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In 2004, a focused assessment with sonography for trauma (FAST) exam was prospectively validated in traumatized dogs, translating the four acoustic windows described in human medicine (Boysen et al. 2004) (Figure 6.1). Interestingly, intraabdominal injury, more specifically hemoabdomen, was far more prevalent than previously reported with a prevalence of 38–45% versus a pre‐FAST rate of 12–23% (Boysen et al. 2004).

In 2005, the original FAST examination was modified in the following ways, including renaming the study AFAST (Lisciandro et al. 2009) (Table 6.1).

 The probe was directed into the gravity‐dependent regions of each acoustic window.

 The views were renamed by their target organs rather than external anatomy.

 The probe was maneuvered differently, making the major orientation longitudinal with fanning and rocking of the probe at each AFAST acoustic window without rotating.

 The patient was not shaved but rather the hair was parted to maximize probe–skin contact.

 A simple AFAST‐applied fluid scoring system (0–4) was developed for semiquantitating volume of the effusion, with more recent modifications.

 Serial AFAST examinations were performed as standard of care for all admitted patients four hours post admission and sooner if questionable or unstable patient status.

 AFAST investigated many important clinical questions rather than a single binary question of fluid positive or negative.

The AFAST study documented that its simple abdominal fluid scoring system (0–4) reliably predicted the degree of anticipated anemia in dogs with hemoabdomen. The abdominal fluid score (AFS) differentiated lower scoring small‐volume bleeders (AFS 1 and 2) from higher scoring large‐volume bleeders (AFS 3 and 4). Moreover, the study answered what was implied in the original FAST study, that the historical use of radiographic abdominal serosal detail was an unreliable test for the presence or absence of free peritoneal fluid and its volume (Boysen et al. 2004; Lisciandro et al. 2009). In fact, 24% of dogs with normal abdominal radiographic serosal detail were AFAST positive, and 32% with decreased abdominal radiographic serosal detail were in fact AFAST negative (Lisciandro et al. 2009). Thus, in summary, not only was abdominal radiographic serosal detail unreliable for the presence and absence of free fluid, but abdominal serosal detail also could not reliably estimate the volume of free fluid present (see Figure 7.9).

The repeating of at least one more AFAST and assigning an AFS allowed the attending clinician to not only screen for the presence of free fluid that may have been missed or absent on the first AFAST examinations, but also to reassign an AFS and evaluate the urinary bladder (Lisciandro et al. 2009; Lisciandro 2011, 2012; Boysen and Lisciandro 2013). AFAST and the use of the patient’s AFS were shown to be invaluable for the detection of developing hemoabdomen (initially negative [AFS 0] turned AFAST positive [AFS 1‐4]), the detection of ongoing hemorrhage (increasing fluid score), and evidence‐based resolution of hemoabdomen (decreasing fluid score) (see Figure 7.9). Interestingly, the American College of Emergency Physicians has advocated the use of a serial four‐hour postadmission FAST examination for all at‐risk human patients since 2001 yet at the time of writing this chapter, the number one cause of death in hospitalized human trauma patients surviving traumatic brain injury during their first 48 hours of care remains ongoing, unrecognized bleeding (Bilello et al. 2011; Sobrino and Shafi 2013).

Figure 6.1. AFAST on a dog in right and left lateral recumbency. In (A) AFAST is shown on a dog in right lateral recumbency and in (B) left lateral recumbency. Sites are named by their target organs. The AFAST order is always the same. In right lateral, (1) DH view, (2) SR view, (3) CC view, (4) HRU view. In left lateral recumbency, (1) DH view, (2) HR view, (3) CC view, (4) SRU view. These AFAST views are part of the abdominal fluid scoring (AFS) system and the order ends at the most gravity‐dependent view where abdominocentesis is likely to be performed in higher‐scoring patients. Note that the 5th AFAST bonus view is not shown in these images. The AFAST views are nearly identical sonographically no matter the positioning (lateral recumbency versus standing‐sternal). AFAST target organs are imaged in the same standardized manner regarding probe maneuvering with the “fan, rock (cranially) and return to your starting point” approach.

Source: Reproduced with permission of Dr Gregory Lisciandro, Hill Country Veterinary Specialists and FASTVet.com, Spicewood, TX.

Table 6.1. Changes in methodology from FAST to AFAST.

Source: Reproduced with permission of Dr Gregory Lisciandro, Hill Country Veterinary Specialists, FASTVet.com, Spicewood, TX.

Parameters	FAST (Boysen 2004)	AFAST (Lisciandro et al. 2009)
Shaving patient	Shaving	No shaving
Primary probe orientation	Longitudinal and transverse	Only longitudinal
Primary probe maneuver	Sliding, rotating and sweeping	Fanning and rocking
Main probe direction	Toward spine	Gravity‐dependent pouches
Laterala	Left	Right
Fluid scoring	No	Yes
Naming acoustic views	External locations	Target organs
Timing of examination (median time presentation to ultrasound examination)	Post resuscitation (median 1 hour)	Presentation and serially post resuscitation (median <5 minutes)

^a Lateral recumbency was a brilliant proposition, being markedly safer than dorsal recumbency (see Figure 6.5).

More recently, a human study showed that in people with prehospital hypotension, the only intervention that prevented the “crump factor,” the phenomenon of a patient decompensating unexpectedly, was the liberal use of FAST examinations (Bilello et al. 2011). The upshot is veterinarians have a better tool, the AFAST and its applied fluid scoring system, to determine within minutes of presentation or during hospitalized care when patients are becoming unstable, to not only “see” if the patient is positive or negative for free fluid, but also the degree of bleeding (or effusion) by easily calculating the patient's AFS (0–4 scale). AFAST and AFS are the missing link to traditional trauma, triage and tracking algorithms, and by adding the target organ approach, a huge amount of clinical information is easily gained within minutes, when minutes count.

The comparison of the original FAST to the subsequent AFAST study is fascinating and some important differences are noted (see Table 6.1) (Boysen et al. 2004; Lisciandro et al. 2009). Remarkably, degree of trauma was very similar, including numbers of pelvic fractures and pneumothoraces (Table 6.2), suggesting that the overall degree of trauma between studies was comparable and thus inferences may be loosely drawn (Boysen et al. 2004; Lisciandro et al. 2009).

One involves the case management and decision making for blood transfusion(s), and that knowing if the dog at triage was AFS positive affected fluid therapy administration strategies. In other words, intravenous fluid resuscitation was likely titrated more closely to low normal endpoints, such as mean arterial pressure, thus mitigating exacerbation of hemorrhage by lessening the probability of “popping the clot” and diluting clotting factors through overresuscitation in bleeding dogs (Lisciandro et al. 2009). The differences in median time from trauma to FAST/AFAST, median time presentation to FAST/AFAST (240 versus <5 minutes), and numbers of transfusions FAST/AFAST (9 versus 3) support this conclusion. AFAST was performed as part of the physical exam versus FAST, which was a second line test after initial assessment, intravenous fluid resuscitation, and blind abdominocentesis possibly to the dog's detriment by the much higher positive rate (45% versus 27%).

The original FAST study lacked a fluid scoring system, and as simple as the AFAST system is, with a range of 0–4 (AFS 0 negative all AFAST views to a maximum of four being positive for fluid at all four AFAST views), AFS provides an effective tool for decision making (see Table 7.3). This decision making, ranging from intravenous fluid resuscitation strategies to administration of blood transfusion products to the need for exploratory surgery, importantly carries the potential to improve outcome and decrease complications, as shown in people (see Chapter 7) (Blackbourne et al. 2004; Ollerton et al. 2006; Bilello et al. 2011).

Table 6.2. Comparison of FAST and AFAST in dogs.

Source: Reproduced with permission of Dr Gregory Lisciandro, Hill Country Veterinary Specialists, FASTVet.com, Spicewood, TX.

Parameters	FAST (Boysen et al. 2004)	AFAST (Lisciandro et al. 2009)
Primary presentations	65%	96%
FAST positive cases	45%	27%
Low‐scoring (AFS 1 and 2) small‐volume bleeders	NA	13
High‐scoring (AFS 3 and 4) large‐volume bleeders	NA	14
Cases of abdominocentesis prior to AFAST/FAST examination	16	0
Median time trauma to AFAST/FAST examination	240 minutes	60 minutes
Median time presentation to AFAST/FAST examination	60 minutesFAST was a secondary evaluation post initial resuscitation	<5 minutesAFAST was a first‐line screening test
Median time for AFAST/FAST examination	6 minutesShaved sites	3 minutesNo shaving
Pelvic fractures	20	22
Pneumothorax	21	22
Appendicular fractures	15	25
Diaphragmatic hernia	NA	2
Number of blood transfusions	9	3

Of note, dogs with pneumothorax (55%), pelvic fractures (40%), and high alanine transaminase (ALT) (>400 U/L) were also more likely to concurrently have or develop hemoabdomen detected by either their initial or serial AFAST examinations than dogs without these findings (Lisciandro et al. 2009; Lisciandro 2014c). The serial use of AFAST is helpful in determining the integrity of the urinary bladder, estimating urinary bladder volume and urine output during resuscitation (Lisciandro et al. 2009; Lisciandro 2011; Lisciandro and Fosgate 2017). Both FAST and AFAST studies documented that when the urinary bladder was imaged with an expected, smooth, rounded contour, it was unlikely to be ruptured, holding advantages over traditional means of palpation, characterization of urine post micturition, and plain radiography (Boysen et al. 2004; Lisciandro et al. 2009; Boysen and Lisciandro 2013).

More recently, a urinary bladder estimation formula for use during AFAST has been published and provides a noninvasive way to estimate urine output when serial calculations are made over time (Lisciandro and Fosgate 2017). AFAST additionally remains useful to survey for intrathoracic trauma, pleural and pericardial effusion, and lung conditions, through the acoustic window of the liver and gallbladder by imaging cranial to the diaphragm in every patient, dependent on patient size, coupled with depth limitations of the ultrasound machine (Boysen et al. 2004; Lisciandro et al. 2009; Lisciandro 2011, 2016a; McMurray et al. 2016).

Lastly, AFAST was never meant to be a “flash exam,” meaning that it was never meant to only answer a single binary question of whether free fluid was present or absent (Table 6.3). AFAST provides much more clinical information by:

Table 6.3. What clinical questions are answered using AFAST? Binary? Qualitative‐quantitive?.

Source: Reproduced with permission of Dr Gregory Lisciandro, Hill Country Veterinary Specialists and FASTVet.com, Spicewood, TX.

	Binary	Qualitative‐quantitive	aSensitivity (Se) aSpecificity (Sp)
Does the patient have free fluid in the abdominal cavity?	√Yes or no	√Use AFAST‐applied fluid scoring system (1–4)	Se – HighSp – High
Does the patient have free fluid in the retroperitoneal space?	√Yes or no	√Trivial, mild, moderate, severe	Se – High to variableSp – High
Does the patient have any obvious AFAST target organ abnormalities?	√Yes or no	√	Se – Variable, operator dependentSp – High
Does the patient have pleural effusion?	√Yes or no	√Trivial, mild, moderate, severe via its DH view	Se – HighSp – High
Does the patient have pericardial effusion?	√Yes or no	√Trivial (<0.5 cm), nild (>0.5 and <1.0 cm), moderate (>1.0 and <2 cm), severe (>2 cm) via its DH view (Candotti and Arntfield 2015)	Se – HighSp – High
Does the patient have lung pathology along the pulmonary–diaphragmatic interface?	√Yes or no	√Vet BLUE B‐line scoringVet BLUE 6 lung ultrasound signs (Lisciandro 2014b,c; Lisciandro and Fosgate 2017)	Se – Unknown, operator dependentSp – Likely high
What is the patient's volume status?	√Unremarkable or abnormal	√Characterizing the dynamic changes in height of caudal vena cava (bounce, fluid responsive; FAT, fluid intolerant; or flat, hypovolemic) (see Figures 36.7, 36.10–36.12); coupled with hepatic venous characterization (presence or absence of the “tree trunk sign” – see Figure 36.8); and absolute maximum CVC height measurements (see Table 36.3)	aHypervolemia Se – Likely high Sp – Likely high aHypovolemia Se – Likely variable Sp – Likely high aEuvolemia Se – Variable Sp ‐ Variable aIntegrating TFAST echo and Vet BLUE pulmonary information likely improves both Se and Sp
What is the patient's urine production?		√Length (cm) × width (cm) × height (cm) × 0.625 = volume estimation (mL)	Unknown

^a Clinical experience, limited veterinary studies, human studies.

 having a fluid scoring system

 looking cranial to the diaphragm into the thorax at the DH view for pleural and pericardial effusion and lung conditions

 examining the gallbladder wall for signs of intramural edema

 characterizing the caudal vena cava and its associated hepatic venous system

 observing the urinary bladder for its expected rounded contour and measuring it (when applicable) for bladder volume estimation and urine output

 calculating the AFS to better make sense of the volume of blood in hemorrhaging small animals

 serving as monitoring tool for any and all effusive conditions

 taking advantage of its target organ approach.

In other words, an AFAST not only provides a highly sensitive and specific means to detect intraabdominal and retroperitoneal effusions, but also serves as an abdominal soft tissue screening test for obvious target organ pathology. Patient information is acquired rapidly during AFAST (<3–4 minutes) with low patient impact (minimal restraint, no shaving) and point of care (Lisciandro et al. 2009; Lisciandro 2012, 2016a; Boysen and Lisciandro 2013; McMurray et al. 2016).

Abbreviations and terminology are listed in Table 6.4.

POCUS abdominal, thoracic, ocular, neurological, and musculoskeletal examinations are more extensively described in their respective chapters; however, the POCUS approach should always include minimally an AFAST, with its target organ approach, and AFS, and, much better, the Global FAST approach, as an extension of your physical exam for best practice. Global FAST has been advocated by the author as an extension of the physical examination for virtually any small animal patient since 2005 (Lisciandro 2011, 2012, 2014a–c, 2016a,b; Lisciandro et al. 2019), with a similar approach more recently advocated in human medicine (Lichtenstein 2010; Narasimhan et al. 2016).