1. Fever and hyperthermia
FEVER- Fever is an elevation of body temperature that exceeds the normal daily variation and occurs in conjunction with an increase in the
hypothalamic set point. An A.M. temperature of >37.2°C (>98.9°F) or a P.M. temperature of >37.7°C (>99.9°F) would define a fever.
According to studies of healthy individuals 18–40 years of age, the mean oral temperature is 36.8° ± 0.4°C (98.2° ± 0.7°F), with low
levels at 6 A.M. and higher levels at 4–6 P.M. The maximum normal oral temperature is 37.2°C (98.9°F) at 6 A.M. and 37.7°C (99.9°F) at 4 P.M.;
these values define the 99th percentile for healthy individuals. Rectal temperatures are generally 0.4°C (0.7°F) higher than oral readings.
TYPES- 1. CONTINOUS FEVER- Temperature remains above normal throughout the day and does not fluctuate more than 1 °C in 24 hours,
e.g. lobar pneumonia, typhoid, urinary tract infection.
2. INTERMITTENT FEVER- Fever is present only for several hours and always touches the baseline at some time of the day. Subdivided
based on periodicity into,
Quotidian(24 hrs, tuberculosis), Tertian(48 hrs, P.vivax), Quartan(72hrs P.malariae), Double Quotidian(two spikes in a day, Kala-azar).
3. REMITTANT- Temperature remains above normal throughout the day and fluctuates more than 1°C in 24 hours, e.g., infective
endocarditis, amoebic liver abscess, acute tonsillitis.
4. PEL-EBSTEIN FEVER- It is a cylindrical fever where several days or weeks of fever alternates with afebrile period seen in Hodgkin’s
lymphoma. This pattern is also noted in brucellosis and hypernephroma.
5. HEPATIC or SEPTIC FEVER- In this type the fluctuation of temperature between peak and nadir is very high and usually more than 5
degree celcius. It may be present in some septicemias.
6. HECTIC FEVER- A daily recurring fever with profound sweating, chills, and flushed appearance often associated with pulmonary
tuberculosis and septic poisoning.
7. RELAPSING FEVER- Multiple episodes of fever occur and each may last up to 3 days. Individuals may be free of fever for up to 2
weeks before it returns. , e.g., Tick-borne relapsing fever.
8. SADDLEBACK or BIPHASIC FEVER- Fever that is constant for several days (5 to 7 days), spontaneously reduce for 1 or 2 days, and
then increase again. Saddleback fevers can be seen in such infections as Dengue, yellow fever, and influenza.
9. STEP LADDER FEVER- A specific fever pattern, with a slow stepwise increase and a high plateau characteristic of enteric fever.
10. CYCLIC NEUTROPENIC FEVER- Fever cycle periodicity as multiples of 7 days, that is, most commonly at 21 or 28-day intervals.
HYPERPYREXIA - A fever of >41.5°C (>106.7°F) is hyperpyrexia. Most commonly caused by intracranial hemorrhage. Other causes include
sepsis, serotonin syndrome, thyroid strom, infections include roseola, rubeola and enteroviral infections.
PATHOGENESIS-
EXOGENOUS PYROGENS- Derived from outside the patient and include
microbes and their products , e.g. lipopolysaccharide endotoxin produced by
all gram negative bacteria, enterotoxins produced by staphylococcus and
group A &B Streptococcal toxins.
ENDOGENOUS PYROGENS- Cytokines are small proteins (molecular mass,
10,000–20,000 Da) that regulate immune, inflammatory, and hematopoietic
processes produced from the patient, e.g. IL-1,IL-6, tumor necrosis factor(TNF),
ciliary neutrophilic factor(CNF) and interferon (INF) α.
Pathways of fever production are depicted in the adjacent figure. AMP
adenosine 5'-monophosphate; IFN, interferon; IL, interleukin; PGE2, prostaglandin E2;
TNF, tumor necrosis factor.
TREATMENT- NSAIDS such as Ibuprofen, specific inhibitors of COX-2, aspirin, acetaminophen, cold sponging.
HYPERTHERMIA- Hyperthermia is characterized by an uncontrolled increase in body temperature that exceeds the body's ability to lose
heat. The setting of the hypothalamic thermoregulatory center is unchanged. In contrast to fever in infections, hyperthermia does not involve
pyrogenic molecules. Causes are,
1.HEAT STROKE- Heat stroke is defined as a core body temperature of 40.5 °C(105°F) with associated central nervous system dysfunction in
the setting of large environmental heat load that cannot be dissipated. Exertional heat stroke typically occurs in individuals exercising at
elevated ambient temperatures and/or humidities. Nonexertionalheat stroke typically occurs in either very young or elderly individuals,
particularly during heat waves.
2.NEUROLEPTIC MALIGNANT SYNDROME- is an idiosyncratic reaction to antipsychotic agents. It generally presents with muscle rigidity,
fever, autonomic instability and cognitive changes such as delirium.
3.DRUG INDUCED HYPERTHERMIA- caused by Tricyclic antidepressants, MAOIs and Amphetamines.
4.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.
5. CENTRAL NERVOUS SYSTEM DAMAGE- Cerebral hemorrhage, status epilepticus, hypothalamic injury.
TREATMENT- Rapid reduction of body temperature by physical means accomplished by cool or tepid, not cold bathing, Antipyretics are of
no use, submersion and to be avoided, cooling blankets are of potential danger because of excessive vasoconstriction.
Ref- Harrison’s principles of internal medicine, Up To Date, Annals of internal medicine. GOPI KRISHNA JALADI