This post is part of our continuing induction podcast series, designed to guide you through the common conditions we see in the department and to help you avoid common pitfalls.
One of the presenting complaints that gives an every Emergency Physician a sense of dread is “Collapse ?Cause”. In this post and podcast we will try to give you a structure to work out which of these patients need further investigation and which can be safely discharged.
REMEMBER: A prolonged episode of syncope can also be described as “Death”.
First listen to Simon and Iain talk about Syncope and a structure for its evaluation.
What have you learned about Syncope?
What’s the first question we need to ask ourselves when we see patients with fall/collapse?
The first decision is to decide if the patient has had a syncopal episode. Using our philosophy of “Rule Out the Worst Case Scenario” we would recommend you consider syncope as a possible cause for all patients who have had a fall and that the latter is a diagnosis of exclusion.
For patients presenting with a “fit” remember to think, could this be a syncopal episode? A really good history – especially from a witness who can give a description of what happened – and examination is vital.
All patients with collapse should have an ECG recorded and remember to seek out a paramedic ECG if one was recorded on scene for patients who come to the department by ambulance.
A postural blood pressure measurement (lying and standing) may show a drop in blood pressure on standing which is abnormal – but don’t be reassured if the numbers don’t show a drop. If the patient is symptomatic on standing that should be considered to be significant.
Female patients who could possibly be pregnant (child-bearing age with a uterus and an ovary!) should have a pregnancy test to exclude ectopic pregnancy.
Consider abdominal aortic aneurysm in older patients – male and female – and whether these patients need aortic imaging. Be wary of common conditions presenting for the first time in elderly patients – in particular “migraine” (could this headache be a cerebral bleeding event?), “renal colic” (think AAA!) and “fainting”.
So what is syncope?
Syncope is a transient loss of consciousness caused by global cerebral hypoperfusion.
We can then use simple physiological equations to give a structure to our history taking, examination and investigations.
In a patient with syncope the “cerebral perfusion pressure” (CPP) has fallen, tending towards zero, causing that global cerebral hypoperfusion.
As we remember from our undergraduate days
CPP = Mean Arterial Blood Pressure (MABP) – Intracranial Pressure (ICP).
Therefore anything that causes the MABP to fall will cause the CPP to also fall. Two further simple physiogical equations can then give us the likely causes of syncope:
MABP = Cardiac Output (CO) x Systemic Vascular Resistance (SVR)
CO = Stroke Volume (SV) x Heart Rate (HR)
CPP ∝ SV x HR x SVR
so if any of these variables temporarily tend towards zero our CPP will fall causing a transient loss of consiousness.
a. SV decreases: This occurs when the heart is beating too fast, ineffectively or against increasing outflow pressure:
- Tachyarrthymias – the heart is beating too fast to allow ventricular filling,
- Ineffective pumping – episodes of VF
- Outflow tract obstruction – eg aortic stenosis, hypertrophic cardiomyopathy
b. HR decreases:
- Bradyarrthymias caused by heart blocks (complete heart block, trifasicular block, bifasicular block)
- Vasovagal episode (always remember that this is a diagnosis of exclusion)
c, SVR decreases:
- Postural hypotension – this may be caused by medications (ACE inhibitors etc), autonomic dysfunction or
- Hypovolaemia – think especially about ruptured abdominal aortic aneurysm in older patients and ectopic pregnancy in younger women