Long duration anaesthesia in pigs with an infusion of alfaxalone and dexmedetomidine.

Pigs are commonly maintained on total intravenous anaesthesia when used in comparative medical research to study controlled manual ventilation of the lung. In this case study, four pigs were anaesthetised with a total intravenous anaesthetic infusion of alfaxalone and dexmedetomidine for up to 24 h whilst being mechanically ventilated. Cardiovascular parameters, blood gas values and body temperature were minimally affected throughout the anaesthetic period. Additional analgesia is recommended when utilising this drug combination for procedures that involve noxious stimuli.

Bias Associated with Peripheral Non-Invasive Compared to Invasive Arterial Blood Pressure Monitoring in Healthy Anaesthetised and Standing Horses Using the Bionet BM7Vet.

To compare arterial blood pressure (ABP) measured invasively (IBP) to ABP measured non-invasively (NIBP) via oscillometry in healthy anaesthetised and standing horses using the Bionet BM7Vet. Fourteen horses were anaesthetised for elective procedures (anaesthetised group) and 10 horses were enrolled for standing blood pressure manipulation (standing group). In both groups, IBP and NIBP-corrected to heart level were measured every 3 min using the Bionet BM7Vet. The overall mean difference (bias), standard deviation and limits of agreement (LOA) were calculated for paired IBP and NIBP systolic (SAP), mean (MAP) and diastolic (DAP) blood pressure measurements. In anaesthetised horses, the NIBP cuff was placed at either the proximal tail base or the metacarpus. Invasive MAP was used to retrospectively characterise measurements into hypotensive (≤70 mm Hg), normotensive (71-110 mm Hg) or hypertensive (≥111 mm Hg) subgroups. In standing horses, the NIBP cuff was placed at the tail base only and invasive MAP was manipulated to achieve hypertension (≥126 mm Hg) and hypotension (≤90 mm Hg) using phenylephrine and acepromazine, respectively. When measuring NIBP at the tail in anaesthetised horses, the Bionet BM7Vet failed on 8/185 occasions and overestimated SAP, MAP and DAP during hypotension and normotension. The biases (lower, upper LOA) for MAP were -11.4 (-33.3, 10.5) and -6.0 (-25.8, 13.8) mm Hg, respectively. Hypertension could not be evaluated. When measuring NIBP at the metacarpus in anaesthetised horses, the Bionet BM7Vet failed on 24/65 occasions and underestimated SAP, MAP and DAP when all ABP subgroups were combined. The bias (lower, upper LOA) for pooled MAP was 3.6 (-44.3, 51.6) mm Hg. When measuring NIBP at the tail in standing horses, the Bionet BM7Vet failed on 64/268 occasions and underestimated SAP, MAP and DAP during hypotension, normotension and hypertension. The biases (lower, upper LOA) for MAP were 16.3 (-10.5, 43.1), 16.6 (-19.5, 52.7) and 30.0 (-8.1, 68.0) mm Hg, respectively. Monitoring NIBP on the Bionet BM7Vet in anaesthetised horses overestimated ABP at the tail and underestimated ABP at the metacarpus. The device inaccurately detected hypotension and should be used cautiously. In standing horses, the Bionet BM7Vet underestimated ABP at the tail, especially during pharmacologically induced hypertension.

Measurement of Tissue Oximetry in Standing Unsedated and Sedated Horses.

Near infrared spectroscopy (NIRS) noninvasively measures peripheral tissue oxygen saturation (StO2) and may be useful to detect early changes in StO2 in anaesthetized and critically ill horses. This study aimed to identify the muscle belly that provided the highest percentage of successful StO2 readings and the highest mean StO2 value. Fifty adult horses were enrolled in a prospective controlled study. StO2 was measured at six different muscles in each horse, for each intervention: hair overlying the muscle was clipped (post clipping: PC), clipped skin was cleaned with chlorhexidine (post-surgical prepping: PP) and medetomidine was administered intravenously (post medetomidine: PM). Mean StO2 values were calculated for each muscle, and a linear effects model was used to assess the effect of muscle group and intervention on StO2. The sartorius muscle gave the highest percentage of successful StO2 values (p < 0.001) and the highest mean (90% CI) StO2 values for the PC, PP and PM interventions. Surgical prepping of the skin increased the success for measurement of StO2 values. For all muscles, administration of medetomidine was associated with lower StO2 values (p < 0.001). In conclusion, of the muscles examined, the sartorius muscle may be the preferred muscle to measure StO2 in horses, and clipping and cleaning of the probe placement site is recommended.

Increasing ventilator surge capacity in COVID 19 pandemic: design, manufacture and in vitro-in vivo testing in anaesthetized healthy pigs of a rapid prototyped mechanical ventilator.

OBJECTIVE: The advent of new technologies has made it possible to explore alternative ventilator manufacturing to meet the worldwide shortfall for mechanical ventilators especially in pandemics. We describe a method using rapid prototyping technologies to create an electro-mechanical ventilator in a cost effective, timely manner and provide results of testing using an in vitro-in vivo testing model. RESULTS: Rapid prototyping technologies (3D printing and 2D cutting) were used to create a modular ventilator. The artificial manual breathing unit (AMBU) bag connected to wall oxygen source using a flow meter was used as air reservoir. Controlled variables include respiratory rate, tidal volume and inspiratory: expiratory (I:E) ratio. In vitro testing and In vivo testing in the pig model demonstrated comparable mechanical efficiency of the test ventilator to that of standard ventilator but showed the material limits of 3D printed gears. Improved gear design resulted in better ventilator durability whilst reducing manufacturing time (< 2-h). The entire cost of manufacture of ventilator was estimated at 300 Australian dollars. A cost-effective novel rapid prototyped ventilator for use in patients with respiratory failure was developed in < 2-h and was effective in anesthetized, healthy pig model.

Evaluation of the effect of laser salpingopharyngostomy on the guttural pouch environment in horses.

BACKGROUND: Laser salpingopharyngostomy has been used as an adjunct to primary medical therapy allowing for topical debridement, topical treatment or to potentially alter the guttural pouch environment in horses with guttural pouch disease. OBJECTIVES: To evaluate the effect of a laser salpingopharyngostomy on the guttural pouch environment in healthy horses. STUDY DESIGN: Experimental study. METHODS: In six adult Standardbred female horses, under standing sedation a stab incision was made ventral to the sternocephalicus tendon and a customised trocar inserted into the medial guttural pouch compartment. Baseline (day 0) temperature, humidity, oxygen (O2 ) and carbon dioxide (CO2 ) levels were recorded. A laser salpingopharyngostomy was subsequently made into the right guttural pouch. The guttural pouch environment was re-sampled as above on days 7 and 14 to detect differences in the local environment of the guttural pouch caused by the laser salpingopharyngostomy. RESULTS: The guttural pouch environment was altered by the laser salpingopharyngostomy. Baseline recorded values within the guttural pouch were highly constant within each horse. Post laser salpingopharyngostomy there was considerable variation within the guttural pouch between horse and during the period of sampling. Specifically, CO2 levels post laser salpingopharyngostomy appeared to be linked directly to the horse's respiratory pattern with peaks and troughs recorded post laser salpingopharyngostomy. The variation in CO2 was significantly different at days 7 and 14 post laser salpingopharyngostomy compared with baseline levels (day 7 = 6 mm Hg, day 14 = 8.83 mm Hg). Oxygen levels were also more varied during sampling compared with baseline (day 7 = 3.4%, day 14 = 1.83%). There was no change in humidity or temperature during the study. MAIN LIMITATIONS: This study was conducted on horses with no evidence of guttural pouch abnormalities or disease. CONCLUSIONS: Laser salpingopharyngostomy alters the guttural pouch environment and this may be useful in the treatment of guttural pouch disease where this alteration is desirable.

Osteocyte expression of caspase-3, COX-2, IL-6 and sclerostin are spatially and temporally associated following stress fracture initiation.

Stress fractures (SFxs) are debilitating injuries and exact mechanisms that initiate their repair incompletely understood. We hypothesised that osteocyte apoptosis and expression of cytokines and proteins such as sclerostin, VEGF, TGF-ß, COX-2 and IL-6 were early signalling events to facilitate the formation of periosteal woven bone and recruitment of osteoclast precursors to the site of remodelling. A SFx was created in the right ulna of mature female wistar rats using cyclic end loading. Rats were killed 1, 4 and 7 days after loading (n=5 per group). Standard histological staining was used to examine SFx morphology and immunohistochemistry to detect the localisation of these proteins and in situ hybridisation to detect mRNA along the SFx line or gene expression to quantify the target genes. Unloaded ulnae served as controls. The labelling index of caspase-3, COX-2 and IL-6 was significantly elevated in the region of SFxs at all time points compared with controls (P<0.001). In addition, the labelling index of sclerostin protein was significantly reduced in osteocytes adjacent to the SFx region when compared with controls at all three time points (P<0.001). Both VEGF and TGF-ß expressions were only localised in the woven bone. These data reinforce the involvement of osteocyte apoptosis in the healing of fatigue damage in bone, and demonstrate that local regulation of sclerostin, COX-2 and IL-6 are important signalling events associated with new bone formation and SFx remodelling.