Induction – TLoC

Author: Tania Minns / Codes: CA5, CAP15, CAP32, HAP35 / Published: 06/02/2018

This is a very common but also very varied ED presentation. A triage of “collapse ?cause” can mean anything from a young patient having fainted in phlebotomy to an elderly patient being found on the floor. We probably all have a gut feeling that the second patient is higher risk for having had a potentially serious event but do you know who to investigate, who is high risk and who needs admitting? What about Bessie who collapsed after standing from the dinner table, Fred who woke up on the floor after going to the bathroom in the middle of the night or Tom who collapsed at the gym? Unfortunately the guidance out there is based mainly in expert consensus as there is a limited amount of evidence on this topic.
The first thing to do is to determine whether your patient has actually had a transient loss of consciousness (TLoC) or is there another serious condition accounting for a loss of consciousness e.g. pulmonary embolism, gastro-intestinal haemorrhage, sub arachnoid haemorrhage, ruptured ectopic pregnancy etc.

A useful definition of TLoC for this purpose is:

a loss of consciousness of rapid onset, short duration with spontaneous complete recovery.

If your patient has still not returned to their baseline at the time of your assessment or has required some resuscitation you need to start thinking about other pathologies.
All patients require a thorough history, examination and ECG (lying and standing BP is also useful if it sounds orthostatic). Based on these you will probably be able to ascertain a diagnosis in about half of your patients.

They can be put into one of 5 categories:

1. Neurocardiogenic (vasovagal): including situational e.g. micturition/cough syncope- low risk
2. Orthostatic: beware a postural drop can occur in cardiac causes of syncope too
3. Neurological: least common
4. Cardiac cause: most likely to be life-threatening- 30% increase in risk of sudden death within 1 year
5. Unknown cause: these patients have a 30% higher mortality than in those who have not had a syncopal episode
Patients who may have had an uncomplicated faint include those with the 3 P’s:

A Prodrome (sweating or feeling warm/hot before TLoC, pallor), Provoking factors (e.g. pain or a medical procedure) or associated with Posture e.g. prolonged standing or similar episodes prevented by lying down, but with no features suggesting an alternative diagnosis (see box 1). It is important to note that brief seizure-like activity can occur during an uncomplicated faint. If these patients have normal vital signs and examination, they can probably be discharged with safety netting advice and no further investigation.

If any features from box 1 are present consider a seizure as the cause for the TLoC and follow your local guidelines/referral pathways as appropriate.
The trickier patients are ones without the 3 Ps or features suggestive of a seizure – in these patients you need to consider the possibility of a cardiac collapse. The NICE guidelines (CG109) list some red flags to help guide you as to which of these patients need an urgent cardiology assessment, these include:
1. ECG abnormalities (see box 2)
2. Heart failure (history or physical signs)
3. TLoC during exertion (note TLoC AFTER exertion more likely to be vasovagal)
4. Family history of sudden cardiac death aged 65 year olds
These patients require assessment for a structural or arrhythmic cause for their TLoC and will therefore need assessment by a cardiologist and likely an echocardiogram and/or ambulatory monitoring. Some hospitals have rapid referral pathways, dedicated clinics or observation units for these patients as inpatient assessment is not always required and often leads to a lot of expensive tests without an increase in diagnostic yield.

If we apply the above reasoning to the patients in the first paragraph, the young patient who collapsed after having blood taken in phlebotomy is likely to have had a simple faint and can probably be discharged, the elderly person found on the floor needs a bit more of a workup, it could be cardiac. Bessie, who collapsed on standing may have postural hypotension and might be able to go home if she has no red flags so could Fred who may have micturition syncope (depends on your history and examination). Tom, who collapsed at the gym may need to come in, especially if he collapsed during exertion, has a murmur or a concerning family history, but if he had a prodrome, collapsed after his workout and has no red flags has probably had a vasovagal episode. In all of these a collateral history can make or break your diagnosis and every effort should be made to get one even if it means calling someone, it is worth the extra time and effort. If, for example, Fred’s wife states he passed urine and then collapsed and has had previous episodes like this before, or Bessie’s family state she went pale, complained of being hot and dizzy and then collapsed your assessment of their level of risk and your decision making becomes much easier.

Some of these patients won’t be drivers – but don’t assume just because they’re old, they don’t drive. Don’t forget to tell patients that they cannot drive after an unexplained syncope for 4 weeks or maybe longer, depending on the risk of recurrence as per DVLA guidance.

In summary, this can be a challenging presentation with a range of causes from the benign to life-threatening. Remember an ECG in all patients, a collateral history is always helpful and may provide your diagnosis, if in doubt the NICE guidelines Transient Loss of Consciousness in over 16s (guideline CG109) and local or departmental guidelines are good ports of call if you get stuck. Good Luck.


  1. Raghavendra Bada Kamblu says:

    It’s very useful,

  2. williamsond says:

    This is very good, but don’t forget to tell patients that they cannot drive after an unexplained syncope for 4 weeks or maybe longer, depending on the risk of recurrence. Refer to pages 23-27 in the DVLA ‘Assessing fitness to drive – a guide for medical professionals’ document for more details. (

    1. Charlotte Davies says:

      Great point! Have updated the blog…

  3. Andrew Smith says:

    Really good summary

  4. Gerard Joseph Bowdren says:

    good straight forward summary

  5. Rida Tariq says:

    Overall good summary

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