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If AFAST is negative in standing or sternal positioning, then moving the patient to lateral recumbency is unnecessary. However, if the AFAST examination is positive in standing or sternal, then move the patient to lateral recumbency (if unstable, delay until more stable) and wait for three minutes for fluid to settle before assigning an AFS (Lisciandro et al. 2009; Lisciandro 2011; Boysen and Lisciandro 2013).

When performing AFAST in standing or sternal, the sonographer must keep in mind the following points.

 As long as the AFAST is negative and the target organs are imaged at each respective view, the AFAST is complete.

 When free intraabdominal fluid is present, it will pool in different regions relative to the target organs because gravity‐dependent locations differ from lateral recumbency, being at the probe head, in the near‐field, for the DH, CC, and SR/HR umbilical views.

 The gravity‐dependent regions within the lumen of the gallbladder and urinary bladder also differ from lateral recumbency and the sonographer must consider the direction of the beam (its scanning plane) to best detect and interpret findings.

 The AFAST views, when performed properly, should look nearly the same independent of positioning.

Dorsal recumbency should never be used for AFAST (TFAST and Vet BLUE) for several reasons but most importantly because of increasing patient risk (Figure 6.5). A hemodynamically fragile patient placed in dorsal recumbency undergoes significant negative changes in ventilation and circulation, specifically venous return. Add to these respiratory and cardiovascular stresses and the increased oxygen demand in a struggling, anxious patient, and the patient risks acute and potentially catastrophic decompensation. Considering trauma, most dogs and cats have concurrent lung contusions and other thoracic‐related injuries (Powell et al. 1999; Sigrist et al. 2011; Lisciandro et al. 2008) and intraabdominal bleeding (Boysen et al. 2004; Lisciandro et al. 2009). Considering nontrauma, many hypotensive triaged patients have pleural and/or pericardial effusion, and intracavitary bleeds often accompanied by anemia (McMurray et al. 2016; Lisciandro 2016a,b). Moreover, the AFS system is not validated in dorsal recumbency and only subjective terms of mild, moderate, and severe can be used (Stander et al. 2010; Sutherland‐Smith et al. 2006). For clinicians who prefer performing complete detailed abdominal ultrasound in dorsal recumbency, perform a Global FAST first before moving the patient to the restraint of dorsal recumbency to best ensure patient safety.

Figure 6.4. Modified lateral‐sternal recumbency. The AFAST views are performed in the same order every time as follows: DH to SR to CC to HRU to HR5th bonus view. The final HR5th bonus view is not part of the abdominal fluid score.DH, diaphragmatico‐hepatic view; SR, spleno‐renal view; CC, cysto‐colic view; HRU, hepato‐renal umbilical view; HR5th, hepato‐renal 5th bonus view. Note that the images should look identical for each AFAST view regardless of positioning (including standing/sternal, modified sternal). AFAST views are nearly identical no matter the positioning because the respective target organs are imaged with the same methodology.

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