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Transient Loss of Consciousness

Transient loss of consciousness is ( TLoC ) is defined as an apparent loss of consciousness with an abrupt onset , a short duration and a spontaneous and complete recovery (Gert van Dikl et al 2009 )

Consciousness is defined as the ability to maintain awareness of the self and of the environment Syncope is the form of TLoC which is caused by cerebral hypoperfusion characterized by a rapid onset , short duration and spontaneous and complete recovery Syncope can be divided into
○ reflex syncope
○ syncope due to orthostatic hypotension
○ cardiac syncope Pre-syncope if often used to describe period before syncope , it has possibly the same pathophysiology but is not followed by syncope TLoC is very common A frequent cause of attendance to A&E and subsequent admission A TLoC episode may be a first symptom of fatal arrhythmia which causes over 100,000 deaths / year in the UK In young people most sudden deaths are due to inherited cardiomyopathies and arrhythmias The European Society of Cardiology Guideline recognises this and states the identifying the cardiac causes of syncope is critically important as several interventions/ drugs / devices are now available for treatment Recurrent TLoC episodes carry significant morbidity , increased need for medical care and also determines significant changes in QoL Neurally mediated syncope is considered to be the commonest cause of TLoC In one study of patients presenting with TLoc , syncope was diagnosed in 84 % of patients and 25 % of them were admitted to hospital TLoC poses diagnostic difficulties , cause can be diverse carry vastly different risks , and span various specialities



Described in literature as very common Despite publication of studies as Framingham in 2002 data about epidemiology and prognosis of TLoC in the community is lacking if person has sustained an injury full recovery of consciousness event 2ary to a condition that requires immediate attention circumstances of the event posture immediately before LOC prodromal symptoms ( eg sweating , warm/hot) appearance , colour presence or absence of movement (eg limb jerking) tongue biting ( record side or tip ) any injury duration if confused during recovery period weakness down one side during recovery period details from any witness details of any previous TLoC ( number and frequency ) medical history and any family history of cardiac disease current medications vital signs lying and standing bp if appropriate other CV and neurological signs Record a 12 lead Automated ECG for all patients with TLoC

Treat as red flag if any of the following abnormalities are reported on the ECG printout
 conduction abnormality ( eg complete RBBB or LBBB or any degree of heart block ) long or short QT interval any ST or T wave abnormality Additional tests
 Consider checking glucose if indicated FBC if anaemia suspected EEG not indicated routinely


an ECG abnormality heart failure TLoC during exertion family h/o sudden cardiac death in people < 40 yrs and / or an inherited cardiac condition new or unexplained breathlessness a heart murmur older than 65 yrs who had TLoc without prodromal symptoms No further immediate action is required Reassure that the prognosis is good Advice people -
○ on possible triggers and strategies to avoid them
○ keep a record of their symptoms
○ consult GP if they experience further TLoC particularly if this differs from their recent episode Refer for specialist CV assessment within 24 hrs If pt presents to ambulance → adv attend A&E Driving – advice all who have had TLoC that they must not drive while awaiting specilist assessment Suspect epilepsy if presentation has 1 or more of the following features
 a bitten tongue head turning to 1 side during TLoC no memory of abnormal behaviour (if witnessed before , during or after by someone else ) unusual posturing prolonged limb – jerking ( brief seizure like activity can happen during uncomplicated faint ) confusion after the event prodromal dèjá vu or jamais vu ( opposite of dèjà vu- never seen )


Suspect if there are no features from 
initial assessment that suggest an alternative diagnosis and the history is atypical

Measure lying and standing BP- repeat measurements while standing for 3 minutes Confirms Orthostatic hypotension
Consider likely cause and manage Do not confirm orthostatic hypotension


  1. Gudkova, S et al. “Lifetime Prevalence of Transient Loss of Consciousness in an Urban Russian Population.” Arquivos brasileiros de cardiologia vol. 106,5 (2016): 382-8. doi:10.5935/abc.20160056
  2. Baron-Esquivias G, Martínez-Alday J, Martín A, et al. Epidemiological characteristics and diagnostic approach in patients admitted to the emergency room for transient loss of consciousness: Group for Syncope Study in the Emergency Room (GESINUR) study. Europace. 2010;12(6):869-876. doi:10.1093/europace/euq018 ( Abstract )
  3. Rogers, Greg, and Norma O’Flynn. “NICE guideline: transient loss of consciousness (blackouts) in adults and young people.” The British journal of general practice : the journal of the Royal College of General Practitioners vol. 61,582 (2011): 40-2. doi:10.3399/bjgp11X548965
  4. Half a dozen things to know about transient loss of consciousness -The College of Emergency Medicine via
  5. van Dijk JG, Thijs RD, Benditt DG, Wieling W. A guide to disorders causing transient loss of consciousness: focus on syncope. Nat Rev Neurol. 2009;5(8):438-448. doi:10.1038/nrneurol.2009.99 ( Abstract )
  6. Furlan, L., Costantino, G., Solbiati, M., & Alboni, P. (2015). Definition and classification of transient loss of consciousness. In Vasovagal Syncope (pp. 27-39). Springer International Publishing. ( Abstract )
  7. Michele Brignole, Angel Moya, Frederik J de Lange, Jean-Claude Deharo, Perry M Elliott, Alessandra Fanciulli, Artur Fedorowski, Raffaello Furlan, Rose Anne Kenny, Alfonso Martín, Vincent Probst, Matthew J Reed, Ciara P Rice, Richard Sutton, Andrea Ungar, J Gert van Dijk, 2018 ESC Guidelines for the diagnosis and management of syncope, European Heart Journal, Volume 39, Issue 21, 01 June 2018, Pages 1883–1948,
  8. Syncope in the Elderly Joseph S Alpert MD The American Journal of Medicine  VOLUME 132, ISSUE 10, P1115-1116, OCTOBER 01, 2019 ( Abstract )
  9.  Transient loss of consciousness – initial assessment , diagnosis and referral : summary of NICE guidance BMJ 2010 ; 341:cc4457
  10. NICE Pathways Transient loss of consciousness accesses via
  11. Silva, Marianaa, *; Godinho, Anab; Freitas, Joãoa, b Transient loss of consciousness assessment in a University Hospital: From diagnosis to prognosis, Porto Biomedical Journal: July 2016 – Volume 1 – Issue 3 – p 118-123 doi: 10.1016/j.pbj.2016.07.001

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