Infant and Children | June 28, 2014 | Author: The Super Pharmacist
Hyperthermia is an abnormally elevated temperature. While the term hyperthermia is often used interchangeably with fever, there are some subtle and important differences. Fever is a biological response that is produced by the brain usually (but not always) as a reaction to an infectious process. There are other causes for hyperthermia in infants and children, however which include heat stroke and other heat illnesses, drug intoxication/drug fever and allergic reactions.
Most people know that normal body temperature is 37.0°C, but this value is determined from studies done over 200 years ago. Studies of modern human body temperature suggests that the upper limit of normal body temperature is actually 37.7°C. Moreover, infants and young children usually have higher normal body temperatures than older children and adults. The rule of thumb is that a “fever” is not a fever until body temperature reaches above 38°C. Keep in mind that this value was based on the use of a rectal thermometer and that oral temperatures may be 0.5°C lower than rectal temperatures. Temperatures taken in the ear (infrared tympanic membrane thermometers) provide readings that are very close to core temperature, just like rectal temperatures. Paracetamol and ibuprofen are acceptable treatments for fever in infants and children.
Fever is actually the result of a highly coordinated and complex series of biological events. It is usually started when some sort of microorganism or foreign body enters the blood or other tissue.
The immune system recognises the invader and launches an immune attack, releasing various types of molecular signals called cytokines. These cytokines change the brains “thermostat” so that it raises body temperature by conserving and producing heat. There is convincing scientific evidence that fever actually helps them immune system fight off infection. Fever can slow down the growth of bacteria and viruses and can improve immune system function.
Nevertheless, fever can be uncomfortable for children and it is the common inclination of parents and even doctors to treat fever with paraceamol and non-steroidal anti-inflammatory drugs (NSAIDS). Bacterial infections are treated with antibiotics.
Heat stroke is a condition in which the core body temperature rises to 40°C or higher from external heat exposure and causes neurological dysfunction. It is sometimes also referred to as sunstroke. The neurological dysfunction that occurs in heat stroke can be difficult to detect in infants. Children may exhibit strange behavior, experience hallucinations, become delirious, have slurred speech, or even have seizures. Importantly, if a child's core body temperature is 40°C or higher and does not seem to have neurological problems, they still should be treated for hyperthermia.
Non-exertional or classic heatstroke is more common in infants and young children because it occurs without physical activity and is usually the result of a child who cannot escape a hot environment. Sadly, one of the more common causes of non-exertional heatstroke is children left in hot cars on summer days.
Exertional heat stroke also occurs on hot days, but usually after periods of extreme exertion in high humidity environments when sweating does not sufficiently cool the body.
The treatment for heat stroke, either exertional or non-exertional, is to bring the core body temperature down quickly and safely. The child should be removed from the hot environment and physical exertion should be stopped. The patient with heatstroke can be placed in a cool bath, if available, or ice packs can be placed on the neck, groin, and armpit areas. These areas are where arteries run near the surface of the skin so that the temperature of the blood can be rapidly reduced. A core body temperature above 41°C is dangerous and is considered a medical emergency. A child with a body temperature at this level may experience delirium, convulsions, coma, and the condition can be rapidly fatal. Efforts should be made to lower the body temperatures as quickly as possible.
Heat exhaustion is similar to heat stroke in that it occurs from heat exposure but arises at lower core body temperatures, specifically between 37.7 and 40°C. Children with heat exhaustion may have elevated heart rate, nausea/vomiting, headache, weakness/fatigue, dizziness, and severe thirst. Any child that has neurological disturbances that do not respond to treatment should be assumed to have heat stroke.
Various drugs, both illicit and prescription drugs can cause hyperthermia. They can either cause a fever when they are administered or, if the drug is taken ongoing, hyperthermia results when the drug is withdrawn.
Some of the more common causes of drug fever include anticonvulsants such as carbamazepine, phenytoin, and phenobarbital, minocycline and certain other antibiotics, allopurinol, and heparin. Illegal drugs such as ecstasy (MDMA), phencyclidine (PCP), and cocaine may cause hyperthermia, but these are fortunately rare cases of elevated body temperature in infants and children and usually arise from child abuse or child neglect.
The patient may be allergic to the drug or the drug may affect the brain’s “thermostat.” The drug may stimulate muscle activity, which generates body heat. Regardless of the mechanism, drug fever should be considered when hyperthermia occurs in an infant or child who is taking a drug. In most cases, the treatment for drug fever is to simply stop the offending drug. Once the drug is stopped, virtually all patients’ body temperature will return to normal within 72 to 96 hours.
A rare but potentially life-threatening drug reaction is called malignant hyperthermia. It is only known to occur during anesthesia and is recognised by a sudden fever over 40°C, muscle rigidity, and blood pressure instability. Anesthesiologists are trained to look for malignant hyperthermia and know to treat it with dantrolene as soon as symptoms arise.
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