7.6 and 36.3 and Figures 36.9–36.12).Flat: lacks respirophasic dynamic change (<10%) in CVC maximum height and having an abnormally small maximum height; also called “hypovolemic CVC” or “fluid starved CVC”; maximum heights of <0.25 cm, <0.35 cm, <0.50 cm for dogs weighing <9 kg, >9 kg, <15 kg and >15 kg, respectively (modified by Lisciandro from Darnis et al. 2018).FAT: lacks respirophasic dynamic change (<10%) in CVC diameter during inspiration and expiration having an abnormally large maximum height (Ferrada et al. 2012a,b); also called a “fluid‐intolerant CVC”; maximum heights of >1.0 cm and >1.5 cm for dogs weighing <9 kg and >9 kg, respectively (modified by Lisciandro from Darnis et al. 2018).Cardiac bumpObservation at the FAST DH view where the muscular apex of the heart is beating and often indenting along the diaphragm; helps rule in and rule out pericardial effusion through presence or absence of the “racetrack sign” (Lisciandro 2014a,b, 2016a) (see Figures 7.13, 7.14 and 39.5)Racetrack signSign indicative of pericardial effusion at the FAST DH view through the observation of free fluid rounding the apex of the heart being contained within the pericardial sac (Lisciandro 2014a,b, 2016a) (see Figure 7.13)Tree trunk signObservation of distended hepatic veins as they drain into a distended (FAT) caudal vena cava (abnormal finding); represents conditions impeding blood flow from the liver to the right heart, most commonly right‐sided failure, pericardial effusion, and dilated cardiomyopathy (DCM), and right‐sided volume overload during fluid resuscitation (Lisciandro 2014a,b; Nelson et al. 2010) (see Figure 36.8)Urinary bladder volume estimation formula (mL)Length (cm) × width (cm) × height (cm) × 0.625 (Lisciandro and Fosgate 2017)
AFAST misses peritonitis in some dehydrated and hypotensive patients, so should always be repeated post resuscitation and rehydration, with continued serial (repeat) exams as long as necessary until assured that the patient is not a surgical candidate.
The AFAST AFS system is effective in cats, but cats as a species lack a large splenic blood reservoir and thus felines generally do not survive large‐volume bleeds, and larger volume intraabdominal effusions are more likely to be due to uroabdomen.
Understand that serial (repeat) exams using the Global FAST approach is an even better strategy because the thorax, heart, and lung are also surveyed.
Cannot replace a complete detailed abdominal ultrasound.
Cannot replace proper training.
Indications
All blunt and penetrating trauma cases as standard of care for screening for indirect evidence of intraabdominal and retroperitoneal injury.
All collapsed both recovered and unrecovered cases with unexplained hypotension, tachycardia, or mentation changes.
All anemic cases.
All “ain’t doing right” (ADR) cases.
All postinterventional cases including intravenous fluid therapy, postsurgical cases, postpercutaneous procedures, etc. that are at risk for bleeding, infections, vascular complications.
All peritonitis suspects, including acute abdomen, for expedient diagnosis through the detection of free fluid (and subsequent sampling, fluid analysis testing as deemed appropriate) and free air.Preanesthetic screening test.Extension of the physical exam for patients presenting once or twice a year for routine care.
Objectives
Be able to perform the AFAST views and apply its fluid scoring system.
Be able to recognize basic abnormalities of the AFAST target organs in each of its views.
Know how to assign an AFS during AFAST.
Be able to recognize sonographic striation of the gallbladder wall, referred to as the “halo effect” or “double rim effect” or “halo sign,” that can be present in both dogs and cats from different causes.
Be able to recognize retroperitoneal free fluid and distinguish it from intraabdominal fluid.
Know common artifacts at each AFAST view.
Know the major pitfalls at each AFAST view.
Know how to do a focused (POCUS) spleen examination and its importance following the completion of AFAST and after assigning an AFS.
Understand why best practice would be to add on the Global FAST approach for all AFAST and POCUS exams (abdomen, thorax, eye, brain, musculoskeletal, etc.) to make sure that forms of peritonitis and pleuritis, presence of bleeding, and cardiac and pulmonary conditions are not being missed.
How to Perform an AFAST Exam
Ultrasound Settings and Probe Preferences
Standard abdominal settings, presets, with adequate depth to be able to visualize the target organs of each AFAST view.
Curvilinear (microconvex) probe with a range of 5–10 MHz and a maximum depth of 12–15 cm is acceptable for most dogs and cats.
Optimizing Image Quality and Probe–Skin Contact
Hair is generally not shaved but rather parted for the best probe–skin contact with the use of isopropyl alcohol, and/or alcohol‐based hand sanitizer, and/or acoustic coupling gel. The author prefers the use of minimal amounts of isopropyl alcohol to effectively part the hair followed by alcohol‐based hand sanitizer. The strategy is much less noxious to your patient by minimizing the cold wetness of isopropyl alcohol and its fumes, especially when moved to an oxygen cage. Alcohol‐based hand sanitizer has the added benefit of being easily wiped off and it also evaporates quickly. Isopropyl alcohol should not be used if electrical defibrillation is anticipated because it poses a burn/fire hazard. The clinician should be aware that isopropyl alcohol may cause probe head damage (see Figure 4.13).
Pearl: By not shaving (or limiting shaving to small acoustic windows), the cosmetic appearance of the patient is preserved (happier clients), the exam time is lessened, and imaging quality is sufficient with most newer ultrasound machines (median AFAST time <3–3.5 minutes) (Lisciandro et al. 2009; Lisciandro 2011, 2012; Boysen and Lisciandro 2013).
Pearl: Maximize image quality by parting the hair and getting the probe head and its acoustic coupling medium in direct contact with the patient's skin to minimize air trapping, which is your imaging enemy because ultrasound does not transmit through air. Placing the probe head on a wetted mat of hair full of trapped air will produce a poor image (see Figures 5.1 and 5.2).
Pearl: Hold the probe in a way that is most comfortable while
