Chapter 53: Fever and chills

Although fever is a sign of disease and usually occurs in response to infection (mainly viral), its presence is recognised as playing an important role in the individual’s defence against infection. The infecting pathogen triggers hypothalamic receptors, causing the thermostatic mechanisms to be reset to maintain core temperature at a higher level. The elevation in temperature results from increased heat production (e.g. shivering) or decreased loss (e.g. peripheral vasoconstriction). The elevation in body temperature activates T-cell production, increases the effectiveness of interferons and limits the replication of some common viruses.¹

Chills/rigors²

The abrupt onset of fever with a chill or rigor is a feature of some diseases. Examples include:

• bacteraemia/septicaemia

• pneumococcal pneumonia

• pyogenic infection with bacteraemia

• lymphoma

• pyelonephritis

• visceral abscesses (e.g. perinephric, lung)

• malaria

• biliary sepsis (Charcot triad—jaundice, right hypochondrial pain, fever/rigors)

Features of a true chill are teeth chattering and bed shaking, which is quite different from the chilly sensations that occur in almost all fevers, particularly those in viral infections. The event lasts 10–20 minutes.

Other features:

• shaking cannot be stopped voluntarily

• absence of sweating

• cold extremities and pallor (peripheral vascular shutdown)

• dry mouth and pilo-erection: lasts 10–20 minutes

Hyperthermia or hyperpyrexia is a temperature greater than 41.1°C. A more accurate definition is a state when the body’s metabolic heat production or environmental heat load exceeds normal heat loss capacity. Hyperthermia may be observed particularly in the tropics, in malaria and heatstroke. It can occur with CNS tumours, infections or haemorrhages because of its effect on the hypothalamus.

Heatstroke (sunstroke, thermic fever)⁵

This is the sudden onset of hot, dry, flushed skin with a rapid pulse, temperature above 40°C, and confusion or altered conscious state in a person exposed to a very hot environment. The BP is usually not affected initially but circulatory collapse may precede death. It is a life-threatening emergency. The diagnosis is clinical. Differential diagnoses include severe acute infection, toxic shock, food, chemical and drug poisoning. The elderly and debilitated are susceptible as are children left in cars.

Treatment

• Immediate effective cooling water applied to skin

• Icepacks at critical points (e.g. axillae, neck, head)

• Ice water bath if possible

• Aim to bring down temperature by 1°C every 10 minutes

Malignant hyperthermia

This is a rare hereditary disorder characterised by rapidly developing hyperpyrexia, muscular rigidity and acidosis in patients undergoing major surgery.

Sweating is a heat loss mechanism, and diffuse sweating that may soak clothing and bedclothing permits rapid release of heat by evaporation. In febrile patients the skin is usually hot and dry—sweating occurs in most when the temperature falls. It is characteristic of only some fevers (e.g. septic infections and rheumatic fever).

Factitious fever

Factitious fever is usually encountered in hospitalised patients attempting to malinger. The situation is usually suspected when:

• a series of high temperatures is recorded to form an atypical pattern of fluctuation

• there is excessively high temperature (41.1°C) and above

• a recorded high temperature is unaccompanied by warm skin, tachycardia and other signs of fever such as a flushed face and sweating

• there is an absence of diurnal variation

The patient may have surreptitiously dipped the thermometer in warm water, placed it in contact with a heat source or heated the bulb by friction with bedclothes or even mucous membranes of the mouth.

Neuroleptic malignant syndrome

This is often confused with ‘malignant’ hyperthermia and heat stroke. The syndrome includes high temperature, muscle rigidity, autonomic dysfunction and altered consciousness. It is a rare and potentially lethal reaction in patients taking antipsychotic drugs, particularly occurring with haloperidol alone or with other drugs especially lithium carbonate. Refer to CHAPTER 45.

Temperature can be measured by several methods, including the mercury thermometer, the liquid crystal thermometer and the electronic probe thermometer. The mercury thermometer is a most widely used and effective temperature-measuring instrument. However, it is less popular now and not favoured for infant use by the American Academy of Paediatricians.

Basic rules of usage for the mercury thermometer

1. Before use, shake down to 35–36°C.

2. After use:

   • – shake down and store in antiseptic

   • – do not run under hot water

   • – wipe rectal thermometer with alcohol and store separately

3. Recording time is 3 minutes orally and 1–2 minutes rectally.

Accidental breakage in the mouth

If a child bites off the end of a mercury thermometer there is no need for alarm, as the small amount of mercury is non-toxic and the piece of glass will usually pass in the stool.

Oral use

1. Place under the tongue at the junction of the base of the tongue and the floor of the mouth to one side of the frenulum—the ‘heat’ pocket.

2. Ensure that the mouth is kept shut.

3. Remove dentures.

Note: This is unsuitable for children 4 years and under, especially if irritable.

Rectal use

This is an appropriate route for babies and young children under the age of 4 years but should be used with care. The rule is ‘2–3 cm in for 2–3 minutes’ and some authorities claim that this method is the gold standard, especially in infants.

1. Lubricate the stub with petroleum or KY jelly.

2. Insert for 2–3 cm past anal verge.

3. Keep the thermometer between the flexed fingers with the hand resting on the buttocks (see FIG. 53.1).

Don’t:

• dig thermometer in too hard

• hold it too rigidly

• allow the child to move around

Axillary use

This is unreliable with poor sensitivity and generally should be avoided but may be practical in young children.⁶

If used, place high in the axilla for 3 minutes. Fever is present if the temperature is above 37.2°C.

Groin use

This route is not ideal but is more reliable than the axilla. It closely approximates oral temperature. In infants, the thigh should be flexed against the abdomen.

Vaginal use

This is mainly used as an adjunct to the assessment of ovulation during the menstrual cycle. It should be placed deeply in the vagina for 5 minutes before leaving bed in the morning.

Digital peak hold thermometer

Otic thermography is now accepted standard practice. The temperature can be measured in 3 seconds, with the infrared device (e–2 therm) placed in the ear canal. First, hold the child’s head firmly to avoid any movement, then take temperature. Wait 2 minutes before taking the temperature in the same ear. The tympanic membrane (TM) accurately reflects hypothalamic temperature, which in turn reflects core body temperature. The TM is also immune from the effects of eating, drinking and smoking. A systematic review in the Cochrane study questions its reliability. It is poor in small infants but useful over the age of 6 months.⁷ However, some Australian authorities believe that in general practice the benefits of convenience outweigh the lack of accuracy.⁸ The normal range is the same as for rectal temperature.

Digital electronic pacifier (dummy) thermometer

This is a popular method for infants and younger children, favoured by many paediatricians in the US.

Skin use

Plastic strip thermometers placed on the forehead are very inaccurate and should not be used.

The initial approach is to evaluate the severity of the problem and the nature of the illness. Some infections, particularly bacterial infections, are life-threatening and this requires urgent diagnosis and hospital admission.

According to Yung and Stanley³ it is helpful to consider fever in three categories: less than 3 days duration; between 4 and 14 days duration; and protracted fever (more than 14 days).

Fever of less than 3 days duration

This is very commonly encountered in family practice, often due to a self-limiting viral infection of the respiratory tract. It is important, however, to be vigilant for other infections, so evidence of an infectious disease, urinary tract infection, pneumonia or other infection should be sought. A routine urine examination, especially in females, is an important screening investigation. The majority of patients can be managed conservatively.

Fever present for 4–14 days

If fever persists beyond 4–5 days a less common infection should be suspected since most common viral infections will have resolved by about 4 days.³ A careful history is mandatory, as outlined later in the chapter for fever of unknown origin (FUO). The basic examination and investigations are along similar lines.

Temperature chart

Charting the patterns of fever may be a diagnostic help because some febrile conditions follow a predictable temperature pattern.⁹ Examples are presented in FIGURE 53.2.

Intermittent fever

This is a fever in which the temperature rises for a few hours each day and then returns to normal (see FIG. 53.2a). Examples include various pyogenic infections, cytomegalovirus and lymphoma.

Relapsing fever

The fever returns to normal for days before rising again. Malaria is the classic example of periodic relapsing fever: in quartan fever, caused by Plasmodium malariae (see FIG. 53.2a), the attacks occur every 72 hours (the term quartan means every 4th day by inclusive counting). This compares with tertian fever from Plasmodium vivax in which paroxysms of malaria occur every 48 hours, that is, every 3rd day.

Remittent fever

This is a fever in which the temperature returns towards normal for a variable period but is always elevated (see FIG. 53.2d). Common examples are collections of pus (e.g. pelvic abscess, wound infection, empyema and carcinoma). It is a common feature of empyema.

Undulant fever

Undulant fever is characterised by bouts of continuous or remittent fever for several days, followed by afebrile remissions lasting a variable number of days. It is commonly a feature of brucellosis infection but is also seen in the lymphomas, especially Hodgkin lymphoma (see FIG. 53.2b). The latter is referred to as Pel–Ebstein fever with fevers lasting 3–10 days followed by afebrile periods of 3–10 days.

Continuous fever pattern

This is common with viral infections such as influenza (see FIG. 53.2c).

Quotidian fever

In this pattern the fever recurs daily (see FIG. 53.2d). Daily fever spikes in the morning are characteristic of Pseudomonas infection (e.g. pulmonary superinfection); afternoon spikes are indicative of cytomegalovirus infection; and evening spikes suggest localised collection of pus (e.g. empyema of the gall bladder).

Double quotidian fever (two fever spikes in a day) is caused by adult Still syndrome, gonococcal endocarditis and visceral leishmaniasis.

If risk factors are present, especially if taking antibiotics, consider the investigations outlined in TABLE 96.1, in CHAPTER 96.

Postoperative fever

This is fever occurring within 24 hours after surgery—common with abdominal surgery.

Causes to consider:

• pulmonary atelectasis (common)

• wound haematoma

• deep venous thrombosis

• myocardial infarction

• allergic drug reaction

• transfusion reaction

Septic problems related to the operation usually develop after several days.

In children, most authorities would consider a fever of 38.5°C and above to be significant and warrant close scrutiny.¹⁰ If it is below this, it is not caused by teething or swaddling.

Important causes not to be missed:

• urinary infection

• meningitis/encephalitis

• pneumonia

• septicaemia/bacteraemia

• osteomyelitis

• septic arthritis

• pertussis

• abscess

The fever is usually a response to a viral infection. Fever itself is not harmful until it reaches a level of 41.5°C.¹ Hyperthermia is uncommon in children. Temperatures above 41°C are usually due to CNS infection or the result of human error, for example:

• shutting a child in a car on a hot day

• overwrapping a febrile child

Complications include dehydration (usually mild) and febrile convulsions, which occur in 5% of febrile children between 6 months and 5 years. Febrile convulsions are triggered by a rapid rise in temperature rather than its absolute level.

Note: Teething does not cause fever.

Approach to the febrile infant

It is important to decide whether the child looks well or seriously ill. Identification of the very ill child is presented in CHAPTER 96.

If the child is well and has no risk factors (e.g. unreliable caregiver, poor access to treatment, medical risk factors, taking antibiotics) treat expectantly. The only test required is urine microscopy and culture. Educate the caregiver about review if serious signs develop. Treat the fever as outlined in TABLE 96.1, in CHAPTER 96.

Management

• Treatment of low-grade fevers should be discouraged.

• Treatment of high-grade fevers includes:

  • – treatment of the causes of the fever (if appropriate)

  • – adequate fluid intake/increased fluids

  • – paracetamol (acetaminophen) is the preferred antipyretic since aspirin is potentially dangerous in young children (use paracetamol if temperature >38.5°C). The usual dose of 10–15 mg/kg every 4–6 hours may represent undertreatment. Use 20 mg/kg as a loading dose and then 15 mg/kg maintenance

  • – evidence favours tepid sponging for first 30 minutes combined with paracetamol¹¹

  • – ibuprofen 5–10 mg/kg every 6 hours is a suitable antipyretic

Advice to parents

• Dress the child in light clothing (stripping off is unnecessary).

• Do not overheat with too many clothes, rugs or blankets.

• Give frequent small drinks of light fluids, especially water.

• Sponging with cool water and using fans is not effective.

Febrile convulsions

Refer to CHAPTER 96.

The elderly tend to have a problem with impaired thermoregulation and so they may not develop a fever in response to suppurative infection compared with younger people. This can be misleading in the diagnostic process.

Important facts

• Any fever in the elderly is significant.

• Viral infection is a less common cause of fever in the elderly.

• Fever in the elderly is sepsis until proven otherwise (common sites are the lungs and urinary tract).

The elderly are more vulnerable to hyperthermia and hypothermia. Heatstroke classically occurs in epidemic form during a heatwave. The syndrome consists of hyperpyrexia, decreased sweating, delirium and coma. The core temperature is usually over 41°C.

In many patients the existence of a life-threatening infective illness is obvious and prompt action is essential. In others the diagnosis is not clear-cut but there are certain warning signs (see Red flags box).

These ‘red flag’ symptoms and signs are obviously super ‘sensitive’. Patients with some of these features may have potentially life-threatening diseases, but this list would include many with viral infections.

Fever of undetermined origin (FUO), also referred to as pyrexia of unknown origin (PUO), has the following (Petersdorf–Beeson modified) criteria:¹²

• illness for at least 3 weeks

• fevers >38.3°C (100.9°F) on several occasions

• undiagnosed after 1 week of intensive study

Most cases represent unusual manifestations of common diseases and not rare or exotic diseases. Examples are tuberculosis, bacterial endocarditis, hepatobiliary disease and lung cancer.¹³

Keep in mind that the longer the duration of fever, the less likely the diagnosis is to be infectious—fevers that last greater than 6 months are rarely infectious (only 6%). One study showed that 9% are factitious.¹⁴

Patients with FUO in definite need of further investigation are:

• babies <3 months of age

• children with fever >40°C

• adults >50 years

• diabetics

• the immunocompromised

• travellers

A diagnostic approach

A knowledge of the more common causes of FUO is helpful in planning a diagnostic approach (refer to TABLE 53.1).

History

The history should include consideration of past history, occupation, travel history, sexual history, IV drug use (leads to endocarditis and abscesses), animal contact, medication and other relevant factors. Symptoms such as pruritus, a skin rash and fever patterns may provide clues for the diagnosis. The average patient with a difficult FUO needs to have a careful history taken on at least three separate occasions.¹⁵

Examination

A common mistake is the tendency to examine the patient only once and not re-examine. The patient should be examined regularly (as for history taking) as physical signs can develop eventually. HIV infection must be excluded. Special attention should be paid to the following (see FIG. 53.3):

• skin—look for rashes, vesicles and nodules

• the eyes and ocular fundi

• temporal arteries

• sinuses and ears (canal and TM)

• teeth and oral cavity—? dental abscess, other signs

• heart—murmurs, pericardial rubs

• lungs—abnormalities including consolidation, pleuritic rub

• abdomen—enlarged/tender liver, spleen or kidney

• rectal and pelvic examination (note genitalia)

• lymph nodes, especially cervical (supraclavicular)

• blood vessels, especially of the legs—? thrombosis

• urine (analysis)

Investigations¹⁶

Basic investigations include:

• haemoglobin, red cell indices and blood film

• white cell count

• ESR/C-reactive protein

• chest X-ray and sinus films

• urine examination (analysis and culture)

• routine blood chemistry

• blood cultures

Further possible investigations (depending on clinical features):

• stool microscopy and culture

• culture of sputum (if any)

• specific tests for malaria, typhoid, EBM, Q fever, brucellosis, psittacosis, cytomegalovirus, toxoplasmosis, syphilis, various tropical diseases and others

• NAAT (e.g. PCR) tests

• HIV screening

• tests for rheumatic fever

• tuberculin test

• tests for connective tissue disorders (e.g. DNA antibodies, C-reactive protein)

• upper GIT series with small bowel follow-through

• CT and ultrasound scanning for primary and secondary neoplasia

• gall bladder functioning

• occult abscesses

• MRI—best for detecting lesions of the nervous system

• echocardiography—for suspected endocarditis

• isotope scanning for specific causes

• aspiration or needle biopsy

• laparoscopy for suspected pelvic infection

• tissue biopsies (e.g. lymph nodes, skin, liver, bone marrow) as indicated

FUO in children

Fever in children is usually a transient phenomenon and subsides within 4–5 days. At least 70% of all infections are viral. Occasionally a child will present with FUO which may be masked from antibiotic administration. Common causes of prolonged fever in children differ from those in adults. Most cases are not due to unusual or esoteric disorders,¹⁷ the majority representing atypical manifestation of common diseases.

A summary of the common causes (with the most common ranked first) is as follows.¹⁷

Infectious causes (40%)

• Viral syndrome

• Urinary tract infection

• Pneumonia

• Pharyngitis

• Sinusitis

• Meningitis

Collagen–vascular disorders (15%)

• Rheumatic arthritis

• Systemic lupus erythematosus

• Rheumatic fever

• Henoch–Schönlein syndrome

Neoplastic disorders (7%)

• Leukaemia

• Reticulum cell sarcoma

• Lymphoma

Inflammatory diseases of the bowel (4%)

Septicaemia

The diagnosis of septicaemia can be easily missed, especially in small children, the elderly and the immunocompromised, and in the absence of classic signs, which are:

• fever

• rash (suggestive of meningococcus)

• tachycardia

• tachypnoea

• cool extremities

Patients with septicaemia require urgent referral as it has a very high mortality rate.¹⁸ Investigations should include two sets of blood cultures and other appropriate cultures (e.g. urine, wound, sputum). Empirical initial treatment in adults (after blood cultures) is di/flucloxacillin IV and gentamicin IV.¹⁹

Hand-out sheets from Murtagh’s Patient Education 7th edition:

• Febrile convulsions

• Fever