Lung volume changes in Apnoeic Oxygenation using Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE) compared to mechanical ventilation in adults undergoing laryngeal surgery.

BACKGROUND: Transnasal Humidified Rapid-Insufflation Ventilatory Exchange (THRIVE) using high-flow 100% oxygen during apnoea has gained increased use during difficult airway management and laryngeal surgery due to a slower carbon dioxide rise compared to traditional apnoeic oxygenation. We have previously demonstrated high arterial oxygen partial pressures and an increasing arterial-alveolar carbon dioxide difference during THRIVE. Primary aim of this study was to characterise lung volume changes measured with electrical impedance tomography during THRIVE compared to mechanical ventilation. METHODS: Thirty adult patients undergoing laryngeal surgery under general anaesthesia were randomised to THRIVE or mechanical ventilation. Subjects were monitored with electrical impedance tomography and repeated blood gas measurement perioperatively. The THRIVE group received 100% oxygen at 70 l min-1 during apnoea. The mechanical ventilation group was intubated and normoventilated with an FiO2 of 0.4. RESULTS: Mean age were 48.2 (19.9) and 51.3 (12.3) years, and BMI 26.0 (4.5) and 26.0 (3.9) in the THRIVE and mechanical ventilation group respectively. Mean apnoea time in the THRIVE group was 17.9 (4.8) min. Mean apnoea to end-of-surgery time was 28.1 (12.8) min in the mechanical ventilation group. No difference in delta End Expiratory Lung Impedance was seen between groups over time. In the THRIVE group all but three subjects were well oxygenated during apnoea. THRIVE was discontinued for the three patients who desaturated. CONCLUSIONS: No difference in lung volume change over time, measured by electrical impedance tomography, was detected when using THRIVE compared to mechanical ventilation during laryngeal surgery.

Preliminary anatomic investigation of three approaches to the equine cranium and brain for limited craniectomy procedures.

OBJECTIVE: To describe surgical approaches to the equine cranium and brain for limited craniectomy. STUDY DESIGN: Descriptive anatomic study. SAMPLE POPULATION: Equine cadavers (n=7). METHODS: Head and neck sections from cadavers were used to establish techniques for exposing areas of the equine brain. Three basic approaches were used: rostrotentorial, suboccipital, and transfrontal. Techniques were adapted from small animal descriptions and modified to account for anatomic differences. RESULTS: Descriptions of the rostrotentorial, suboccipital, and transfrontal approaches to the equine cranium and brain were defined. CONCLUSIONS: Dorsal, caudal, lateral, and rostral aspects of the cranium and underlying cerebral cortex can be accessed using the rostrotentorial, suboccipital, and transfrontal approaches. Access to the dorsal, dorsolateral, and rostral aspects of the cerebral cortex is uncomplicated and more superficial compared with access to the extreme caudolateral cerebrum and cerebellum, which is complicated by the location of the transverse and temporal sinuses and deep exposure. CLINICAL RELEVANCE: Many cases of equine brain disorders involve intracranial abscessation or hematoma formation because of trauma. Components of therapy may include microbial culture and surgical drainage or decompression of the affected area through limited craniectomy procedures. Increased use of advanced imaging in equine brain disease has resulted in earlier diagnosis and more precise lesion localization. Subsequently, the number of horses likely to improve with limited surgical intervention has increased. When surgery is indicated, descriptions of surgical approaches to the equine cranium and brain provide important information.

Intracranial magnetic resonance imaging artifacts and pseudolesions in dogs and cats.

Normal anatomic variation, study design, external factors, and tissue characteristics can all influence the manifestation of structures on magnetic resonance images (MRI). For the purpose of this review, imaging artifacts are considered to be nonpathologic abnormalities resulting from study design, intrinsic tissue characteristics, or external factors, while MRI pseudolesions are due to normal anatomic variation. Awareness of imaging artifacts and pseudolesions, as well as normal anatomic structures, is important when determining pathologic vs. normal or clinically insignificant abnormalities. The purpose of this report is to examine the literature to compile a review of selected artifacts and pseudolesions that are commonly encountered when imaging the canine and feline brain.

Imaging diagnosis--magnetic resonance imaging pseudolesion associated with the petrous temporal bone.

Normal anatomic variation in the amount of fat within the petrous temporal bone of dogs can result in a magnetic resonance (MR) imaging pseudolesion. Focal hyperintense areas in the region of the hippocampus on T1-weighted, T1-weighted, and fluid-attenuated inversion recovery imaging sequences were noted in a dog being imaged for seizure activity. Further investigation of this region, aided by the use of cadaveric specimens, led to the identification of normal anatomic variability in the amount of fat in the substantia spongiosa of the petrous temporal bone. The presence of normal adipose tissue was confirmed histopathologically. Fat suppression MR imaging sequences can be used to differentiate whether hyperintensity ventral to the hippocampus is a result of a pathologic process, or fat in the substantia spongiosa of the petrous temporal bone.