Echography is mandatory for the initial management of critically ill patients: No
The potentials of point-of-care ultrasound (US) and fair expectations of its utility in the ICU are sometimes reappraised by the general paucity of the literature on the topic, mainly due to the relative novelty of many applications of US. While many studies showed the practical utility and diagnostic accuracy of US, bedside application of US does not necessarily improve patient outcome. Moreover, the convenience of US based on saving costs and time and also in terms of improved efficiency has been hypothesized, but not so far fully demonstrated. This may have influenced the fact that US is still not considered the standard of care for many applications in the ICU.
In gastrointestinal perforation, US has the potential of visualizing free peritoneal air more reliably than plain radiography . This may be a great advantage in critically ill patients, because US may be performed at bedside in emergency scenes, when patients cannot be moved to a radiographic examination area. However, abdominal US diagnosis is based on artifacts imaging and free peritoneal air may not always be easily differentiated from other high-echoic findings of different origin . Thus, the main problem in analyzing any study on the US diagnosis of gastrointestinal perforation is the real accuracy of the interpretation of the US signs and findings, which is still too much based on a subjective impression of the examiner rather than on a systematic method. The duration of the procedure makes US for free peritoneal air unsuitable during extreme emergencies and as a primary survey application in traumatology. Moreover, it is known that intestinal perforation does not always imply free peritoneal air. While abdominal US may be useful in the identification of free air, it cannot be used to make a diagnosis of gastrointestinal perforation without any air leakage in the peritoneal space .
US is useful for the very early diagnostic process of critically ill patients with trauma, undifferentiated hypotension and shock. However, US may not identify the site of infection in septic shock, particularly when intestinal, retroperitoneal or musculoskeletal sources are in the differential . When there is a suspicion of cholecystitis in critically ill patients with sepsis, US may be of help. However, although US remains highly reliable in detecting the presence of cholelithiasis, other signs, like the thickened wall and intraluminal sludge, are considered less accurate in predicting cholecystitis as a source of infection. In particular, thickened wall, pericholecystic fluid and emphysematous gallbladder show as non-specific signs in the setting of critically ill trauma patients . Thickened gallbladder remains a non-specific US finding, and US has insufficient sensitivity to apply it as a routine method to rule out cholecystitis in the ICU (Fig. 1a, b, d). Exclusion of obstructive uropathy is a routine in patients with renal insufficiency and in search of a source of sepsis. US may detect dilation of the urinary tract, but attention should be paid to renal cysts and hypotonic renal pelvis as challenging differential diagnosis. US is also limited in the diagnosis of retroperitoneal bleeding compared to newer multidetector CT. These limitations of US are even more evident in morbidly obese patients and in subcutaneous emphysema . Moreover, US is a powerful tool to detect peritoneal effusion but is of limited usefulness in the differential diagnosis between blood, ascites or purulent collections. In septic shock, Doppler-based evaluation of the renal arteries for resistive index is a bedside method to assess renal injury. It is a promising method, but there is uncertainty about its applicability on the general ICU population. Evidence published so far has been limited to single-center studies, performed by few highly skilled operators, on selected populations . Moreover, the influence of catecholamine treatment on the US determinants of the renal resistive index has not been tested.
Supported in part from project reg.no. CZ.2.16/3.1.00/21565 from OP Prague Competitiveness.
Conflicts of interest
None of the authors has a conflict of interest to declare.
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