Effects of alfaxalone, propofol and isoflurane on cerebral blood flow and cerebrovascular reactivity to carbon dioxide in dogs: A pilot study.

Propofol total intravenous anesthesia is a common choice to anesthetize patients with increased intracranial pressure, reducing cerebral blood flow while maintaining cerebrovascular reactivity to CO2. Propofol and alfaxalone are commonly used for total intravenous anesthesia in dogs, but the effects of alfaxalone on cerebral blood flow and cerebrovascular reactivity to CO2 are unknown. Our hypothesis was that alfaxalone would not be significantly different to propofol, while isoflurane would increase cerebral blood flow and decrease cerebrovascular reactivity to CO2. Six healthy hound dogs were evaluated in this randomized crossover trial. Dogs were anesthetized with 7.5 mg/kg propofol, 3 mg/kg alfaxalone or 8 % sevoflurane, mechanically ventilated and maintained with propofol (400 µg/kg/min), alfaxalone (150 µg/kg/min) or 1.7 % end-tidal isoflurane, respectively, with one week washout between treatments. Cerebral blood flow and cerebrovascular reactivity to CO2 during hypercapnic and hypocapnic challenges were measured using arterial spin labelling and blood oxygen level-dependent magnetic resonance imaging sequences, respectively. Median (interquartile range, IQR) normocapnic cerebral blood flow was significantly lower (P = 0.016) with alfaxalone compared to isoflurane, in the whole brain 15.39 mL/min/100 g (14.90-19.90 mL/min/100 g) vs. 34.10 mL/min/100 g (33.35-43.17 mL/min/100 g), the grey matter 14.57 mL/min/100 g (13.66-18.72 mL/min/100 g) vs. 32.37 mL/min/100 g (31.03-42.99 mL/min/100 g), the caudal brain 15.47 mL/min/100 g (13.37-21.45 mL/min/100 g) vs. 36.85 mL/min/100 g (32.50-47.18 mL/min/100 g) and the temporal lobe grey matter 18.80 mL/min/100 g (15.89-20.84 mL/min/100 g) vs. 43.32 (36.07-43.58 mL/min/100 g). Median (IQR) hypocapnic cerebrovascular reactivity to CO2 was significantly higher (P = 0.016) for alfaxalone compared to isoflurane 8.85 %S/mm Hg (6.92-10.44 %S/mm Hg) vs. 3.90 %S/mm Hg (3.80-4.33 %S/mm Hg). Alfaxalone maintained lower cerebral blood flow and higher hypocapnic cerebrovascular reactivity to CO2 than isoflurane.

Pulmonary lipoma in a dog.

An eight-year-old, neutered, male German short-haired pointer was presented for a chronic cough and an intrathoracic mass. Computed tomography revealed a mass with low attenuation in the right caudal lung lobe that invaded the principal bronchi. The mass was removed by right caudal and accessory lung lobectomy. The histopathological diagnosis was pulmonary lipoma. The clinical signs resolved following surgery. There was no evidence of recurrence or de novo lesions on computed tomography performed 12 months post-surgery. To the authors' knowledge, this is the first report of a pulmonary lipoma in a dog.

Canine meningeal disease: associations between magnetic resonance imaging signs and histologic findings.

In order to compare the accuracy of MR sequences for diagnosis of meningeal disease, MR images of the brain, and histopathologic specimens including the meninges of 60 dogs were reviewed retrospectively by independent observers in a cross-sectional study. MR images included T1-weighted pre- and postgadolinium images, subtraction images, T2-weighted images, and T2-weighted fluid-attenuated inversion-recovery (FLAIR) images. Pathologic changes affected the pachymeninges in 16 dogs, leptomeninges in 35 dogs, and brain in 38 dogs. The meninges were normal in 12 dogs. Meninges were classified histopathologically as normal (grade 0), slightly or inconsistently affected (grade 1), or markedly affected (grade 2). When applying relaxed pathologic criteria (grades 0 and 1 considered normal), the results of ROC analysis (area under curve, AUC) were: T1-weighted postcontrast images 0.74; subtraction images 0.7; T2-weighted images 0.68; FLAIR images 0.56. The difference in AUC between T1-weighted postgadolinium images and FLAIR images was significant (P = 0.04). AUC for FLAIR images was not significantly different from 0.5. When applying strict pathologic criteria (only grade 0 considered normal), none of the MR sequences had AUC significantly different from 0.5. On the basis of T1-weighted postgadolinium images and subtraction images, correct anatomic classification of lesions occurred more often for pachymeningeal than leptomeningeal lesions (P < 0.001). Overall, MR imaging had low sensitivity for diagnosis of meningeal pathology in dogs, particularly for changes affecting the leptomeninges. Subtraction images had similar accuracy to T1-weighted postgadolinium images for meningeal lesions in dogs. T2-weighted FLAIR images appear to have limited diagnostic utility for meningeal lesions.