Point-of-Care Ultrasound Techniques for the Small Animal Practitioner. Группа авторов
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situation in which there are no resources for blood transfusion administration and whether leaving the blood in the abdominal cavity is acceptable. The argument is that by leaving the intraabdominal blood, the patient has the benefit of resorbing the cavitary blood postoperatively, and common sense should always prevail in the quest to improve the probability of patient survival. However, when possible, “dry the abdomen” to better interpret the clinical relevance of postoperative effusions.
How Long Does It Take for Lavage Fluid to be Resorbed?
A fascinating question because, in contrast to cavitary blood that is resorbed quite rapidly within the “AFAST‐TFAST 48‐hour rule,” lavage fluid lasts much longer (several days) in the author's experience. Thus, our recommendation is always “dry the abdomen” before abdominal closure using suction and running lap sponges through the left (mesocolon) and right (mesoduodenum) sided abdominal “gutters.” Drying the abdomen gives you a negative AFS (AFS of 0) post‐operatively and helps you better interpret the finding of free fluid post‐procedure. Moreover, neutrophils work much more effectively in a “dry abdomen” environment than one bathed in lavage fluid.
Pearl: Expect abdominal cavitary blood to be resorbed with decreasing AFS and be nearly resolved or at an AFS of 0 within 48 hours – the “AFAST‐TFAST 48‐hour rule” – once bleeding has stopped.
Pearl: Spend an extra few minutes to suction and “dry the abdomen” with lap sponges prior to closure. Neutrophils function better, and your patient has an AFS 0 prior to closure, which helps to interpret positive AFS postoperatively.
Cats Don’t Survive Large‐Volume Traumatic Bleeds
AFAST and the AFS system were prospectively studied in 49 traumatized cats. Although 17% of cats had positive fluid scores, feline “large‐volume bleeders” were almost nonexistent and those with an AFS of 3 and 4 died during triage or were dead on arrival and not enrolled (Lisciandro 2012). Originally, the conclusion was that AFS was less reliable in cats, but several years of experience suggest that AFS for bleeding works just as well in cats. However, bluntly traumatized cats generally do not survive large‐volume bleeds as dogs might (Mandell and Drobatz 1995; Lisciandro 2012). This is likely because the canine spleen serves as a large reservoir of blood whereas the feline spleen does not. Moreover, cats have over the years presented with “soft” positives at multiple AFAST views that would be better scored as a ½ rather than a full 1. The modification of the AFAST‐applied AFS system thus recategorizes more accurately these feline cases as “small‐volume bleeders” (Figure 7.8).
Figure 7.8. Example in a cat using the modified AFS system. (A) AFAST in right lateral recumbency and the four AFAST views used for the AFS. In (B) small triangulations (½ + ½ + ½) are found at three of the four views which calculates as an AFS of 1.5, a “small‐volume bleeder/effusion.” In (C) there are larger pockets of free fluid (1 + 1 + 1) at the same three AFAST views as in (A) and the AFS calculates as 3, a “large‐volume bleeder/effusion.” In (D) there are small triangulations at the DH and SR views and a larger pocket at the HRU view with a calculated AFS of 2 (½ + ½ + 1), a “small‐volume bleeder/effusion.” The same concept is applied to dogs.
Source: Reproduced with permission of Dr Gregory Lisciandro, Hill Country Veterinary Specialists and FASTVet.com, Spicewood, TX. Illustration by Hannah M. Cole, Adkins, TX.
Pearl: Cats with automobile‐induced traumatic hemoabdomen are often nonsurvivors before making it to veterinarians because they cannot compensate as dogs do and because of their smaller size, making injury more severe and lacking a splenic blood reservior. Free fluid on AFAST in surviving cats (>12–24 hours) is more likely to be urine than blood.
Importance of Recording Locations of Where Patients are Positive
It is imperative to not only record the AFS but also locations of where the patient is positive and negative. This is important because the locations of AFAST‐positive views in lower‐scoring “small‐volume bleeders” may be helpful for the localization of the bleeder (Table 7.4). For example, consider a hit‐by‐car dog or cat with an AFS of 1 at the AFAST DH view that continues to bleed with an increase in AFS to 3 or 4 and that despite blood transfusions becomes a surgical case. Logic would dictate that the source of intraabdominal bleeding is likely associated with the liver and its vasculature. This information would potentially better prepare the surgeon for the anticipated type of injury, such as liver laceration, hepatic venous or vena caval injury, and for the needed procedure(s) as well as relevant resources. On the other hand, in the same trauma scenario the AFS 1 is positive at an AFAST view further caudally, such as the CC or HR umbilical view, and now logic would dictate that the source of bleeding would be more likely intestinal tract or spleen. Thus, the definitive procedure would likely be less technically challenging than a liver laceration or vascular hepatic injury.
Table 7.4. Possible sources of abdominal bleeding on AFAST views.
Source: Reproduced with permission of Dr Gregory Lisciandro, Hill Country Veterinary Specialists and FASTVet.com, Spicewood, TX.
| View | Possible source |
|---|---|
| DH | LiverVascularCaudal vena cavaHepatic vesselsPortal vessels |
| SR, HR, SR5th, HR5th | Spleen (SR, SR5th)Liver (HR, HR5th)AdrenalOvaryVascularCaudal vena cavaAortaRenal vesselsVertebrae |
| CC | Small intestineLarge intestineReproductive tractUterusProstateVascularCaudal vena cavaAorta |
| HRU, SRU | LiverSpleenUterusGastrointestinal tract |
In nontrauma, another example would be a postovariohysterectomy bleeding case with an AFS of 1 that is positive at the SR view. Let's say that over time, the patient progresses to an AFS of 3 or 4 that requires surgical exploratory. Logic would dictate the source of bleeding is most likely in the vicinity of the SR view and the left ovarian pedicle would be suspect. This information would again help direct the surgeon to that region as initially AFAST positive for the source of bleeding. In fact, for bleeding postoperative ovariohysterectomy surgeries, the AFAST acoustic windows are in regions of the left ovarian pedicle (SR view), the right ovarian pedicle (HR5th bonus view), and the uterine stump (CC view), which is important to consider in “small‐volume bleeders” that progress to “large‐volume bleeders” requiring surgical intervention. The upshot is that the sonographer should record both the AFS and specifically what AFAST views are positive and negative to maximize patient information as dictated in AFAST goal‐directed templates (see last section of this chapter).
Pearl: Use the AFAST and AFS system as a postinterventional exit exam evaluation, e.g., postoperative and postpercutaneous ultrasound‐guided procedures, before patients are sent home to ensure no occult bleeding is occurring. The use of this strategy is more sensitive than a physical exam, vital signs, and packed cell volume and total solids.
Most Common AFAST‐Positive Sites in Low‐Scoring AFS 1 and 2 Patients
In trauma, the most commonly reported positive sites are the nongravity‐dependent DH and CC views, which is against