Loss of Consciousness

Chapter: Loss of Consciousness
McMaster Section Editor(s): Akbar A. Panju
Section Editor(s) in Interna Szczeklika: Miłosz Jankowski
McMaster Author(s): Serena Gundy, Jason Cheung, Mohamed Panju, Ameen Patel
Author(s) in Interna Szczeklika: Jan Ciećkiewicz
Additional Information

Loss of consciousness may be caused by syncope (the patient usually recovers within a minute) or may signal the onset of coma. For altered mental status, see Consciousness.

Basic ManagementTop

1. Evaluate the patient using the ABCD scheme (see General Rules of First Aid); for 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). For advanced life support, see Cardiac Arrest.

2. Clear the airway (see Cardiac Arrest) (in trauma patients, particularly after head and/or neck injury, do not tilt the head backwards or in other directions [see Head Injury]), administer 100% oxygen via a face mask (see Oxygen Therapy), check the capillary blood glucose level, and establish a peripheral intravenous line (see Peripheral Venous Catheters).

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 and/or neck injury is suspected, stabilize the cervical spine (apply a rigid cervical collar if available; see Head Injury) and carry out a rapid trauma survey (see General Rules of First Aid).

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. Safe transfer of an unconscious…). 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 (Figure. Placing an unconscious patient in…).

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 <8), and investigate for causes of coma (Table. Table 1. Typical manifestations of…).

8. If the patient recovers rapidly, investigate for causes of the transient loss of consciousness.


Figure. Safe transfer of an unconscious nontrauma patient by 2 persons.

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