POCUS FOCUS: Lung Ultrasound for Pneumonia

BY: MAX RUBINSTEIN, MD

The Case: A 5 year old previously healthy boy presents to the ED with three days of fever and progressive shortness of breath. His exam is notable for course rhonchi and decreased aeration in the right anterior lung. There was no personal or family history of asthma, eczema, or food allergies. He received an albuterol nebulizer with no effect.

The Diagnostic Intervention: Lung Ultrasound

Point of Care Lung Ultrasound:

Point of care lung ultrasound is highly useful in detecting pulmonary pathology commonly encountered in the emergency department, most notably pneumothorax, pulmonary edema, and pneumonia.  The basic technique of lung ultrasound in children is the same no matter what underlying process is suspected. The linear probe is used and oriented perpendicular to the rib in the longitudinal axis. This allows detailed visualization of the pleural line. This is perhaps the most important aspect of lung ultrasonography as 90% of respiratory dysfunction attributable to the lungs affects the pleura.1 Differences in the appearance of the pleural line help the clinician distinguish between causes of respiratory distress. There are several techniques described to adequately assess the lungs by ultrasound, the simplest of which is to image at three interspaces in the midclavicular, mid-axillary, and posterior lung fields.1,2

Figure 1.  Normal Lung Anatomy on Ultrasound

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Pneumonia on Ultrasound:

Pneumonia on lung ultrasound has a characteristic appearance. One can see “hepatization” of the lung as this normally echogenic and artifact filled tissue (see Figure 1) becomes echo-poor and increasingly tissue-like, resembling the liver on ultrasound (see Figure 2).  This is accompanied by “dynamic air bronchograms,” a branching lesion that courses through affected lung and moves with breathing. 3 This mobility helps distinguish pneumonia from atelectasis. A recent study found that dynamic air bronchograms have a 97% positive predictive value for pneumonia.4

How good is lung ultrasound for detecting pneumonia?

  • Sensitivity & Specificity in children > 90%5
  • When performed by emergency medicine physicians who have received a 1 hour training session, sensitivity drops to 86% but specificity is 97%.6
  • Ultrasound may also be better at detecting small pneumonias than standard chest x-ray.6 However, the clinical significance of this finding has yet to be determined.

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EUS: Pyloric Stenosis, Early Pregnancy, Serratus Plane block

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Brown Ultrasound Tape Review – 11:19:15
At this week’s BUTR, we again reviewed some great ultrasound images that were scanned over the past week.
Resident reviewer: Dr. Mike Hunihan
Faculty reviewers: Drs. Erika Constantine and Otto Liebmann
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PYLORIC STENOSIS
When to suspect pyloric stenosis:
– Onset between 3-5 weeks old, but can occur up to 12 weeks old.
– More commonly affects males.
– Risk factors include family history of pyloric stenosis, maternal smoking, macrolide antibiotics administered to infant, and bottle-feeding.
– Classic presentation is “hungry vomiter”; postprandial forceful non-bilious vomiting.
How to diagnose: 
– “Olive-shaped” mass that can be palpated along the R rectus sheath is pathognomonic, but rarely found.
– Ultrasound is the gold standard test when done by an experienced ultrasonographer.
– Additional studies, when ultrasound and exam are nondiagnostic, include barium swallow and upper endoscopy.
Ultrasound diagnostic criteria: 
Pyloric Muscle Thickness = >3mm
Pyloric Muscle Length = >14mm
Helpful mnemonic to remember this: Pi =3.14 (PYloric stenosis, >3mm thick, >14mm long)
Screen Shot 2015-11-30 at 12.26.58 PM Screen Shot 2015-11-30 at 12.27.12 PM
Abnormal findings: (Upper) Channel length (Lower) Muscle wall thickness
Another component of the US exam is to watch for passage of gastric contents through the pylorus. If you visualize passage of gastric contents, this is reassuring that there is no pyloric stenosis. However, sometimes you can get passage of small volumes of liquid through a tight pylorus and still have pyloric stenosis – it’s called the string sign with barium studies.
The other pertinent signs of pyloric stenosis:
1. Antral Nipple Sign: Redundant pyloric mucosa that protrudes into gastric antrum resembling a nipple.
 image
2. Target Sign: Hypertrophied hypoechoic muscle surrounding echogenic mucosa layer, visualized in short axis.
target sign
www.radiopaedia.org
3. Cervix Sign: Indentation of the pylorus into the fluid filled antrum. image (1)
In 2013, there was a prospective observational trial of PEM fellows performing bedside US for diagnosis of pyloric stenosis. They had a convenience sample of patients who were suspected to have pyloric stenosis based on history and physical exam, and who were ordered to have a formal ultrasound in the radiology department. The PEM fellows also performed bedside ultrasound on those same patients and compared their results to the radiology results. They enrolled 67 patients into their study, of which, 10 patients (15%) were found to have pyloric stenosis. The results of their study showed a 100% sensitivity and 100% specificity for PEM fellows performing bedside ultrasound. They had zero false positives or false negatives. This study suggests that bedside ultrasound for evaluation of pyloric stenosis is feasible for our residents, fellows, and attendings in the ED.
Sivitz, Adam B., Cena Tejani, and Stephanie G. Cohen. “Evaluation of hypertrophic pyloric stenosis by pediatric emergency physician sonography.”Academic Emergency Medicine 20.7 (2013): 646-651.
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EARLY PREGNANCY

We also discussed the use of ultrasound in early pregnancy patients. From the ED perspective, our main question should be: IUP or no IUP?  If we cannot visualize a definitive IUP (gestational sac + yolk sac) then we need to be concerned about ectopic pregnancy.
But what about heterotopic pregnancy?
-A heterotopic pregnancy is the presence of both an IUP AND an ectopic pregnancy at the same time!
– In females who become pregnant by natural means, the chance is 1 in 10,000.
– In females who have assisted reproduction (IVF or even just hormone therapy) that chance increases to 1 in 1,000.

Moral of the story: When performing ultrasound in early pregnancy be sure to take a good history of any assisted reproduction techniques used for that pregnancy 
 
In addition to determining the location of an early pregnancy, we discussed the diagnostic criteria for non-viable IUP. A helpful review article in NEJM by Doubilet et al reviews the topic at length. 
 
Important measurements on US that are diagnostic for nonviable pregnancy: 
CRL >7mm with no heartbeat 
GS diameter >25mm with no embryo 
 
image (2)
Doubilet, Peter M., et al. “Diagnostic criteria for nonviable pregnancy early in the first trimester.” New England Journal of Medicine 369.15 (2013): 1443-1451.

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SERRATUS NERVE BLOCK
Finally, we discussed a novel serratus plane nerve block that could be useful for anesthesia for axillary abscesses, rib fractures, or even chest tube placement. The aim is to block the thoracic intercostal nerves and provide anesthesia to the lateral hemithorax. The images below show the two options for serratus nerve plane block; injecting superior or inferior to the serratus anterior.
image (3)
 image (4)
Although this study gave the initial description of a serratus nerve plane block, there is still further studies to be performed. Something to keep an eye out for!
Blanco, R., et al. “Serratus plane block: a novel ultrasound‐guided thoracic wall nerve block.” Anaesthesia 68.11 (2013): 1107-1113.

Overly Traumatic: A Teenager Elbowed in the Stomach

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Overly Traumatic: A Teenager Elbowed in the Stomach

Case: 

A 17 yo healthy M presents with abdominal pain and a syncopal episode several hours after getting elbowed in the stomach at a soccer game.

PMH: Intermittent asthma

ROS: Sore throat, cough and fatigue x 1 week.

Physical Exam:

VS: T 98.3 °F | HR 90 | BP 129/60 | RR 16 | SpO2 100%

Pale but comfortable and alert. Abdomen diffusely tender, guarding in the upper quadrants. Exam otherwise unremarkable.

FAST exam: 

RUQ: Free fluid in Morrison’s pouch & at the tip of the liver

LUQ: Free fluid in splenorenal recess & bowel floating in free fluid

Transverse Bladder: Large amount of fluid & clotted blood anterior to the bladder

Click ahead to reveal diagnosis

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ROCKSTARS: Ultrasound vs Chest X-ray in the Detection of Traumatic Pneumothorax

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Picture this…A 45 year old male is activated as a trauma after falling off 30 feet off scaffolding. He is flown from the scene and the report from the paramedics notes concern for spinal cord injury, as he has no sensation below the nipple line and flaccid extremities. On primary exam the resident notes diminished breath sounds on the right, however he asks the question to the rest of the trauma team: “are the decreased breath sounds from a pneumo/hemothorax or from a partially paralyzed/weakened diaphragm, in a patient with a high c-spine injury”. In a minute of clinical reasoning in an otherwise algorithmic setting, the resident challenges his clinical exam (inspection, palpation, auscultation) and places an ultrasound on the patient acquiring the following images:

Video: Lung point–the most specific sign for pneumothorax on thoracic ultrasound.

Lung Sliding

Image 1: M-mode of lung point showing both seashore and stratosphere

A chest tube is placed and the remainder of the trauma survey proceeds.

At our institution, we wait for a chest x-ray that shows no pneumothorax before sending a patient to the CT scanner. This is despite the studies that show the sensitivity of supine chest x-rays is 28 % to 75%.[i] This begs the question, would a bedside ultrasound be quicker and more sensitive to evaluate for a pneumothorax. A quick review of the literature says a definitive yes.

Three articles are at the core of the US for pneumothorax evidence. First in 2005, Blaivas et al published a paper that used EM attendings in a prospective single blinded trial to evaluate 176 patients for pneumothorax. They used 4 protocol views in each hemithorax (2nd intercostal mid clavicular, 4th intercostal ant. Axillary, 6th intercostal midaxillary and 6th intercostal post axillary) and evaluated only for lung sliding. No M-mode, no doppler. Their results were compared to the Trauma attending read of the supine CXR and the Radiologist’s view of the chest CT.

In this study: the sensitivity and specificity for thoracic US was :

Ultrasound (95% CI) CXR (95% CI)
Sensitivity 98.1% (89.9%-99.9%) 75.5% (61.7-86.2%)
Specificity 99.2% (95.6%-99.9%) 100% (97.1%-100%)

Wilkerson and Stone in 2009 published a meta-analysis of 4 trials including the Blaivas trial noted above. This meta-analysis looked at EM physicians as US operators in the analyses of pneumothorax or no pneumothorax in the setting of trauma. This study again found superior outcomes for thoracic ultrasound:

Ultrasound CXR
Sensitivity 86%-98% 28%-75%
Specificity 97%-100% 100%

Lastly in 2012, Hyacinthe et al. published a paper that aimed to assess the ability of thoracic ultrasound to detect, on arrival, the occurrence of common thoracic lesions in a cohort of chest trauma patients. This is likely the most relevant study as the methods consisted of a prospective observational cohort study where two separate EM physicians were used. First the physician taking care of the patient primarily used the Clinical Exam (Inspection, palpation, percussion and auscultation) and chest x-ray to determine the presence of pneumothorax. The physician performed their exam, looked at the supine chest x-ray then was asked to give the patient a score of how likely they are to have a thoracic lesion (0=no chance, 3=sure presence of lesion). A separate EM attending blinded to the initial exam and CXR then performed a thoracic ultrasound in both lung fields, including the upper, middle and lower parts of the anterior and lateral regions of both chest walls. Pneumothorax was defined as the absence of lung sliding or by the presence of lung point. The performing physician then, in a similar way, recorded their findings on a scale from 0-3. Results for this study included the sensitivity and specificity for each modality however, given the scales of probability entered by each physician, the more encompassing statistic is the area under the curve (AUC) for each modality.

Ultrasound CE+CXR
Sensitivity 53% 19%
Specificity 95% 100%
Area Under the Curve, mean (95% CI) 0.75 (0.67-0.83) 0.62 (0.54-0.70)

These articles make a strong case for the increased use of ultrasound in trauma. In the hands of an experienced user, a bilateral thoracic ultrasound takes 2-4 minutes, is arguably shorter than the time to call an x-ray tech, shoot the x-ray, develop the images and walk down the hall to view them, not to mention the test is overwhelmingly more sensitive.

References:

[i] Gentry Wilkerson, R. and Stone, M. B. (2010), Sensitivity of Bedside Ultrasound and Supine Anteroposterior Chest Radiographs for the Identification of Pneumothorax After Blunt Trauma. Academic Emergency Medicine, 17: 11–17. doi: 10.1111/j.1553-2712.2009.00628.x

[ii]Blaivas, M., Lyon, M. and Duggal, S. (2005), A Prospective Comparison of Supine Chest Radiography and Bedside Ultrasound for the Diagnosis of Traumatic Pneumothorax. Academic Emergency Medicine, 12: 844–849. doi: 10.1197/j.aem.2005.05.005

[iii]Hyacinthe AC, Broux C, Francony G, et al. Diagnostic accuracy of ultrasonography in the acute assessment of common thoracic lesions after trauma.Chest. 2012;141(5):1177–83

 

US articles: PTX in trauma, FAST for Thoracotomy, Pedi Hip Effusions

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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.

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EUS: Retinal Detachment & SSTIs

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Brown Ultrasound Tape Review:  9:24:2015

 

ARTICLE #1  –  Suddenly, painlessly blind?  Keep calm and get the Ultrasound.

Vrablik et al.  The Diagnostic Accuracy of Bedside Ocular Ultrasonography for the Diagnosis of Retinal Detachment: A Systematic Review and Meta-analysis.  Annals of Emergency Medicine 2014; 20: 1-6.

 In this systematic review, Vrablik et al assessed the diagnostic accuracy of ED Ocular US for retinal detachment.  They whittled 7771 unique citations down to 4 trials that included a total of 201 ED patients, where EUS Dx was compared to Ophthalmologic evaluation and/or Orbital CT.  Prevalence was 15-38%, sensitivity and specificity of EUS were 97-100% and 83-100%, respectively.

 This modality may be helpful because 1) vision-threatening complaints are time sensitive, 2) formal dilated fundoscopic exam may be impractical or impossible in the busy ED setting, and 3) formal Ophtho consultation may be limited or unavailable in some EDs.  These studies were small and participating physician training was variable, but results showed that we can reliably make this diagnosis in the ED with a linear array probe.

  We discussed distinguishing retinal detachment from vitreous hemorrhage or vitreous detachment (keeping in mind these are not mutually exclusive).  Retinal detachment classically presents as sudden, painless, monocular visual impairment, like “looking through a curtain.”  EUS will show the “sail sign”, a funnel shaped, sharply defined, reflective, linear membrane anchored to the optic disc and waving serpiginously as the patient moves their eyes.  In vitreous detachment the patient may describe “floaters” or “flashes of light” that move with eye movement, and EUS will show the “seaweed sign”: fine, granular, swirling echogenic debris in the posterior eye, with no tethering to the disc.

Retinal_detachment  Retinal Detachment  (www.foamem.com)

Vtreous_Detachment_main  Vitreous Detachment  (www.ultrasoundvillage.com)

 

 

ARTICLE #2  –  To incise, or not to incise, that is the question.

Squire et al.  ABSCESS: Applied Bedside Sonography for Convenient Evaluation of Superficial Soft Tissue Infections.  Academic Emergency Medicine 2005; 12(7): 6011-607.

 This study investigated the utility of EUS in detecting subcutaneous abscesses in 107 patients with presentations concerning for cellulitis vs abscess.  Residents and Attendings who had received a 30min training session were eligible, and their Clinical and EUS diagnoses for “+/- abscess” were compared to +/- pus with I&D, or +/- antibiotic failure at 7 day follow up (failure meaning most likely it was an abscess).

 

Sensitivity NPV Specificity PPV
Clinical Dx 86% 77% 70% 81%
EUS Dx 98% 97% 88% 93%

 

Interestingly, there were 18 cases where EUS and Clinical Dx disagreed, and EUS proved correct in 94% (n=17) of them: 9 of the negative Clinical Dx cases (23%) became positive with EUS, and 9 of the positive Clinical Dx cases (13%) became negative with EUS.  Many of the ED sonographers also discovered nerves and vessels, which changed management…most significantly for 4 of the falsely positive Clinical Dx patients, of whom 3 had hematomas and 1 had an aneurysm (#whoathatwasclose).  But while the investigators did prove that EUS can more accurately identify abscesses, they did not report any patient-centered outcomes, such as less antibiotic use, faster recovery, fewer complications, fewer return visits, or less recurrence.  So in summary, it remains to be seen whether the findings here should definitely change practice at this time.

 We also reviewed the EUS-for-abscess technique: with the linear probe placed on the skin, an abscess will appear as a hypoechoic heterogeneic mass, generally spherical with ill-defined borders, and with variable internal echoes (pus) that will “swirl” with compression.  Cellulitis is generally more hyperechoic and more uniform.

 

BROWNsound BONUS:   TAPE REVIEW RAPID FIRE!

– Achilles Tendon rupture: appears as a defect with surrounding hypoechoic hemorrhage

– B lines (lung US):

     1) must obliterate the A lines

     2) must be linear

     3) must go 18cm deep

     4) must be persistent

     5) must be more than 3 per zone

     6) must be more than 2 rib spaces per side to support HF

– Appendicitis:

     1) must be non-compressible

     2) must be a blind-ended pouch

     3) must be tender-to-palpation

     4) must be 6mm outside-to-outside to be “too big”

– Tamponade:  RV must collapse during diastole

– IUP:

     1) In the sagittal view the bladder apex correlates with the cervix, which may helps avoid confusion between the vagina and the endometrial stripe

     2) Key cutoff:  fluid tracking <2/3 up the uterus (in the caudal direction) may be physiologic; >2/3 is more likely pathologic

 

EUS: Comprehensive LE DVT studies & LP Guidance

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Brown Ultrasound Tape Review – 9:17:15

 

ARTICLE #1  –  If “2-Point Compression” is Good, Would “5-Point Compression” Be More Good?

Srikar et al.  Isolated Deep Venous Thrombosis: Implications for 2-Point Compression Ultrasonography of the Lower Extremity. Annals of Emergency Medicine 2015; 66: 262-267

For the evaluation of DVT, the American Institute of Ultrasound in Medicine recommends compressibility and spectral Doppler waveforms of the Common Femoral, proximal Deep Femoral, Femoral, Popliteal, and proximal Great Saphenous veins.  But ever since Bernardi et al found equivalence with “2-Point Compression” plus D-Dimer, many ER physicians have been employing this faster technique at the bedside, which uses compressibility and direct visualization of the Common Femoral and Popliteal veins only.  This study questioned whether we should consider assessing more veins by investigating the prevalence of thrombi elsewhere in symptomatic patients.  This was a 6 year retrospective study of 2451 symptomatic patients who received “comprehensive” studies of the Common Femoral, Deep Femoral, Femoral, Popliteal, and Calf veins, which were interpreted by vascular surgeons. Continue reading

ROCKstars – Case 1: US-Guided Central Venous Access (CIV)

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An elderly patient is in the RIH Critical Care bay with severe sepsis and needs central access.  Luckily, Drs. Adam “Hyperechoic” Haag and Eddie “Rule ‘Em Out” Ruhland are on shift.  They settle on the right Internal Jugular vein, but traditional sternocleidomastoid muscle (SCM) and clavicular bone landmarks are not apparent.  So a linear-array probe is correctly placed transversely over the triangle formed by the bifurcation of the SCM, to where the IJ and Carotid are seen in parallel…but there is some sort of hyperechoic, noncompressible mass…

They identify the thrombus, and instead find the Femoral vein, where CIV access is successfully achieved on the first attempt with no immediate complications.  The use of US to guide this procedure changed this patient’s course and potentially saved a complication.  

But exactly how much safer, faster, and more reliable is US-guided CIV placement?

THE ISSUE

  • Vascular access is critical in emergent situations
  • Body habitus, dehydration, poor perfusion, anatomical abnormalities, or history of IVDU can cause difficulties and delays when using landmark-based techniques
  • Complications of CIV placement include arterial puncture, excessive bleeding, vessel laceration, pneumothorax, hemothorax, and necessitation of multiple attempts
  • US guidance was identified in 2001 by United States Agency for Healthcare Research and Quality as one of the top 11 means of increasing patient safety, but this was based on one study of subclavian lines at one large urban center (1)

The “SOAP-3” Trial (2005)

  • A concealed, randomized, controlled study of 201 patients
  • Studies dating back to the 1990s in EM and Anesthesia (4) had demonstrated the efficacy of ultrasound-guidance, but this was the first study in the ED setting comparing the anatomical landmark method, the static “quick look” US-guided method, and dynamic “real time” US-guided method
  • In the “quick look” group, US was used to identify landmarks, the skin was marked, and the catheter was placed without real-time US guidance
  • EM residents and Attendings passed a 1h training course, then placed 10 CIVs with dynamic US guidance to qualify to participate

RESULTS

Dynamic

US Guidance

Static

US Guidance

Anatomical Landmarks Method
Overall Success 98% 82% 64%
First-Attempt Success

(OR vs LM)

5.8 3.4
Avg # of Attempts 1.7 1.6 3.2
Avg Total Sec 30 20 150
Complications 2 2 8

DISCUSSION

  • Dynamic guidance is superior but requires the most training
  • Static guidance is vastly superior to Landmark, and while slightly inferior to Dynamic, it requires less training
  • 10% of the study patients had “extremely narrow” (<5mm) IJs bilaterally, which could explain the inferior performance of the LM technique, even with experienced practitioners
  • All the complications were arterial punctures, and these were not statistically significant

References

  1. Agency for Health Care Research and Quality (AHRQ). Evidence Report/Technology Assessment: Number 43. Making Health Care Safer. A Critical Analysis of Patient Safety Practices: Summary 2001. 2007.
  1. Milling, et al. Randomized, controlled clinical trial of point-of-care limited ultrasonography assistance of central venous cannulation: The Third Sonography Outcomes Assessment Program (SOAP-3) Trial.  Critical Care Medicine, 2005, Aug;33(8); 1764-9.
  1. Sulek et al.  A Randomized Study of Left versus Right Internal Jugular Vein Cannulation in Adults.  J Clin Anesth, 2000, Mar; 12(2): 142-5
  1. www.sonoguide.com/line_placement.html

EUS for Increased ICP & Proximal Lower Extremity DVT

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Brown Ultrasound Tape Review  –  9:3:2015

 

Article #1:  Increased ICP via Optic Nerve Sheath Diameter (ONSD)

Amini, et al. (2013). Use of the Sonographic Diameter of Optic Nerve Sheath to Estimate Intracranial Pressure. American Journal of Emergency Medicine 2013; 31: 236–239.

In this 2013 study, Amini et al measured the ONSD of 50 non-traumatized patients undergoing LP and found that an ONSD >5.5mm correlated with an ICP >20mm Hg with a sensitivity and specificity of 100%.  While this sounds great, we discussed well known concerns regarding inter-operator reliability and the technical aspects of accurately measuring the ONSD; measuring Optic Disc elevation is an alternative strategy.

The bottom line:   while normal ONSD measurements cannot rule out increased ICP, it may be a useful adjunct in patients with low pre-test probability.

 

Article #2:  Proximal Lower Extremity DVT

Crisp, et al. (2010).  Compression Ultrasonography of the Lower Extremity with Portable Vascular Ultrasonography Can Accurately Detect Deep Vein Thrombosis in the Emergency Department.  Annals of Emergency Medicine 2010; 56 (6): 601-611.

In this 2010 study by Crisp et al, 47 ED physicians performed “2 Point Compression” on the Common Femoral and Popliteal veins in 199 patients, and their results were compared to the “comprehensive” results from the Department of Radiology studies that each patient also received.  The physicians took a 10 minutes training session, and the test was “positive” if a thrombus was visualized, or if the vein was non-compressible.  When compared to the Radiology results, the ED docs were 100% sensitive and specific for DVTs in these locations.  Our discussion centered around whether calf veins (which 2 Point Compression does not search for) are worth searching for (no one knows).

The bottom line:  2-point compression with a D-Dimer (and follow up comprehensive study if positive) may be an acceptable strategy for the management of DVT in the ED.

 

Special thanks and credit to Jon Thorndike

Double-Line Sign? It’s benign.

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To truly understand the FAST exam, you need to be familiar with the common structures and well-known findings, but you also have to know the FAST “fake-outs”.  This post will discuss one common fake-out, the “Double-Line Sign,” and after reading it, you’ll be better armed to avoid a false positive study.

Think FAST, what do you need for a complete study?

Quick review: the FAST is comprised of a series of 4 “views”, each requiring visualization of key structures to be considered complete.

  • Hepatorenal – Look at 5 locations:
    1. Pleural space – Watch for anechoic fluid with lung floating in it and a visible spine (aka “spine sign” indicating supra-diaphragmatic fluid).  Lung tissue which appears to be liver is actually normal; this is called “multi-path reflection”, “duplication” or “mirror” artifact, and it’s due to magic/wave reflection).
    2. Sub-diaphragmatic space
    3. Morison’s Pouch (between liver and kidney)
    4. Tip of Liver – Easy to miss a positive FAST if you don’t check here
    5. Inferior pole of Kidney
    6. Splenorenal –Similar to the 5 locations in the RUQ, but substituting the spleen for the liver The most dependent position is peri-splenic recess, so don’t just stop at the kidney.  (Below, #1: Free fluid in the Pleural Space.  Below, #2: Normal RUQ – note the lack of anechoic fluid above the diaphragm, no visible spine, and the appearance of liver above the diaphragm due to artifact).                                                   Freefluid1
      Freefluid2
  • Pelvic – Both axial and longitudinal views are needed, as well as a full bladder for a complete scan. Watch for sharp areas of anechoic fluid.  (Below: Positive FAST, showing pelvic free fluid)                                                                                                                                                       https://i0.wp.com/www.jultrasoundmed.org/content/21/7/789/F4.large.jpg?resize=423%2C274
  • Pericardial – Subxiphoid views for pericardial effusion.  (Below: Pericardial effusion as seen from subxiphoid view)

https://i1.wp.com/img.medscape.com/pi/emed/ckb/cardiology/150072-1332319-157325-1840270.jpg?resize=301%2C209

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