last authored: Oct 2010, David LaPierre
Consciousness involves appropriate arousal and awareness. Altered level of consciousness (LOC) can include poor responsiveness, agitation, confusion, and other cognitive symptoms.
There are a number of specific terms used to describe altered LOC:
The differential for altered level of consciousness follows. Please note that many of these are also causes for delirium. A helpful acronym is DIMS: Drugs, Infections, Metabolic, and Structural.
Cardiac: amiodarone, beta-blockers, digoxin, diuretics
A variety of infections can lead to delirium, including:
Other infections specifically affecting the central nervous system can lead to direct changes in congition. These include:
In medical patients electrolyte abnormalities are common causes of altered LOC. These include:
Organ failure, leading to accumulation of toxic metabolic products or affecting perfusion, can also affect cognition:
Structural insults to the brain can lead to direct changes in brain function. Causes include:
cerebral venous thrombosis
Another helpful acronym follows:
The differential diagnosis of altered LOC includes:
It is important to get a history from witnesses. Ask about onset, seizure, setting, medical history.
San Francisco Syncope Rules (CHESS)
shortness of breath history
Systolic BP <90 mmHg at triage?
Syncope can be characterized by the following:
cardiac (postural blood pressure and heart rate), respiratory, and neurological exams
Neurological exam to localize
asymmetry suggests structural lesion
levels of motor response can help in localization
signs of trauma and rashes
nail bed pressure
fibger stick for glucose
CBC, glucose, lytes, osmolality, Ca2+, PO4-, BUN, creatinine
drug screen: ASA, tylenol, EtoK
CK, troponin, TSH, Mg, beta-hCG
CT head, MRI, EEG
Airway, Breathing, Circulation, Deficit/Neurological, Exposure
Stabilite neck if trauma.
Intubation may be needed; note respiratory pattern prior to intubation
Glucose 50g IV + thiamine 100mg
Narcan 0.4 mg and repeat
Obtain early lab values
Arousal is mediated by the reticular activating system in the brainstem, and disruption can occur due to physical or metabolic
Awareness is mediated by the cortex.
Damage to the hemispheres can be due to a number of causes.
It appears cerebellar or thalamic damage can also result in coma.
The upper pons and midbrain contain the ascending reticular activating system, containing noradrenergic, serotonergic, cholinergic, and histaminergic pathways that ascend to the thalamus and thereby to the cortex. Stroke affecting the reticular activiating system may lose a sudden loss of consciousness.
Syncope is caused by decreased cerebral perfusion.
Pre-syncope is often described as 'dizziness', and needs to be distinguished from vertigo.
Shemie SD et al. Brain Arrest: CMAJ 2006 174...
created: DLP, Aug 09
authors: DLP, Aug 09