Point-of-Care Ultrasound Techniques for the Small Animal Practitioner. Группа авторов

Fosgate 2017).

       What AFAST Cannot Do

       Cannot sonographically characterize fluid, thus sample acquisition via abdominocentesis is required when fluid is safely accessible; and fluid analysis should be performed.

       In penetrating trauma, AFAST lacks sensitivity (in contrast to blunt trauma where it has high sensitivity) but likely is highly specific for intraabdominal and retroperitoneal injury similar to human studies (Udobi et al. 2001).

       In penetrating trauma, AFAST should always be repeated post resuscitation as long as necessary until assured that the patient is not a surgical candidate by repeating at 2–4 hours post admission as standard of care and then continued at eight hours, 12 hours, 24 hours, two days, three days, five days, etc. post trauma at any time the patient is not doing well, for example to detect a septic abdomen or pyothorax that would otherwise be missed.Table 6.4. Abbreviations and terminology. As lengthy as the list seems, the abbreviations and terminology allow for more rapid communication verbally and in medical records.Source: Reproduced with permission of Dr Gregory Lisciandro, Hill Country Veterinary Specialists, FASTVet.com, Spicewood, TX.Terminology for standardized ultrasound examsAbdominal FASTAFASTThoracic FASTTFASTVeterinary Bedside Lung Ultrasound ExamVet BLUEGlobal FASTAFAST, TFAST and Vet BLUE combined as a single ultrasound examinationComplete Detailed Abdominal UltrasoundComplete Detailed EchocardiographySerial ExaminationRepeating the standardized protocol and recording your findings. Serial examinations have also been referred to as “secondary examinations.” We prefer the term “serial” (Blackbourne et al. 2004; Lisciandro et al. 2009)Ultrasound signs and characterizations used during AFASTAFAST views:DH view = diaphragmatico‐hepatic viewSR view = spleno‐renal viewHR view = hepato‐renal viewCC view = cysto‐colic viewHRU view = hepato‐renal umbilical viewSRU view = spleno‐renal umbilical viewHR5th bonus view = the final view of small animals when in right lateral recumbency imaging the right kidney and adjacent right liver (not part of the abdominal fluid scoring system)SR5th bonus view = the final view of small animals when in left lateral recumbency imaging the left kidney and adjacent spleen (not part of the abdominal fluid scoring system)CC pouch = most gravity‐dependent region where free fluid would accumulate at the CC viewHRU (SRU) pouch = most gravity‐dependent region where free fluid would accumulate at the HRU (SRU) viewPouch = most gravity‐dependent region at that acoustic windowGallbladder “halo sign,” also called “halo effect,” “double rim effect”Occurs with the presence of intramural gallbladder edema, recognized as sonographic striation, and supports the diagnosis of canine anaphylaxis (along with acute collapse and gastrointestinal signs and a flat CVC) versus right‐sided heart failure/generalized systolic dysfunction, pericardial effusion (along with a FAT CVC) versus right‐sided volume overload (FAT CVC) in collapsed, weak, hypotensive dogs (see Figures 36.7 and 36.9). There are other causes for gallbladder wall edema (see Table 7.5 and Chapter 8), however, canine anaphylaxis and heart conditions present more emergently with acute weakness or collapse in a previously healthy dog (Lisciandro 2014a)Caudal vena cava (CVC) characterization by assessing maximum heights in the longitudinal orientation at the FAST DH viewBounce: expected ~35–50% dynamic respirophasic changes in CVC height during the respiratory cycle; also called a “fluid‐responsive CVC”; an expected maximum height in longitudinal at the DH view is available for dogs of various weights and cats (see Tables 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