May 2017

Authors: Andy Neill / Codes: Podcast / Published: 01/05/2017

Welcome back to the RCEM Learning podcast for May 2017. We have lots to cover and you can find each of the individual segments below. Don’t forget to subscribe.

Clinical Question:

  • How useful is PoCUS in diagnosing the cause of SOB in the ED

Title of Paper:

  • Point-of-care ultrasonography for evaluation of acute dyspnea in the emergency department

Journal

  • Chest 2017

Author

  • Maurizio Zanobetti

Background

  • SOB is a common presenting complaint and particularly when it comes to diagnosing heart failure vs penumonia (two of the commonest causes) then the typical ED work up is imperfect
  • Thoracic PoCUS has gained lots of traction, especially for heart failure but is PoCUS accurate in diagnosing other causes of SOB

Patients studied

  • ED patients in Italy over a year presenting with undifferentiated SOB. Only included if they ultimately got admitted so obviously this is a sicker cohort than most.
  • They had a clinical assessment by an EP and an ECG. At this point the patient also got a structured PoCUS by an EP sonographer (who was well trained and experienced it seems). Based on the clinical assessment and PoCUS, the doc who did the PoCUS had to name his diagnosis. The doctor responsible for the patient could then order his usual work up and once that was completed he had to name his diagnosis.
  • The gold standard here was final diagnosis with every bit of available info obtained during the patient’s stay (unclear if the PoCUS formed part of this – incorporation bias a risk here). This final diangosis was decided by 2 EPs reviewing all this data. This isn’t an ideal gold standard by any means but it is the usual standard used in heart failure studies.

Study Type

  • This is an observational diagnostic study. Which means you need to look for the index test (the one under investigation) and the reference standard (the gold standard)
  • There are actually 2 index tests here
    • First is the diagnosis made by the doc doing the PoCUS
    • Second is the diagnosis made by the treating doc after the full ED work up
  • The reference test here is the final diagnosis by the 2 EPs with all the data
  • There was no clear statement of primary outcome here but it seems to be the diagnostic characteristics of ED diagnosis and PoCUS diagnosis

Results

  • 2700 pts
  • in terms of the frequency of final diagnosis it was pneumonia (35%), COPD/asthma (25%) and CHF (20%) with a smattering of others in the list
  • PoCUS wins at heart failure and is equivalent at pneumonia. Not so much for the others.
  • The eye catching bit of the paper is table 4 which collects all the diagnostic characteristics for each different diagnosis. The LR presented here are a little crazy
    • PoCUS for heart failure +LR = 21, for ACS 105, for PE 350
    • I have a few issues with these first of which being the question – was the PoCUS part of the reference standard – if so then it’s not surprising that it comes out great. Second, these just don’t pass sniff test for me – there’s a recent systematic review in Acad EM that found b lines to have the best characteristics for diagnosing heart failure but still only around a +LR of 8

Thoughts

  • For heart failure this is increasingly becoming a well tested investigation that we should get well trained in
  • Similar things can be said for penumonia but there’s definitely a steeper learning curve
  • As for all things PoCUS, a lot of it is new, and while its increasingly evidence based, you still have to do the work and get as much practice and training and reading as you can.

Kudos

Clinical Question:

Is Contrast Induced Nephropathy really a thing?

Title of Paper:

Risk of Acute Kidney Injury After Intravenous Contrast Media Administration

Journal and Year:

Annals of Emergency Medicine, 2016

Lead Author:

Jeremiah Hinson

Overview of study methods:

  • Single centre, retrospective review
  • ED patients undergoing CT scan with IV contrast media were compared to both patients having CT without IV contrast and to patients who did not have a CT scan.
  • Patients had to have a serum creatinine measurement in the 8 hours preceding the scan, and a repeat measurement in the following 48-72 hours
  • Patients were excluded initial creatinine too low (<35 umol/L) or too high (>354 mol/L), had a renal transplant, were on dialysis, had a visit to ED in previous 6 months, had a contrast CT within 72 hours of ED departure or had incomplete data
  • Primary outcome measure was the incidence of Acute Kidney Injury, both using published criteria for Contrast Induced Nephropathy and the Acute Kidney Injury Networks definition ok AKI
  • Powered to find difference between groups as low as 1.5%

Summary of Results:

  • 17,934 patient visits included overall
  • 12,700 patient visits with CT scan performed
    • 56.7% received IV contrast
  • No difference found in incidence of AKI between the three groups
    • Incidence by AKIN definition: Contrast 6.8%, Non-Contrast 8.9%, No CT 8.1%
    • Incidence by CIN definition: Contrast 10.6%, Non-Contrast 10.2%, No CT 10.9%

Thoughts:

  • A well structured, methodical retrospective review with decent attempts to minimise bias
  • Authors recognised that the group receiving contrast were likely to be selected by clinical gestalt as less likely to develop AKI in first place, and would be more likely to receive nephroprotective treatment. They used propensity-score-matching adjustment and multiple logistic regression analysis (clever statistical voodoo) to minimise the effect of this bias and other known predictors of AKI and still found no difference between groups.

Clinical Bottom Line:

I don’t see radiology policies changing over this paper but it certainly adds to the body of literature showing that there may not be the causation between contrast administration and AKI that has been presumed from previous publications demonstrating association.

This is probably the best performed study we are going to get on this topic until a prospective RCT is performed.

Other #FOAMed Resources:

  • LITFL have a nice summary of Contrast Induced Nephropathy

emDocs give a good written summary of this paper and outline the history of previous studies too

Upper Limb Fractures

A common problem in our EDs is distal radius fractures with displacement needing manipulation.

The NICE guideline recommends the use of Biers Blocks for anaesthesia/analgesia of distal radius fractures that require manipulation. Here is a link to the RCEM guidance on Biers blocks.

Chris uses these as first line in his practice, but does use other modalities such as haematoma block or sedation.

Both Becky and Chris find that a busy room is often the rate limiting step to either a Biers or sedation.

DO NOT USE ENTONOX ALONE!

Lower limb injuries

Remember to use validated decision tools when deciding if to X-ray or not. NICE recommends use of the Ottawa ankle rules. See below for a refresher.

Managing stable unilateral fractures (Weber A) is given the guideline treatment and advise unrestricted weight bearing, arrange follow up in 2 weeks if unclear about stability, return for review if ongoing symptoms at 6 weeks.

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