Caudal vena cava collapsibility index as a tool to predict fluid responsiveness in dogs

Prediction of Fluid Responsiveness Based on the External Jugular Vein Distensibility Index After Changes in Volume Status in Healthy, Anesthetized, and Mechanically Ventilated Dogs

OBJECTIVE

To investigate whether point-of-care ultrasound of the external jugular vein (EJV) can predict fluid responsiveness (FR) in healthy, anesthetized, mechanically ventilated dogs.

DESIGN

Prospective, nonrandomized experimental study.

SETTING

University-based small animal research facility.

ANIMALS

Six healthy Beagle dogs.

INTERVENTIONS

Dogs were investigated at six time points (TPs): baseline (TP1); 20 mL/kg of circulating blood was collected over 10 min (TP2); half of the collected blood was autotransfused for 10 min (TP3); remaining collected blood was autotransfused for 10 min (TP4); 0.9% normal saline (10 mL/kg for 10 min) was administered (TP5); and an additional dose of 0.9% normal saline (10 mL/kg for 10 min) was administered (TP6). Hemodynamic variables, Doppler images of the left ventricular outflow tract (LVOT), and M-mode images of the EJV were obtained at each TP. FR was evaluated during TP3-6. FR was defined as an increase of >15% in the LVOT velocity time integral following fluid challenge, while other results were defined as fluid nonresponsiveness (FNR). The external jugular vein distensibility index (EJVDI) was calculated as follows: [(maximal EJV diameter - minimal EJV diameter)/minimal EJV diameter] × 100%. The maximal EJV diameter was measured during inspiration, and the minimal EJV diameter was measured during expiration. In addition, gray zones indicating the range of diagnostic uncertainty were proposed in various indices for predicting FR.

MEASUREMENTS AND MAIN RESULTS

Among the 24 fluid challenges performed between TP3 and TP6, 11 FR and 13 FNR were identified. The area under the receiver operating characteristic curve for the EJVDI in predicting FR was 0.92, with a cut-ff value of 22.7%, and the gray zone was identified as 22.6%-27.3%.

CONCLUSIONS

The EJVDI could be used to predict FR in healthy, anesthetized, mechanically ventilated dogs. Further studies are required before point-of-care ultrasound of the EJV can be applied in various clinical settings.

Splenic Doppler Resistance Index for Detection of Circulatory Shock in Dogs

OBJECTIVE

To assess the splenic flow resistance index (RI) and its response to a fluid bolus in dogs showing circulatory abnormalities upon hospital admission.

DESIGN

Prospective clinical study.

SETTING

Veterinary referral hospital.

ANIMALS

Nine dogs with circulatory shock and nine dogs without circulatory abnormalities.

INTERVENTIONS

Dogs with circulatory abnormalities received an IV bolus of 30 mL/kg of balanced isotonic crystalloid fluid.

MEASUREMENTS AND MAIN RESULTS

The splenic flow RI and the baseline aortic velocity-time integral of both groups of dogs were evaluated upon hospital admission. Measurements were repeated after the fluid bolus in dogs with circulatory shock. The Mann-Whitney U-test or the Wilcoxon rank sign test was used as appropriate. The median RI in dogs with circulatory shock was higher than that in dogs without hemodynamic disorders (median [interquartile range]: 0.64 [0.62-0.77] vs. 0.54 [0.51-0.54], P < 0.001). The best cutoff value to discriminate between the two groups was 0.61, with an area under the receiver operating characteristic curve of 1.00 (95% confidence interval [CI]: 1.00-1.00), a sensitivity of 100% (95% CI: 66.4-100), a specificity of 100% (95% CI: 66.4-100), a positive predictive value of 100% (95% CI: 66.4-100), and a negative predictive value of 100% (95% CI: 66.4-100). After fluid expansion, a significant decrease in the median splenic flow RI was observed (0.57 [0.54-0.71], P = 0.007 vs. basal).

CONCLUSIONS

The splenic flow RI may be a dependable tool for identifying circulatory shock in dogs and assessing their response to fluid therapy. Additional studies are required to evaluate the use of this index for the monitoring of organ perfusion, changes in cardiac output, and fluid responsiveness in critically ill dogs.

Feline caudal vena cava to aorta ratio reference interval

OBJECTIVES

The primary objective of this investigation was to ultrasonographically evaluate the caudal vena cava to aorta (CVC:Ao) ratio in healthy, conscious cats and to generate reference intervals. A secondary objective was to identify the site of examination with the least intra- and inter-observer variability. This investigation was undertaken to assess whether the CVC:Ao ratio holds promise as a technique to assess intravascular volume responsiveness in cats.

METHODS

In total, 42 healthy cats were included for reference interval generation. Ultrasound examinations were performed by two operators with each examination performed twice by each operator on the same occasion. Examinations were performed on conscious cats in left lateral recumbency. Ultrasound sites investigated were the subxiphoid, hepatic intercostal, hepatorenal and iliac bifurcation. Operators also assessed each site for 'ease of visualisation' on a scale of 0-3.

RESULTS

Reference intervals were generated for the CVC:Ao ratio at all four ultrasonographic sites. While each site demonstrated low variability around its mean ratio, all sites exhibited significant intra- and inter-observer variability. The hepatorenal and iliac bifurcation sites were found to be the easiest to visualise (score 3; well-defined visualisation of both vessels) and had reference intervals of 0.8-1.41 and 0.75-1.2, respectively.

CONCLUSIONS AND RELEVANCE

The ultrasonographic assessment of the CVC:Ao ratio was possible at four anatomical locations in the cat. The hepatorenal and iliac bifurcation may offer more readily assessable CVC:Ao ratios. Further studies are necessary to assess the utility of the CVC:Ao ratio in disease states, including in hypovolaemia and hypervolaemia.

Point of care ultrasound measurement of paralumbar caudal vena cava diameter and caudal vena cava to aortic ratio in hypovolemic dogs

Background

Accurate assessment of intravascular volume is critical for precise fluid prescription. In people, bedside or point of care ultrasound is used to measure the inferior vena cava, with or without paired aortic measurement, to estimate intravascular volume.

Objective

To determine if point of care ultrasound measurement of the caudal vena cava (CVC) diameter or the CVC diameter to the abdominal aorta (Ao) diameter (CVC:Ao) at the paralumbar view are associated with changes in intravascular volume, mean arterial pressure (MAP), or cardiac output in normovolemic and hypovolemic dogs.

Animals

8 purpose-bred dogs.

Methods

Pressure-targeted hemorrhagic shock was induced in purpose-bred dogs under general anesthesia. Dogs were exsanguinated to a mean arterial pressure of 40 mmHg, or a maximum 60% blood volume lost, then auto-transfused shed blood. At a left paralumbar view, longitudinal plane measurements of the abdominal CVC diameter and aortic diameter were obtained. Measurements were performed at 4 timepoints: baseline under anesthesia (TP1), after hemorrhagic shock was induced (TP2), after ½ of shed blood had been re-transfused (TP3), and post-resuscitation with completed re-transfusion (TP4). Additional variables collected included cardiac output using thermodilution and arterial blood pressure.

Results

CVC:Ao was not significantly different between timepoints and was not associated with changes in CO (p = 0.28) or MAP (p = 0.50). CVC diameter was significantly different between baseline (TP1) and hemorrhagic shock (TP2). CVC diameter was significantly different at TP2 compared to TP1 after controlling for the effect of CO (p = 0.03) and MAP (p = 0.001). Aortic diameter was also significantly different at TP2 (p = 0.002, p = 0.001) and TP3 (p = 0.023, p = 0.017) compared to TP1 after controlling for CO and MAP.

Conclusions and clinical importance

Obtaining point of care ultrasound images for CVC:Ao measurement was feasible. With a marked decrease in intravascular volume, both CVC and Ao diameter decreased, resulting in an unchanged CVC:Ao. Despite changes in CVC and Ao diameters, these changes were not associated with measured changes in CO, emphasizing that CO is not a direct estimate of intravascular volume and is affected by many compensatory mechanisms. Additional studies are needed to determine the most accurate method for bedside measurement of intravascular volume status.

Intravenous fluid therapy compared to no treatment following blood donation in cats: a randomised controlled trial

OBJECTIVES

There is currently no consensus regarding the use of intravenous fluid therapy in feline patients post-blood donation in veterinary medicine. The primary aim of this study was to determine whether blood donation can be performed safely without post-donation intravenous fluid therapy. The secondary aim was to report owner-noted post-donation changes.

MATERIALS AND METHODS

The study aimed to enrol 100 conscious feline blood donations by client-owned cats performed at a veterinary teaching hospital. Donors were randomised to either receive intravenous compound sodium lactate (twice the volume of blood donated over 2 hours) immediately after blood donation, or to receive no post-blood donation intravenous fluid therapy. Systolic blood pressure was measured non-invasively at 0, 60 and 120 minutes post-donation. Median blood pressures were compared between the two groups using a Shapiro-Wilk test. Owners were called the day following the donation to collect information on changes in their cat post-donation.

RESULTS

One hundred cats were enrolled and the data of 97 cats were analysed; 46 who received intravenous fluid therapy and 51 who did not. Mean donation volume was 9.95 mL/kg for the intravenous fluid therapy group and 9.72 mL/kg for the non-intravenous fluid therapy group. At each time point, the median blood pressure did not differ significantly between the two groups. The main reported changes in both goups were bruising at the venepuncture site with 27.3% (12/44) in the IVFT group and 23.4% (9/37) in the no-IVFT group, and mild lethargy up to a maximum of 24 hours post donation with 11.4% (5/44) in the IVFT group and 18.9% (7/37) in the no-IVFT group.

CLINICAL SIGNIFICANCE

This study suggests that the use of intravenous fluid therapy post-feline blood donation may not be necessary. This could mean reduced hospitalisation time for feline donors, possibly decreasing feline stress.

2024 AAHA Fluid Therapy Guidelines for Dogs and Cats

Fluids are drugs used in veterinary patients capable of producing beneficial therapeutic or inadvertent harmful effects within the body's intravascular, interstitial, and intracellular fluid spaces. The individualized design of a fluid therapy plan requires careful patient assessment and targeted selection of proper fluid types, administration routes, and rates, along with adjustments during therapy tailored specifically as per the individual patient's fluid requirement and therapeutic response. Personalized fluid prescriptions and vigilant patient monitoring help avoid patient morbidity from body fluid deficiencies, fluid excess, and electrolyte derangements and support better patient outcomes. These guidelines provide an overview of fluid dynamics within the fluid spaces of the body, describe various types of fluids and their uses, and outline recommendations for fluid administration for resuscitation, rehydration, and maintenance purposes. The guidelines also outline approaches to fluid therapy for anesthetized patients and reiterate the recommendations of reduced fluid rates in this population of patients. Additionally, the guidelines include practical fluid therapy strategies for patients with various common disorders. The goal of these guidelines is to help veterinary professionals safely and effectively prescribe and administer fluid therapy for canine and feline patients.

International Renal Interest Society best practice consensus guidelines for the diagnosis and management of acute kidney injury in cats and dogs

Acute kidney injury (AKI) is defined as an injury to the renal parenchyma, with or without a decrease in kidney function, as reflected by accumulation of uremic toxins or altered urine production (i.e., increased or decreased). AKI might result from any of several factors, including ischemia, inflammation, nephrotoxins, and infectious diseases. AKI can be community- or hospital-acquired. The latter was not previously considered a common cause for AKI in animals; however, recent evidence suggests that the prevalence of hospital-acquired AKI is increasing in veterinary medicine. This is likely due to a combination of increased recognition and awareness of AKI, as well as increased treatment intensity (e.g., ventilation and prolonged hospitalization) in some veterinary patients and increased management of geriatric veterinary patients with multiple comorbidities. Advancements in the management of AKI, including the increased availability of renal replacement therapies, have been made; however, the overall mortality of animals with AKI remains high. Despite the high prevalence of AKI and the high mortality rate, the body of evidence regarding the diagnosis and the management of AKI in veterinary medicine is very limited. Consequently, the International Renal Interest Society (IRIS) constructed a working group to provide guidelines for animals with AKI. Recommendations are based on the available literature and the clinical experience of the members of the working group and reflect consensus of opinion. Fifty statements were generated and were voted on in all aspects of AKI and explanatory text can be found either before or after each statement.

On Whether Ca-125 Is the Answer for Diagnosing Overhydration, Particularly in End-Stage Kidney Disease Patients-A Systematic Review

Overhydration (OH) is a prevalent medical problem that occurs in patients with kidney failure, but a specific marker has still not been found. Patients requiring kidney replacement therapy suffer from a water imbalance, which is correlated with mortality rates in this population. Currently, clinicians employ techniques such as bioimpedance spectroscopy (BIS) and ultrasound (USG) markers of overhydration or markers of heart and kidney function, namely NT-pro-BNP, GFR, or creatinine levels. New serum markers, including but not limited to Ca-125, galectin-3 (Gal-3), adrenomedullin (AMD), and urocortin-2 (UCN-2), are presently under research and have displayed promising results. Ca-125, which is a protein mainly used in ovarian cancer diagnoses, holds great potential to become an OH marker. It is currently being investigated by cardiologists as it corresponds to the volume status in heart failure (HF) and ventricular hypertrophy, which are also associated with OH. The need to ascertain a more precise marker of overhydration is urgent mainly because physical examinations are exceptionally inaccurate. The signs and symptoms of overhydration, such as edema or a gradual increase in body mass, are not always present, notably in patients with chronic kidney disease. Metabolic disruptions and cachexia can give a false picture of the hydration status. This review paper summarizes the existing knowledge on the assessment of a patient's hydration status, focusing specifically on kidney diseases and the role of Ca-125.

Point of Care Ultrasound in Exotic Animal Emergency and Critical Care

Exotic pets are presented to veterinary clinics with increasing frequency for routine, urgent, and emergency needs. With these increased visits, owners' expectations for high-quality veterinary care are also increasing. Many presenting complaints of reptiles, birds, and small mammals can benefit from the use of point of care ultrasound (POCUS) to establish a minimum database, aid in triage, and help guide further diagnostics, treatment, and prognostic discussions with the owner. Hospitalized exotic patients can also have their progress tracked and better assessed with the aid of POCUS.

Ecografía de la vena cava caudal pre, trans y post quirúrgica como determinación de hipotensión en perros

El volumen sanguíneo es un factor fundamental en la funcionabilidad hemodinámica determinante de la correcta homeostasis en los seres vivos. La hipovolemia, así como la hipervolemia son factores perjudiciales en el paciente que los padece. La medición del índice de colapsabilidad de la vena cava caudal (ICVCC) es un marcador predictor de ciertos trastornos, que pueden ser corregidos mediante la administración intravenosa de fluidos y así poder evaluar su adecuada respuesta mediante el uso de la ultrasonografía. Mediante el uso de la ultrasonografía, realizando una medición del diámetro máximo y mínimo de la VCC usando el modo M del equipo ecográfico, permite medir el diámetro interno de la VCC, antes, durante y después del procedimiento quirúrgico. En los pacientes que se evidenció un colapso de la VCC, independientemente del momento quirúrgico se administró una solución de Ringer Lactato para posteriormente medir nuevamente la VCC y verificar que fueron responsivos a la fluidoterapia.

Management of refractory hypoxemia using recruitment maneuvers and rescue therapies: A comprehensive review

Refractory hypoxemia in patients with acute respiratory distress syndrome treated with mechanical ventilation is one of the most challenging conditions in human and veterinary intensive care units. When a conventional lung protective approach fails to restore adequate oxygenation to the patient, the use of recruitment maneuvers and positive end-expiratory pressure to maximize alveolar recruitment, improve gas exchange and respiratory mechanics, while reducing the risk of ventilator-induced lung injury has been suggested in people as the open lung approach. Although the proposed physiological rationale of opening and keeping open previously collapsed or obstructed airways is sound, the technique for doing so, as well as the potential benefits regarding patient outcome are highly controversial in light of recent randomized controlled trials. Moreover, a variety of alternative therapies that provide even less robust evidence have been investigated, including prone positioning, neuromuscular blockade, inhaled pulmonary vasodilators, extracorporeal membrane oxygenation, and unconventional ventilatory modes such as airway pressure release ventilation. With the exception of prone positioning, these modalities are limited by their own balance of risks and benefits, which can be significantly influenced by the practitioner's experience. This review explores the rationale, evidence, advantages and disadvantages of each of these therapies as well as available methods to identify suitable candidates for recruitment maneuvers, with a summary on their application in veterinary medicine. Undoubtedly, the heterogeneous and evolving nature of acute respiratory distress syndrome and individual lung phenotypes call for a personalized approach using new non-invasive bedside assessment tools, such as electrical impedance tomography, lung ultrasound, and the recruitment-to-inflation ratio to assess lung recruitability. Data available in human medicine provide valuable insights that could, and should, be used to improve the management of veterinary patients with severe respiratory failure with respect to their intrinsic anatomy and physiology.

Echocardiographic indicators of fluid responsiveness in hospitalized dogs with compromised hemodynamics and tissue hypoperfusion

OBJECTIVE

To evaluate the accuracy of selected echocardiographic variables used to predict fluid responsiveness in hospitalized dogs with compromised hemodynamics and tissue hypoperfusion.

DESIGN

Diagnostic test study in a prospective cohort of hospitalized dogs.

SETTING

Veterinary referral clinics.

ANIMALS

Forty-four hospitalized dogs with compromised hemodynamics and tissue hypoperfusion were utilized in this study.

INTERVENTIONS

Echocardiographic examination before and after fluid replacement with 30 ml/kg of lactated Ringer's solution.

MEASUREMENTS AND MAIN RESULTS

Pre-fluid replacement measurements of velocity of transmitral E wave (E-peak), the left ventricular end-diastolic internal diameter normalized to body weight (LVIDdN), and the left ventricular end-systolic internal diameter normalized to body weight (LVIDsN) were significantly lower in fluid-responsive patients compared with nonresponders (P < 0.001). The area under the receiver operating characteristic curve (AUROC) with its 95% confidence interval (CI) for each significant predictor was as follows: E-peak 0.907 (0.776-1.000, P < 0.001) and LVIDdN 0.919 (0.801-1.000, P < 0.001). The predictive capacity of LVIDsN was not significantly better than chance (AUROC, 0.753; 95% CI, 0.472-1.000, P = 0.078). A significant negative linear correlation was observed between the percentage of increase in velocity-time integral after expansion and the echocardiographic variables LVIDdN (r_s  = -0.452, P = 0.023) and E-peak (r_s  = -0.396, P = 0.008) pre-fluid replacement. The intraobserver and interobserver variability was very low (<5 %) for all measurements.

CONCLUSIONS

In this study using critically ill dogs with compromised hemodynamics and tissue hypoperfusion, pre-fluid replacement measurements of LVIDdN and E-peak adequately predict fluid responsiveness. Because a small number of fluid nonresponders were involved in the present study (11.4%), further studies that include larger numbers of fluid-nonresponsive animals are required.

Caudal vena cava measurements and fluid responsiveness in hospitalized cats with compromised hemodynamics and tissue hypoperfusion

OBJECTIVE

To evaluate the use of the caudal vena cava collapsibility index (CVCCI) and the inspiratory/minimum and expiratory/maximum diameters of the vena cava to predict fluid responsiveness in hospitalized, critically ill cats with hemodynamic and tissue perfusion abnormalities.

DESIGN

Diagnostic test study in a prospective cohort of hospitalized cats.

SETTING

Private practice referral hospital.

ANIMALS

Twenty-four hospitalized cats with spontaneous breathing and compromised hemodynamics and tissue hypoperfusion.

INTERVENTIONS

Ultrasonographic examination before and after fluid expansion with 10 ml/kg of lactated Ringer's solution.

MEASUREMENTS AND MAIN RESULTS

Fluid responsiveness was evaluated using the velocity-time integral (VTI) of the subaortic blood flow, by measuring it before and after a fluid load of 10 ml/kg of lactated Ringer's solution. The CVCCI was calculated using the following formula: (maximum diameter - minimum diameter / maximum diameter) × 100. Ten cats were fluid responders (42 %) and 14 were nonresponders (58 %). The area under the receiver operating characteristic curve (AUROC) with their 95% confidence interval for the predictors and the best cutoff values were as follows: CVCCI, AUROC = 0.83 (0.66-1.00) and cutoff = 31%; inspiratory/minimum diameter, AUROC = 0.86 (0.70-1.00) and cutoff = 0.24 cm; expiratory/maximum diameter, AUROC = 0.88 (0.74-1.00) and cutoff = 0.22 cm. A significant lineal correlation was observed between the percentage of increase in VTI after expansion and CVCCI (r_s  = 0.68, P < 0.001), expiratory/maximum diameter (r_s  = -0.72, P < 0.001), and inspiratory/minimum diameter (r_s  = -0.71, P < 0.001). The intraobserver and interobserver variability was low for VTI, and the expiratory/maximum diameter and inspiratory/minimum diameter were high for CVCCI.

CONCLUSIONS

Caudal vena cava measurements could be useful to predict the response to fluids in hospitalized cats with hemodynamic and tissue perfusion alterations. Additional studies are required to draw definitive conclusions about the role of these variables to guide fluid administration in cats.

Ultrasonographically derived caudal vena cava parameters acquired in a standing position and lateral recumbency in healthy, lightly sedated cats: a pilot study

OBJECTIVES

The aim of this study was to determine the feasibility of ultrasonographically measuring the caudal vena cava (CVC) at the subxiphoid view of healthy, lightly sedated cats in a standing position and lateral recumbency.

METHODS

This was a prospective, observational, experimental single-centre study. Twenty healthy research-purposed cats were enrolled. Two trained operators scanned each cat in two positions - standing and lateral recumbency - in a randomised order. CVC diameter was measured at the narrowest diameter during inspiration and at the widest diameter during expiration, at two anatomical locations along the CVC - where the CVC crosses the diaphragm (base) and 2 mm caudal to the diaphragm. The CVC collapsibility index (CVC-CI) was calculated for each site. Normalcy was assessed with a Shapiro-Wilk test. A one-way ANOVA with post-hoc Tukey's test was used to compare inspiratory with expiratory values within and between groups. A paired t-test compared the CVC-CI between groups (P ⩽0.05 indicated statistical significance). Spearman's correlation and Bland-Altman analysis assessed inter-operator variability.

RESULTS

All ultrasonographic data passed normalcy and were reported as mean ± SD. When compared with each other, inspiratory and expiratory values were statistically different for position, location and operator (all P <0.0001). There was no statistically significant difference between lateral recumbency or standing position for inspiratory, expiratory and CVC-CI values. Inter-operator variability was substantial, with operator 2 consistently obtaining smaller measurements than operator 1. The mean CVC-CI in lateral recumbency at the base was 24% for operator 1 and 37% for operator 2. For the same site in standing position, CVC-CI was 27% and 41% for operators 1 and 2, respectively.

CONCLUSIONS AND RELEVANCE

This pilot study demonstrates that it is possible to ultrasonographically measure the CVC diameter in both lateral recumbency and a standing position in healthy, lightly sedated cats. However, measurements obtained are operator dependent with variability between individuals. Further studies are needed to determine if ultrasonographic CVC assessment will prove helpful in estimating intravascular volume status in cats.

Relationship between tricuspid annular plane systolic excursion, fluid responsiveness and volume status in hospitalised dogs with circulatory abnormalities

AIMS

To evaluate the echocardiographic variable tricuspid annular plane systolic excursion normalised to body weight (TAPSEnorm) as a predictor of fluid responsiveness in hospitalised dogs with haemodynamic and tissue perfusion alterations and to investigate the association of left ventricular internal diameter in diastole normalised to body weight (LVIDdN) and aortic velocity time integral (VTI_Ao) with TAPSEnorm.

METHODS

A single-centre, prospective study was carried out in a cohort of spontaneously breathing dogs, hospitalised for any reason, with severe haemodynamic and tissue perfusion alterations. The echocardiographic variables TAPSEnorm, LVIDdN, and VTI_AO were measured. A bolus of 30 mL/kg of lactated Ringer's solution was administered and then VTI_Ao was subsequently remeasured. Patients were classified as fluid responsive if VTI_Ao increased by ≥15% after fluid expansion, or non-responsive if VTI_Ao increased by <15% after fluid expansion. The area under the receiver operating characteristic (AUROC) curve was generated to evaluate the ability of TAPSE to predict fluid responsiveness. Simple regression models were used to assess the linear relationship between TAPSEnorm and LVIDdN or VTI_AO.

RESULTS

TAPSEnorm was lower in fluid responsive dog (mean 0.57 (95% CI=0.50-0.64) cm/kg) compared to non-responders (mean 0.76 (95% CI=0.62-0.90) cm/kg). The AUROC for TAPSEnorm was 0.827 (95% CI=0.65-1.00). The optimal cut-off point was 0.76 with sensitivity of 80 (95% CI=28.4-99.5)% and specificity of 86.7 (95% CI=69.3-99.2)%, positive predictive value of 50 (95% CI=15.7-84.3)% and negative predictive value of 96.3 (95% CI=81-99.9)%. A monotonic linear relationship was observed between TAPSEnorm and LVIDdN (p<0.001) and between TAPSEnorm and VTI_Ao (p=0.001).

CONCLUSIONS AND CLINICAL RELEVANCE

TAPSEnorm could be useful in determining those dogs that are likely to respond to a fluid bolus from those that are likely to be non-responsive. Additionally, a positive linear association between the LVIDdN and the TAPSEnorm suggests that TAPSEnorm decreases at lower preload values. The present study results suggest that TAPSEnorm could be a valuable tool for evaluating blood volume status and fluid responsiveness in hospitalised dogs.

Fluid Therapy in Pulmonary Disease: How Careful Do We Need to Be?

Intravenous fluid therapy is a vital and life-saving therapeutic in veterinary medicine. In the absence of heart or lung disease, trauma or sepsis there is limited evidence that fluid therapy will have a detrimental effect on lung function. In healthy dogs there is a reasonable level of experimental evidence that supraphysiologic rates of fluid are required before signs of fluid overload are made evident. In cats, however, this may not be the case. There are higher rates of asymptomatic myocardial disease, but even in the absence of that it seems that some cats may be susceptible to fluid overload. Where systemic inflammation already exists the careful homeostatic and protective mechanisms within the lung are deranged and increases in hydrostatic pressure are more likely to result in fluid movement into the lung tissues. Strategies including restricting the use of intravenous crystalloid fluid administration and using blood products for management of severe hemorrhage are of increasing importance in human trauma and seem to be associated with fewer pulmonary complications, and lower mortality. Managing dogs and cats with sepsis and acute respiratory distress syndrome is already challenging, but ensuring adequate vascular expansion needs to be balanced with avoiding excessive volume administration which may negatively impact pulmonary function. While fluids remain crucial to management of these conditions, there will be an ongoing requirement to balance need without providing excess. The use of point of care ultrasound may provide clinicians with a non-invasive and accessible way to do this.

Fluid Overload

Fluid overload (FO) is characterized by hypervolemia, edema, or both. In clinical practice it is usually suspected when a patient shows evidence of pulmonary edema, peripheral edema, or body cavity effusion. FO may be a consequence of spontaneous disease, or may be a complication of intravenous fluid therapy. Most clinical studies of the association of FO with fluid therapy and risk of harm define it in terms of an increase in body weight of at least 5–10%, or a positive fluid balance of the same magnitude when fluid intake and urine output are measured. Numerous observational clinical studies in humans have demonstrated an association between FO, adverse events, and mortality, as have two retrospective observational studies in dogs and cats. The risk of FO may be minimized by limiting resuscitation fluid to the smallest amount needed to optimize cardiac output and then limiting maintenance fluid to the amount needed to replace ongoing normal and pathological losses of water and sodium.

Assessment of Volume Status and Fluid Responsiveness in Small Animals

Intravenous fluids are an essential component of shock management in human and veterinary emergency and critical care to increase cardiac output and improve tissue perfusion. Unfortunately, there are very few evidence-based guidelines to help direct fluid therapy in the clinical setting. Giving insufficient fluids and/or administering fluids too slowly to hypotensive patients with hypovolemia can contribute to continued hypoperfusion and increased morbidity and mortality. Similarly, giving excessive fluids to a volume unresponsive patient can contribute to volume overload and can equally increase morbidity and mortality. Therefore, assessing a patient's volume status and fluid responsiveness, and monitoring patient's response to fluid administration is critical in maintaining the balance between meeting a patient's fluid needs vs. contributing to complications of volume overload. This article will focus on the physiology behind fluid responsiveness and the methodologies used to estimate volume status and fluid responsiveness in the clinical setting.

Focused ultrasound of the caudal vena cava in dogs with cavitary effusions or congestive heart failure: A prospective, observational study

INTRODUCTION

Ultrasonographic indices of the inferior vena cava are useful for predicting right heart filling pressures in people.

OBJECTIVES

To determine whether ultrasonographic indices of caudal vena cava (CVC) differ between dogs with right-sided CHF (R-CHF), left-sided CHF (L-CHF), and noncardiac causes of cavitary effusion (NC).

MATERIALS AND METHODS

113 dogs diagnosed with R-CHF (n = 51), L-CHF (30), or NC effusion (32) were enrolled. Seventeen of the R-CHF dogs had pericardial effusion and tamponade. Focused ultrasound was performed prospectively to obtain 2-dimensional and M-mode subxiphoid measures of CVC maximal and minimal size (CVCmax and CVCmin), CVCmax indexed to aortic dimension (CVC:Ao), and CVC collapsibility index (CVC-CI). Variables were compared between study groups using Kruskal-Wallis and Dunn's-Bonferroni testing, and receiver operating characteristics curves were used to assess sensitivity and specificity.

RESULTS

All sonographic CVC indices were significantly different between R-CHF and NC dogs (P < 0.001). Variables demonstrating the highest diagnostic accuracy for discriminating R-CHF versus NC were CVC-CI <33% in 2D (91% sensitive and 96% specific) and presence of hepatic venous distension (84% sensitive and 90% specific). L-CHF dogs had higher CVC:Ao and lower CVC-CI compared to NC dogs (P = 0.016 and P = 0.043 in 2D, respectively) but increased CVC-CI compared to the R-CHF group (P < 0.001).

CONCLUSIONS

Ultrasonographic indices of CVC size and collapsibility differed between dogs with R-CHF compared to NC causes of cavitary effusions. Dogs with L-CHF have CVC measurements intermediate between R-CHF and NC dogs.