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The primary focus of the emergency department (ED) evaluation of a patient with altered mental state (AMS) is as follows:
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To address easily reversible causes, e.g. hypoxaemia, hypercarbia and hypoglycaemia.
To differentiate structural from toxic-metabolic causes since the former require emergent central nervous system imaging, whereas the latter are usually more readily identified by laboratory studies.
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SPECIAL TIP FOR GPs
Always consider reversible causes of AMS that you can initiate treatment for in your office: e.g. hypoglycaemia (oral sugar or IV Dextrose 50%), hypoxaemia (supplemental oxygen), or heat stroke (cooling measures and IV normal saline), before sending the patient to the ED by ambulance.
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See Figure 1 for approach to differential diagnosis of altered mental state.
The patient should be managed initially in the critical care area.
If a promptly reversible cause of AMS is found, then the patient can be downgraded to the intermediate acuity area.
Positive airway control/C-spine restriction of movement.
Open the airway and search for foreign bodies.
Insert oral or nasopharyngeal airway.
Apply stiff collar or manual restriction of movement if history does not exclude trauma.
Assessment of airway if patient is comatose: with altered mental state comes the potential for loss of a patent airway. This demands at the very least an assessment of the patient’s airway. If active intervention is required, please reference Chapter 30: Airway Management/Rapid Sequence Intubation.
Oxygenation/ventilation.
Provide supplemental high-flow oxygen if patient is hypoxaemic.
In general, target a pCO2 level between 35–40 mmHg.
Cardiac output.
Check that there is a major pulse; if not, start CPR!
Obvious external haemorrhage should be stopped with direct pressure.
Do stat capillary blood sugar.
Monitoring: ECG, pulse oximetry, vital signs q5–15 minutes.
Start peripheral IV at a slow rate (unless hypoperfusion is present) with isotonic crystalloid.
Labs: mandatory for FBC, urea/electrolytes/creatinine, ABG (look for metabolic acidosis and hypercarbia).
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Note: CO2 narcosis does not necessarily present with respiratory distress; instead, respiratory depression is usually present.
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Consider serum calcium, drug screen, serum ethanol, carboxyhaemoglobin level and GXM.
AMS cocktail: consider its use in part or whole. Its role is basically empirical reversal of hypoglycaemia, opioid toxicity, benzodiazepine toxicity and Wernicke’s encephalopathy.
D50W 40 ml IV if patient is hypoglycaemic, followed by infusion of D10W over 3–4 hours.
Naloxone (Narcan®) 0.8–2.0 mg IV bolus.
Thiamine 100 mg IV bolus in alcoholics or malnourished patients.
Flumazenil (Anexate®) 0.5 mg IV bolus.
Can be repeated within 5 minutes if necessary.
Do not use empirically unless the history is strongly against a mixed OD. If the patient has been taking cyclic antidepressants ...