Whole-heart 4D flow cardiac magnetic resonance in healthy dogs

In cardiac magnetic resonance imaging (CMR), accurate flow measurements rely on perpendicular plane-alignment with flow direction. For 2D phase contrast (PC) cardiac magnetic resonance measurements, planes have to be defined during the examination of the heart, which is time consuming and error-prone. Collection of flow information of the entire volume of the heart by a 4D flow CMR postpones plane alignment to post-processing. Sampling of such a large amount of data requires acceleration of data acquisition with techniques such as SENSitivity Encoding (k-t SENSE) or Broad-use Linear Acquisition Speed-up Technique (k-t BLAST). Objectives of the study were to compare 4D flow CMR, accelerated with two different acceleration methods with the established 2D PC CMR based on assessment of stroke volume at all four cardiac valves. The values of stroke volume acquired with the 4D flow CMR SENSE did not differ significantly when compared to the 2D PC CMR SENSE at the left side of the heart (aortic and mitral valve). Significant differences between the techniques were seen at the pulmonic and tricuspid valves. Acceleration with k-t BLAST revealed significantly lower values of stroke volume at all cardiac valves, except at the mitral valve

Effects of acepromazine and dexmedetomidine, followed by propofol induction and maintenance with isoflurane anaesthesia, on the microcirculation of Beagle dogs evaluated by sidestream dark field imaging: an experimental trial

Objective: To investigate the effects of intramuscularly administered acepromazine or dexmedetomidine on buccal mucosa microcirculation in Beagle dogs. Study design: Experimental, blinded, crossover study Animals: A group of seven Beagle dogs aged 7.5 ± 1.4 years (mean ± standard deviation). Methods: Microcirculation was assessed on buccal mucosa using sidestream dark field videomicroscopy. After baseline measurements, 5 μg kg–1 dexmedetomidine or 30 μg kg–1 acepromazine were administered intramuscularly. After 10, 20 and 30 minutes, measurements were repeated. At 40 minutes after premedication, anaesthesia was induced with propofol intravenously and maintained with isoflurane. Measurements were repeated 50, 60 and 65 minutes after the injection of the investigated drugs. Analysed microcirculatory variables were: Perfused de Backer density, Perfused de Backer density of vessels < 20 μm, Proportion of perfused vessels and Proportion of perfused vessels < 20 μm. Heart rate (HR), systolic, diastolic (DAP) and mean (MAP) arterial pressures were recorded at the same time points. Macro- and microcirculatory variables were analysed using a linear mixed model with baseline as a covariate, treatment, trial period and repetition as fixed effects and time and dog as random effect. Results are presented as effect size and confidence interval; p values < 0.05 were considered significant. Results: After acepromazine, Perfused de Backer density was greater during sedation and anaesthesia [3.71 (1.93–5.48 mm mm–2, p < 0.0001) and 2.3 (0.86–3.75 mm mm–2, p < 0.003)], respectively, than after dexmedetomidine. HR was significantly lower, whereas MAP and DAP were significantly higher with dexmedetomidine during sedation and anaesthesia (p < 0.0001 for all) compared with acepromazine. Conclusions and clinical relevance: The sedative drugs tested exerted a significant effect on buccal mucosal microcirculation with a higher Perfused de Backer density after the administration of acepromazine compared with dexmedetomidine. This should be considered when microcirculation is evaluated using these drugs

Comparison of the effects of propofol or alfaxalone for anaesthesia induction and maintenance on respiration in cats

Objective: To compare the effects of propofol and alfaxalone on respiration in cats. Study design: Randomized, ‘blinded’, prospective clinical trial. Animals: Twenty cats undergoing ovariohysterectomy. Methods: After premedication with medetomidine 0.01 mg kg−1 intramuscularly and meloxicam 0.3 mg kg−1 subcutaneously, the cats were assigned randomly into two groups: group A (n = 10) were administered alfaxalone 5 mg kg−1 minute−1 followed by 10 mg kg−1 hour−1 intravenously (IV) and group P (n = 10) were administered propofol 6 mg kg−1 minute−1 followed by 12 mg kg−1hour−1 IV for induction and maintenance of anaesthesia, respectively. After endotracheal intubation, the tube was connected to a non-rebreathing system delivering 100% oxygen. The anaesthetic maintenance drug rate was adjusted (± 0.5 mg kg−1 hour−1) every 5 minutes according to a scoring sheet based on physiologic variables and clinical signs. If apnoea > 30 seconds, end-tidal carbon dioxide (Pe′CO2) > 7.3 kPa (55 mmHg) or arterial haemoglobin oxygen saturation (SpO2) < 90% occurred, manual ventilation was provided. Methadone was administered postoperatively. Data were analyzed using independent-samples t-tests, Fisher's exact test, linear mixed-effects models and binomial test. Results: Manual ventilation was required in two and eight of the cats in group A and P, respectively (p = 0.02). Two cats in both groups showed apnoea. Pe′CO2 > 7.3 kPa was recorded in zero versus four and SpO2 < 90% in zero versus six cats in groups A and P respectively. Induction and maintenance dose rates (mean ± SD) were 11.6 ± 0.3 mg kg−1 and 10.7 ± 0.8 mg kg−1 hour−1 for alfaxalone and 11.7 ± 2.7 mg kg−1 and 12.4 ± 0.5 mg kg−1 hour−1 for propofol. Conclusion and clinical relevance: Alfaxalone had less adverse influence on respiration than propofol in cats premedicated with medetomidine. Alfaxalone might be better than propofol for induction and maintenance of anaesthesia when artificial ventilation cannot be provided

Echocardiographic assessment of right ventricular systolic function in healthy Beagle dogs compared to high field cardiac magnetic resonance imaging

Ten healthy Beagle dogs were used to compare selected echocardiographic parameters of right ventricular (RV) systolic function with high field cardiac magnetic resonance imaging (MRI). All dogs underwent complete transthoracic echocardiography before and during anesthesia, as well as cardiac MRI with determination of morphology-based ejection fraction, and phase contrast angiography-derived stroke volume. A correlation analysis was carried out between echocardiographic and MRI parameters. The values of fractional area change, tricuspid annular plane systolic excursion, tissue Doppler imaging derived peak velocity of the isovolumic contraction wave and systolic wave of the lateral tricuspid valve annulus showed lower values under general anesthesia. Of all echocardiographic parameters of RV systolic function, only fractional area change (r = 0.671, P = 0.034) and tissue Doppler imaging derived peak velocity of the systolic wave of the lateral tricuspid valve annulus (r = 0.768; P = 0.01), showed a significant correlation with MRI derived stroke volume. None of the echocardiographic parameters correlated with MRI derived ejection fraction. When evaluating the RV echocardiographically, fractional area change and peak velocity of the systolic wave of the lateral tricuspid valve annulus appear to be the most reliable predictors of RV systolic function when compared to MRI under anesthesia

Intraperitoneal bupivacaine with or without incisional bupivacaine for postoperative analgesia in dogs undergoing ovariohysterectomy

OBJECTIVE: Intraperitoneal (IP) bupivacaine provides postoperative analgesia in dogs undergoing ovariohysterectomy (OHE) alone or in combination with incisional (INC) bupivacaine. This study investigated whether the combination of INC and IP bupivacaine is superior to IP bupivacaine alone. STUDY DESIGN: Prospective, randomized, blinded clinical study. ANIMALS: Thirty-nine privately owned dogs undergoing OHE, aged 25 ± 23 months and weighing 11.8 ± 5.7 kg. METHODS: Dogs were premedicated with acepromazine (0.05 mg kg-1 ) and morphine (0.5 mg kg-1 ) intramuscularly (IM); anaesthesia was induced with propofol and maintained with isoflurane in oxygen. Carprofen (4 mg kg-1 ) was administered subcutaneously (SC) after intubation. Bupivacaine (3 mg kg-1 ) IP was administered before complete closure of the linea alba to all dogs. Dogs were randomly assigned into two groups: group B received bupivacaine (n = 20; 1 mg kg-1 ) and group S received saline (n = 19; 0.2 mL kg-1 ) INC as a subcutaneous 'splash' before skin closure. Postoperative analgesia was assessed with a dynamic interactive visual analogue scale, the short form of the Glasgow Composite Pain Scale, and mechanical nociceptive threshold (MNT) measurement at 0.5, 1, 2, 4, 6, 8, 12 and 20 hours after surgery by one blinded observer. Parametric data were tested using t-test; nonparametric data were analysed using the two-sample Wilcoxon test (p < 0.05). RESULTS: There was no significant difference between groups with regard to age, weight, surgical and anaesthetic duration, incision length, sedation and pain scores. MNT values decreased in both groups at all time points as compared with the baseline. No dog required rescue analgesia. No postoperative complications were observed. CONCLUSION AND CLINICAL RELEVANCE: Bupivacaine IP and carprofen SC after morphine IM did provide satisfactory postoperative analgesia in dogs undergoing OHE with the anaesthetic protocol used. There appears to be no clinical advantage to adding bupivacaine INC. Neither protocol could prevent the development of primary hyperalgesia

Comparison of left and right ventricular stroke volume of dogs calculated on the basis of morphology and blood flow determined by use of cardiac magnetic resonance imaging

OBJECTIVE To compare stroke volume (SV) calculated on the basis of cardiac morphology determined by MRI and results of phase-contrast angiography (PCA) of ventricular inflow and outflow in dogs. ANIMALS 10 healthy Beagles. PROCEDURES Cardiac MRI was performed twice on each Beagle. Cine gradient echo sequences of both ventricles in short-axis planes were used for morphological quantification of SVs by assessment of myocardial contours. From the long-axis plane, SVs in 4-chamber and left ventricular 2-chamber views were acquired at end diastole and end systole. For calculation of SV on the basis of blood flow, PCA was performed for cardiac valves. RESULTS Mean ± SD values for SV quantified on the basis of blood flow were similar in all valves (aortic, 17.8 ± 4.1 mL; pulmonary, 17.2 ± 5.4 mL; mitral, 17.2 ± 3.9 mL; and tricuspid, 16.9 ± 5.1 mL). Morphological quantification of SV in the short-axis plane yielded significant differences between left (13.4 ± 2.7 mL) and right (8.6 ± 2.4 mL) sides. Morphological quantification of left ventricular SV in the long-axis plane (15.2 ± 3.3 mL and 20.7 ± 3.8 mL in the 4- and 2-chamber views) yielded variable results, which differed significantly from values for flow-based quantification, except for values for the morphological 4-chamber view and PCA for the atrioventricular valves, for which no significant differences were identified. CONCLUSIONS AND CLINICAL RELEVANCE In contrast to quantification based on blood flow, calculation on the basis of morphology for the short-axis plane significantly underestimated SV, probably because of through-plane motion and complex right ventricular anatomy

Comparison of left and right ventricular stroke volume of dogs calculated on the basis of morphology and blood flow determined by use of cardiac magnetic resonance imaging

OBJECTIVE To compare stroke volume (SV) calculated on the basis of cardiac morphology determined by MRI and results of phase-contrast angiography (PCA) of ventricular inflow and outflow in dogs. ANIMALS 10 healthy Beagles. PROCEDURES Cardiac MRI was performed twice on each Beagle. Cine gradient echo sequences of both ventricles in short-axis planes were used for morphological quantification of SVs by assessment of myocardial contours. From the long-axis plane, SVs in 4-chamber and left ventricular 2-chamber views were acquired at end diastole and end systole. For calculation of SV on the basis of blood flow, PCA was performed for cardiac valves. RESULTS Mean \ub1 SD values for SV quantified on the basis of blood flow were similar in all valves (aortic, 17.8 \ub1 4.1 mL; pulmonary, 17.2 \ub1 5.4 mL; mitral, 17.2 \ub1 3.9 mL; and tricuspid, 16.9 \ub1 5.1 mL). Morphological quantification of SV in the short-axis plane yielded significant differences between left (13.4 \ub1 2.7 mL) and right (8.6 \ub1 2.4 mL) sides. Morphological quantification of left ventricular SV in the long-axis plane (15.2 \ub1 3.3 mL and 20.7 \ub1 3.8 mL in the 4- and 2-chamber views) yielded variable results, which differed significantly from values for flow-based quantification, except for values for the morphological 4-chamber view and PCA for the atrioventricular valves, for which no significant differences were identified. CONCLUSIONS AND CLINICAL RELEVANCE In contrast to quantification based on blood flow, calculation on the basis of morphology for the short-axis plane significantly underestimated SV, probably because of through-plane motion and complex right ventricular anatomy