Red flag symptoms: Drowsiness

Investigate drowsiness in a normally well person. By Dr Tillmann Jacobi.

Accidental or deliberate overdose may be the reason for drowsiness (BSIP, KOOS / PITA / SCIENCE PHOTO LIBRARY)
Accidental or deliberate overdose may be the reason for drowsiness (BSIP, KOOS / PITA / SCIENCE PHOTO LIBRARY)

Unexpected drowsiness should demand a prompt assessment until it is proved manageable and harmless.

Drowsiness can be a warning sign of drug side-effects.

Much depends on the history. Establish the circumstances of the onset of drowsiness.

Intoxication or poisoning are likely to be high on the list of suspected causes. In particular, consider medication (new medication, interaction between medications, or a stopped medication), accidental or deliberate overdoses, and other toxins which have been ingested, inhaled (always consider carbon monoxide) or injected.

Red flag symptoms
  • Sudden onset
  • Depression
  • Head injury
  • Behaviour change
  • Neurological symptoms

Consider that toxins could be legal or illegal, and they could have been self-induced or induced by others, either with intent or accidentally.

The possibility of 'spiked drinks' is increasingly in the public awareness, although reports suggest the incidence is over-estimated.

Neurological causes
Drowsiness due to cerebral pathology (such as head injury, bleeds, stroke, tumour) or acute cardiovascular incidents is quite likely to have a more clear-cut past medical history or description of the event leading to drowsiness.

Neurological causes such as epilepsy or narcolepsy (which is thought to be under-diagnosed) tend to develop characteristic patterns over time with their recurrence.

A variety of chronic mental conditions can cause drowsiness - dementia, for example.

Other causes
Drowsiness with fever sug-gests infection or sepsis, especially from UTI, pneumonia or meningitis, possibly with dehydration.

Upper or lower respiratory causes such as complications of asthma or COPD may result in drowsiness. Choking or (near-) drowning is important to consider in a drowsy patient.

Surgical emergencies including internal bleeds or bowel obstruction are likely to present with additional clinical signs. Possible complications of pregnancy and during the puerperium need to be excluded in all women of child-bearing age.

Endocrine causes (e.g. diabetic coma, Addisonian crisis) and tropical diseases are rare but possible causes.

Examination of the drowsy patient must include a check of the airways and a detailed cardiovascular assessment, as well as psychiatric and neurological signs, if possible.

Drowsiness itself is a red flag for a multitude of underlying conditions. Therefore refer immediately to emergency services if you have any doubts or concerns.

  • Dr Jacobi is a salaried GP in York
Possible causes
  • Medication side-effects
  • Trauma
  • Infection
  • Dehydration
  • Respiratory compromise
  • Cardiovascular disturbance
  • Epilepsy and narcolepsy
  • Psychiatric conditions

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