Early diagnosis of acute kidney injury subsequent to severe hypotension and fluid resuscitation in anaesthetized dogs.

OBJECTIVES: To document changes in urinary biomarker concentration and conventional diagnostic tests of acute kidney injury (AKI) following hypotension and fluid resuscitation in anaesthetized dogs. STUDY DESIGN: Experimental, repeated measures, prospective study. ANIMALS: A group of six male adult Greyhound dogs. METHODS: Following general anaesthesia, severe hypotension was induced by phlebotomy, maintaining mean arterial blood pressure (MAP) < 40 mmHg for 60 minutes, followed by resuscitation with intravenous gelatine solution to maintain MAP > 60 mmHg for 3 hours. Following euthanasia, renal tissue was examined by light microscopy (LM) and transmission electron microscopy (TEM). Urinary and serum concentrations of neutrophil gelatinase-associated lipocalin (NGAL), cystatin C (CysC), and gamma-glutamyl transpeptidase (GGT), serum creatinine and urine output were measured at baseline and hourly until euthanasia. Data are presented as mean and 95% confidence interval and analysed using repeated measures analysis of variance with Dunnett's adjustment, p < 0.05. RESULTS: Structural damage to proximal renal tubular cells was evident on LM and TEM. Urinary biomarker concentrations were significantly elevated from baseline, peaking 2 hours after haemorrhage at 19.8 (15.1-25.9) ng mL-1 NGAL (p = 0.002), 2.54 (1.64-3.43) mg mL-1 CysC (p = 0.009) and 2043 (790-5458) U L-1 GGT (p < 0.001). Serum creatinine remained within a breed-specific reference interval in all dogs. Urinary protein-creatinine ratio (UPC) was significantly elevated in all dogs from 1 hour following haemorrhage. CONCLUSIONS AND CLINICAL RELEVANCE: Urinary NGAL, CysC and GGT concentrations, and UPC were consistently elevated within 1 hour of severe hypotension, suggesting that proximal renal tubules are damaged in the earliest stage of ischaemia-reperfusion AKI. Measurement of urinary biomarkers may allow early diagnosis of AKI in anaesthetized dogs. Urinary GGT concentration and UPC are particularly useful as they can be measured on standard biochemistry analysers.

Hydroxyethyl starch 130/0.4 (6%) and succinylated gelatine (4%) interfere with refractometry in dogs with haemorrhagic shock.

OBJECTIVE: To determine if low molecular weight synthetic colloid fluids administered to dogs interfere with refractometric estimates of total plasma protein (TPPr) and urine osmolality (UOsm). STUDY DESIGN: Experimental study. ANIMALS: Eighteen healthy Greyhound dogs. METHODS: Anaesthetized Greyhounds subjected to haemorrhage for 60 minutes were given 80 mL kg-1 of Plasma-Lyte 148 (CRYST), or 20 mL kg-1 of hydroxyethyl starch 130/0.4 (HES) or succinylated gelatine (GELO) (n = 6 per group) intravenously over 20 minutes. Refractometric (TPPr) and biuret total plasma protein (TPPb) were measured before haemorrhage (Baseline), at end of shock (Shock), immediately (T20), then 40 minutes (T60), 100 minutes (T120) and 160 minutes (T180) after fluid administration. Urine specific gravity (USG) and UOsm were measured at all time points except T20. Estimated UOsm (eUOsm) was calculated from USG. Bias and limits of agreement (LOA) for TPPr versus TPPb, and eUOsm versus UOsm were calculated at each time point. RESULTS: For dogs given CRYST and GELO, median TPPr and TPPb decreased in parallel, with a small consistent TPP bias (CRYST range of bias, 0.38-0.67 g dL-1; GELO range of bias, 0.42-0.58 g dL-1). Dogs given HES showed divergence between median TPPr and TPPb after T20, with a peak bias at T20 of 1.62 g dL-1 (LOA 1.29-1.95). Dogs given HES and GELO had markedly increased USG [HES peak median USG at T180 of 1.119 (Q1-Q3 1.103-1.122); GELO peak median USG at T120 of 1.114 (Q1-Q3 1.082-1.119)], with large increases in bias between eUOsm and UOsm [HES peak bias at T60 of 2995 mOsm kg-1 (LOA 2032-3958 mOsm kg-1); GELO peak bias at T120 of 2465 mOsm kg-1 (LOA 940-3990 mOsm kg-1)]. CONCLUSIONS AND CLINICAL RELEVANCE: Administration of HES and GELO to dogs with haemorrhagic shock interferes with refractometric measurements for at least 3 hours after administration.

The practicalities of establishing a porcine isolated heart model.

BACKGROUND: The isolated heart apparatus is over 100 years old, but remains a useful research tool today. While designs of many large animal systems have been described in the literature, trouble-shooting and refining such a model to yield a stable, workable system has not been previously described. This paper outlines the issues, in tabular form, that our group encountered in developing our own porcine isolated heart rig with the aim of assisting other workers in the field planning similar work. The paper also highlights some of the modern applications of the isolated heart apparatus. Methods Landrace pigs (50-80 kg) were used in a pilot project to develop the model. The model was then used in a study examining the effects of various cardioplegic solutions on function after reanimation of porcine hearts. During the two projects, non-protocol issues were documented as well as their solutions. These were aggregated in this paper. RESULTS: Issues faced by the group without explicit literature solutions included pig size selection, animal acclimatisation, porcine transoesophageal echocardiography, cannulation and phlebotomy for cross-clamping, cardioplegia delivery, heart suspension and rig tuning. CONCLUSION: Prior recognition of issues and possible solutions faced by workers establishing a porcine isolated heart system will speed progress towards a useable system for research. The isolated heart apparatus remains applicable in transplant, ischaemia reperfusion, heart failure and organ preservation research.

Agreement between invasive blood pressures measured in three peripheral arteries in anaesthetized horses under clinical conditions.

OBJECTIVE: To determine agreement between invasive blood pressures measured in three peripheral arteries in anaesthetized horses undergoing elective surgery. STUDY DESIGN: Prospective balanced incomplete block design. ANIMALS: A total of 18 client-owned horses. METHODS: Invasive blood pressure (IBP) was measured simultaneously in one of the following three combinations: 1) transverse facial and facial artery; 2) transverse facial and metatarsal artery; and 3) facial and metatarsal artery. The agreement in blood pressure measured for each combination was performed in six horses. At each sample time, systolic (SAP), mean (MAP) and diastolic (DAP) arterial pressures were measured concurrently in each artery, and the mean of three consecutive measurements was recorded. The position of horse, heart rate and use of dobutamine were also recorded. Bland-Altman analysis was used to assess agreement between sites. RESULTS: A total of 54 paired measurements were obtained, with 18 paired measurements from each combination. All paired measurements showed poor and haphazard (nonsystematic) agreement. The widest limit of agreement was 51 mmHg for SAP measured in the facial artery and metatarsal artery, with a bias of -11 mmHg. The smallest limit of agreement was 16 mmHg for MAP measured in the transverse facial and metatarsal artery, with a bias of 1 mmHg. CONCLUSIONS AND CLINICAL RELEVANCE: There was poor and haphazard agreement for SAP, MAP and DAP measured in each pair of peripheral arteries in this study. These results show that blood pressure measured in different peripheral arteries cannot be used interchangeably. This has implications for studies that use IBP as an outcome variable and studies determining agreement between noninvasive blood pressure and IBP measurements in horses under general anaesthesia.

Agreement between invasive blood pressure measured centrally and peripherally in anaesthetized horses.

OBJECTIVE: To determine the agreement of invasive blood pressure measured in the facial, metatarsal and carotid arteries, and evaluate the effects of two haemodynamic conditions on agreement. STUDY DESIGN: Prospective randomized study. ANIMALS: A group of eight horses aged 7 (4-23) years with a body weight of 493 ± 33 kg. METHODS: Horses were anaesthetized and positioned in dorsal recumbency. Invasive blood pressure was measured simultaneously via catheters placed in the facial, metatarsal and carotid arteries. Cardiovascular function and agreement between arteries was assessed before and during administration of phenylephrine and sodium nitroprusside. These were administered until carotid mean pressure (MAPc) increased or decreased from baseline (65 ± 5) to >90 or <50 mmHg, respectively. Data recorded at each sample time included systolic (SAP), mean (MAP) and diastolic (DAP) arterial pressures for carotid (c), facial (f) and metatarsal (m) arteries as well as cardiac output (Q˙t) and systemic vascular resistance (SVR). Bland-Altman analysis was used to assess agreement between peripheral and central sites, and regression analysis to determine influence of Q˙t and SVR. RESULTS: The largest difference was observed in SAPc and SAPm with a bias and limits of agreement (LOA) of 2 (-15 to 19) mmHg. The bias (LOA) for MAPc and MAPf was 2 (-4 to 9) mmHg and for MAPc and MAPm was 5 (-4 to 14) mmHg. The best agreement for DAP was seen between DAPc and DAPf with bias (LOA) of 1 (-3 to 5) mmHg. Regression analysis indicated marginal influence on agreement by Q˙t on MAPc and MAPf. CONCLUSIONS AND CLINICAL RELEVANCE: MAP and DAP of the carotid artery were higher than those of the peripheral arteries, which may lead to overzealous treatment of hypotension, albeit maintaining central pressures. Q˙t and SVR did not largely influence the difference between sites.

Hydroxyethyl starch 130/0.4 compared with 0.9% NaCl administered to greyhounds with haemorrhagic shock.

OBJECTIVE: To determine the cardiovascular and acid-base effects of 6% hydroxyethyl starch (HES) 130/0.4 and 0.9% sodium chloride (NaCl) administered to anaesthetized greyhounds with haemorrhagic shock. STUDY DESIGN: Prospective, experimental, complete randomized block design. ANIMALS: Twelve healthy adult greyhounds. METHODS: After 60 minutes of isoflurane anaesthesia, 48 mL kg-1 of blood was removed to induce hypotension. Dogs were randomized to receive either 20 mL kg-1 of HES 130/0.4 or 80 mL kg-1 of 0.9% NaCl over 20 minutes. Haemoglobin, arterial and central venous blood gas and electrolytes, lactate, mean arterial pressure (MAP) and cardiac index were measured at: T0, 60 minutes after induction of anaesthesia, immediately prior to blood removal; T1, immediately after blood removal; T2, immediately after fluid administration; and T3, 40 minutes after fluid administration. Oxygen extraction ratio (O2ER) was calculated at each sample time. RESULTS: O2ER increased at T1 and decreased at T2 and T3, with no difference between the two groups. Dogs administered HES 130/0.4 had higher lactate at T2 [mean (95% confidence interval) 1.3 (0.8-1.9) mmol L-1] than dogs administered 0.9% NaCl [0.8 (0.5-1.1) mmol L-1]; p = 0.045. Dogs administered HES 130/0.4 had a higher MAP at T3 [88 (74-102) mmHg] than dogs administered 0.9% NaCl [69 (60-79) mmHg]; p = 0.019. Dogs administered 0.9% NaCl were more acidaemic at T2 and T3, including higher hydrogen ion, lower bicarbonate, lower base excess and higher chloride concentrations. CONCLUSION: and clinical relevance The effect of 20 mL kg-1 of HES 130/0.4 on shock, as measured by O2ER, was no different than that of 80 mL kg-1 of 0.9% NaCl in dogs under general anaesthesia. Acidaemia in the NaCl group is likely attributable to hyperchloraemic metabolic acidosis from the larger volume administered.

Comparison of invasive and noninvasive blood pressure measurements in anaesthetized horses using the Surgivet V9203.

OBJECTIVES: To determine the bias and precision of noninvasive versus invasive blood pressure measurements obtained using the Surgivet V9203 in anaesthetized horses; to compare these with the current American College of Veterinary Internal Medicine Hypertension Consensus Panel (AHCP) and Veterinary Blood Pressure Society (VBPS) recommendations; and to investigate whether noninvasive blood pressure monitoring could be a clinically useful alternative to invasive blood pressure monitoring in anaesthetized horses. STUDY DESIGN: Prospective clinical study in a university teaching hospital. ANIMALS: Forty-three horses with an average weight of 485 ± 90 kg and a mean age of 103.4 ± 57.6 months. METHODS: Arterial blood pressure (BP) was measured noninvasively (NIBP) via a cuff placed over either the ventral coccygeal artery or the metacarpal artery, and invasively (IBP) via a catheter in either the facial artery or the metatarsal artery. A total of 143 paired readings were obtained. Comparison of measurements was carried out using the Bland-Altman method. Analysis was performed using all the data, and these data were subdivided according to the position of the horse and the magnitude of the pressure measurement. To determine the accuracy of the noninvasive measurements, the calculated precision and bias were compared with AHCP and VBPS guidelines. RESULTS: For all categories, NIBP measurements were generally lower than IBP measurements. For pooled data, the bias and precision for systolic arterial pressure (SAP) were 6.8 and 11.9 mmHg; for mean arterial pressure (MAP) the values were 1.9 and 10.0 mmHg; and for diastolic arterial pressure (DAP) they were 5.7 and 10.8 mmHg. The bias and precision for MAP and DAP measurements were within the recommended guidelines defined by the AHCP and VBPS. CONCLUSIONS AND CLINICAL RELEVANCE: These results suggests that systolic, mean and diastolic NIBP measured using the Surgivet V9203 are a clinically acceptable alternative to IBP measurements in anaesthetized horses undergoing routine elective surgeries.

Urinary neutrophil gelatinase-associated lipocalin concentration changes after acute haemorrhage and colloid-mediated reperfusion in anaesthetized dogs.

OBJECTIVE: To determine changes in urine neutrophil gelatinase-associated lipocalin concentration (uNGAL) in anaesthetized Greyhound dogs that developed acute tubular damage following haemorrhage and resuscitation with colloid-based fluids. STUDY DESIGN: Prospective experimental study. ANIMALS: Seven healthy adult entire male Greyhound dogs. METHODS: During isoflurane anaesthesia, approximately 50 mL kg(-1) of blood was removed to maintain mean arterial pressure (MAP) ≤40 mmHg for 1 hour followed by gelatin-based colloid administration to maintain MAP ≥60 mmHg for 3 hours. Data, including oxygen extraction ratio and uNGAL, were collected before (T0) and immediately following (T1) haemorrhage, and hourly during reperfusion (T2-T4). After T4, dogs were euthanized and renal tissue was collected for histology. Statistical analysis was performed using repeated-measures one-way anova. Data are presented as means (95% confidence interval). RESULTS: Histology identified renal tubular epithelial damage in all dogs. Urine NGAL concentration increased from 12.1 (0-30.6) ng mL(-1) at T0 to 122.0 (64.1-180.0) ng mL(-1) by T3. Compared with T0, uNGAL was significantly higher at T3 (p = 0.016) and was increased 24-fold. CONCLUSIONS AND CLINICAL RELEVANCE: Despite wide individual variation in baseline uNGAL, increases in uNGAL were observed in all dogs, suggesting that this biomarker has the potential to detect renal tubular injury following haemorrhage-induced hypotension and colloid-mediated reperfusion.

Cardiovascular function during maintenance of anaesthesia with isoflurane or alfaxalone infusion in greyhounds experiencing blood loss.

OBJECTIVE: To compare adequacy of oxygen delivery and severity of shock during maintenance of anaesthesia with isoflurane or alfaxalone infusion in greyhounds experiencing blood loss. STUDY DESIGN: Prospective, randomised study. ANIMALS: Twenty-four greyhounds (ASA I). METHODS: All greyhounds were premedicated with methadone (0.2 mg kg(-1) ) intramuscularly. Anaesthesia was induced with alfaxalone 2.5 mg kg(-1) intravenously. Following endotracheal intubation, the dogs were connected to an anaesthetic circle circuit delivering oxygen. Dogs were allocated to receive inhaled isoflurane or an intravenous infusion of alfaxalone for maintenance of anaesthesia. Isoflurane was initially administered to achieve an end-tidal concentration of 1.4% and alfaxalone was initially administered at 0.13 mg kg(-1)  minute(-1) . The dose of isoflurane or alfaxalone was adjusted during instrumentation to produce a clinically equivalent depth of anaesthesia. All dogs were mechanically ventilated to normocapnia (Pa CO2 35-40 mmHg; 4.67-5.33 kPa). Passive warming maintained core body temperature between 37 and 38 °C. Measured and calculated indices of cardiovascular function, including mean arterial blood pressure (MAP), cardiac index (CI), systemic vascular resistance index (SVRI), oxygen delivery index (D˙O2I), oxygen consumption index (V˙O2I) and oxygen extraction ratio (OER), were determined at baseline (60 minutes after start of anaesthesia) and after removal of 32 mL kg(-1) and 48 mL kg(-1) of blood. RESULTS: In all dogs, blood loss resulted in a significant decrease in MAP, CI, D˙O2 , and a significant increase in SVRI, V˙O2I , and OER. The changes in each of the indices did not differ significantly between dogs receiving isoflurane and dogs receiving alfaxalone. CONCLUSION AND CLINICAL RELEVANCE: No difference in oxygen delivery or severity of shock was observed when either inhaled isoflurane or intravenous alfaxalone infusion was used for maintenance of anaesthesia in greyhounds experiencing blood loss. There appears to be no clinical advantage to choosing one anaesthetic agent for maintenance of anaesthesia over the other in a dog experiencing blood loss.

Breath-by-breath assessment of acute pulmonary edema using electrical impedance tomography, spirometry and volumetric capnography in a sheep (Ovis Aries) model.

Background: The bedside diagnosis of acute pulmonary edema is challenging. This study evaluated the breath-by-breath information from electrical impedance tomography (EIT), respiratory mechanics and volumetric capnography (VCap) to assess acute pulmonary edema induced by xylazine administration in anesthetized sheep. Objective: To determine the ability and efficiency of each monitoring modality in detecting changes in lung function associated with onset of pulmonary edema. Methods: Twenty healthy ewes were anesthetized, positioned in sternal (prone) recumbency and instrumented. Synchronized recordings of EIT, spirometry and VCap were performed for 60 s prior to start of injection, during xylazine injection over 60 s (0-60 s) and continuously for 1 min (60-120 s) after the end of injection. After visual assessment of the recorded mean variables, statistical analysis was performed using a mixed effect model for repeated measures with Bonferroni's correction for multiple comparisons, to determine at which breath after start of injection the variable was significantly different from baseline. A significant change over time was defined as an adjusted p < 0.05. All statistics were performed using GraphPad Prism 0.1.0. Results: Electrical impedance tomography showed significant changes from baseline in all but two variables. These changes were observed simultaneously during xylazine injection at 48 s and were consistent with development of edema in dependent lung (decreased end-expiratory lung impedance, ventilation in centro-ventral and ventral lung region) and shift of ventilation into non-dependent lung (decreased non-dependent silent spaces and increased center of ventilation ventral to dorsal and increased ventilation in centro-dorsal and dorsal lung region). All changes in lung mechanics also occurred during injection, including decreased dynamic respiratory system compliance and increased peak expiratory flow, peak inspiratory pressure and airway resistance at 48, 54 and 60 s, respectively. Changes in VCap variables were delayed with all occurring after completion of the injection. Conclusion: In this model of pulmonary edema, EIT detected significant and rapid change in all assessed variables of lung function with changes in regional ventilation indicative of pulmonary edema. Volumetric capnography complemented the EIT findings, while respiratory mechanics were not specific to lung edema. Thus, EIT offers the most comprehensive method for pulmonary edema evaluation, including the assessment of ventilation distribution, thereby enhancing diagnostic capabilities.

Validation of three-dimensional thoracic electrical impedance tomography of horses during normal and increased tidal volumes.

Objective. Data from two-plane electrical impedance tomography (EIT) can be reconstructed into various slices of functional lung images, allowing for more complete visualisation and assessment of lung physiology in health and disease. The aim of this study was to confirm the ability of 3D EIT to visualise normal lung anatomy and physiology at rest and during increased ventilation (represented by rebreathing).Approach. Two-plane EIT data, using two electrode planes 20 cm apart, were collected in 20 standing sedate horses at baseline (resting) conditions, and during rebreathing. EIT data were reconstructed into 3D EIT whereby tidal impedance variation (TIV), ventilated area, and right-left and ventral-dorsal centres of ventilation (CoVRLand CoVVD, respectively) were calculated in cranial, middle and caudal slices of lung, from data collected using the two planes of electrodes.Main results. There was a significant interaction of time and slice for TIV (p< 0.0001) with TIV increasing during rebreathing in both caudal and middle slices. The ratio of right to left ventilated area was higher in the cranial slice, in comparison to the caudal slice (p= 0.0002). There were significant effects of time and slice on CoVVDwhereby the cranial slice was more ventrally distributed than the caudal slice (p< 0.0009 for the interaction).Significance. The distribution of ventilation in the three slices corresponds with topographical anatomy of the equine lung. This study confirms that 3D EIT can accurately represent lung anatomy and changes in ventilation distribution during rebreathing in standing sedate horses.

Evaluation of Masimo signal extraction technology pulse oximetry in anaesthetized pregnant sheep.

OBJECTIVE: Evaluation of the accuracy of Masimo signal extraction technology (SET) pulse oximetry in anaesthetized late gestational pregnant sheep. STUDY DESIGN: Prospective experimental study. ANIMALS: Seventeen pregnant Merino ewes. METHODS: Animals included in study were late gestation ewes undergoing general anaesthesia for Caesarean delivery or foetal surgery in a medical research laboratory. Masimo Radical-7 pulse oximetry (SpO(2) ) measurements were compared to co-oximetry (SaO(2) ) measurements from arterial blood gas analyses. The failure rate of the pulse oximeter was calculated. Accuracy was assessed by Bland & Altman's (2007) limits of agreement method. The effect of mean arterial blood pressure (MAP), perfusion index (PI) and haemoglobin (Hb) concentration on accuracy were assessed by regression analysis. RESULTS: Forty arterial blood samples paired with SpO(2) and blood pressure measurements were obtained. SpO(2) ranged from 42 to 99% and SaO(2) from 43.7 to 99.9%. MAP ranged from 24 to 82 mmHg, PI from 0.1 to 1.56 and Hb concentration from 71 to 114 g L(-1) . Masimo pulse oximetry measurements tended to underestimate oxyhaemoglobin saturation compared to co-oximetry with a bias (mean difference) of -2% and precision (standard deviation of the differences) of 6%. Accuracy appeared to decrease when SpO(2) was <75%, however numbers were too small for statistical comparisons. Hb concentration and PI had no significant effect on accuracy, whereas MAP was negatively correlated with SpO(2) bias. CONCLUSIONS AND CLINICAL RELEVANCE: Masimo SET pulse oximetry can provide reliable and continuous monitoring of arterial oxyhaemoglobin saturation in anaesthetized pregnant sheep during clinically relevant levels of cardiopulmonary dysfunction. Further work is needed to assess pulse oximeter function during extreme hypotension and hypoxaemia.

Thoracic electrical impedance tomography identifies heterogeneity in lungs associated with respiratory disease in cattle. A pilot study.

Respiratory disease in cattle is a significant global concern, yet current diagnostic methods are limited, and there is a lack of crush-side tests for detecting active disease. To address this gap, we propose utilizing electrical impedance tomography (EIT), a non-invasive imaging technique that provides real-time visualization of lung ventilation dynamics. The study included adult cattle from farms in Western Australia. The cattle were restrained in a crush. A standardized respiratory scoring system, which combined visual, auscultation, and clinical scores, was conducted by two non-conferring clinicians for each animal. The scores were blinded and averaged. During assessment, an EIT electrode belt was placed around the thorax. EIT recordings of ten suitable breaths were taken for analysis before the cattle were released back to the herd. Based on the combined examination scoring, the cattle were categorized as having healthy or diseased lungs. To allow visual interpretation of each breath and enable the creation of the quartile ventilation ratio (VQR), Flow/Tidal Impedance Variation curves (F/TIV) were generated for each breath. The analysis focused on two EIT variables: The novel VQR over time during inhalation and exhalation and global expiratory impedance (TIVEXP) adjusted by breath length. A mixed effects model was used to compare these variables between healthy and diseased cattle. Ten adult cattle of mixed ages were used in the current analysis. Five cattle were scored as healthy and five as diseased. There was a significant difference in the examination scores between the healthy and diseased group (P = 0.03). A significant difference in VQR during inhalation (P = 0.03) was observed between the healthy and diseased groups. No difference was seen in VQR over time during exhalation (P = 0.3). The TIVEXP was not different between groups (P = 0.36). In this study, EIT was able to detect differences in inhalation mechanics when comparing healthy and diseased cattle as defined via clinical examination, highlighting the clinical utility of EIT.

Effect of Deferoxamine on Post-Transfusion Iron, Inflammation, and In Vitro Microbial Growth in a Canine Hemorrhagic Shock Model: A Randomized Controlled Blinded Pilot Study.

Red blood cell (RBC) transfusion is associated with recipient inflammation and infection, which may be triggered by excessive circulating iron. Iron chelation following transfusion may reduce these risks. The aim of this study was to evaluate the effect of deferoxamine on circulating iron and inflammation biomarkers over time and in vitro growth of Escherichia coli (E. coli) following RBC transfusion in dogs with atraumatic hemorrhage. Anesthetized dogs were subject to atraumatic hemorrhage and transfusion of RBCs, then randomized to receive either deferoxamine or saline placebo of equivalent volume (n = 10 per group) in a blinded fashion. Blood was sampled before hemorrhage and then 2, 4, and 6 h later. Following hemorrhage and RBC transfusion, free iron increased in all dogs over time (both p < 0.001). Inflammation biomarkers interleukin-6 (IL6), CXC motif chemokine-8 (CXCL8), interleukin-10 (IL10), and keratinocyte-derived chemokine (KC) increased in all dogs over time (all p < 0.001). Logarithmic growth of E. coli clones within blood collected 6 h post-transfusion was not different between groups. Only total iron-binding capacity was different between groups over time, being significantly increased in the deferoxamine group at 2 and 4 h post-transfusion (both p < 0.001). In summary, while free iron and inflammation biomarkers increased post-RBC transfusion, deferoxamine administration did not impact circulating free iron, inflammation biomarkers, or in vitro growth of E. coli when compared with placebo.

Comparison of Effects of an Endotracheal Tube or Facemask on Breathing Pattern and Distribution of Ventilation in Anesthetized Horses.

Equine respiratory physiology might be influenced by the presence of an endotracheal tube (ETT). This experimental, randomized cross-over study aimed to compare breathing pattern (BrP) and ventilation distribution in anesthetized horses spontaneously breathing room air via ETT or facemask (MASK). Six healthy adult horses were anesthetized with total intravenous anesthesia (TIVA; xylazine, ketamine, guaiphenesin), breathing spontaneously in right lateral recumbency, and randomly assigned to ETT or MASK for 30 min, followed by the other treatment for an additional 30 min. During a second anesthesia 1 month later, the treatment order was inversed. Electrical impedance tomography (EIT) using a thoracic electrode belt, spirometry, volumetric capnography, esophageal pressure difference (ΔPoes), venous admixture, and laryngoscopy data were recorded over 2 min every 15 min. Breaths were classified as normal or alternate (sigh or crown-like) according to the EIT impedance curve. A mixed linear model was used to test the effect of treatment on continuous outcomes. Cochran-Mantel-Haenszel analysis was used to test for associations between global BrP and treatment. Global BrP was associated with treatment (p = 0.012) with more alternate breaths during ETT. The center of ventilation right-to-left (CoVRL) showed more ventilation in the non-dependent lung during ETT (p = 0.025). The I:E ratio (p = 0.017) and ΔPoes (p < 0.001) were smaller, and peak expiratory flow (p = 0.009) and physiologic dead space (p = 0.034) were larger with ETT. The presence of an ETT alters BrP and shifts ventilation toward the non-dependent lung in spontaneously breathing horses anesthetized with TIVA.

Determination of tidal volume by electrical impedance tomography (EIT) after indirect two-point calibration.

Objective. A linear relationship between impedance change (ΔZ) measured by thoracic electrical impedance tomography (EIT) and tidal volume (VT) has been demonstrated. This study evaluated the agreement between the displayed VT calculated by the EIT software (VTEIT) and spirometry (VTSPIRO) after an indirect two-point calibration.Approach.The EIT software was programmed to execute a bedside two-point calibration from the subject-specific, linear equation defining the relationship between ΔZand VTSPIROand displaying VTEITbreath-by-breath in 20 neutered male, juvenile pigs. After EIT calibration VTs of 8, 12, 16 and 20 ml kg-1were applied to the lungs. VTEITand VTSPIROwere recorded and analysed using Bland-Altman plot for multiple subject measurements. Volumetric capnography (VCap) and spirometry data were explored as components of variance using multiple regression.Main results.A mean relative difference (bias) of 0.7% with 95% confidence interval (CI) of -10.4% to 10.7% were found between VTEITand VTSPIROfor the analysed data set. The variance in VTEITcould not be explained by any of the measured VCap or spirometry variables.Significance.The narrow CI estimated in this study allows the conclusion that EIT and its software can be used to measure and accurately convert ΔZinto mililitre VT at the bedside after applying an indirect two-point calibration.

Biomarkers of Coagulation and Inflammation in Dogs after Randomized Administration of 6% Hydroxyethyl Starch 130/0.4 or Hartmann's Solution.

Synthetic colloid fluids containing hydroxyethyl starch (HES) have been associated with impairment of coagulation in dogs. It is unknown if HES causes coagulation impairment in dogs with naturally occurring critical illness. This study used banked plasma samples from a blinded, randomized clinical trial comparing HES and balanced isotonic crystalloid for bolus fluid therapy in 39 critically ill dogs. Blood was collected prior to fluid administration and 6, 12, and 24 h thereafter. Coagulation biomarkers measured at each time point included prothrombin time, activated partial thromboplastin time, thrombin time, fibrinogen concentration, and the activities of coagulation factors V, VII, VIII, IX, and X, von Willebrand factor antigen, antithrombin, and protein C. Given the links between coagulation and inflammation, cytokine concentrations were also measured, including interleukins 6, 8, 10, and 18, keratinocyte-derived chemokine, and monocyte chemoattractant protein-1. Data were analyzed with linear mixed effects models. No significant treatment-by-time interactions were found for any biomarker, indicating that the pattern of change over time was not modified by treatment. Examining the main effect of time showed significant changes in several coagulation biomarkers and keratinocyte-derived chemokines. This study could not detect evidence of coagulation impairment with HES.

Performance evaluation of electrode design and material for a large animal electrical impedance tomography belt.

BACKGROUND: Electrical impedance tomography (EIT) produces lung ventilation images via a thoracic electrode belt. Robust electrode design and material, providing low electrode skin contact impedance (SCI), is needed in veterinary medicine. The aim of this study was to compare three EIT electrode designs and materials. METHODS: Simulations of cylindrical, rectangular and spiked electrode designs were used to evaluate electrode SCI as a function of electrode size, where skin contact was uneven. Gold-plated washers (EGW ), zinc-plated rivets (EZR ) and zinc-galvanised spikes (EZS ) were assigned randomly on two interconnected EIT belts. Gel was applied to the cranial or caudal belt and placed on 17 standing cattle. SCI was recorded at baseline and 3, 5, 7, 9 and 11 minutes later. RESULTS: Simulations that involved electrodes with a greater skin contact area had lower and more uniform SCI. In cattle, SCI decreased with all electrodes over time (p < 0.01). Without gel, no difference was found between EGW and EZS , while SCI was higher for EZR (p < 0.03). With gel, SCI was lower in EGW and EZR (p < 0.026), with the SCI in EGW being the lowest (p < 0.01). LIMITATIONS: Low numbers of animals and static electrode position may affect SCI. CONCLUSIONS: Electrode design is important for EIT measurement, with larger electrode designs able to compensate for the use of less conductive materials. Gel is not necessary to achieve acceptable SCI in large animals.

Cannula cricothyroidotomy in the impalpable neck: An observational study of simulated 'can't intubate, can't oxygenate' scenarios by teams following a cannula-first algorithm in live anaesthetised pigs.

Live animal models can be used to train anaesthetists to perform emergency front-of-neck-access. Cannula cricothyroidotomy success reported in previous wet lab studies contradicts human clinical data. This prospective, observational study reports success of a cannula-first 'can't intubate, can't oxygenate' algorithm for impalpable anatomy during high fidelity team simulations using live, anaesthetised pigs.Forty-two trained anaesthesia teams were instructed to follow the Royal Perth Hospital can't intubate, can't oxygenate algorithm to re-oxygenate a desaturating pig with impalpable neck anatomy (mean (standard deviation, SD) 16.2 (3.5) kg); mean (SD) tracheal internal diameter 11 (1.4) mm. Teams were informed that failure would prompt veterinary-led euthanasia.All teams performed percutaneous cannula cricothyroidotomy as the initial technique, with a median (interquartile range, IQR (range)) start time of 42 (35-50 (24-93)) s. First-pass percutaneous cannula success was 29% to both insufflate tracheal oxygen and re-oxygenate. Insufflation success improved with repeated percutaneous attempts (up to three), but prolonged hypoxia time increasingly necessitated euthanasia (insufflation 57%; re-oxygenation 48%). First, second and third percutaneous attempts achieved insufflation at median (IQR (range)) 74 (64-91 (46-110)) s, 111 (95-136 (79-150)) s and 141 (127-159 (122-179)) s, respectively. Eighteen teams failed with percutaneous cannulae and performed scalpel techniques, predominantly dissection cannulation (n = 17) which achieved insufflation in all cases (insufflation 100%; re-oxygenation 47%). Scalpel attempts were started at median (IQR (range)) 142 (133-218 (97-293)) s and achieved insufflation at 232 (205-303 (152-344)) s.While percutaneous cannula cricothyroidotomy could rapidly re-oxygenate, the success rate was low and teams repeated attempts beyond the recommended 60 s time frame, delaying transition to the more successful dissection cannula technique. We recommend this 'cannula-first' can't intubate, can't oxygenate algorithm adopts a 'single best effort' strategy for percutaneous cannula, with failure prompting a scalpel technique.

Thoracic Electrical Impedance Tomography-The 2022 Veterinary Consensus Statement.

Electrical impedance tomography (EIT) is a non-invasive real-time non-ionising imaging modality that has many applications. Since the first recorded use in 1978, the technology has become more widely used especially in human adult and neonatal critical care monitoring. Recently, there has been an increase in research on thoracic EIT in veterinary medicine. Real-time imaging of the thorax allows evaluation of ventilation distribution in anesthetised and conscious animals. As the technology becomes recognised in the veterinary community there is a need to standardize approaches to data collection, analysis, interpretation and nomenclature, ensuring comparison and repeatability between researchers and studies. A group of nineteen veterinarians and two biomedical engineers experienced in veterinary EIT were consulted and contributed to the preparation of this statement. The aim of this consensus is to provide an introduction to this imaging modality, to highlight clinical relevance and to include recommendations on how to effectively use thoracic EIT in veterinary species. Based on this, the consensus statement aims to address the need for a streamlined approach to veterinary thoracic EIT and includes: an introduction to the use of EIT in veterinary species, the technical background to creation of the functional images, a consensus from all contributing authors on the practical application and use of the technology, descriptions and interpretation of current available variables including appropriate statistical analysis, nomenclature recommended for consistency and future developments in thoracic EIT. The information provided in this consensus statement may benefit researchers and clinicians working within the field of veterinary thoracic EIT. We endeavor to inform future users of the benefits of this imaging modality and provide opportunities to further explore applications of this technology with regards to perfusion imaging and pathology diagnosis.