How to Cite This Chapter: Masoom H, Gundy S, Cheung J, Panju M, Patel A, Ciećkiewicz J. Loss of Consciousness. McMaster Textbook of Internal Medicine. Kraków: Medycyna Praktyczna. https://empendium.com/mcmtextbook/chapter/B31.III.23.2 Accessed April 02, 2020.
Last Updated: April 5, 2015
Last Reviewed: June 5, 2019
McMaster University Editorial Office
Section Editors: Akbar A. Panju
Authors: Hassan Masoom, Serena Gundy, Jason Cheung, Mohamed Panju, Ameen Patel
Polish Institute for Evidence Based Medicine Editorial Office
Section Editors: Miłosz Jankowski
Authors: Jan Ciećkiewicz
Main Documents Taken Into Account:
Sheldon RS, Morillo CA, Krahn AD, et al. Standardized approaches to the investigation of syncope: Canadian Cardiovascular Society position paper.
Can J Cardiol. 2011 Mar-Apr;27(2):246-53. doi: 10.1016/j.cjca.2010.11.002. Review. PubMed PMID: 21459273.
Thiruganasambandamoorthy V, Hess EP, Alreesi A, Perry JJ, Wells GA, Stiell IG. External validation of the San Francisco Syncope Rule in the Canadian setting.
Ann Emerg Med. 2010 May;55(5):464-72. doi: 10.1016/j.annemergmed.2009.10.001. Epub 2009 Nov 27. PubMed PMID: 19944489.
Task Force for the Diagnosis and Management of Syncope; European Society of Cardiology (ESC); European Heart Rhythm Association (EHRA); Heart Failure Association (HFA); Heart Rhythm Society (HRS), Moya A, Sutton R, Ammirati F, et al. Guidelines for the diagnosis and management of syncope (version 2009).
Eur Heart J. 2009 Nov;30(21):2631-71. doi: 10.1093/eurheartj/ehp298. Epub 2009 Aug 27. PubMed PMID: 19713422; PubMed Central PMCID: PMC3295536.
Sheldon R, Rose S, Connolly S, Ritchie D, Koshman ML, Frenneaux M. Diagnostic criteria for vasovagal syncope based on a quantitative history.
Eur Heart J. 2006 Feb;27(3):344-50. Epub 2005 Oct 13. PubMed PMID: 16223744.
Colivicchi F, Ammirati F, Melina D, Guido V, Imperoli G, Santini M; OESIL (Osservatorio Epidemiologico sulla Sincope nel Lazio) Study Investigators. Development and prospective validation of a risk stratification system for patients with syncope in the emergency department: the OESIL risk score.
Eur Heart J. 2003 May;24(9):811-9. PubMed PMID: 12727148.
Quinn JV, Stiell IG, McDermott DA, Sellers KL, Kohn MA, Wells GA. Derivation of the San Francisco Syncope Rule to predict patients with short-term serious outcomes.
Ann Emerg Med. 2004 Feb;43(2):224-32. PubMed PMID: 14747812.
Loss of consciousness may be caused by syncope (the patient usually recovers within a minute) or may signal the onset of coma. Altered mental status: see Impaired Consciousness.
1. Evaluate the patient using the ABCD scheme. Basic life support: see Cardiac Arrest. Assess the patient’s response to verbal and tactile stimuli. If a pulse is absent, begin cardiopulmonary resuscitation (CPR). If available, ask a bystander to call for help (or if in hospital, consider activating the emergency response team). Advanced life support: see Cardiac Arrest.
2. Clear the airway (see Cardiac Arrest; in trauma patients, particularly after head or neck injury, do not tilt the head backwards or in other directions), administer 100% oxygen via a face mask, check the capillary blood glucose level, and establish a peripheral IV line.
3. Monitor the vital signs. If blood pressure is low, administer 1 L crystalloid solution (eg, 0.9% NaCl) or, if not available, elevate the lower limbs to 45 degrees.
4. If the loss of consciousness is a result of trauma or a head or neck injury is suspected, stabilize the cervical spine (apply a rigid cervical collar if available) and carry out a rapid trauma survey.
5. Protect the patient from environmental extremes. If the loss of consciousness may have been caused by external factors (eg, hyperthermia, hypothermia, or gas poisoning [most frequently carbon monoxide]), and it is safe for you to do so, remove the patient from the environment (transferring a nontrauma patient: Figure 10.4-1). If the patient is already in hospital, ensure he or she is moved to an area capable of providing appropriate support.
6. If the loss of consciousness (in a nontrauma patient) is prolonged but the patient is hemodynamically stable (heart rate, blood pressure, and respiratory rate are within normal limits), you may place the patient in the recovery position (see Figure 3.3-4).
7. If the patient does not regain consciousness, continue the management you have already initiated. Call for advanced help as required, depending on the patient’s requirements as well as your level of expertise and comfort (eg, unstable arrhythmia, refractory hypotension, a persistent Glasgow Coma Scale score <8 [see Table 10.3-2]), and investigate for causes of coma (see Table 10.4-1).
8. If the patient recovers rapidly, investigate for causes of the transient loss of consciousness.
Figure 10.4-1. Safe transfer of an unconscious nontrauma patient by 2 persons.