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Serge Chalhoub

Faculty of Veterinary Medicine, University of Calgary Veterinary Clinical and Diagnostic Sciences
Born and raised in Montreal, Dr. Chalhoub graduated from the DVM program at the Faculty of Veterinary Medicine (FMV) of the University of Montreal in 2004. He then completed a one-year rotating small animal internship at the same institution. After working for two years as a general practitioner and emergency veterinarian at the DMV Centre in Montreal, Dr. Chalhoub pursued a residency in small animal internal medicine at the Animal Medical Center (AMC) in New York City. Once completed in 2009 he stayed on at the AMC as their first renal/hemodialysis fellow. Dr. Chalhoub is currently a senior instructor at the University of Calgary’s Faculty of Veterinary Medicine (UCVM). He was the recipient of the 2013 Canadian Veterinary Medical Association’s Teacher of the Year Award, the 2015 University of Calgary Team Teacher of the Year Award, and the 2017 Carl J. Norden Distinguished Teacher Award. He is the coordinator of the UCVM-CUPS Pet Health Clinic for disadvantaged Calgarians. He has authored and co-authored numerous scientific articles and book chapters on renal and urinary medicine, and he is a co-author on the International Society of Feline Medicine’s 2016 consensus guidelines on the diagnosis and treatment of feline chronic kidney disease. Dr. Chalhoub also participates in multiple research studies and co-lectures in veterinary point of care ultrasound along with Dr. Søren Boysen.

Author Of 7 Presentations

Associated Lectures

Use of ultrasound in emergency medicine: indications, benefits, and pitfalls

Lecture Time
08:30 AM - 08:55 AM
Room
Hall 711
Date
07/16/19, Tuesday
Time
08:30 AM - 09:20 AM

Abstract

Abstract Body

THE USE OF ULTRASOUND IN EMERGENCY MEDICINE: INDICATIONS, BENEFITS, AND PITFALLS

Soren Boysen DVM, DACVECC; Serge Chalhoub DVM, DACVIM (SAIM);

Faculty of Veterinary Medicine, University of Calgary

Calgary, AB Canada

srboysen@ucalgary.ca

Introduction:

Veterinary Point of Care Ultrasound (VPOCUS) now includes multiple ultrasound- techniques that allow practitioners’ to rapidly assess patients for underlying conditions, often life-threatening, without compromising patient safety. They are specifically designed to detect injury within the abdomen, thorax and pericardial space including free abdominal fluid, pneumothorax, pleural effusion, general lung pathology, basic cardiac pathology, and assess intravascular volume status within minutes of patient arrival. They are extremely valuable in trauma patients, unstable emergency patients, daily assessment of critically ill patients, and for general patient evaluation. The information provided by these exams is instrumental in the management of these patients and they can be implemented into everyday practice. It is important to note that VPOCUS exams are not extensive abdominal or thoracic ultrasound nor are they echocardiograms. They are point of care rapid ultrasound techniques that are performed at the same time as the initial patient evaluation and treatment (physical exam, blood pressure, IV catheter, IV fluids, sedation, analgesia, SPO2, minimum emergency database) or as part of continued daily patient monitoring. They are repeatable and objective, and findings are often answered by simple binary questions. They are validated, evidence-based, sensitive and specific, and take under 10 minutes to complete. Indications to VPOCUS exams include, but are not limited to:

Any small animal trauma patient, blunt or penetrating, particularly those that are unstable, that have a total solids less than 60 g/L and/or a decreased PCV, or that show external injury

Any small animal patient presenting with unstable cardiovascular or respiratory signs, particularly if the underlying cause is uncertain

Any patient in which pericardial effusion is suspected (pulses paradoxes, muffled heart sounds, electrical alternans)

Any patient suspected to have pneumothorax (dyspnea with decreased breath sounds dorsally)

Any patient suspected to have pleural effusion (dyspnea with decreased breath sounds ventrally)

Any patient in which intra-abdominal free fluid is suspected

Any collapsed and/or unstable patient (i.e. elevated shock index, hyperlactatemia, unexplained hypotension, tachycardia, or decreased mentation) regardless of trauma, particularly if the underlying cause is uncertain.

Any patient with acute abdomen/abdominal pain

Post-surgical patients that become unstable or in whom there is a concern for bleeding or risk of dehiscence/peritonitis

Some keys points:

Veterinary point of care ultrasound (VPOCUS) exams cannot replace a physical exam and are in fact often guided by the initial findings of the triage exam (pulses paradoxes, shock, respiratory distress, abdominal pain and vomiting, muffled lung sounds etc.)

They often provide complimentary information which in many situations directs further direct diagnostics and therapies that may be lifesaving

Do the entire VPOCUS scan but answer the most urgent lifesaving question(s) first!

BRING THE MACHINE TO THE PATIENT! Don’t discontinue stabilization efforts to perform VPOCUS.

A key approach to learning and expanding the role of VPOCUS is to get comfortable asking yes/no binary questions.

By clearly defining the objectives of the rapid ultrasound, one can avoid “fishing expeditions” that are often associated with low pre-test probabilities and can lead to significant increases in the likelihood of false positive results

Human studies show the likelihood of false negative and false positive results are markedly decreased when asking binary questions

Do a complete thorough POCUS assessment to answer the binary question being asked (if you are looking for abdominal fluid, do a complete fluid search at each site you evaluate!)

Abdominal VPOCUS

The FAST abdominal exam, described in 2004 (Boysen et al 2004), was the first VPOCUS exam to be validated in small animals. The goal was to detect free peritoneal fluid following blunt abdominal trauma, and therefor concentrated on 4 key sites of the abdomen; sites where target organs were most likely to be injured following trauma; liver, spleen, kidneys and urinary bladder, and where fluid is most likely to accumulate based on patient positioning and gravitational forces. The study demonstrated that this FAST abdominal protocol was sensitive and specific for the detection of free abdominal fluid. The study also demonstrated that abdominal FAST can be performed during resuscitation, was rapid (<5 minutes), required minimal experience, was repeatable, and was noninvasive. Abdominal VPOCUS has now been validated in non-trauma cases (McMurray, Boysen, Chalhoub; JVECCS 2016). How accurate is abdominal VPOCUS?

The detection of free abdominal fluid via sonography is more sensitive than radiographs

A recent study by Walters (JVECC 2018), compared the original 2004 Abdominal FAST to CT for detection of free fluid by minimally trained ER docs and found excellent agreement (Kappa 0.82)

Although abdominal VPOCUS localizes fluid to the abdominal cavity, which permits centesis and fluid analysis, it cannot identify the actual abdominal organ injured in most cases (contrast enhanced ultrasound not done much in veterinary medicine)

Limitations: penetrating trauma and retroperitoneal injury have lower sensitivity for finding effusion, trauma does not always produce effusion and sometimes there is a delay in the appearance of effusion (hence why serial exams are recommended).

Thoracic VPOCUS: Lung, focused Heart and Pleural Space

Arguably, patients presenting with respiratory distress can be quite challenging as it is not always easy to differentiate cardiac, pleural space and parenchymal disease, particularly in cats. An incorrect diagnosis may result in life threatening interventions being delayed, or lead to an incorrect therapy being administered, which may cause patients to deteriorate. There are several algorithms that have been developed to help differentiate cardiac from non-cardiac causes of respiratory distress, most of which rely on radiographs and a cardiology consult if the patient is sufficiently stable, and/or physical exam findings and history of the patient is unstable. Most algorithms unfortunately do not incorporate the use of point of care ultrasound by non-specialists in differentiating causes of respiratory distress in cats or dogs. The skills required to perform pleural space and lung point of care ultrasound are easily learned with minimal formal training and can differentiate the major causes of respiratory distress. A particular advantage of pleural space and lung ultrasound is the fact it can be performed while the patient is receiving oxygen therapy, anxiolytics, and other stabilization efforts. In general, if it’s possible to auscult the patient with a stethoscope, thoracic VPOCUS can also be performed, even in an oxygen cage if necessary.

Following the original TFAST study, additional thoracic VPOCUS techniques have been developed with different objectives. A study by Rademacher et al (2014 Vet Rad Ultrasound) developed a lung ultrasound protocol which was the first to demonstrate that alveolar interstitial syndrome (AIS) can be diagnosed in dogs using sonography. Subsequently multiple VPOCUS techniques (Ward et al, JAVMA 2017; Lisciandro et al, 2014 Vet rad Ultrasound; Vezzosi et al, 2017 JVIM; Armenise A, Rudloff E, Boysen SB et al, JVECC 2017 in press) have been used for the detection of AIS.

In addition to advancements in detecting lung pathology, thoracic VPOCUS can also detect underlying cardiac function abnormalities in cats and dogs. Recent studies clearly show cardiovascular POCUS performed by non-specialists helps to differentiate respiratory from cardiac causes of dyspnea in both cats and dogs (Ostroski C et al, JVECC 2016 abstract; Hezzell MJ et al, JVIM 2017 abstract, in press). Finally, thoracic VPOCUS has recently been demonstrated to help detect intravascular volume changes in dogs and cats via assessment of the caudal vena cava (references)

With so many thoracic protocols being used in small animals there is some confusion as to what clinicians mean when they state “I did a TFAST exam” or “I assessed the thorax with sonography”. It is therefore important to standardize the approach to thoracic VPOCUS (e.g. searching for pleural effusion, pericardial effusion, pneumothorax, basic cardiac function, volume status, etc.) so that the information stays objective and translatable. One approach to solving the confusion surrounding the ever-expanding exams incorporated into VPOCUS is to return to the binary questions VPOCUS was originally designed to answer (pleural fluid yes/no, pneumothorax yes/no etc.). This approach helps in keeping these exams standardized, as well as answering important clinical questions (hence why we do these exams).

In the thorax, the broad clinically relevant questions we ask include:

Pleural space:

Is there pneumothorax (is there a glide sign or B lines)?

Is there pleural effusion?

Lung: Is there AIS (are there an increased number of B lines)?

Heart:

Is there pericardial effusion?

Is there adequate contractility (decreased)?

Is there left atrial enlargement (subjective left atrial aortic root ratio enlargement)?

Caudal vena cava:

Is there evidence of caudal venal caval distention?

Does the caudal vena cava decrease in size during inspiration?

Limitations: certain normal and abnormal artefacts (z lines, e lines) can be confused for b-lines, a glide sign can be difficult to detect, pneumothorax can be challenging to rule in, small amounts of effusion can be missed if not careful, steeper learning curve for the heart).

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Associated Lectures

Lung ultrasound and confirming pericardial effusion

Lecture Time
09:50 AM - 10:15 AM
Room
Hall 711
Date
07/16/19, Tuesday
Time
09:25 AM - 10:15 AM

Abstract

Abstract Body

LUNG ULTRASOUND AND CONFIRMING PERICARDIAL EFFUSION

Soren Boysen DVM, DACVECC; Serge Chalhoub DVM, DACVIM (SAIM);

Faculty of Veterinary Medicine, University of Calgary

Calgary, AB Canada

srboysen@ucalgary.ca

Introduction

There are 5 key structures that can be identified during thoracic VPOCUS of the pleural space and lungs in healthy animals: Bat sign, Glide sign, A lines, B lines, Curtain sign. Patients can be in sternal (preferred position for dyspneic patients), standing or in lateral recumbency.

Shaving is not required, the fur is parted, and alcohol is used as the coupling agent. Depth for pleural and lung ultrasound is generally set at 4-6 cm in most cases. A 6-10 MHz (7 MHz) microconvex probe is generally used. Remember that the two key enemies of ultrasound, bone and air, are encountered when performing ultrasound of the pleural space and lung. This is advantageous as bone and the subsequent rib shadowing provides landmarks to work with, and artifacts are often present when the ultrasound beam encounters air.

Normal Findings on Thoracic VPOCUS

Bat sign/Gator sign: When the ultrasound probe is placed over the lung and perpendicular to the ribs we can see the rib heads, rib shadowing, and the pleural line. The image obtained is called a “bat sign” or “gator sign” as the rib heads and pleural line resemble the wings and body of a bat, or a gator’s eyes peaking above the water line, respectively.

Glide sign visualized as a shimmering along the pleural line (pulmonary-parietal interface), which represents normal to-and-fro motion of the lung sliding along the chest well during respiration. This normal.

There are two key rules to remember when assessing the glide sign: 1) the lining of the lung (visceral pleura) MUST be in contact with the thoracic pleura (parietal pleura) to create the shimmer of the glide sign; and 2) the patient must breathe to create the shimmering glide sign. These points are important to remember.

A-lines: A stands for air.

Air is located below the pleural line when the lungs are filled with air and when there is air in the pleural space which occurs with pneumothorax. Therefore, A lines are seen with normal lung and when a pneumothorax is present.

A lines are horizontal white lines equidistant from the skin surface to the pleural line that project through the far field of the ultrasound image.

They are a type of reverberation artifact that occurs when ultrasound beams are reflected back and forth between the probe and pleural line due to the presence of air below the pleural line

B-lines:

Hyperechoic streaks originating from the lung surface of the pleural line, extending through the far field without fading, and swinging to-and-fro with the motion of the lung during respiration.

B lines occur as the result of air and fluid in proximity to each other at the lung surface.

The presence of a small number of isolated B-lines may be normal in healthy dogs and cats (noted in 10-30% of patients). Up to 3 at a single site can still be normal. Anything more than 3 B lines at a single site is associated with pathology.

Curtain sign: The caudal border of the thorax is located by identifying the curtain sign; the transition between the thorax and abdomen, which is easily seen with sonography.

Alveolar interstitial syndrome (AIS)

AIS is diagnosed when there are an increased number of B-lines.

>3 B-lines at any single location, or multiple sites is indicative of AIS.

“Wet lungs” are present when there are increased B lines present (>3 B lines at a single site).

“Dry lungs” are present when there is a glide sign, A lines and 3 or fewer B lines at an occasional site evaluated.

B-lines can originate anywhere, which is why it is important to scan multiple portions of the lung.

The number of B lines correlates with the severity of AIS (the more B lines the “wetter” the lungs.

When AIS is identified on lung ultrasound, the same differential diagnosis should be considered as an interstitial alveolar pattern on thoracic radiographs.

It is important to note that lung ultrasound will only detect lung pathology if the pathology is at the periphery of the lung (outer 3mm) – fortunately most diseases that cause AIS (cardiogenic pulmonary edema, trauma induced contusions, aspiration pneumonia, etc.) will reach the lung surface.

Pitfalls:

Z-lines: these lines arise from the parietal pleura (thoracic wall side of the pleural line), not the lung surface. Therefore, they do not move with the glide sign and the do not erase A-lines. They are ill-defined and disappear after 2-5 cm. Significance unknown (not associated with known pathology). They are present in 80% of healthy humans. They can be seen in patients with pneumothorax.

E-lines come from subcutaneous emphysema and they do form a comet tail like b-lines. They are identified by the fact they originate proximal (superficial) to the pleural line and therefor pass through and obliterate the pleural line. Caused by accumulation of air in the subcutaneous tissues. They do extend to the bottom of the ultrasound screen, but do not move with respirations.

Placing the probe over the stomach or at the curtain sign and failing to realize the probe location can sometime lead to a false positive finding of B lines.

Sonographic Technique to Identify AIS

As a general rule of thumb, the authors’ scan 9 sites in a sliding fashion on each side of the chest, plus the subxiphoid site, to ensure adequate exploration of the lungs.

The thorax is generally divided into thirds from dorsal to ventral

The dorsal third of the thorax is scanned first. Start at the same caudal dorsal location as described for identification of pneumothorax (the most caudo-dorsal site of the thorax)

From this site, the probe is slid cranially between intercostal spaces, pausing as necessary to assess the presence of lung pathology.

Once the dorsal sites of the thorax have been examined, the probe is slid ventrally within the intercostal space just caudal to the scapula until the middle third of the thorax is reached (roughly the height of the heart base or peri-hilar region). The probe is then slid caudally, pausing as necessary to assess lung the presence of lung pathology, until the curtain sign is encountered.

Lastly, the probe is slid cranially and ventrally along the curtain sign until the cardio-diaphragmatic window is identified. The probe is then turned parallel to the ribs at this location and slid ventrally until the sternal muscles are seen. The prove is then slid cranially a rib space at a time until the cranial thoracic inlet is identified at roughly the third intercostal space.

The heart will be encountered using this technique, at which point the probe can be slide dorsally off from the ventral region until lung is encountered to look for the lung pathology. The probe remains parallel to the ribs while it is slid dorsally.

The probe is then returned to the ventral regions, remaining parallel to the ribs (to ensure pleural effusion is not missed while also looking for lung pathology).

Pericardial Effusion

One of the best places to identify pericardial effusion is the subxiphoid view.

By rocking the probe until it is parallel to the patient, the ventral region of the thoracic cavity is visible.

In dogs, the pericardium usually contacts the diaphragm (5% of dogs may not have the heart contact the diaphragm, and it is therefore not possible to find the heart at the subxiphoid location).

If the left ventricular free wall can be seen blending with the diaphragm or liver, then pericardial effusion is ruled out.

If the left ventricular free wall is separated from the diaphragm by anechoic fluid, it indicates one of two things; pericardial effusion or pleural effusion.

Identification of the heart in healthy cats via the subxiphoid view is difficult as the heart does not contact the diaphragm on most cats. However, in the case of pericardial effusion (most often seen in cats with heart failure) the pericardial sac may extend to the diaphragm allowing pericardial effusion to be diagnosed at this site in cats.

Pericardial effusion can also be detected in a right parasternal short axis view of the heart.

Sonographic Technique to Identify Pericardial Effusion

The patient can be standing or sternal and the probe placed just behind the right forelimb, or in right lateral recumbency.

It is often easiest to obtain a short axis view of the heart at the level of the papillary muscles, referred to as the “mushroom” view.

The probe is then slowly slid dorsally (a few mm at a time). The left ventricle and mitral valves will become more and more apparent, and this will lead to what we refer to as the “fish mouth view”.

If these structures are identified it then becomes apparent when pericardial effusion is present; a circular collection of fluid surrounding the heart contained within the pericardial sac.

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Associated Lectures

Chronic kidney disease: The new paradigm of early diagnosis and evolving treatments

Lecture Time
11:15 AM - 12:05 PM
Room
Hall 711
Date
07/16/19, Tuesday
Time
11:15 AM - 12:05 PM

Abstract

Abstract Body

CHRONIC KIDNEY DISEASE: THE NEW PARADIGM OF EARLY DIAGNOSIS AND EVOLVING TREATMENTS

Serge Chalhoub DVM, DACVIM (SAIM); Soren Boysen DVM, DACVECC

Faculty of Veterinary Medicine, University of Calgary

Calgary, AB Canada

schalhou@ucalgary.ca

It is generally accepted that 30% of cats may develop chronic renal azotemia after 9 years of age. Above age 15, it is thought that over 50% of cats will have some form of CKD. In dogs, the prevalence of CKD is accepted to be less than 1% based on a recent U.K. study. Therefore, most of the discussion below will be based on cats and CKD. There are numerous possible causes of CKD in cats, but its exact pathophysiology has not yet been established. There is increasing suspicion that CKD evolves from possible multiple mini active kidney injuries secondary to ischemia or chronic inflammation (IRIS Napa meeting 2016). Unfortunately, as of now we do not have biomarkers sensitive enough to catch these mini-AKIs. However, this may change our future approach to chronic kidney disease in cats as it may highlight certain preventative stratgies.

Traditionally, the diagnosis of CKD has been based on the presence of renal azotemia and inappropriate USG for at least 3 months’ duration. However, this assumes that we have eliminated post renal causes of azotemia (such as ureteroliths) AND that the azotemia has been chronic. AIt takes a 75% decrease in nephron mass for azotemia to appear, which is defined as an increase in creatinine (MUCH more stable and predictable) and/or BUN (MUCH less reliable and variable) above established reference ranges. These references ranges can vary greatly from one reference laboratory to another. TThe development of isosthenuria is not much better in diagnosing CKD, as its appearance signifies a 68-70% decrease in renal function. Also, multiple conditions will affect USG (endocrine disease, afternoon urine sample, diet etc.).

Symmetric dimethylarginine (SDMA) is a molecule that has become quite important in the early diagnosis and also staging of CKD in cats and dogs. SDMA has no physiologic role in the body. Studies in veterinary medicine have shown that SDMA increases at roughly at 40% of renal dysfunction, and in some cases will detect a 25% in renal function. Using this biomarker will take some getting used to because we are so used to seeing a normal creatinine and USG and concluding there is no CKD! We are now able to diagnose CKD much earlier than before, and this will hopefully lead to new treatments. SDMA is more sensitive than creatinine at detecting CKD especially at earlier stages of CKD. It is a specific biomarker as well based on studies. In cats with CKD, SDMA shown to increase 17 months earlier; and in dogs an average of 9 months earlier (Hall et al, JVIM 2014). SDMA is not impacted by muscle mass, thereby much more accurate in low BCS geriatric animals. This is very important because most of our geriatric cats have decreased muscle mass. In addition, with CKD there is progressive muscle mass loss and therefore CKD stage may be understated because of the reliance on creatinine. SDMA is stable, and intraday and interday variability negligible. There is no impact from hemolysis, icterus, lipemia.

Once CKD has been diagnosed, it is important to then refer to staging principles. The IRIS staging guidelines have become a mainstay of staging cats and dogs with CKD. They have permitted us to create clear and objective guidelines on how to treat our patients based on creatinine (because it is more stable and predictable than BUN), proteinuria, and hypertension. The IRIS guidelines underline the importance of regular physical exam and lab work for our patients. For instance, proteinuria and hypertension are often silent. If left undiagnosed and untreated, not only will organ damage occur, but CKD also progresses much faster.

IRIS guidelines have been modified in 2015-2016 to reflect the addition of SDMA as both a diagnostic tool and also a staging tool. An SDMA that is persistently above 14ug/dl is consistent with CKD. This values reflects IRIS stage 1 and 2 patients if the SDMA is below 25ug/dl. These patients often have minimal to absent clinical signs. SDMA above 25ug/dl usually indicates IRIS stage 3, and this is important for cats and dogs with creatinine values in stage 2 but that have muscle mass loss. Therefore, these patients have an underestimated renal function and are likely in stage 3 with that SDMA level. This changes their prognosis and treatment recommendations. The same is true for a creatinine above 45ug/dl. If a cat or dog has a creatinine that puts them in IRIS stage 3 but an SDMA of 45ug/dl, this pet is actually in stage 4. The treatment recommendations and prognosis vary greatly between these 2 stages (prognosis 778 days for IRIS stage 3 vs. 30-60 days for IRIS stage 4).

Stage 1 has long been a mystery. It was almost impossible to diagnose as there are usually no clinical signs associated with this stage, and our diagnostics tests were not sensitive enough. However, now with SDMA we can diagnose cat in this stage. This has helped us learn a lot more about early stage CKD and discovered that in fact some cats do have symptoms such as mild weight loss. In addition, we are understanding that stage 1 is not a benign state as previously thought. Because of early diagnosis, this is allowing research to advance in early stage treatments (especially diets).

TREATMENT OF CKD

The treatment for CKD should be tailored to an individual patient’s needs. It is important to avoid standard “recipes” for every case. Not every cat or dog will need the same treatments. Treatments are not benign, can lead to a decrease in quality of life (anxiety, adverse reactions) and also decreased compliance by the owner (if there are many treatments to give or if they have to struggle with the cat to administer the treatments). As CKD progresses, especially to stage 4, quality of life is primordial.

Evidence-based medicine is often limited in veterinary medicine compared to human medicine, but studies do exist and their findings should be interpreted to guide our treatment choices as much as possible. Only diet as a treatment will be discussed below based on current new trends, but other therapies will be discussed in lecture.

The use of renal diets in cats and dogs is considered grade 1 evidence. It has been shown that cats fed a renal diet in upper-stage 2 or stage over 24 months had no uremic crisis compared to control cats eating a formulated “grocery store” diet (26% uremic crisis). Deaths from renal causes were 0% vs. 22% on the other diet. These diets generally contain reduced protein, phosphorous, sodium, and modified lipid and fatty acid content. They usually come in dry and wet food formula. Wet food diets have the advantage of bringing more water to a cat, thus limiting dehydration and pre-renal azotemia. Dogs have similar beneficial evidence. At least 3 separate studies show the benefits of a renal diet (Ross et al, Elliott et al 2000, Plantinga et 2005)

The IRIS recommendation is to feed these diets at IRIS upper Stage 2 and certainly stage 3 (dogs +/- stage 2-3). One common complaint is that cats will not eat the new renal diet. It is important to remember that cats with CKD are likely uremic at upper stage 2 and stage 3, and therefore have nausea. In addition, cats in general don’t like change. Therefore, it may be of some value to slowly introduce the new renal diet by mixing it with the cat’s old food over multiple weeks. In addition, it may be worthwhile working on nausea and appetite (mirtazapine, maropitant). There is recent debate on the use of renal diets and the fact that they may promote muscle loss in cats, which is detrimental to their survival. There are suggestions that cats with CKD should be fed higher protein diets but that phosphorus should be controlled. This is certainly an interesting debate on multiple fronts.

There is a new paradigm shift when it comes to renal diets.Current recommendation is to start renal diets once a cat or dog was in IRIS stage 2 CKD. However, now that we have the ability to diagnose CKD earlier than before, we can better diagnose stage 1 and early stage 2 cats and also recognize that they would benefit from early nutritional intervention. As such, cats in stage 1 may likely benefit from a geriatric-type diet or an early-stage kidney diet. A study by Hall et al demonstrated possible benefits of cats in stage 1 eating an early kidney disease diet, and a similar study done on dogs by the same author also showed a similar benefit. There are multiple reasons why these diets are likely beneficial including decreased phosphorus and increased omega-3 fatty acids.

Sparkes AH, Caney S, Chalhoub S et al. ISFM consensus guidelines on the diagnosis and management of feline chronic kidney disease. J Feline Med Surg. 2016;18(3):219-39.

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CVMA Sessions

Introduction

Lecture Time
02:15 PM - 02:30 PM
Authors
Room
Hall 717
Date
07/16/19, Tuesday
Time
02:15 PM - 05:05 PM
Affiliated Society Sessions

An update on thoracic FAST ultrasound: diagnosing pleural effusion and pneumothorax

Lecture Time
08:25 AM - 08:50 AM
Room
Hall 713
Date
07/17/19, Wednesday
Time
08:00 AM - 08:50 AM

Abstract

Abstract Body

AN UPDATE ON THORACIC FAST (THORACIC VETERINARY POINT OF CARE ULTRASOUND): DIAGNOSING PLEURAL EFFUSION AND PNEUMOTHORAX

Soren Boysen DVM, DACVECC; Serge Chalhoub DVM, DACVIM (SAIM);

Faculty of Veterinary Medicine, University of Calgary

Calgary, AB Canada

srboysen@ucalgary.ca

Introduction

There are 5 key structures that can be identified during thoracic VPOCUS of the pleural space and lungs in healthy animals: Bat sign, Glide sign, A lines, B lines, Curtain sign.

Patient Position, Probe Selection and Settings for Thoracic VPOCUS

Patients can be in sternal (preferred position for dyspneic patients), standing or in lateral recumbency (the latter is reserved for patients that are not experiencing respiratory distress). Dorsal recumbency should be avoided.

Similar to VPOCUS of the abdomen, shaving is not required, the fur is parted, and alcohol is used as the coupling agent. Depth for pleural and lung ultrasound is generally set at 4-6 cm in most cases. A 6-10 MHz (7 MHz) microconvex probe is generally used. Remember that the two key enemies of ultrasound, bone and air, are encountered when performing ultrasound of the pleural space and lung. This is advantageous as bone and the subsequent rib shadowing provides landmarks to work with, and artifacts are often present when the ultrasound beam encounters air. These artifacts change depending on the underlying status of the lung and pleural space. Assess the patient to decide which clinically important binary questions need answering first. Make sure a thorough evaluation for the specific underlying pathology is undertaken for each question asked.

Normal Findings on Thoracic VPOCUS

Bat sign/Gator sign: When the ultrasound probe is placed over the lung and perpendicular to the ribs we can see the rib heads, rib shadowing, and the pleural line. The image obtained is called a “bat sign” or “gator sign” as the rib heads and pleural line resemble the wings and body of a bat, or a gator’s eyes peaking above the water line, respectively. Identifying the Bat sign assists novice sonographers in locating the pleural line; the first white line below the rib heads. The pleural line is essential to identify as it is the interface between the parietal pleura of the thorax and the visceral pleura of the lung, and is location we assess for most pleural and lung pathology.

Glide sign visualized as a shimmering along the pleural line (pulmonary-parietal interface), which represents normal to-and-fro motion of the lung sliding along the chest well during respiration. This normal.

There are two key rules to remember when assessing the glide sign: 1) the lining of the lung (visceral pleura) MUST be in contact with the thoracic pleura (parietal pleura) to create the shimmer of the glide sign and 2) the patient must breathe to create the shimmering glide sign.

A-lines: A stands for air.

Air is located below the pleural line when the lungs are filled with air and when there is air in the pleural space which occurs with pneumothorax. Therefore, A lines are seen with normal lung and when a pneumothorax is present.

A lines are horizontal white lines equidistant from the skin surface to the pleural line that project through the far field of the ultrasound image.

They are a type of reverberation artifact that occurs when ultrasound beams are reflected back and forth between the probe and pleural line due to the presence of air below the pleural line

B-lines:

Hyperechoic streaks originating from the lung surface of the pleural line, extending through the far field without fading, and swinging to-and-fro with the motion of the lung during respiration.

B lines occur as the result of air and fluid in proximity to each other at the lung surface.

The presence of a small number of isolated B-lines may be normal in healthy dogs and cats (noted in 10-30% of patients). Up to 3 at a single site can still be normal. Anything more than 3 B lines at a single site is associated with pathology.

Key criteria to identify a B line (ALL criteria must be present):

*Vertical white lines

*Originate at the lung surface

*Moves with the pleura

*Extends to the far field

Obscures A lines if present

Curtain sign (figure 5): The caudal border of the thorax is located by identifying the curtain sign; the transition between the thorax and abdomen, which is easily seen with sonography (see figure below).

Pneumothorax

It is essential that patient positioning and the underlying pathology be considered when it comes to diagnosing pleural space pathology.

Air and fluid accumulate in different regions of the pleural space depending on the position in which the patient is evaluated.

Fluid tends to accumulate in the most gravity dependent areas while air tends to rise to the non-gravity dependent areas of the pleural space.

There are 3 key findings that help identify the presence of a pneumothorax, two are exclusion criteria, one is an inclusion criteria.

Pneumothorax appears as the absence of a glide sign. The presence of a glide sign rules out pneumothorax with confidence. Lack of a glide sign should prompt consideration of pneumothorax but a glide sign is not always easy to identify, even in healthy patients.

The presence of B-lines excludes pneumothorax at those focal probe placement sites because B-lines originate from the lung surface.

Finding a lung point confirms a pneumothorax on that side of the thorax. If the glide sign is not seen and there is strong suspicion of a pneumothorax a search for the lung point should be undertaken as identification of the lung point is pathognomonic for a pneumothorax.

The presence of a glide sign excludes pneumothorax at the probe placement site, as the presence of a glide sign requires contact of the surface of the lung with the chest well (air or fluid in the pleural space will prevent the lung from contacting the chest wall and prevent shimmer of the glide sign from occurring). Sonographically locating the most sensitive thoracic site to diagnose pneumothorax in a standardized manner:

Air will accumulate at the most caudal dorsal portion of the thorax when the patient is sternal recumbency or in the standing position.

Sternal is the preferred position in which to scan acutely dyspneic patients as it minimizes respiratory distress and subsequently the work of breathing associated with restraining the patient in lateral recumbency.

Identify the most caudal-dorsal site, which is the most sensitive site for air to accumulate with the patient in sternal, and also the region that has the most lung movement making it easier to identify a glide sign.

Defining the lung point:

If the glide sign is identified with confidence it rules out pneumothorax. Unfortunately, it is not always easy to identify a glide sign with confidence. If this is the case, a pneumothorax can be confirmed by identifying the lung point.

The lung point is defined as the site within the thorax where the lung recontacts the parietal pleura and creates an intermittent glide sign within half the ultrasound beam when the patient breathes. It is the exact point within the thorax where there is a return of the glide sign: movement of the probe from an area where there is no perceived glide sign, to an area where the glide sign reappears intermittently within a region of the ultrasound image. To find the lung point slide the probe cranially and ventrally until you note a point of lung reconnecting with the thorax wall OR you see a glide again.

In patients with extensive pneumothorax, there will not be a lung point if the lung does not recontact the parietal pleura on that side of the thorax. Most of these patients are sufficiently dyspneic to justify thoracentesis without the need to confirm a lung point.

Pleural effusion

The presence of a glide sign excludes pleural effusion at the site of probe placement, as the presence of a glide sign requires contact of the surface of the lung with the chest well (air or fluid in the chest cavity prevent the lung from contacting the chest wall).

Pleural effusion appears as the absence of a glide sign with anechoic fluid between the chest wall and the hypoechoic lung, or as anechoic triangles adjacent to the heart and outlining the diaphragm (outside the pericardial sac).

The two pleural VPOCUS techniques used to identify pleural effusion include 1) subxiphoid window and 2) the transthoracic windows in the ventral regions of the thorax

Patient positioning is important to consider when searching for pleural effusion and different techniques are required to identify small quantities of fluid with patients in lateral vs. sternal/standing positions.

In lateral recumbency, fluid accumulates at the widest gravity dependent sites of the thorax, generally at the pericardial window.

In sternal recumbency (preferred position to scan acutely dyspneic patients), effusion will accumulate ventrally.

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Affiliated Society Sessions

An update on vascular FAST ultrasound: predicting vascular volume, response to fluid therapy and guiding difficult peripheral vascular catheter

Lecture Time
09:20 AM - 09:45 AM
Room
Hall 713
Date
07/17/19, Wednesday
Time
08:55 AM - 09:45 AM

Abstract

Abstract Body

Introduction

The goal of vascular VPOCUS is not an extensive evaluation of the great vessels. Rather, vascular VPOCUS, in conjunction with other clinical, history and VPOCUS findings (cardiac assessment of volume status, contraindication suggestive of volume overload), is used to assess changes in vena cava volume that can help us assess if we should be giving a bolus of fluids.

Caudal vena cava volume estimation

Emergency and critical care patients are often at risk to develop hypo and hypervolemia. Unfortunately, predicting which patient can be challenging.

Although results are preliminary, evaluating the caudal vena cava (CVC) shows promise in estimating the intravascular volume status in veterinary patients.

By placing the probe longitudinally at the subxiphoid site and slowly tilting/fanning the probe to the right of midline the CVC can be seen crossing the diaphragm.

The caudal vena cava diameter and the change in the CVC diameter between the expiratory and inspiratory phases of respiration can be detected at this site.

The diameter and change in diameter with the respiratory cycle reflect the patient's volume status.

The CVC has a larger diameter at the end of expiration than it does at the end of inspiration.

The changes between expiration and inspiration varies but is approximately 25-60%.

The opposite is true in hypervolemic patients, or patients with increased right atrial pressures (i.e. pericardial effusion, right sided heart failure, etc.), where the CVC becomes "fatter" than normal, hardly changing (<20%) between expiration and inspiration.

This is important because if the vena cava is “fatter” than normal, we should ask ourselves why and if IV fluids would be detrimental.

If the hepatic veins are visualized (often seen at the site, they enter the CVC just caudal to the diaphragm) they are often distended as well in cases with increased right atrial pressures and/or hypervolemia. There are a number of artifacts that can make the CVC appear smaller than normal.

This includes 1) pressure artifact, that occurs when too much pressure is placed on the probe when trying to visualize the CVC, 2) increased abdominal pressure which may occur with organ enlargement or significant abdominal effusion and 3) increased respiratory effort which creates greater negative pleural pressure and therefore more collapse of the CVC.

Although these factors are likely to impact euvolemic or hypovolemic patients, they are less likely to change the findings noted in patients with hypervolemia or right atrial pressure increases (FAT CVC).

For these reasons the author tends to ask the questions, “if the patient has clinical signs suggestive of hypovolemia (tachycardia, pale mucous membranes, weak pulses etc.) is it likely to be a fluid responder”?

If the CVC is consistent with euvolemia or hypovolemia, then a bolus of fluids is administered provided there is no contraindication to giving a bolus (e.g. no increased B lines, normal left atrial: aortic ratio, no cerebral edema etc.).

If the patient has a FAT CVC, further work up is required to determine if a fluid bolus is contraindicated.

Ultrasound guided vascular access for difficult IV access

The following study (Costantino et al, Ultrasonography-guided peripheral intravenous access versus traditional approaches in patients with difficult intravenous access. Ann Emerg Med. 2005 Nov;46(5):456-61) is just one of many in the human literature demonstrating the value of ultrasound guided vascular access when traditional percutaneous IV access attempts fail.

The summary of this study is as follows:

If a nurse failed to place an IV catheter after 3 attempts…

Emergency physicians attempt to place percutaneous IV catheter

One group using ultrasound guidance

One group using ”blind” traditional techniques

Success rate was greater for the ultrasonographic group (97%) versus traditional (33%)

Less time to successful cannulation from first percutaneous puncture (4 minutes versus 15 minutes)

There is emergency veterinary evidence that ultrasound guided peripheral vascular access is also helpful in small animal veterinary patients.

Advantageous of ultrasound guided vascular access include the fact the vessel can be assessed for thrombosis prior to attempting placement of an IV catheter

In cases of hematoma or perivascular fluid (edema) the vessel can still be visualized making ultrasound guided access easier.

It should be pointed out that in an emergency unstable patient presenting in shock venous cut downs and automated intraosseous devices (EZIO) are preferred and ultrasound guided catheter placement is generally reserved for difficult IV catheter patients that are cardiovascular stable (figures 4-6).

Either longitudinal (in plane) or transvers (out of plane) vascular access ultrasound guided peripheral IV catheter placement can be used, although the author prefers out of plan/transverse placement, which will be demonstrated in the lab.

Ultrasound guided arterial blood gas sampling is also advantageous to help ensure an artery and not a vein is punctured during sampling.

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Affiliated Society Sessions

Abdominal FAST ultrasound: Gall bladder wall oedema in the collapsed patient, abdominal effusion and pneumoperitoneum

Lecture Time
11:10 AM - 11:35 AM
Room
Hall 713
Date
07/17/19, Wednesday
Time
10:45 AM - 11:35 AM

Abstract

Abstract Body

ABDOMINAL FAST ULTRASOUND: GALLBLADDER WALL EDEMA IN THE COLLAPSED PATIENT, ABDOMINAL EFFUSION AND PNEUMOPERITONEUM

Soren Boysen DVM, DACVECC; Serge Chalhoub DVM, DACVIM (SAIM);

Faculty of Veterinary Medicine, University of Calgary

Calgary, AB Canada

srboysen@ucalgary.ca

Introduction:

The FAST abdominal exam, described in 2004 (Boysen et al 2004), was the first VPOCUS exam to be validated in small animals. The goal was to detect free peritoneal fluid following blunt abdominal trauma, and therefor concentrated on 4 key sites of the abdomen; sites where target organs were most likely to be injured following trauma; liver, spleen, kidneys and urinary bladder, and where fluid is most likely to accumulate based on patient positioning and gravitational forces. The study demonstrated that this FAST abdominal protocol was sensitive and specific for the detection of free abdominal fluid. The study also demonstrated that abdominal FAST can be performed during resuscitation, was rapid (<5 minutes), required minimal experience, was repeatable, and was noninvasive. Abdominal VPOCUS has now been demonstrated to be sensitive for finding effusion in non-trauma patients.

Abdominal VPOCUS patient position, probe and coupling agent

Patients are placed in either left or right lateral recumbency. In some instances, abdominal VPOCUS can be performed in a sternal or standing position (consider the effects of gravity and patient positioning when looking for pathology). Minimal restraint is required.

A microconvex/curvilinear probe is used for all abdominal VPOCUS scanning, with a frequency generally between 5 MHz (patients >15 kg) and 7.5 MHz (patients < 15kg).

Gain is adjusted to maximize detection of anechoic fluid using either bile in the gall bladder or urine in the urinary bladder as a reference echogenicity for fluid.

Depth is adjusted as needed during the abdominal VPOCUS with the greatest depth setting generally at the subxiphiod location which allows evaluation of the pleural and pericardial spaces.

It is not wrong to shave the patient, but shaving is not required unless the patient’s fur coat is too thick to allow good image resolution (e.g. Husky and Northern breeds with thick undercoats).

Alcohol is used but it is important to part the fur before or after applying the alcohol. Gel is not necessary (but can be used with shaving if higher resolution is desired or can be applied after the fur is parted and alcohol is applied). Hand sanitizers that combine alcohol and gel can be used.

Patients should NOT be placed in dorsal recumbency as this can compromise the patient (increased work of breathing, decreased venous return and cardiovascular collapse).

Abdominal VPOCUS (abdominal FAST) Protocol

The probe is placed on 4 regions of the abdomen in a consistent systematic approach. At each site, the probe is fanned and rocked through an angle of 45

NOTE a 5th umbilical region view can be performed (5th site, see description below) prior to the gravity dependent renal view as it might detect smaller quantities of fluid that would be displaced when the ultrasound probe is slid under the patient when trying to find the gravity dependent kidney (the authors prefer to examine all 4 original sites as well as the umbilical site essentially making the exam a rapid 5-point evaluation).

The original 4 sites:

Subxiphoid or Diaphragmatico-hepatic (DH) site: just caudal to the xiphoid process

Key structures to identify include the diaphragm, liver, gallbladder, caudal vena cava, pleural and pericardial spaces (see later sections on volume status for more detail on the vena cava evaluation, and the respective sections on pleural and pericardial space evaluation).

Mirror image artifact distal to the diaphragm can only occur when there is air distal to the diaphragm, and therefore can be used to rule out pleural effusion at that location if it is noted.

It is important to consider patient positioning and the effects of gravity when evaluating any VPOCUS sites, including the subxiphoid location. Be sure to fan the probe through all liver planes to ensure a thorough evaluation of the liver is complete, and to rock the probe to assess the most ventral and cranial parts of the liver, where small accumulations of fluid may gather between the liver and diaphragm.

Urinary bladder or Cysto-colic (CC) site: Key organs and structures to identify include the urinary bladder, the gravity dependent body wall and the apex of the bladder. Fluid tend to accumulate between the body wall and the bladder, at the apex of the bladder and between the bladder and the body wall. The probe is placed in long axis to the body between the pelvic limbs. Once the bladder is found, it is important to manipulate the depth to see both dorsal and ventral walls of the bladder, and then to slide the probe to find the apex. Once at the apex, fanning, rocking, and then rotating the probe to short axis (and fanning, rocking in short axis) will allow visualization of abdominal effusion. The probe should also be placed on the non-gravity dependent lateral side of patient and the ultrasound bean angled through bladder and fanned to catch fluid in deeper gravity-dependent sites at the body wall. Pushing too hard will compress and can displace the bladder making it a challenge to identify.

Right paralumbar or Hepato-renal (HR) site: Key organs/structures to identify include the liver, right kidney, body wall and intestines. This view can be difficult to obtain as often it is necessary to go between ribs to visualize the normal structures. It may sometimes be necessary to start in short axis to the body so that the probe can be placed within an intercostal space between ribs. In smaller dogs and in cats, the probe can be placed in long axis to the body caudal to the 13th and final rib. In dogs, if the liver is visualized in the right paralumbar region, or between ribs, the probe can be slid caudally until the kidney is visualized. The right kidney is located quite lateral relative to midline.

Left paralumbar or Spleno-renal (SR) site: Key organs and structures to identify include the spleen and left kidney, and to evaluate regions between the kidney, body wall, spleen and intestines. The probe has to be placed quite lateral to midline to find the left kidney and spleen. The spleen is located cranial and often lateral to the left kidney. The probe is placed in long axis to the body often mid abdomen and lateral to start. It is often easier to find the spleen at first, and then to slide the probe caudally until the left kidney is found. Fanning and rocking the probe helps to find the organs of interest.

Free fluid in the abdomen typically appears as dark (anechoic or hypoechoic) triangles between organs, commonly visualized at the apex of the bladder, between the bladder and the body wall, at the poles of the kidneys, between the spleen and left kidney, between liver lobes, between the liver and diaphragm, between the liver and right kidney, and/or surrounding small intestinal loops.

Is there free abdominal air in the abdomen Y/N?

Free abdominal air can be detected in many sites of the abdomen; however, it is most commonly identified at the left and right paralumbar locations with the patient in right or left lateral recumbency. Again, it is important to consider patient positioning and where free air will accumulate when searching for free abdominal air. The author prefers to have the patient remain in lateral recumbency for a few minutes to allow air to track to the non-gravity dependent locations before trying to identify pneumoperitoneum. Steps:

The peritoneal lining must be identified. This is essential so as not to confuse free air within the GI tract for free air in the abdomen.

Identify the presence of reverberation artifact that originates at the peritoneal lining. This is very important to differentiate from reverberation artifact contained within the GI tract, which again, emphasizes the importance of clearly identifying the peritoneal lining.

Identify the enhanced peritoneal stripe sign. This sonographic finding occurs when free abdominal air comes in contact with the peritoneal lining. At the point where free abdominal air comes in contact with the peritoneal lining it will cause the peritoneal lining to become more hyper-echoic.

Does the patient have a gall bladder halo sign Y/N?

A study by Quantz et al 2009 demonstrated that patients with acute anaphylaxis often have a halo (double rimmed gall bladder wall) sign (the gall bladder wall is normally very thin or not easily visualized on ultrasound), and this can be seen during abdominal VPOCUS. A thicker gallbladder wall (often due to edema with or without surrounding fluid) can be seen with a “halo” effect. However, this is not specific for anaphylaxis and can be seen in patients with a number of conditions (anything that causes edema). However, with unstable patients presenting for collapse, the finding of a “halo” sign should prompt consideration of anaphylaxis, right-sided heart failure, pericardial effusion, fluid overload or changes to vascular permeability and sepsis.

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Moderator Of 1 Session

CVMA Sessions
Moderators
Room
Hall 717
Date
07/16/19, Tuesday
Time
02:15 PM - 05:05 PM
Presentation Type
Level 1: Requires little or no prior knowledge or experience of the areas covered