Brown Ultrasound Tape Review: 10/15/15
Article 1: FAST Exam to Predict Survivors of ED Thoracotomy
Inabi, et al. FAST Ultrasound Examination as a Predictor of Outcomes After Resuscitative Thoracotomy. Annals of Surgery 262(3):512-518, 2015.
Fresh off the trauma surgical press last month, this study examined the utility of FAST exam (specifically parasternal and subxiphoid cardiac views) to predict positive outcomes (survival to discharge or organ donation) of ED resuscitative thoracotomy (RT).
This was a prospective cohort study at LA County/USC Medical Center. In 3.5 years, 187 patients arrived in traumatic arrest and underwent FAST and RT (that’s 4-5 thoracotomies a month – WOW!). They documented +/- pericardial fluid and +/- cardiac motion. PGY2-4 EM residents performed the FAST exams after some formal training, and they were supervised by “faculty” – not clear if those were surgeons or EM attendings.
About ½ patients lost vitals at the scene and another ¼ both en route and in the ED. Overall survival – 6 patients (3.2%). Overall organ donation – 3 patients (1.6%). Cardiac motion on FAST was 100% sensitive for the identification of survivors and organ donors (and 73.7% specific). While the tables and discussion include a lot on the presence or absence of pericardial fluid, this did not impact the sensitivity or specificity of FAST. If cardiac motion was absent, the likelihood of survival was 0.
Bottom line: Given that RT is such a high risk, low survival procedure, cardiac FAST can be used (with excellent sensitivity) to identify traumatic arrest patients with better odds of survival or organ donation from ED thoracotomy. No cardiac motion means pretty much no chance of survival or organ donation.
Article 2: Handheld E-FAST for Pneumothorax
Kirkpatrick, et al. Hand-Held Thoracic Sonography for Detecting Post-Traumatic Pneumothoraces: The Extended Focused Assessment With Sonography for Trauma (EFAST). Journal of Trauma 57:288-295, 2004.
This was another trauma surgery study out of Vancouver Hospital and Health Sciences Centre interested in the test characteristics of hand-held US to look for PTX in trauma patients. They compared EFAST examinations for PTX to:
(1) CXR results
(2) a “composite standard” of clinical information, which included some combination of CXR, CT if it happened, clinical course, and need for chest tubes/needle decompression
(3) CT alone (the gold standard for patients who had a CT).
This was a retrospective chart review on trauma patients (note – those who were in “physiologic extremis” with suspected PTX were excluded). All EFASTs were done by the attending trauma surgeon using a linear transducer. They looked for lung sliding or comet tail artifacts or color power Doppler evidence of pleural sliding in at least 3 rib spaces. PTX was diagnosed if neither sliding nor comet tail artifacts were seen.
225 patients were enrolled but 17 excluded (that pesky handheld ultrasound went missing or the battery died a few times). 52 patients (22%) had a PTX, 13 of which were bilateral. EFAST correctly identified bilateral PTX in only 1 out of 13 (moral here: if you see a PTX, excited as you are, make sure you really look closely on the contralateral side). Compared to composite standard, E-FAST had a sensitivity of 58.9%, specificity of 99.1%, PPV 91.6%, NPV 93.8% (the test characteristics were similar comparing EFAST to CT gold standard in the patients who had one). CXR was superior compared to EFAST in 6 cases, but EFAST was superior to CXR in 16 cases. In 266 out of 411 lung fields that had a CT gold standard of comparison, EFAST showed superior sensitivity over CXR (48.8% vs. 20.9%) but both were very specific (about 99%).
So all in all, E-FAST has a comparable specificity but a much better sensitivity than CXR to identify PTX in trauma patients. CT is, of course, is still the best diagnostic tool.
Article 3: POCUS for Pedi Hip Effusions
Rebecca L Vieira and Jason A Levy. Bedside Ultrasonography to Identify Hip Effusions in Pediatric Patients. Annals of Emergency Medicine 55(3): 284-288, 2010.
This study out of Boston Children’s looked at the diagnostic accuracy of point of care ultrasound (POCUS) of the hip by PEM physicians. Three PEM docs who received some training performed bedside ultrasounds of a convenience sample of 55 hips belonging to 28 little patients who needed comprehensive hip US as part of their ED evaluation. They defined a hip effusion on POCUS as >5mm between the anterior surface of the femoral neck and the posterior surface of the iliopsoas muscle OR >2mm difference in this measurement when comparing the two hips. These results were compared to comprehensive radiology hip US. The PEM docs also rated how confident they were in their ultrasound findings.
POCUS had a sensitivity of 80%, specificity of 98%, PPV of 92%, NPV of 93% overall. When the PEM docs felt confident in their findings, the test characteristics improved: sensitivity of 90%, specificity of 100%, PPV of 100%, and NPV of 92% in the symptomatic hips. Only 3 true hip effusions were missed (i.e. 3 false negatives on POCUS) and of those, 2 were called a positive hip effusion by radiology but the capsule measurements taken did not meet the study authors’ definition of an effusion. So really, the sensitive may technically be a little higher than the authors gave themselves credit for.
A small study, but it suggests that PEM docs, with some training, can use POCUS to identify hip effusions in pediatric patients with pretty good test characteristics. As with many other ultrasound applications, confidence in your POCUS image acquisition/interpretation, improves its clinical utility.