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How Does the ER Treat a Fever?

May 14, 2024 • read

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How Does the ER Treat a Fever?

A fever is one of your body’s best defence mechanisms and often a sign that your body is fighting off an infection. Your body does this by increasing the ‘normal’ temperature in your internal thermostat (the part of the brain called the hippocampus) in an attempt to make the environment uninhabitable for viruses and bacteria. At the same time, your immune system tries to mount a vigorous response to kill the invading microbes. 

Normal body temperature differs slightly from person to person and changes about 0.5°C throughout the day with different activity levels. The average normal body temperature for an adult is 37°C (98.6°F). A fever is anything over your normal body temperature. 

Fever alone may not be a reason to visit your nearest emergency room (ER), but this article will highlight red flag symptoms that may drive you to the ER with fever and how your fever may be investigated and treated. 

How does the ER treat a fever?

Understanding how the ER treats fevers may give you some insight into what to expect and when to seek help. The ER’s first goal will be reducing your body temperature before discovering and treating the cause of the fever. The goals of treating a fever in the ER will be to first reduce your body temperature, then to discover and treat the cause of the fever.

Dosing for both fever and pain meds will be based on weight for children and timed accordingly with the last dose it was received at home: 

  • Acetaminophen can be taken every four to six hours
  • Ibuprofen can be taken every six to eight hours 
  • Aspirin (ASA) should never be given to a child with a fever

When medications alone will not bring down a fever, there are cooling methods the ER medical staff may use. Cooling methods available in most ERs can include things like: 

  • Cooling blankets 
  • Cold saline 
  • Ice packs 
  • Cool water baths 

A fever is your body’s way of fighting unwanted microbes. With supportive care, resting, and staying hydrated, fevers can often be managed in the comforts of your home most of the time and resolved within a few days. When red flags present, however, it is best to take a trip to your nearest ER. 

What is a fever? 

In light of many factors influencing temperature (like activity level, time of day, sleep-wake cycles, and hormonal variability) there is no one single cutoff to define a fever. 

For children, normal temperature can be up to 37.9°C when measured by rectal or ear and differs depending on the measurement method. For these reasons, the accuracy in measurement is even more important.

The Canadian Paediatric Society defines a fever in a child as anything over the normal temperature range: 

Method Normal temperature range

  • Rectum 36.6°C to 37.9°C (97.9°F to 100.2°F)
  • Mouth 35.5°C to 37.5°C (95.9°F to 99.5°F)
  • Armpit 36.5°C to 37.5°C (97.8°F to 99.5°F)
  • Ear 35.8°C to 37.9°C (96.4°F to 100.2°F)

For children under the age of five, rectal temperature taking is the most accurate method. For children aged two to five, the ear or armpit are alternative options. For anyone over the age of fives, the best method is by mouth, with ears or armpits as alternatives for measuring temperature. 

Recognizing high fever 

Keep in mind, that temperature is not an indicator of illness severity. This means that someone very sick can have a low or normal temperature, and someone with a mild infection could have a very high temperature. A better indicator is how the person looks and behaves (more on this below). Recognizing a fever can be easier when you know the common associated symptoms like:

  • Sweats and chills or shivering
  • Reduced appetite
  • Fatigue or generalized weakness

The Canadian Paediatric Society recommends babies under six months with a fever should be seen by a physician, and babies younger than three months should be seen more urgently. 

For adults, we can consider the following ranges for fever severity. 

  • Low-grade fever 37.3 – 38°C (99.1 – 100.4°F)
  • Moderate grade fever 38.1 – 39°C (100.5 – 102.2°F)
  • High-grade fever 39.1 – 41°C (102.3 – 105.8°F)
  • Hyperthermic >41°C (>105.8°F)

It is important to recognize, and treat high fevers because prolonged periods of severely elevated temperatures can lead to potentially lethal consequences by damaging cells in your brain, heart, gastrointestinal tract, liver, kidneys, and blood. 

Causes of high fever 

There are hundreds of infectious causes of fever, most commonly viruses and bacteria, but parasites and fungi can also instigate this immune response.

Similar to pneumonia or strep throat, there are other reasons why your body could be mounting a fever.

Some non-infectious causes of fever include:

  • Trauma or recent surgery 
  • Reactions to certain medications or immunizations 
  • Some long-term or chronic health conditions like rheumatoid arthritis 
  • Some kinds of cancers 

When to seek medical care with a fever 

A fever can often be treated at home. Try to stay cool and hydrated by drinking plenty of fluids;  dressing in a single layer, and avoiding extra blankets and clothing, can help prevent overheating.

Rest, and eat foods that are easier to digest to allow most of your energy to be directed at fighting off the infection. With supportive care, fevers typically resolve in about three days.

It’s recommended to seek medical care if the fever lasts longer than three days, or: 

  • Your child with fever is under six months
  • Excessively irritable, fussy, or cranky 
  • Wheezing, or persistently coughing
  • Have a rash or any other worrisome signs to you
  • Has a temperature > 40°C

A higher temperature does not always indicate a more severe illness. A better gauge is behaviour.

Red flags that warrant a trip to the ER with a fever are when: 

  • A baby under three months old has a fever
  • Headache, stiff neck, or neck pain does not improve with acetaminophen or ibuprofen 
  • There is difficulty breathing
  • They are excessively sleepy, lethargic, or not responding normally
  • There are signs of dehydration (dry mouth, not peeing at least every 8 hours)
  • There is a loss of consciousness or confusion 
  • There are seizures 
  • There is severe pain or swelling anywhere in the body 

Assessments of fever in the ER 

A fever is a symptom, not a diagnosis. Treating the fever will help temporarily improve symptoms but it does not treat the underlying cause of the fever.

Making a diagnosis requires a lot of information gathering. This can be done with a thorough history and physical examination. Your accompanying symptoms can give the medical team clues into the potential causes of your fever. Investigations like bloodwork, urine samples, lumbar punctures, or imaging like x-rays can often confirm, support, or rule out a diagnosis.

The medical professionals you meet may ask the same or additional questions to gather more information. You may be asked about the presence of any:

  • Cold or flu-like symptoms
  • Nausea, vomiting or diarrhea
  • Urinary symptoms like pain, frequency, or urgency 
  • Pain in one particular area of your body
  • Recent travel or sick contacts
  • Recent surgeries or wounds
  • Implanted devices like a mechanical heart valve

When you visit the emergency room with a fever, you or a family member should be ready to provide a history and more than once. Your visit to the ER may resemble this sequence:

  1. You will likely first meet the administration desk to exchange health card information and the reason for your visit. 
  2. Then, you will be seen by the triage team (usually nurses), with whom you will share more details about your condition,  medications you are taking, and pertinent past medical history. They will check your vital signs including heart rate (HR), respiratory rate (RR), temperature, weight, and sometimes oxygen levels using a small sensor that gently clamps onto the tip of your finger (called a pulse oximeter). 
  3. This is all done before you get moved to an examination room where you will be seen by more nursing staff before meeting the medical team. This team could consist of physician assistants (PAs), medical residents (MDs), or medical or PA students all working in collaboration with the supervising ER physicians. 
  4. Investigations may be ordered, or other medical specialties may be consulted to assist in differentiating your diagnosis. 

If a fever is just beginning, consider speaking to your family doctor about managing your symptoms.  If you’re among the 6.5 million Canadians without a family doctor, then consider using Maple to speak with a primary care provider — such as a nurse practitioner or Canadian-licensed doctor — without experiencing the long wait times in the waiting room. It’s important to note that while virtual care is effective for non-emergencies, you should head to the nearest ER if you are experiencing severe symptoms. 

The information presented here is for educational purposes and is not meant to replace the advice from your medical professional. Virtual care is not meant for medical emergencies. If you are experiencing an emergency like chest pain or difficulties breathing, for example, please call 911 or go to your nearest emergency room.


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