Tag Archives: ultrasound

General
Gallery Leave a comment

Technology: Real Time Cerebral Blood Flow Monitoring For TBI

Here’s a new toy that has recently received some funding from the US military. It allows real-time monitoring of cerebral blood flow. It may help identify flow problems from elevated intracranial pressure (ICP) or vasospasm early on, allowing prompt initiation of appropriate therapies to increase blood flow.

This device uses an array of ultrasound beams and locks onto the middle cerebral artery. It then continuously monitors blood flow and displays the result in real time. I predict that there will be a learning curve with this one, similar to near infrared monitoring of tissue perfusion. What’s a normal baseline? What kind of variation is considered “normal?” We’ll have to answer these questions before this tool is ready for prime time. Ultimately, it may allow noninvasive monitoring of ICP in the intensive care unit.

Credit: Physiosonics, Bellevue, WA.

General

Sonography In Place of CT For Pediatric Abdominal Trauma

Leave a comment

Pediatric blunt abdominal trauma is not common, but if present it has the potential to cause significant morbidity or mortality. Evaluation of the abdomen at the trauma center is crucial, and most trauma professionals are aware of the trade-offs in the use of CT scan in children (radiation exposure, need for sedation).

Ultrasound is widely available and allows for imaging of most areas of concern in the abdomen. Could sonography be used in place of CT in specific cases? Pediatric surgeons in Germany (who have been using ultrasound far longer than the US has) published a paper last year looking at their experience with children who were diagnosed with an intra-abdominal organ injury after blunt trauma. Their 7 year experience only produced 35 such children, and they were evaluated with examination and one or more serial FAST ultrasound exams. Equivocal results were scanned with CT.

They found that ultrasound was effective in diagnosing abdominal injury 97% of the time. Although 11 of the 35 children had subsequent CT scanning, it only changed management in one case. 

Bottom line: Obviously, this is a very small retrospective series, but it is provocative. The German pediatric surgeons go above and beyond the typical FAST exam in the US, using it for diagnostic purposes as well. Could a complete diagnostic ultrasound take the place of CT in select children in the US? Probably so, as they are very sensitive in detecting free fluid and solid organ injury. But what about blunt intestinal injury? I’ll review that tomorrow and sum up my thoughts on a possible algorithm.

Related posts:

Reference: Is sonography reliable for the diagnosis of pediatric blunt abdominal trauma? J Pediatric Surg 45(5):912-915, 2010.

General

Extended FAST Exam in Trauma Patients

Leave a comment

By now, every emergency medicine physician and surgeon knows what FAST is. This valuable technique allows us to quickly (get it?) determine whether a patient has blood in the abdomen or around the heart which might require operative management. Extended FAST (E-FAST) is an extension of the original technique that allows us to detect the presence of pneumothorax or hemothorax more quickly and accurately than with the conventional chest x-ray.

Both hemothorax and pneumothorax can be missed by x-ray. It takes at least 200cc of free fluid in the chest to show on the chest x-ray, assuming an ideal body habitus. As little as 20cc can be detected using the E-FAST. Studies have also shown that 30-50% of pneumothoraces are missed by x-ray. This diagnostic inaccuracy is due to the fact that hemothoraces settle out posteriorly and pneumothoraces anteriorly. Since the vast majority of chest x-rays in major trauma patients are taken with the patient supine to protect their spine, the bulk of the blood or air have layered out and cannot be seen well. A chest x-ray is still needed, however, to determine injury to the mediastinum and lung parenchyma.

E-FAST exam can be performed by using the standard curvilinear probe. It is usually placed longitudinally on the anterior chest to detect pneumothorax, using the space between two ribs as the “window” to the pleura. The depth setting should be adjusted so that only about 4cm is visible on the display. The junction of the visceral and parietal pleura should be visualized at the backside of the ribs. With a very steady hand, the junction between the two sets of pleura should be scrutinized closely.

If the two sets of pleura slide freely over each other, pneumothorax is unlikely. If not, it may be present. Pneumothorax is not a uniform phenomenon, except when it is of large size. It may be necessary to move the probe to a few other rib spaces to ensure that a smaller pneumothorax is not present.

FALSE POSITIVE ALERT! If the patient is not ventilating well, or if they have a right mainstem intubation, the affected lung(s) may not show the sliding sign, leading the examiner to think they have a problem when they may not.

To detect a hemothorax, the probe is directed upward somewhat when doing the right and left upper abdominal views. A dark triangle located above the diaphragm indicates fluid in the chest (blood). The dark crescent on the left in the image below is a large hemothorax.

E-FAST hemothorax

The bottom line: Extended FAST can be helpful in detecting a significant hemothorax or pneumothorax and can expedite the definitive management of those conditions. If you are already familiar with FAST, a little extra ultrasound training may be very helpful.