (Gp or Sp), or G was administered concurrently (Gc) with romifidine (RO). Treatments were: T₁, Sp + RO (40 μg kg^?1); T₂, Gp + RO (40 μg kg^?1); T₃, Sp + RO (120 μg kg^?1); T₄, Gp + RO (120 μg kg^?1); and T₅, Sp + Gc +RO (120 μg kg^?1). Romifidine or RO + Gc was administered SC 20 minutes after pre‐medication (time 0), and further measurements were taken 10, 20, 30, 60, and 90 minutes after RO. Results Echocardiographic indices of cardiac systolic function (LVID‐S, FS, Amp‐LVFW) and HR were decreased in RO‐sedated dogs (p < 0.0001) . The magnitude of change in cardiac indices was least with low‐dose RO. At most sampling times, high‐dose RO produced significantly more alteration in cardiac indices. Systolic blood pressure increased in all treatment groups, with the greatest increases in those groups receiving G. Glycopyrrolate significantly increased HR; however, cardiac indices were further reduced. Wall stress significantly increased, with a more dramatic increase in groups receiving G. Conclusions Indices of LV systolic function were reduced in RO‐sedated dogs in a dose‐related manner. Glycopyrrolate further reduced these indices and dramatically increased measurements of wall stress in dogs sedated with RO. Clinical relevance Use of low‐dose RO minimizes cardiac dysfunction; however, it should still be used cautiously in dogs with cardiomyopathy or heart failure. The routine use of G is not recommended to alleviate the bradycardia associated with RO in conscious dogs.     

Comparative analgesic and cardiopulmonary effects of bupivacaine and ropivacaine in the epidural space of the conscious dog

Objective To compare the cardiopulmonary effects and sensory blockade of epidural bupivacaine and ropivacaine. Study Design Prospective randomized study. Animals Six young adult medium‐sized crossbred dogs weighing 25.7 ± 7.1 kg. Method Dogs were chronically implanted with a lumbosacral epidural catheter. Acepromazine sedated dogs received all treatments: 0.5% bupivacaine at 0.14 mL kg^?1 (LB5) or 0.22 mL kg^?1 (HB5); 0.5% ropivacaine at 0.14 mL kg^?1 (LR5) or 0.22 mL kg^?1 (HR5); 0.75% bupivacaine at 0.22 mL kg^?1 (HB7.5) or 0.75% ropivacaine at 0.22 mL kg^?1 (HR7.5). Loss of sensation was tested at the level of the perineum, hind toe webs, flank, and caudodorsal rib areas before injection, and post‐injection (PI) up to 150 minutes PI. Systemic arterial blood pressure and heart rate were recorded before injection, and every 10 minutes PI until 150 minutes PI. Arterial blood gas analyses were performed prior to injection, and at 30, 60 and 150 minutes PI. Results No statistical differences existed between groups for the cardiopulmonary data or time to onset of block. Group HR7.5 had lower systolic (10–70 minutes PI) and diastolic (10–70 minutes PI) blood pressures and group HR5 had lower mean (10–90 minutes PI) and diastolic (10–90 minutes PI) blood pressures compared to baseline. Heart rate was lower compared to baseline in groups LR5 and HB7.5. A significant, but mild metabolic acidosis developed in groups LR5 and HB7.5 (150 minutes PI). No differences were present for the duration of block between groups, but duration of block in the dorsocaudal rib area was shorter in group HR5 compared to HR7.5. Conclusion Epidural ropivacaine and bupivacaine at the doses used have mild effects on the cardiopulmonary system, and extent of block are similar. Clinical Relevance The 0.75% concentration of bupivacaine and ropivacaine at 0.22 mL kg^?1 appeared to contribute to greater success of block (>80%) at dermatomes L₅–L₇.     

Sedative effects of intramuscular administration of a low dose of romifidine in dogs

OBJECTIVE: To evaluate sedative effects of IM administration of a low dose of romifidine in dogs. ANIMALS: 13 healthy adult Beagles. PROCEDURE: Physiologic saline solution (0.2 ml), 0.1 % romifidine (10, 20, or 40 microg/kg), or 10% xylazine (1 mg/kg) was given IM in a crossover study design. Heart rate, respiratory rate, rectal temperature, hemoglobin saturation, and scores for sedation, muscle relaxation, posture, auditory response, and positioning response were recorded before and at regular intervals for up to 240 minutes after drug administration. RESULTS: Scores for sedation, muscle relaxation, posture, auditory response, and positioning response increased in a dose-dependent manner after romifidine administration. Sedation induced by the highest dose of romifidine (40 microg/kg) was comparable to that induced by xylazine (1 mg/kg). Heart rate, respiratory rate, and rectal temperature decreased in a dose-dependent manner after romifidine administration, but hemoglobin saturation did not change. CONCLUSIONS AND CLINICAL IMPLICATIONS: Romifidine (10, 20, or 40 microg/kg, IM) is an effective sedative in dogs, but causes a decrease in heart rate, respiratory rate, and rectal temperature.     

Efficacy of open patch-grafting under cardiopulmonary bypass for pulmonic stenosis in small dogs

Objective   To assess the efficacy of an open patch-graft technique under cardiopulmonary bypass (CPB) in small dogs.
Design and methods   A retrospective analysis of 10 dogs with pulmonic stenosis. Records between 1992 and 2002 were reviewed. The effect of surgical correction was evaluated and perioperative parameters were compared between survivors and non-survivors.
Results   The postoperative pulmonary pressure gradient was reduced in all seven surviving patients. Mean ± SE was 21.5 ± 7.4 mmHg (range 3.0–54.2 mmHg) and 6/7 dogs were < 40 mmHg at 3 months postoperatively. Comparing the data between those patients that survived and those that did not, the preoperative pressure gradient (P = 0.04) and volume of the Glucose-Insulin-Kalium solution used (P = 0.001) were significantly higher in those that did not survive.
Conclusion   Open patch-grafting can be performed in small-breed dogs and decreased the pulmonary pressure gradient in survivors at 3 months postoperatively. However, this technique is more invasive than balloon valvuloplasty and should be used cautiously in severely stenosed patients.     

Pharmacokinetics of a florfenicol-tylosin combination after intravenous and intramuscular administration to beagle dogs

A pharmacokinetic study of a commercial florfenicol-tylosin (2:1) combination product was conducted in six beagle dogs after intravenous (IV) and intramuscular (IM) administration at doses of 10 mg/kg (florfenicol) and 5 mg/kg (tylosin). Serum drug concentrations were determined by a validated high performance liquid chromatography (HPLC) using UV detection. A rapid and nearly complete absorption of both drugs with a mean IM bioavailability of 103.9% (florfenicol) and 92.6% (tylosin), prolonged elimination half-life, and high tissue penetration with steady state volume of distribution of 2.63 l/kg (florfenicol) and 1.98 l/kg (tylosin) were observed. Additional studies, including pharmacodynamic and toxicological evaluation are required before recommendations can be made regarding the clinical application of the product in dogs.     

Cardiovascular effects of romifidine in dogs

OBJECTIVE: To characterize the cardiovascular effects of romifidine at doses ranging from 5 to 100 microg/kg of body weight, IV. ANIMALS: 25 clinically normal male Beagles. PROCEDURE: Romifidine was administered IV at a dose of 5, 10, 25, 50, or 100 microg/kg (n = 5/group). Heart rate, arterial pressure, central venous pressure, mean pulmonary arterial pressure, pulmonary capillary wedge pressure, body temperature, cardiac output, and PCV were measured immediately prior to and at selected times after romifidine administration. Cardiac index, stroke index, rate-pressure product, systemic and pulmonary vascular resistance indices, and left and right ventricular stroke work indices were calculated. Degree of sedation was assessed by an observer who was blinded to the dose administered. RESULTS: Romifidine induced a decrease in heart rate, pulmonary arterial pressure, rate-pressure product, cardiac index, and right ventricular stroke work index and an increase in central venous pressure, pulmonary capillary wedge pressure, and systemic vascular resistance index. In dogs given romifidine at a dose of 25, 50, or 100 microg/kg, an initial increase followed by a prolonged decrease in arterial pressure was observed. Arterial pressure immediately decreased in dogs given romifidine at a dose of 5 or 10 microg/kg. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that IV administration of romifidine induces dose-dependent cardiovascular changes in dogs. However, the 2 lowest doses (5 and 10 microg/kg) induced less cardiovascular depression, and doses > or = 25 microg/kg induced similar cardiovascular changes, suggesting that there may be a ceiling on the cardiovascular effects of romifidine.     

Effects of intramuscular vatinoxan (MK-467), co-administered with medetomidine and butorphanol,on cardiopulmonary and anaesthetic effects of intravenous ketamine in dogs

ObjectiveTo investigate the impact of intramuscular (IM) co-administration of the peripheral α₂-adrenoceptor agonist vatinoxan (MK-467) with medetomidine and butorphanol prior to intravenous (IV) ketamine on the cardiopulmonary and anaesthetic effects in dogs, followed by atipamezole reversal.Study designRandomized, masked crossover study.AnimalsA total of eight purpose-bred Beagle dogs aged 3 years.MethodsEach dog was instrumented and administered two treatments 2 weeks apart: medetomidine (20 μg kg^–1) and butorphanol (100 μg kg^–1) premedication with vatinoxan (500 μg kg^–1; treatment MVB) or without vatinoxan (treatment MB) IM 20 minutes before IV ketamine (4 mg kg^–1). Atipamezole (100 μg kg^–1) was administered IM 60 minutes after ketamine. Heart rate (HR), mean arterial (MAP) and central venous (CVP) pressures and cardiac output (CO) were measured; cardiac (CI) and systemic vascular resistance (SVRI) indices were calculated before and 10 minutes after MVB or MB, and 10, 25, 40, 55, 70 and 100 minutes after ketamine. Data were analysed with repeated measures analysis of covariance models. A p-value <0.05 was considered statistically significant. Sedation, induction, intubation and recovery scores were assessed.ResultsAt most time points, HR and CI were significantly higher, and SVRI and CVP significantly lower with MVB than with MB. With both treatments, SVRI and MAP decreased after ketamine, whereas HR and CI increased. MAP was significantly lower with MVB than with MB; mild hypotension (57–59 mmHg) was recorded in two dogs with MVB prior to atipamezole administration. Sedation, induction, intubation and recovery scores were not different between treatments, but intolerance to the endotracheal tube was observed earlier with MVB.Conclusions and clinical relevanceHaemodynamic performance was improved by vatinoxan co-administration with medetomidine–butorphanol, before and after ketamine administration. However, vatinoxan was associated with mild hypotension after ketamine with the dose used in this study. Vatinoxan shortened the duration of anaesthesia.     

Pharmacokinetics of tildipirosin in beagle dogs

The objective of this study was to investigate the pharmacokinetic profile of tildipirosin (TD) in 24 beagle dogs following intravenous (i.v.) and intramuscular (i.m.) administration, respectively, at 2, 4, and 6 mg/kg. Plasma samples at certain time points (0–14 days) were collected, and the concentrations of drug were quantified by UPLC‐MS/MS. Plasma concentration–time data and relevant parameters were described by noncompartmental through WinNonlin 6.4 software. After single i.m. injection at 2, 4, and 6 mg/kg body weight, mean maximum concentration (C_max) was 412.73 ± 76.01, 1,051 ± 323, and 1,061 ± 352 ng/ml, respectively. Mean time to reach C_max was 0.36 ± 0.2, 0.08 ± 0.00, and 0.13 ± 0.07 hr after i.m. injection at 2, 4, and 6 mg/kg, respectively. The mean value of T_1/2λz for i.m. administration at doses of 2, 4, and 6 mg/kg was 71.39 ± 28.42, 91 .33 ± 50.02, and 96.43 ± 45.02 hr, respectively. The mean residence times were 63.81 ± 10.96, 35.83 ± 15.13, and 38.18 ± 16.77 hr for doses of 2, 4, and 6 mg/kg, respectively. These pharmacokinetic characteristics after i.m. administration indicated that TD could be rapidly distributed into tissues on account of the high lipid solubility and then released into plasma. In addition, the absolute bioavailability of 2 mg/kg after i.m. injection was 112%. No adverse effects were observed after i.v. and i.m. administration.     

Comparison of sedative effects of romifidine following intravenous, intramuscular, and sublingual administration to horses.

OBJECTIVE: To compare sedative effects of romifidine following IV, IM, or sublingual (SL) administration in horses. ANIMALS: 30 horses that required sedation for routine tooth rasping. PROCEDURE: Horses (n = 10/group) were given romifidine (120 microg/kg) IV, IM, or SL. Heart rate, respiratory rate, head height, distance between the ear tips, thickness of the upper lip, response to auditory stimulation, response to tactile stimulation, and degree of ataxia were recorded every 15 minutes for 180 minutes. Tooth rasping was performed 60 minutes after administration of romifidine, and overall adequacy of sedation was assessed. RESULTS: IV and IM administration of romifidine induced significant sedation, but SL administration did not induce significant sedative effects. Scores for overall adequacy of sedation after IV and IM sedation were not significantly different from each other but were significantly different from scores for horses given romifidine SL. Sedative and other effects varied among groups during the first 60 minutes after drug administration; thereafter, effects of IV and IM administration were similar. CONCLUSIONS AND CLINICAL RELEVANCE: Onset of action was fastest and degree of sedation was greater after IV, compared with IM, administration of romifidine, but duration of action was longer after IM administration. Sublingual administration did not result in clinically important sedative effects.     

Dose requirement and cardiopulmonary effects of diluted and undiluted propofol for induction of anaesthesia in dogs

ObjectiveTo compare the dose, cardiopulmonary effects and quality of anaesthetic induction in dogs using propofol (10 mg mL^–1) and diluted propofol (5 mg mL^–1).Study designRandomized, blinded, clinical study.AnimalsA total of 28 client-owned dogs (12 males/16 females).MethodsFollowing intramuscular acepromazine (0.02 mg kg^–1) and methadone (0.2 mg kg^–1), propofol (UP, 10 mg mL^–1) or diluted propofol (DP, 5 mg mL^–1) was administered intravenously (0.2 mL kg^–1 minute^–1) by an anaesthetist unaware of the allocated group to achieve tracheal intubation. Sedation, intubation and induction quality were scored from 0 to 3. Pre- and post-induction pulse rate (PR), respiratory rate (f_R) and systolic (SAP), mean (MAP) and diastolic (DAP) arterial blood pressure were compared. Time to first breath and induction dose were recorded. Data were analysed for normality and Mann–Whitney U or Student t tests were performed where appropriate. Significance was set at p < 0.05. Data are presented as mean ± standard deviation or median (range).ResultsThe propofol dose administered to achieve induction was lower in the DP group (2.62 ± 0.48 mg kg^–1) than in the UP group (3.48 ± 1.17 mg kg^–1) (p = 0.021). No difference was observed in pre- and post-induction PR, SAP, MAP, DAP and f_R between groups. The differences between post-induction and pre-induction values of these variables were also similar between groups. Time to first breath did not differ between groups. Sedation scores were similar between groups. Quality of tracheal intubation was marginally better with UP 0 (0–1) than with DP 1 (0–2) (p = 0.036), but overall quality of induction was similar between groups [UP 0 (0–1) and DP 0 (0–1), p = 0.549].Conclusion and clinical relevanceDiluting propofol reduced the dose to induce anaesthesia without significantly altering the cardiopulmonary variables.     

The effects of maxillary nerve block,ethmoidal nerve block and their combination on cardiopulmonary responses to nasal stimulation in anesthetized Beagle dogs

ObjectiveTo describe an approach for ethmoidal nerve block (E_BLOCK) and to compare the effects of a maxillary nerve block (M_BLOCK), E_BLOCK and their combination (M-E_BLOCK) on heart rate (HR), systolic (SAP), mean (MAP), diastolic (DAP) arterial pressures and respiratory rate (f_R) during nasal stimulation in dogs.Study designProspective, blinded, randomized, crossover placebo-controlled study.AnimalsBeagle dogs (five cadavers, nine live dogs), with a median (interquartile range) weight of 10.5 (10.3–11.0) kg.MethodsThe accuracy of iohexol injections (each 1 mL) at the maxillary and ethmoidal foramina in cadavers was evaluated using computed tomography. Then, anesthetized dogs were administered four bilateral treatments separated by 1 week, saline or 2% lidocaine 1 mL per injection: injections of saline at the maxillary and ethmoidal foramina (Control), injections of lidocaine at the maxillary foramina and saline at the ethmoidal foramina (M_BLOCK), injections of saline at the maxillary foramina and lidocaine at the ethmoidal foramina (E_BLOCK) and injections of lidocaine at all foramina (M-E_BLOCK). The ventral nasal meatus was bilaterally stimulated using cotton swabs, and HR, SAP, MAP, DAP and f_R were continuously recorded. Values for each variable were compared before and after stimulation using Wilcoxon signed-rank test. Changes in variables among treatments were analyzed using Mann–Whitney U and Kruskal–Wallis tests (p ≤ 0.05).ResultsComputed tomography revealed iohexol distribution around the openings of the target foramina in all cadavers. In living dogs, HR, SAP, MAP, DAP and f_R significantly increased after stimulation within each treatment (p < 0.03). Physiologic responses were significantly attenuated, but not absent, in the M-E_BLOCK [HR (p = 0.019), SAP, MAP, DAP and f_R (all p ≤ 0.001)] compared with those in the Control.Conclusions and clinical relevanceConcurrent injections of lidocaine at the maxillary and ethmoidal foramina attenuated HR, arterial pressure and f_R responses to nasal stimulation in Beagle dogs.     

Analgesic and cardiopulmonary effects of intrathecally administered romifidine or romifidine and ketamine in goats (Capra hircus)

The study was conducted to evaluate the effects of romifidine alone (50 microg/kg) and a combination of romifidine (50 microg/kg) and ketamine (2.5 mg/kg) after intrathecal administration in goats. Ten adult goats of either sex weighing between 15 and 20 kg were randomly placed in 2 groups (groups I and II). The agents were administered at the lumbosacral subarachnoid space. Clinico-physiological parameters such as analgesia, motor incoordination, sedation, salivation, heart rate, respiratory rate, arterial pressure, central venous pressure and rectal temperature were studied. Other haematobiochemical parameters monitored were packed cell volume, haemoglobin, plasma proteins, glucose, urea and creatinine. The onset of analgesia was faster in group II (35.5 +/- 6.25 s) compared to that of group I (5.2 +/- 0.54 min). Analgesia of the tail, perineum, hind limbs, flank and thorax was mild to moderate in group I, but complete analgesia of tail, perineum and hind limbs was recorded in group II. Motor incoordination was mild in group I and severe in group II. Significant reduction in heart rate (more pronounced in group I) and respiratory rate (more pronounced in group II), and a significant increase in central venous pressure were recorded in both groups. Mean arterial pressure was reduced in both groups, but more markedly in group I. Sedation, electrocardiogram, rectal temperature and haemato-biochemical parameters did not show significant differences between the 2 groups. The results of this study indicated a possible synergistic analgesic interaction between intrathecally administered romifidine and ketamine, without causing any marked systemic effects in goats.     

Tissue distribution of sialic acid-linked influenza virus receptors in beagle dogs

Reports of influenza A virus infections in dogs has received considerable attention from veterinarians, virologists, and epidemiologists. Interaction between influenza viral hemagglutinin and cell oligosaccharides containing sialic acid residues results in infection. Sialic acids have an α-2,3-linkage to the penultimate galactose in the avian influenza virus receptor and an α-2,6-linkage in the human receptor. To date, there are no detailed data on the tissue distribution or histological features of either type of sialic acid-linked influenza virus receptors in beagle dogs, which are common laboratory animals and pets. We conducted the current study to visualize the in situ tissue distribution of both sialic acid-linked influenza virus receptors in various organs of beagle dogs using Maackia amurensis lectin II and Sambucus nigra agglutinin. Both α-2,3- and α-2,6-sialic acid-linked receptors were detected in the endothelial cells of the respiratory tract and other organs. Endothelial cells of most gastrointestinal organs were negative for α-2,3-sialic acid-linked receptors in the dogs. Our results suggested that these canine organs may be affected by influenza virus infection. The findings from our study will also help evaluate the occurrence and development of influenza virus infections in dogs.     

Hemodynamic effects of dexmedetomidine,with and without MK-467, following intramuscular administration in cats anesthetized with isoflurane

Objective

To characterize the hemodynamic effects of dexmedetomidine, with or without MK-467, following intramuscular (IM) administration in cats.

Cerebrospinal fluid flow in normal beagle dogs analyzed using magnetic resonance imaging

BackgroundDiseases related to cerebrospinal fluid flow, such as hydrocephalus, syringomyelia, and Chiari malformation, are often found in small dogs. Although studies in human medicine have revealed a correlation with cerebrospinal fluid flow in these diseases by magnetic resonance imaging, there is little information and no standard data for normal dogs.ObjectivesThe purpose of this study was to obtain cerebrospinal fluid flow velocity data from the cerebral aqueduct and subarachnoid space at the foramen magnum in healthy beagle dogs.MethodsSix healthy beagle dogs were used in this experimental study. The dogs underwent phase-contrast and time-spatial labeling inversion pulse magnetic resonance imaging. Flow rate variations in the cerebrospinal fluid were observed using sagittal time-spatial labeling inversion pulse images. The pattern and velocity of cerebrospinal fluid flow were assessed using phase-contrast magnetic resonance imaging within the subarachnoid space at the foramen magnum level and the cerebral aqueduct.ResultsIn the ventral aspect of the subarachnoid space and cerebral aqueduct, the cerebrospinal fluid was characterized by a bidirectional flow throughout the cardiac cycle. The mean ± SD peak velocities through the ventral and dorsal aspects of the subarachnoid space and the cerebral aqueduct were 1.39 ± 0.13, 0.32 ± 0.12, and 0.76 ± 0.43 cm/s, respectively.ConclusionsNoninvasive visualization of cerebrospinal fluid flow movement with magnetic resonance imaging was feasible, and a reference dataset of cerebrospinal fluid flow peak velocities was obtained through the cervical subarachnoid space and cerebral aqueduct in healthy dogs.