Global FAST– Using Ultrasound in Dog and Cats as an Extension of Your Physical Exam

Gregory R. Lisciandro, DVM, Dipl. ABVP, Dipl. ACVECC


Hill Country Veterinary Specialists & FASTvet.com FASTvetTM and FAST Saves Lives!TM


Introduction: FAST acronym stands for Focused Assessment with Sonography for Trauma was developed in the 1990s by trauma surgeons for use in the trauma bay at triage for detecting indirect evidence for intra-abdominal injury through the detection of free fluid (black sonographic triangulations that are unlikely to represent any normal structures). What is often failed to be mentioned is that the formats were also used by trauma surgeons as an extension of the physical examination to detect complications well before human patients were often overtly clinical since ultrasound exceeds the sensitivity of physical examination, vital signs, laboratory findings and radiography for many conditions (bleeding, infection [septic effusions], non-septic effusions).

 

Since the landmark translational FAST validation study by Dr. Soren Boysen, we have developed the target-organ approach, the abdominal fluid scoring system to better characterize the meaning of a positive FAST exam, the thoracic FAST (TFAST), and most recently the application of lung ultrasound called Vet BLUE (Veterinary Bedside Lung Ultrasound Exam). We have suggested the use of the following acronyms, AFAST (Abdominal FAST), TFAST (Thoracic FAST), and Vet BLUE, with a T3 to better clarify their applications which include Trauma, Triage and Tracking (T3) thus avoiding the onslaught of confusion acronyms in human medicine. When all 3 formats are used together we refer to the exam as Global FAST (GFAST). GFAST3 is a format that changes the mindset of traditional abdominal ultrasound and echocardiography and in many instances gives more information helping rule in and rule out conditions missed by these traditional formats. 

KEY POINT: Standardizing terminology is important to prevent confusing acronyms; and Global FAST is the new comprehensive ultrasound format that provides in many instances more information that the traditional approaches of complete abdominal ultrasound and echocardiography.

Abdominal FAST or AFAST

Schematic of the AFAST3 (Abdominal) Ultrasound Exam: This material is reproduced with permission of John Wiley & Sons, Inc, Focused Ultrasound Techniques for the Small Animal Practitioner, Wiley ©2014 The AFAST3 sites (right lateral recumbency is preferred but left lateral is acceptable. To the right of the pictorial labeled A) is a translational depiction on an abdominal radiograph of a dog. The AFAST3 should always be performed in a standardized counter- clockwise manner as follows: 1) Diaphragmatic-Hepatic (DH) View also used to image the pleural and pericardial spaces 2) Spleno-Renal (SR) View also used as a window into the retroperitoneal space 3) Cysto-Colic (CC) View and 4) Hepato-Renal (HR) View which completes the AFAST3 exam. The HR view in higher-scoring dogs and cats is often a favorable site for abdominocentesis. All AFAST3 views are performed in the longitudinal (sagittal) orientation because it is easier to appreciate the anatomy of the respective target organs and less confusing especially for the novice sonographer. Importantly, Boysen et al. showed that when comparing longitudinal (sagittal) to transverse views, they matched 399/400 times.

KEY POINT: Keeping it simple by fanning through only longitudinal orientation expedites the learning process. 

AFAST3-applied Fluid Scoring System:

The AFAST3-applied fluid scoring system is defined as follows (4-point scale): abdominal fluid score (AFS) of 0 (AFS 0) means negative at all 4 views to a maximum score of AFS 4 means positive at all 4 views. Low-scoring AFS1 and 2 dogs are considered major injury, small volume bleeders, unlikely to become anemic from the intra-abdominal bleed if no pre-existing anemia and no other bleeding sites. High-scoring AFS 3 and 4 dogs considered major injury, big or large volume bleeders, likely to become anemic from the intra-abdominal bleed thus helps predict the need for blood transfusion and surgery depending on patient subset. Reproduced with Permission Lisciandro, et al. JVECC 2009; 19(5):426-437.JVECC 2011;20(2);104-122.

Use of Serial AFAST3 Exams and Determining the AFS:

The use of serial AFAST3 and serial application of the abdominal fluid score is imperative to maximize information and improve sensitivity of the exam including searching for fluid, assessing the abdominal fluid score (0-4), and evaluating the presence or absence of the urinary bladder. The author performs 4-hour post-admission serial AFAST and AFS in all stable patients (sooner if unstable); and serial FAST exams are standard of care in human medicine (American College of Emergency Physicians Guidelines [2001]). The use of the AFAST3 and AFS is helpful in trauma, non-trauma and tracking of bleeding dogs and cats; and for monitoring non-hemorrhagic effusions.

KEY POINT: Serial FAST ultrasound exams increase Sensitivity (in other words not missing free fluid) and allow you to re-score (AFS) and evaluate for the presence of the urinary bladder (indirect urine output, and ruling out urinary bladder rupture).

AFAST3 is a Cerebral Exam, Not just Fluid-positive, Fluid-negative:

The Diaphragmatico-Hepatic (DH) View is loaded with information that is readily appreciated during the minutes it takes to perform the AFAST3 including volume status, gallbladder findings, liver findings, and its use for pleural and pericardial effusions. The Spleno-Renal (SR) View is unique since it interrogates both the abdominal cavity and retroperitoneal space with target-organ interrogation of the left kidney and spleen. The Cysto-Colic (CC) View lends itself to suspecting urinary bladder pathology. The colon is a tricky structure that can cause mistakes by the air-filled colon appearing like bladder stones, the fluid-filled or fecal-filled colon like masses. The CC View is the most common AFS-positive site in low-scoring AFS 1 and AFS 2 dogs (and cats) by directing the probe toward the table top into the “CC pouch” where the urinary bladder is immediately against the ventral abdominal wall. The Hepato-Renal (HR) View is completes the AFAST3 format and is this called the “Home Run Site” because in high-scoring dogs and cats the view will likely have abundant fluid amenable to abdominocentesis. Since ultrasound cannot sonographically characterize free fluid, sampling is necessary with fluid analysis, including cytology and chemistry analysis. The HR view is nicknamed by the author the “big lie” since routinely the right kidney and liver are not directly imaged but rather the probe is place in the mid-section umbilical region and directed in the most gravity-dependent “HR Pouch” for the detection of free fluid. In cases in which the right retroperitoneal space is of interest, then the author will interrogate the target-organs as a 5th AFAST3 view. It has not been determined what clinical importance of routinely performing the AFAST3 5th view is (low yield or high yield or if the left retroperitoneal space is adequate without the right retroperitoneal space since they are in such close proximity).

Clinical Indications/Applications of AFAST3:

Blunt trauma, Penetrating trauma, Collapse, apparent collapse, undifferentiated hypotension, Respiratory distress (since there are non-respiratory look-a-likes [hemoabdomen, cardiac tamponade, anaphylaxis, high fever, and others]), Post-interventional at-risk bleeding (surgery, percutaneous procedures, laparoscopy), Post-interventional at-risk peritonitis (surgery, percutaneous procedures, laparoscopy), Patient monitoring during fluid resuscitation and during hospitalized care.

*The use of AFAST3 should be simply stated as an “extension of the physical exam” for nearly ALL dogs and cats that are abnormal. FAST3 formats (AFAST3 and its applied fluid scoring system [AFS], TFAST3 and Vet BLUE) should be adopted as BASIC “screening tests” just as we have been trained to perform minimally basic blood tests (so-called Quick Assessment Tests [PCV/TS, serum character, BUN, Creatinine, Blood Glucose, and ALT]).

Thoracic FAST or TFAST

A Schematic of the TFAST3 Exam: Strengths and Weaknesses of TFAST3 Views The CTS view is best used to rule out pneumothorax (PTX) and survey for lung pathology (the wet lung vs. dry lung concept [see Vet BLUE Proceedings]). The CTS view is the highest point on the thoracic wall where lung may be visualized against the thoracic wall along an intercostal space where a cap of air would rise in the event that PTX was present. To avoid false positives, the search for the “Lung Point” next takes place. Its concept is explained below. The PCS view is best used to screen for the presence of pleural or pericardial fluid. It also may be used for volume status assessment (left ventricular short-axis “mushroom” view) and for the “quick peak” left atrial to aortic ratio (LA:Ao) to rule out left-sided heart failure. However, Vet BLUE can rapidly rule out any clinically-relevant left-sided heart failure by the finding of “dry lungs all fields” (see Vet BLUE Proceedings). The FAST DH View may be superior for the detection of pericardial (and pleural effusion) fluid because of less air interference from the lung at the PCS views; and the acoustic window provided by the liver and gallbladder (Lisciandro, JVECC 2015). The DH strategy is to image near the solid muscular apex of the heart where a heart chamber is unlikely to be misinterpreted for pleural or pericardial effusion (Lisciandro, JVECC 2015). The finding has been described and referred to as the “Racetrack Sign” by the author (Lisciandro, Focused Ultrasound Techniques for the Small Animal Practitioner; Lisciandro, JVECC 2015).

This material is reproduced with permission of John Wiley & Sons, Inc, Focused Ultrasound Techniques for the Small Animal Practitioner, Wiley ©2014

KEY POINT: ALWAYS look into the thorax for the rapid detection of pleural and pericardial effusion (Lisciandro, JVECC 2015). Once these basic structures are proficiently imaged by the sonographer, the caudal vena cava should also become part of the DH view. Depth should be adjusted on your machine so that the pleural and pericardial spaces (25-33% of the far-field) are routinely examined (may not be possible in larger dogs). Questionable findings within the thorax using the DH view should be confirmed via TFAST3 (PCS view) or Vet BLUE or both or by serial exams (repeating TFAST3 and Vet BLUE 4-hours later).

Vet BLUE Lung Ultrasound Exam Use of Lung Ultrasound Formats in Small Animals:

The reluctance to pro-actively apply lung ultrasound to small animals with respiratory distress is irrational in many respects. The overriding belief that air-filled lung creates insurmountable obstacles, and the continued belief in small animal medicine that imaging lung is difficult to perform leading to mistakes, perpetuate lung ultrasound’s delayed use in small animals (dogs and cats). Thoracic FAST called TFAST (Lisciandro et al. 2008) was the first standardized abbreviated ultrasound exam of the thorax that included the Chest Tube Site (CTS) for lung surveillance for detection of PTX. Because of the finding of lung pathology found during TFAST3, the author extended lung surveillance from the TFAST3 CTS with the addition of 6 more lung views. The name of this novel regionally-based lung ultrasound exam is Vet BLUE (“Vet” for veterinary and “BLUE” blue for cyanosis and bedside lung ultrasound exam) (Lisciandro et al. 2014). The Vet BLUE regional sites include the caudodorsal lung lobe region (cdll), the perihilar lung lobe region (phll), the middle lung lobe region (mdll), and the cranial lung lobe region (crll). Each is named as a region because the naming do not directly correlate with anatomical names of lung lobes.

The Vet BLUE lung examination is a screening test performed identically as the probe is positioned at the CTS view of TFAST3. The probe is then moved through regional locations that are bilaterally applied as follows: caudodorsal lung lobe region (cdll - same as the TFAST3 CTS view, upper third, 8-9Th intercostal space)), perihilar lung lobe region (phll – 6-7th intercostal space, middle third), middle lung lobe region (mdll – 4-5th intercostal space, lower thrid), and cranial lung lobe region (crll – 2nd-3rd intercostal space, lower third). The maximum number of ULRs over the respective single intercostal space at each view is recorded. The counting system is as follows: 1, 2, 3, >3 (when ULRs are still recognized as individuals), and infinity ∞ (when the ULRs blend into one another becoming confluent [also called white lung]).

KEY POINT: Perform the Vet BLUE the same way every time. We suggest that you begin on the LEFT and go from dorsal to ventral, move to the right side and do the same, dorsal to ventral. This allows you to think about the pattern in the same manner every time and helps you remember the findings at each site. Also, by completing the Vet BLUE at the right cranial lung lobe region (crll) region increase your depth, and do your right TFAST pericartdial view and proceed with the increased depth to AFAST and Global FAST (GFAST) is finished in < 4 minutes by the appropriately trained FASTVetTM sonographer!

Vet BLUE for Respiratory Distress – 5 Basic Lung Ultrasound Findings

“Wet Lung” vs. “Dry Lung” - Basic Lung Ultrasound 101 Shred Sign, Tissue Sign, Nodule Sign - Advanced Lung Ultrasound 202 Wet vs. Dry Lung: Basic easily recognizable lung ultrasound findings are categoriazed into the Wet Lung vs. Dry Lung concept (Lisciandro, JVECC 2011). A Glide Sign with A-lines (reverberation artifact) at the lung line is considered “Dry Lung” only to be confounded with PTX (A-lines and No Glide Sign). However, many patients in which the probability of PTX is very low, then spending additional time finding the Glide Sign becomes less important and A-lines alone suffice. Ultrasound Lung Rockets (ULRs) are considered “Wet Lung” and oscillate to and fro with inspiration and expiration and must extend to the far field obliterating A-lines (Lisciandro, JVECC 2011).

*This material is reproduced with permission of John Wiley & Sons, Inc, Focused Ultrasound Techniques for the Small Animal Practitioner, Wiley ©2014 and FASTVet.com © 2014

Regionally-based Respiratory Pattern Approach Using Vet BLUE Clinical Cases:

Examples of Vet BLUE regionally-based patterns. A) Dry Lung all fields rules out clinically relevant left-sided heart failure, suggests upper airway obstruction, feline asthma, COPD, PTE and non-respiratory look-a-likes. B) Wet Lung in dorsal, perihilar, and middle lung lobe regions suggests cardiogenic lung edema (left-sided heart failure, volume overload from intravenous fluids). C) Wet Lung in dorsal lung lobe regions suggests forms of non-cardiogenic lung edema. D) Wet Lungs in ventral fields with or without signs of consolidation (Shred Sign/Tissue Sign), suggest pneumonia. E) Solitary nodule. F) Multiple nodules suggest metastatic disease or granulomatous disease.

Global FAST3 should be used for rapid evaluation of patient volume status pre-, during, and post- fluid resuscitation by using the “GFAST3 Triad.” 1) Top Row - the left ventricular short-axis “mushroom” view (TFAST3 right PCS view) for volume status [~ preload] and contractility) 2) Middle Row - Dry Lung vs. Wet Lung help determine the absence or presence of clinically relevant non-cardiogenic and cardiogenic pulmonary edema; and numbers of ULRs correlate with degree of interstitial-alveolar edema. 3) Bottom Row – caudal vena cava at the diaphragm (using the characterization of FAT, flat or bounce) and hepatic vein (HV) distention or “tree trunks” (TFAST3/AFAST3 DH view for right-sided cardiac status and volume [preload]); normally, the hepatic veins are not readily apparent as the drain into the caudal vena cava (CVC).

KEY POINT: Goal-directed templates for medical records are important to direct your ultrasound program and to give value to both colleagues and clients regarding your findings. Templates for TFAST and Vet BLUE are available within the textbook Focused Ultrasound Techniques for the Small Animal Practitioner, Wiley 2014 (www.wiley.com) and at www.FASTVet.com

Images: This material is reproduced with permission of John Wiley & Sons, Inc, Focused Ultrasound Techniques for the Small Animal Practitioner, Wiley ©2014 and FASTVet.com © 2014

References:
1. Lisciandro GR, Lagutchik MS, Mann KA, et al. Evaluation of an abdominal fluid scoring system determined using abdominal focused assessment with sonography for trauma (AFAST) in 101 dogs with motor vehicle trauma. J Vet Emerg Crit Care 2009; 19(5):426-437.
2. Boysen SR, Rozanski EA, Tidwell AS, et al. Evaluation of a focused assessment with sonography for trauma protocol to detect free abdominal fluid in dogs involved in motor vehicle accidents. J Am Vet Med Assoc 2004; 225(8):1198-1204.
3. Lisciandro GR. Chapters 2: The Abdominal (AFAST) Exam; Chapter 16: Focused or COAST3 - CPR, Global FAST and FAST ABCDE. In Focused Ultrasound for the Small Animal Practitioner, Editor, Lisciandro GR. Wiley Blackwell: Ames IA 2014.
4. Lisciandro GR. Chapter 55: Ultrasound in Animals. In Critical Care Ultrasound (human textbook), Editors Lumb and Karakitsos. Elsevier: St. Louis, MO 2014.
5. Lisciandro GR, et al. Frequency and number of ultrasound lung rockets (B-lines) using a regionally based lung ultrasound examination named vet blue (veterinary bedside lung ultrasound exam) in dogs with radiographically normal lung findings. Vet Radiol and Ultrasound 2014;55(3):315-22.
6. Lisciandro GR, et al. Frequency and number of ultrasound lung rockets (B-lines) using a regionally based lung ultrasound examination named vet blue (veterinary bedside lung ultrasound exam) in cats with radiographically normal lung findings. In Review.
7. Lisciandro GR. Focused abdominal (AFAST) and thoracic (TFAST) focused assessment with sonography for trauma, triage and monitoring in small animals. J Vet Emerg Crit Care 2011;20(2):104-122 .
8. Boysen SR, Lisciandro GR. The use of Ultrasound in the Emergency Room (AFAST and TFAST). Vet Clin North Am Small Anim Pract 2013;43(4):773-97.
9. Lisciandro GR. Evaluation of initial and serial combination focused assessment with sonography for trauma (CFAST) examination of the thorax (TFAST) and abdomen (AFAST) with the application of an abdominal fluid scoring system in 49 traumatized cats. J Vet Emerg Crit Care 2012;22(2):S11.
10. Lisciandro GR. The detection of pericardial effusion in 24 dogs using the diaphragmatico-hepatic (DH) view of FAST exams. J Vet Emerg Crit Care, accepted 2014.
11. Lisciandro, GR. Alanine aminotransferase level (ALT) as a marker for hemoabdomen detected by abdominal FAST (AFAST) in dogs with automobile trauma. Abstract. J Vet Emerg Crit Care, 2014; 24(S1):S11.
12. McMurray J, Boysen S, Chalhoub S. Focused Assessment with Sonography in Non-trauma dogs and cats in the emergency and critical care setting. Abstract. J Vet Emerg Crit Care, 2014; 24(S1):S28.