Further Reading
1 Blanco P, Volpicelli G. 2016. Common pitfalls in point‐of‐care ultrasound: a practical guide for emergency and critical care physicians. Crit Ultrasound J 8(1):15.
2 Boivin M. 2014. Basic operation of an ultrasound machine. In: Point‐of Care Ultrasound, edited by Soni N, Arntfield R, Koy P. Philadelphia: Elsevier Saunders, pp 32–37.
3 Brietkrutz R, Uddin S, Steiger H, et al. 2009. Focused echocardiography entry level: new concept of a 1‐day training course. Minerva Anesth 75(2):285–292.
4 Chiem AT. 2014. Transducers. In: Point‐of Care Ultrasound, edited by Soni N, Arntfield R, Koy P. Philadelphia: Elsevier Saunders, pp 19–24.
5 Goodgame B, Debesa O, Lee A, et al. 2014. Imaging artifacts. In: Point‐of Care Ultrasound, edited by Soni N, Arntfield R, Koy P. Philadelphia: Elsevier Saunders, pp 38–48.
6 Hempel D, Stenger T, Campo Dell Orto M, et al. 2014. Analysis of trainees' memory after classroom presentations of didactical ultrasound courses. Crit Ultrasound J 6(1):10.
7 Hock GH, Widmer WR. 2010. Apearance of common ultrasound artifacts in conventional vs. spatial compound imaging. Vet Radiol Ultrasound 51(6):621–627.
8 Mattoon JS, Nyland TG. 2015. Fundamentals of diagnostic ultrasound. In: Small Animal Diagnostic Ultrasound, 3rd edition, edited by Mattoon JS and Nyland TG. St Louis: Elsevier, pp 1–49.
9 Mayette M, Mohabir PK. 2014. Ultrasound physics. In: Point‐of Care Ultrasound, edited by Soni N, Arntfield R, Koy P. Philadelphia: Elsevier Saunders, pp 9–18.
Chapter Six POCUS: AFAST – Introduction and Image Acquisition
Gregory R. Lisciandro
Introduction
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
|