definition of fever,approach to fever and hyperthermia

1. FEVER AND HYPERTHERMIA
Dr.G.VENKATA RAMANA
MBBS DNB FAMILY MEDICINE

2. DEFINITIONS
• FEVER
• Elevation in core body temperature that exceeds the normal daily
variation and occurs in conjunction with an increase in the hypothalamic
set point
• CHILL
• Sensation of cold
• RIGOR
• Profound chill with piloerection (goose flesh) associated with teeth
chattering and severe shivering
• Normal core body temperature in the range of 36.5–37.5°C (97.7–99.5°F)
• An a.m. oral temperature of >37.2°C (>98.9°F) or a p.m. temperature of
>37.7°C (>99.9°F) defines a fever
• However,in practice,a general threshold of Temp >37.8°C (100 °F) or
38°C(100.4 °F) is often used
• Normal daily temperature variation is typically 0.5°C (0.9°F)
• The normal body temperature is more towards the evening because of
increased BMR and increased skeletal muscle activity

3. • HYPERPYREXIA
• Fever >41.5°C (>106.7°F)
• Causes:
• Severe infections
• CNS hemorrhages
• HYPOTHALAMIC FEVER
• Elevated temperature caused by abnormal hypothalamic
function
• However, the majority of patients with hypothalamic damage
have hypothermia not hyperthermia
• HYPERTHERMIA
• Uncontrolled increase in body temperature that exceeds the
body's ability to lose heat
• The setting of the hypothalamic thermoregulatory center is
unchanged
• Newborns, elderly patients, patients with chronic liver or
kidney failure, and patients taking glucocorticoids, fever may
not be present despite infection.

4. • DRUG FEVER
• Fever that coincides with administration of a drug and disappears after
the discontinuation of the drug, when no other cause for the fever is
evident after a careful history, physical examination, and laboratory
investigation
• FACTITIOUS FEVER
• 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 fl
uctuationthere 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 fl ushed 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

7. • Body temperature is controlled by the
hypothalamus
• Neurons in both the preoptic anterior
hypothalamus and the posterior hypothalamus
receive two kinds of signals: one from peripheral
nerves that transmit information from warmth/cold
receptors in the skin and the other from the
temperature of the blood bathing the region
• These two types of signals are integrated by the
thermoregulatory center of the hypothalamus to
maintain normal temperature

8. • Once the hypothalamic set point is raised, neurons in the
vasomotor center are activated and vasoconstriction
Commences in the hands and feet
• Shunting of blood away from the periphery to the internal
organs essentially decreases heat loss from the skin, and the
person feels cold (Heat conservation)
• For most this is sufficient to raise body temperature by 1–2°C
• Shivering, which increases heat production from the muscles,
may begin at this time; however, shivering is not required if
mechanisms of heat conservation raise blood temperature
sufficiently (Heat production)
• Nonshivering heat production from the liver also contributes to
increasing core temperature (Heat production)
• Behavioral adjustments (e.g., putting on more clothing or
bedding) help raise body temperature by decreasing heat loss

9. • The processes of heat conservation (vasoconstriction) and heat
production (shivering and increased nonshivering thermogenesis)
continue until the temperature of the blood bathing the hypothalamic
neurons matches the new “thermostat setting”
• Once that point is reached, the hypothalamus maintains the temperature
at the febrile level by the same mechanisms of heat balance that
function in the afebrile state
• When the hypothalamic set point is again reset downward (in response
to either a reduction in the concentration of pyrogens or the use of
antipyretics), the processes of heat loss through vasodilation and
sweating are initiated
• Loss of heat by sweating and vasodilation continues until the blood
temperature at the hypothalamic level matches the lower setting
• Behavioral changes (e.g., removal of clothing) facilitate heat loss

14. • FEVER WITH RELATIVE BRADYCARDIA
• Typhoid fever
• Meningitis
• Viral fever (Influenza)
• Brucellosis
• Leptospirosis
• Drug induced fever
• Factitious fever
• FEVER WITH EXANTHEMS
• Rash appearing on first day of fever—Chicken pox
• Rash appearing on fourth day of fever—Measles
• Rash appearing on seventh day of fever—Typhoid
• FEBRILE CONVULSIONS
• It occurs in infants and children less than 5 years old
• Convulsions are common at temperatures more than 40°C
• It may not be a sign of cerebral disease

15. • FEVER WITH RIGORS: This occurs in:
• Malaria
• Kala azar
• Filariasis
• Urinary tract infection, pyelonephritis
• Cholangitis
• Septicemia
• Infective endocarditis
• Abscesses,any site
• Lobar pneumonia

16. • FEVER WITH JAUNDICE
• Malaria
• Hepatitis
• Leptospirosis
• Viral fevers
• Hepatoma
• FEVER AND GENERALISED LYMPHADENOPATHY
• Leukemia
• Lymphoma
• HIV infection
• Disseminated tuberculosis
• Brucellosis
• Toxoplasmosis
• FEVER AND EPITROCHLEAR LYMPHNODES
• Milary TB
• Lymphoma
• HIV infection
• Syphilis
• Local infections

17. • FEVER WITH HEPATOSPLENOMEGALY
• Malaria
• Typhoid
• Lymphoma
• Leukemia
• Brucellosis
• Disseminated TB
• Infective endocarditis
• Kala azar
• FEVER WITH ALTERED SENSORIUM
• Meningitis
• Encephalitis
• Meningism-Typhoid
• HIV
• Brain abscess
• Brucellosis
• Sepsis
• CNS neoplasms

18. • FEVER AND NIGHT SWEATS
• TB
• Lymphoma
• Brucellosis
• Abscess
• Infective endocarditis
• Alcohol withdrawl syndrome
• FEVER WITH HIGH ESR
• TB
• Temporal arteritis
• Carcinoma
• Lymphomas
• Abscess
• Myeloproliferative disorder

19. TEMPERATURE MEASUREMENT

20. TEMPERATURE MEASUREMENT
RECTAL TEMPERATURE
TYMPANIC TEMPERATURE

21. TYPES OF THERMOMETER

22. • Rectal temperatures are generally 0.4°C
(0.7°F) higher than oral readings
• In women who menstruate, the a.m.
temperature is generally lower during the 2
weeks before ovulation; it then rises by
~0.6°C (1°F) with ovulation and stays at
that level until menses occur
• During the luteal phase, the amplitude of
the circadian rhythm remains the same
• Body temperature can be elevated in the
postprandial state

23. HISTORY
• Onset
• Duration
• Continuous/remittent/intermittent
• Any evening rise in temperature
• Associated with rash
• Chills/rigors
• Subsides on medication
• Associated symptoms
• cold/cough/headache/bodypains/sweating/
throat pain/vomiting/pain abdomen/
loose stools/ burning micturition

25. LABORATORY TESTS
• CBC/Peripheral smear
• MP
• Urine routine
• Dengue NS1 antigen
• Dengue IGM/IGG antibody
• LFT
• Lactate
• Blood culture
• Urine culture
• Weil felix
• Scrub typhus IGM/IGG antibody
• Brucella agglutination
• Leptospira IGM/IGG antibody
• HIV
• Sputum CBNAAT/Culture

28. MANAGEMENT OF FEVER
• Treatment of the cause
• Tepid sponging
• Anti pyretic agents
• Oral aspirin and NSAIDs effectively reduce fever but can
adversely affect platelets and the gastrointestinal tract.
Therefore, acetaminophen is preferred as an antipyretic.
• In children, acetaminophen or oral ibuprofen must be
used because aspirin increases the risk of Reye’s
syndrome.
• If the patient cannot take oral antipyretics, parenteral
preparations of NSAIDs and rectal suppositories of
various antipyretics can be used
• In hyperpyrexia, the use of cooling blankets facilitates the
reduction of temperature

29. • Mechanism of antipyretic agents
• Inhibitors of cyclooxygenase
• The synthesis of PGE2 depends on the constitutively
expressed enzyme cyclooxygenase
• The substrate for cyclooxygenase is arachidonic acid
released from the cell membrane
• Glucocorticoids act at two levels
• First, similar to the cyclooxygenase inhibitors,
glucocorticoids reduce PGE2 synthesis by inhibiting the
activity of phospholipase A2, which is needed to release
arachidonic acid from the cell membrane
• Second, glucocorticoids block the transcription of the
mRNA for the pyrogenic cytokines

31. Causes of Hyperthermia Syndromes
• Heat Stroke Exertional: Exercise in higher than normal heat and/or humidity
• Nonexertional: Anticholinergics, including antihistamines; antiparkinsonian
drugs; diuretics; phenothiazines
• Drug-Induced Hyperthermia Amphetamines, cocaine, phencyclidine (PCP),
methylenedioxymethamphetamine (MDMA; "ecstasy"), lysergic acid
diethylamide (LSD), salicylates, lithium, anticholinergics, sympathomimetics
• Neuroleptic Malignant Syndrome
• Phenothiazines; butyrophenones, including haloperidol and bromperidol;
fluoxetine; loxapine; tricyclic dibenzodiazepines; metoclopramide;
domperidone; thiothixene; molindone; withdrawal of dopaminergic agents
• Serotonin Syndrome
• Selective serotonin reuptake inhibitors (SSRIs), monoamine oxidase inhibitors
(MAOIs), tricyclic antidepressants
• Malignant Hyperthermia
• Inhalational anesthetics, succinylcholine
• Endocrinopathy
• Thyrotoxicosis, pheochromocytoma
• Central Nervous System Damage
• Cerebral hemorrhage, status epilepticus, hypothalamic injury

32. • Heat stroke
• Exertional heat stroke
• Typically occurs in individuals exercising at elevated
ambient temperatures and/or humidity.
• In a dry environment and at maximal efficiency, sweating
can dissipate 600 kcal/h, requiring the production of >1 L of
sweat.
• Even in healthy individuals, dehydration or the use of
common medications (e.g., over-the-counter
antihistamines with anticholinergic side effects) may
precipitate exertional heat stroke
• Nonexertional heat stroke
• Typically occurs in either very young or elderly individuals,
particularly during heat waves
• The elderly, the bedridden, persons taking anticholinergic
or antiparkinsonian drugs or diuretics, and individuals
confined to poorly ventilated and non-air-conditioned
environments are most susceptible

33. • The serotonin syndrome
• Seen with selective serotonin uptake inhibitors (SSRIs), MAOIs, and
other serotonergic medications, has many features that overlap
with those of the neuroleptic malignant syndrome (including
hyperthermia) but may be distinguished by the presence of
diarrhea, tremor, and myoclonus rather than lead-pipe rigidity
• 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 and other
inhalational anesthetics or to succinylcholine
• Elevated temperature, increased muscle metabolism, muscle
rigidity, rhabdomyolysis, acidosis, and cardiovascular instability
develop within minutes This rare condition is often fatal

34. • The neuroleptic malignant syndrome
• Occurs in the setting of the use of neuroleptic agents
(antipsychotic phenothiazines, haloperidol, prochlorperazine,
metoclopramide) or the withdrawal of dopaminergic drugs and is
characterized by "lead-pipe" muscle rigidity, extrapyramidal side
effects, autonomic dysregulation, and hyperthermia
• This disorder appears to be caused by the inhibition of central
dopamine receptors in the hypothalamus, which results in
increased heat generation and decreased heat dissipation

35. Treatment of hyperthermia
• Physical cooling
• with sponging, fans, cooling blankets, and even ice baths
should be initiated immediately in conjunction with the
administration of IV fluids and appropriate pharmacologic
agents
• If sufficient cooling is not achieved by external means,
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
• Malignant hyperthermia should be treated immediately with
cessation of anesthesia and IV administration of dantrolene
sodium
• Dose 1–2.5 mg/kg given intravenously every 6 h for at least
24–48 h until oral dantrolene can be administered, if needed

36. • Dantrolene at similar doses is indicated in the neuroleptic
malignant syndrome and in drug-induced hyperthermia and may
even be useful in the hyperthermia of the serotonin syndrome
and thyrotoxicosis.
• The neuroleptic malignant syndrome also may be treated with
bromocriptine, levodopa, amantadine, or nifedipine or by
induction of muscle paralysis with curare and pancuronium.
• Tricyclic antidepressant overdose may be treated with
physostigmine