Transient loss of consciousness (T-LOC) is defined as ‘spontaneous loss of consciousness with complete recovery after the event’ (NICE 2014). T-LOC occurs due to global cerebral hypoperfusion and is a common pre-hospital presentation.

  • Syncope = loss of consciousness
  • Loss of consciousness ≠ syncope

T-LOC is an umbrella term that encompasses many conditions:

Potential causes90% of T-LOC cases
Uncomplicated faint
Situational syncope
Other neurally mediated conditions e.g. strokeVasovagal syncope
Structural cardiac conditionsPsychogenic non-epileptic seizures
Cardiac dysrhythmiasEpilepsy
Orthostatic hypotension 

(Reuber et al, 2016)

T-LOC is the symptom. The underlying mechanism and pathophysiology may vary but the assessment and management of these patients should be standardised.

  1. History taking
  2. Clinical assessment
  3. 12 lead ECG
  4. Identification of red flags
  5. ED transport/referral

History Taking:

Detailed history taking must be emphasised. A detailed history will aid in diagnosis and help to identify ‘red flags’. Corroborative history from witnesses and family is imperative (Fulde 2014). These questions are of greater importance in those patients who crews might consider ANR appropriate. These should be clearly documented and assessed for.

  • Injuries sustained
  • Circumstances of the event
  • Duration of the event
  • Posture prior to the T-LOC
  • Prodromal symptoms e.g. sweating, feeling flushed
  • Appearance during the event e.g. head turning to the side
  • Presence or absence of movement during the event
  • Tongue biting
  • Urinary incontinence
  • Confusion during the recovery phase
  • Unilateral weakness during the recovery phase
  • Previous T-LOC episodes
  • Medical, medication and family history e.g. family history of sudden cardiac death

(Nice, 2014)

Clinical Assessment:

A standard and full set of clinical observations should be undertaken. This should also encompass standing/sitting blood pressures and auscultation of heart sounds (if in scope of practice).

Standing/sitting blood pressures

Orthostatic hypotension is a cause of T-LOC. The patient should be seated for 5 minutes and then stand for 3 minutes. Blood pressure is measured just prior to standing and at 1 minute and 3 minutes of standing. A sustained fall of systolic blood pressure of at least 20mmHg or diastolic blood pressure of 10mmHg within 3 minutes of standing is diagnostic of orthostatic hypotension (Gibbons et al 2017).

Auscultating heart sounds

The purpose of auscultation is to identify the presence or absence of a heart murmur. The presence of a murmur may suggest a valvular abnormality (Kumar & Clark 2009). A murmur in conjunction with an episode of T-LOC is a red flag that warrants further investigation. For those patients that refuse hospital transport it provides additional clinical information to be documented.

12-Lead ECG:

All patients who have experienced a T-LOC must undergo a 12-Lead ECG. The following pathologies should be assessed for:

  • Inappropriate persistent bradycardia (consider patient’s medications e.g. beta blockers and a physiological bradycardia due to fitness level)
  • Any ventricular dysrhythmia (VT, VF, Torsade’s de Pointes, PVCs, Idio-ventricular rhythms)
  • Long QT and short QT intervals (review the MRx and Corpuls printout for accurate measurement of this interval)
  • Brugada syndrome (coved ST elevation in V1, V2 and V3)
  • Ventricular pre-excitation (e.g. Wolff-Parkinson-White syndrome – slurred up-stroking of the QRS complex “delta wave”)
  • Left or right ventricular hypertrophy
  • Abnormal T wave inversion (isolated T wave inversion in V1 or lead III may be normal)
  • Pathological Q wave
  • Atrial dysrhythmia (sustained)
  • Paced rhythm
  • Right or left bundle branch block
  • Any degree of heart block
  • Any ST segment or T wave abnormalities

...or, WOBBLER:

 AbnormalityECG Section
WWolff-Parkinson White
OObstructed AV pathway
BBifascicular block
LLeft ventricular hypertrophy (consider Aortic Stenosis or Hypertrophic Obstructive Cardiomyopathy (HOCM))
EEpsilon wave
RRepolarisation abnormality (long QT, short QT)

Red Flags:

The presence of one or more of the following ‘red flags’ in conjunction with a T-LOC should warrant hospital transport:

  • 12-lead ECG abnormality
  • Signs or symptoms consistent with heart failure (breathlessness, crackles, oedema, orthopnoea)
  • T-LOC on exertion
  • Family history of sudden cardiac death
  • New or unexplained breathlessness
  • Undiagnosed heart murmur
  • T-LOC in a patient >65 years of age and the absence of prodromal symptoms. Older patients are more likely to have underlying life-threatening pathology as cause for their syncope. Also less likely to present with typical symptoms (Fulde 2014)

ED transport/Referral:

Situational syncope can be diagnosed when there are no features from the clinical assessment that suggest an alternative diagnosis AND the syncope is clearly provoked by straining during micturition, coughing or swallowing.

Uncomplicated faint (vasovagal syncope) can be diagnosed when there are no features from the clinical assessment that suggest an alternative diagnosis AND there are features suggestive of uncomplicated faint. Consider the three Ps:

  • Posture – prolonged standing
  • Provoking factors – pain, medical procedure such as receiving an injection
  • Prodromal symptoms* – sweating, hot sensation

*the existence of prodromal symptoms is more frequently associated with benign causes

(Nice, 2014)

A diagnosis of situational syncope or uncomplicated faint requires competence in ECG interpretation. If in doubt or if any ‘red flags’ have been identified the patient should be transported to hospital for further investigation.


Assaf, S., & Libby, C. (2017). Asymptomatic Wolff-Parkinson-White Syndrome (WPW). Journal ofEducation and Teaching in Emergency Medicine, 2(3).

Brugada, R., Campuzano, O., Brugada, G., Brugada, P., Brugada, J. & Hong, K. (2005) Brugada Syndrome Synonym: Sudden Unexpected Nocturnal Death Syndrome. GeneReviews

Fulde, G. & Fulde, S. (2014) Emergency Medicine: the principles of practice. (6th ed). Elsevier Australia

Gibbons, C. H., Schmidt, P., Biaggioni, I., Frazier-Mills, C., Freeman, R., Isaacson, S. & Mehdirad, A. (2017). The recommendations of a consensus panel for the screening, diagnosis, and treatment of neurogenic orthostatic hypotension and associated supine hypertension. Journal of neurology, 264, 1567-1582.

Kumar, P. & Clark, M. (2009) Kumar & Clark’s Clinical Medicine. (7th ed). Saunders Elsevier

National Institute of Clinical Excellence (2014) Transient loss of consciousness (‘blackouts’) in over 16s. London: NICE.

Reuber, M., Chen, M., Jamnadas-Khoda, J., Broadhurst, M., Wall, M., Grünewald, R. A. & Walker, M. (2016). Value of patient-reported symptoms in the diagnosis of transient loss of consciousness, 625-633.87, Neurology.

Huszar’s Basic Dysrhythmias and Acute Coronary Syndromes: Interpretation andWesley, K. (2011) Management. (4th ed). Elsevier Mosby JEMS.

Page contributors:

Matt Campbell, AP24017
Ambulance Paramedic, Metropolitan Ambulance Service

Want to help improve this article? Visit our Contribute page.

St John Ambulance Western Australia Ltd © Copyright 2020, All Rights Reserved

Privacy Policy | Copyright Statement & Disclaimer