Page 157 - Basic Monitoring in Canine and Feline Emergency Patients

Table 7.6. Indications for ultrasound-guided vascular access.

VetBooks.ir Indication Comment
Placement of central venous catheters and Rapid identification of the desired vasculature for venipuncture
Helps to identify vessels in patients with peripheral edema, vascular
other peripheral venous catheters
collapse, obesity, hematomas, or of very small size
Confirmation of successful cannulation of a vessel
Arterial catheterization/blood sampling Identify and guide catheterization of arteries
Arterial catheterization allows for hemodynamic monitoring and arterial
blood sampling in the critically ill
Confirmation of successful cannulation of a vessel
Improves the ability to identify and sample blood from peripheral arteries
Surveillance for venous and arterial Serial imaging of veins and arteries to identify and describe thrombosis
thrombosis development

● ● TFAST is meant to be used in conjunction with, the UST for vascular access and thrombus
3
rather than in replacement of, thoracic radio- identification.
graphs because US is limited to the peripheral ● ● Identification of veins is more difficult than
lung tissues. arteries due to lack of pulsatile blood flow
● ● Without the complimentary application of through the veins. Operator training is required
VetBLUE, TFAST is limited in its ability to scan to help with confident identification of espe-
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for pleural effusion and pulmonary parenchymal cially venous structures.
changes throughout the entirety of the lung fields. ● ● Use of ultrasound to guide a catheter or needle
3
● ● In the dyspneic patient, TFAST is limited in into a blood vessel requires training and practice
the ability to diagnose respiratory look-alike for competence.
conditions (examples: diabetic ketoacidosis,
hypocalcemia, hypoglycemia, hypovolemic shock, 7.5 Case Studies
and neurologic disease). Therefore, it is best
used in concert with other bedside imaging Case study 1: AFAST/TFAST/VetBLUE
modalities and biochemical testing. applications in an acutely collapsed
● ● Subcutaneous emphysema can limit the ability patient
to achieve a gator sign on TFAST due to inter- Cash, a 7-year-old castrated male Labrador
3
ruption of sound waves traveling into the retriever, was presented to the emergency depart-
thorax. With sufficient pressure, there is the pos- ment for evaluation after acute collapse. He lives in
sibility that the free gas may be moved suffi- a rural environment and has free access to barns
ciently to enable accurate images. where the family is currently treating for an out-
break of rats. Upon assessment, Cash is tachycardic
Ultrasound-guided vascular access (heart rate 160 bpm), tachypneic (respiratory rate
of 45), pale, and has a capillary refill time (CRT) of
As with all the ultrasound techniques discussed in this 3 seconds. His pulse is weak on palpation and his
chapter, using US to guide vascular access also has ventral lungs are difficult to auscultate while his
some limitations. These include but are not limited to:
dorsal lung fields have harsh bronchovesicular
● ● Superficially located and very small vasculature sounds. While simultaneously attempting to place
is difficult to identify and unable to be catheter- an intravenous catheter and collecting blood work
ized via UST. Even mild pressure by the US for lactate, packed cell volume/total solids (PCV/
probe will collapse the vessel and make it impos- TS), prothrombin/partial thromboplastin times
sible to identify. (PT/aPTT), complete blood count (CBC), and
● ● The ability to identify blood vessels and throm- serum chemistry (CHEM), the point of care ultra-
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bosis within the vessels is highly dependent sound is used to perform an AFAST , TFAST , and
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on the operator’s US technique. Training VetBLUE examination. The AFAST /TFAST /
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and practice is needed for successful use of VetBLUE findings are the following:
Applications of Serial Focal Ultrasound Techniques in the Hospitalized Small Animal Patient 149