Red Flag Symptoms - Differentiate the causes of fever

Know the red flags that could indicate a serious cause of fever. By Dr Harry Brown

Febrile convulsions occur in a small percentage of young children (Photograph: SPL)
Febrile convulsions occur in a small percentage of young children (Photograph: SPL)

Patients commonly present to healthcare professionals with a fever. The generation of temperature represents a sophisticated body reaction, which includes immunological and metabolic responses, to the provoking stimulus.

Assessing fever
Normal body temperature can be variable but a reasonable definition of fever is a temperature measured in the axilla that is more than 37oC.

The causes of fever can be numerous and it can be part of a huge range of clinical problems. These can range from mild self-limiting illnesses to severe life-threatening disease states.

Normally having a temperature is a mild, short-lived problem but occasionally it can be a marker for a more serious condition.

In an adult with either a heart or lung problem, a significant rise in temperature may cause functional deterioration irrespective of the cause of the fever. Similarly, a person with dementia may suffer deterioration in their cognitive state because of the temperature.

In an acute febrile illness, in the initial stages, often the presenting symptoms and signs are non-specific and a detailed history and focused examination are required.

Possible causes

Infection is the most common cause of fever in most age groups. Other causes include:

  • Malignancy.
  • Collagen vascular disorders.
  • Inflammatory bowel disease.
  • Thyrotoxicosis.
  • Vaccination.

Serious concerns
Febrile convulsions occur in a small percentage of children aged between six months and five years. Not uncommonly, the seizure can occur in the very early stages of a viral illness when the rate of rise of temperature is significant.

Often they are brief affairs and do not damage the brain.

There is also a risk of a similar episode in a subsequent illness associated with a temperature. Never underestimate the parental concern and stress that this can cause. All children suffering from this require an urgent and detailed assessment.

Febrile neutropenia can occur in patients who are receiving or have recently received chemotherapy - they are potentially immunosuppressed because of the impact on their bone marrow function. This makes them more at risk from infection and they can deteriorate quickly.

Any patient with a fever, who is currently receiving (or recently received) chemotherapy, should be assessed in secondary care, ideally by the team that is administering the chemotherapy.

Within primary care, all practitioners should have a high index of suspicion in such a patient who is receiving or has recently received chemotherapy, who presents with ill health, particularly when associated with a temperature.

Pyrexia of unknown origin is considered to be a high temperature that has lasted for more than three weeks and to that point no cause has been found. Such cases usually require extensive investigations, with malignancy, connective tissue disorders and infections needing to be excluded.

Patients without a functioning spleen are at high risk of severe infection. There is a significant mortality involved, with most instances occurring within the first two years after losing splenic function.

However, the risk can remain life-long and any feverish asplenic patient needs an immediate and detailed assessment.

With more day-case and rapid discharge surgery, it is not uncommon for primary care to be involved in the management of patients with postoperative pyrexia. Causes can include chest, urine or wound infection, and do not forget to consider a DVT.

  • Dr Brown is a GP in Leeds

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