EmergencyPedia

• On the 21st of May 2014 The Emergency Medicine Interest Group (EMIG) had its annual “Not So Grand Rounds” session at Westmead Hospital.  

• This was a well attended event due to the presence of great speakers (as well as the attraction of free Pizza).

• A case vignette (discussed below) was presented as part of Not So Grand Rounds.

 The Case Vignette

Setting the scene

You are working on a busy shift in the Emergency Department (ED) – a young patient has been admitted with a respiratory infection.  He is in the Short Stay Unit (SSU) and you are called to see him because of increasing Shortness of Breath and Chest Pain at 0200.

Briefly reviewing the notes you find the following history:

• The patient is male and 20 years old
• The previous day he had presented to the ED having been asked to attend by his General Practitioner (GP).
• On arrival in the ED at 10pm he was complaining of moderate Chest Pain.  
• He described a sudden onset of chest pain at 3am (some 12 hours prior to arriving at triage)
• At triage his complaints included:
  • On-going Shortness of Breath 
  • Left sided lateral chest and Scapular pain that woke him from sleep
• The pain was worse on inspiration and intermittently worsening – it is not affected by position
• The patient was recently well and has had no previous hospital admissions
• Although family members had recently had upper respiratory tract infections he had been well up until the onset of symptoms.  He had no fevers and although he had a mild cough there was no haemoptysis.
• There was no history of trauma, travel, immobility or surgery
• There was no past medical history of DVT / PE
• There is no history of smoking
• There is no history of asthma

Initial assessment and management included:

• An initial x-ray had shown no evidence of Pneumothorax (the main concern of the referring GP)

• A temperature of 38 degrees as well as respiratory symptoms

• As there was no evidence of pneumothorax and the team considered him to be “low risk” for Myocardial Infarction and Pulmonary Embolism it was felt reasonable to make a diagnosis of an infective cause

• A clinical impression that the patient had a respiratory infection with significant symptoms

• He was treated with appropriate antimicrobial therapy promptly after arriving

While reviewing the notes the following observations are recorded by the nursing staff:

BP 110/70

HR 109

Saturations 96% on room air

Respiratory Rate 28

Temperature 37.9 degrees celsius

At this point the patient is still complaining of chest pain on the left side…

What are your differentials?

Differentials

• Respiratory
  • Pneumothorax
  • Pneumonia
  • Pulmonary Embolism (PE)
• Cardiac
  • Acute Coronary Syndromes (ACS)
  • Pericarditis
  • Aortic Dissection
• Abdominal
  • Oesophageal Rupture (Boerhaave’s Syndrome)
  • Pancreatitis
• Other Causes
  • Trauma
  • Rib Fractures
  • Epidemic Myalgia
  • Viral Infection
  • Muscular Pain
  • Herpes Zoster (Shingles)
  • Somatoform Disorders

What is the most likely Diagnosis?

Given the sudden onset of symptoms in this case as well as the age of the patient Pneumothorax was thought to be the most likely diagnosis in the first instance.  However, the Chest X-ray (shown below) did not show a Pneumothorax.

The subtle triangular shaped area of opacification seen on the lateral x-ray (at the lung base) was thought to have reflected a diagnosis of early Pneumonia and he was treated for this as a result…

What Happened Next?

• At this point our young patient becomes more tachycardic and dyspnoeic.  He spikes a high temperature.

• After further review it seems likely that he dose have chest infection.  However, we elect to consider Pulmonary Embolism (PE) as a possible diagnosis at this stage…

• A 12 lead ECG is recorded (he was continuing to be markedly Short of Breath while this was taken):

• The 12 lead ECG (shown above) showed a sinus tachycardia with right sided strain pattern

• In the meantime his x-ray (shown below) was repeated.

• His blood tests and blood gas were non-diagnostic and he continued to be symptomatic with breathlessness:

• The patient is appearing clinically worse despite antibiotics – his repeat X-ray (above) is concerning to the treating team.  Could this be a pulmonary infarction associated with PE?

• After a period of consideration of the case it was decided to obtain a CT pulmonary angiogram

• This CT showed multiple bilateral pulmonary emboli

• The patient was treated with anticoagulation.

• 3 days later he was discharged home feeling much better with appropriate follow up.

How do we decide whether to investigate for a disease in the ED?

In this case the first treating clinicians had felt that the risk of PE was low.  

What does this mean?  

How do we decide what a patient’s risk for a given disease is?

The concept of risk is somewhat counter-intuitive.  The individual patient either has the disease (100%) or he doesn’t (0%). However, we cannot do every test for every patient!  Many patients have some (even if a negligible) risk of having a particular disease.  

If we were to throughly investigate 100 health patients for Pulmonary Embolism we may find several individuals with evidence of asymptomatic (silent) PE.   So should we screen and treat everyone for PE?   The answer seems to be no if we want to avoid harm.   We have no evidence that finding or treating a silent PE in a healthy patient is beneficial.  In fact, ia workup for PE in a healthy patient may be harmful.  Harm may be from the risk of investigations (CT scans) or from the risk of subsequent (potentially unnecessary) treatments such as anticoagulation. 

The Test Threshold

Some clinicians use the Test Threshold to determine whether to investigate for a disease (typically we consider common and commonly deadly conditions as important to consider for further diagnostic work-up).  

Click Here for more information on diagnostic workup

So, in summary, the Test Threshold is when the pre-test probability of the considered differential diagnosis (such as MI or PE) is very low.  So much so that it is not worth pursuing the diagnosis in that patient because you will do more harm than good by investigating the patient. The “test threshold” is both mathematical formula and a bit of voodoo.

For PE the level is about 2%

So if you think the patient has less than a 2% chance of having a PE we should pursue another diagnosis.  In a very low risk patient we can have a false positive CTPA, bleeding from the treatment and radiation risk from the CT (illustrated above).  This is not to mention the cost in the healthcare team and patient’s time as well as the health system’s money!

Risk of PE

So, how do we decide what the risk is for PE?

• Gestalt – the opinion of an experienced clinician has shown to an be accurate risk predictor for PE
• Well’s Score
  • Full Score – Click Here 
• • A score of ‘0 or 1’ = pre-test probability of 1.3%
• Pulmonary Embolism Rule out Criteria (PERC)
  • Full Score – Click Here 
  • I think he’s < 10%: use PERC
  • I think he’s > 10%: investigate the patient with further clinical work up and investigations

PE Workup Summary

Alternative PE Workup – Click Here

Summary

Thinking about important causes of chest pain and using judicious investigations for their diagnosis is a cornerstone of good emergency care.

In this Case Vingette we illustrated some of the pitfalls in the diagnosis and workup of the patient with Chest Pain in the Emergency Department.

We considered the ‘test threshold’ and its implications for when to use invasive investigations.

While we must always consider PE, ACS and Aortic Dissection in the patient with chest pain, we must be careful not to cause later harm by use of inappropriate investigations.