FEVER / HYPERTHERMIA

Dr.Mohamad Shaikhani.

Normal & variations:• The mean oral temperature is 36.8+/- 0.4C (98.2+/- 0.7_F), with

low levels at 6 A.M.& higher levels at 4 to 6 P.M.

• In women who menstruate, the A.M. temperature is generally lower in the 2 weeks before ovulation; it then rises by about 0.6 C ( 1 F) with ovulation& remains at that level until menses occur.

• Body temperature is elevated in the postprandial state.

• Elderly individuals have a reduced ability to develop fever, even in severe infections.

Common Sites for Temperature MeasurementCommon Sites for Temperature Measurement

SiteSiteProsProsConsConsUsesUses

Oral cavityOral cavityEasy access

Familiar Minimally invasive

Affected by eating, drinking, etc. Temperature varies within oral cavity. Hard to keep thermometer in place, esp. if edentulous.

Most common site in adults and children over 5.

RectumRectumPreferred by MDs.

Site records highest temp in body. Lags behind other core sites when temp is changing rapidly.

Often requested by MDs as the 'most accurate' site for core temperature.

AxillaAxilla

Easy access Familiar Minimally invasive. Preferred by American Academy of Pediatrics for use in infants.

Reflects skin temperature. Not always a good indicator of core temperature. Must be held in place. Takes long time to reach equilibrium.

Most common site in children under 5. Sometimes used during surgery.

EarEar

Easy access Familiar Minimally invasive. Two sites available. Reflective of brain temperature.

Requires thorough training and attention to technique.

Commonly used in hospitals and clinics.

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Body Normal TemperatureBody Normal Temperature

Mouth36.8 c

Axilla36.4 c

Rectum37.7 c

Ear36.8 c

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Electronic/Disposable Thermometer

                                                  

      

Skill 31-1: Step 6C(7).   Thermometer tip in axilla.View

Fever

• Elevation of body temperature that exceeds the normal daily variation& occurs in conjunction with an increase in

the hypothalamic set point • The processes of heat conservation (vasoconstriction)&

heat production (shivering / increased metabolic activity) continue until the temperature of the blood bathing the hypothalamic neurons matches the new thermostat setting.

Fever• The daily highs& lows of normal temperature are exaggerated

in most fevers, but reversed in typhoid fever& disseminated TB.

• Temperature-pulse dissociation (relative bradycardia) occurs in typhoid fever, brucellosis, leptospirosis, some drug-induced fevers, and factitious fever.

• In newborns,elderly, CRF&patients taking glucocorticoids, fever may not be present despite infection, or core temperature may be hypothermic.

• Hypothermia is observed in patients with septic shock, hypothyroidism & cold exposure.

characteristic patterns.• Of clinical benefit only in malaria.• Relapsing fevers, febrile episodes are separated by intervals of normal

temperature:• Tertian:when paroxysms occur on the first& third daysas in

Plasmodium vivax • Quartan fevers associated with paroxysms on the first & fourth

days,seen with P. malariae. • Borrelia infections& rat-bite fever, both associated with days of fever

followed by a several-day afebrile period& then a relapse of days of fever.

• Pel-Ebstein fever, fevers lasting 3 to 10 days followed by afebrile periods of 3 to 10 days, is classic for Hodgkin’s disease& other lymphomas.

• Cyclic fever, fevers occur every 21 days& accompany cyclic neutropenia.

• Hectic Fever: Daily elevated temperature (>38 C or 100.4 F).

Continuous fever

Remittent:

Intermittent:

Undulant:

Relapsing:

Irregular:

How to Classify Fever?

• Fever can be classified in two ways:

1- Continued, Intermittent, Remittent, Relapsing.

2- Acute, Chronic.

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Typestypecharacterexamples

ContinuedDoes not remitTyphoid fever, typhus, drug fever, malignant hyperthermia.

IntermittentTemperature falls to normal everyday

Pyogenic infection, lymphoma, military T.B.

RemittentDaily fluctuation >2c .temperature dos not return to normal

Not characteristic for any particular disease.

RelapsingTemperature returns to normal for days before

rising again

Malaria:tertian-3days pattern, fever peaks

every other day (plas. Vivax, plas.ovale), quatrain-4day pattern . fever peaks every third day (p.malaria)

lymphoma:HODJKIN lymphomaPyogenic infection

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Hyperpyrexia:

• A fever of >41.5C (>106.7 F).

• Can develop in patients with severe infections but most commonly in patients with CNS hemorrhages, tumor, or intrinsic hypothalamic malfunction.

HYPERTHERMIA • Hyperthermia is characterized by an unchanged (normothermic)

setting of the thermoregulatory center in conjunction with an uncontrolled increase in body temperature that exceeds the body’ ability to lose heat.

• Heat stroke • Drug-induced hyperthermia by MAOIs, tricyclic antidepressants,

& amphetamines,phencyclidine (PCP), LSD, or cocaine.• Malignant hyperthermia occurs in individuals with an inherited

abnormality of skeletal-muscle sarcoplasmic reticulum that causes a rapid increase in intracellular calcium levels in response to halothane& other inhalational anesthetics or to succinylcholine.

HYPERTHERMIA • The neuroleptic malignant syndrome (NMS) with neuroleptic use

(antipsychotic phenothiazines, haloperidol, prochlorperazine, metoclopramide) or the withdrawal of dopaminergic drugs characterized by “lead-pipe” muscle rigidity, extrapyramidal side effects, autonomic dysregulation& hyperthermia.

• The serotonin syndrome, seen with (SSRIs), MAOIs& other serotonergic medications, has many overlapping features, including hyperthermia, distinguished by diarrhea, tremor, myoclonus rather than the leadpipe rigidity of NMS.

• Thyrotoxicosis&pheochromocytoma can also cause increased thermogenesis.

FUO or PUO:

• Classical FUO.

• HIV FUO.

• Neutropenic FUO.

• Nosocomial FUO.

• Fever >38 c persisting for >3 weeks with no clear diagnosis with one week intelligent& intensive investigation.

Causes of FUO:

• BIG 3– Infection – Neoplasm– Autoimmune diseases

• Little 6– Drug fever– Granulomatous diseases– Regional enteritis– Familial Mediterranean fever– Pulmonary emboli– Factitious fever

Treatment:• Oral aspirin & acetaminophen are equally effective in

reducing fever. • NSAIDs as indomethacin / ibuprofen are also excellent

antipyretics.• As effective antipyretics, glucocorticoids; cyclooxygenase

inhibitors, reducing PGE2 synthesis & block the transcription of the mRNA for the pyrogenic cytokines.

Treatment:• Treating fever& its symptoms does no harm or slow the

resolution of common viral& bacterial infections. • Reducing fever with antipyretics also reduces systemic

symptoms of headache, myalgias& arthralgias.• Oral aspirin& NSAIDs effectively reduce fever but can

adversely affect platelets &GIT, so acetaminophen is preferred as an antipyretic.

• In children, acetaminophen must be used because aspirin increases the risk of Reye’s syndrome.

• If the patient cannot take oral antipyretics, parenteral preparations of NSAIDs& rectal suppository can be used.

Treatment:• Treatment of fever in some groups of patients is specially

recommended.• Fever increases the demand for oxygen (i.e., for every increase of

1C over 37C, there is a 13% increase in oxygen consumption) aggravating preexisting cardiac, cerebrovascular, or pulmonary insufficiency.

• Elevated temperature can induce mental changes/hallucinations in patients with or without organic brain disease.

• Children with a history of febrile or nonfebrile seizure should be aggressively treated to reduce fever.

• In hyperpyrexia, the use of cooling blankets facilitates the reduction of temperature; but should not be used without oral antipyretics.

• In hyperpyretic patients with CNS disease or trauma, reducing core temperature reduces the ill effects of high temperature on the brain

Treatment: Hyperthermia • Antipyretics& attempt to lower the already normal hypothalamic

set point is of little use. • Physical cooling with sponging, fans, cooling blankets&ice baths

should be initiated immediately with IVF &appropriate pharmacologic agents.

• Internal cooling can be achieved by gastric or peritoneal lavage with iced saline.

• In extreme circumstances, hemodialysis or even cardiopulmonary bypass with cooling of blood may be performed

Treatment: Malignant hyperthermia • Immediate cessation of anesthesia & use of IV dantrolene.• Procainamide should also be used because of the likelihood of

VF. • Dantrolene also is indicated in NMS& in drug-induced

hyperthermia& may even be useful in the hyperthermia of the serotonin syndrome& thyrotoxicosis.

• NMS may also be treated with bromocriptine, levodopa, amantadine, or nifedipine or by induction of muscle paralysis with curare / pancuronium.

• Tricyclic antidepressant overdose may be treated with physostigmine.