Fever without focus

Dr Abhijeet

Definition

• Fever is defined as a rectal temperature ≥38°C, and a value >40°C is called hyperpyrexia.

Pathogenesis

• Body temperature is regulated by thermosensitive neurons located in the preoptic or anterior hypothalamus that respond to changes in blood temperature as well as cold and warm receptors located in skin and muscles.

• Thermoregulatory responses include redirecting blood to or from cutaneous vascular beds, increased or decreased sweating, regulation of extracellular fluid volume via arginine vasopressin, and behavioral responses, such as seeking a warmer or cooler environmental temperature.

Mechanism of Fever

1.Pyrogens: Endogenous pyrogens include the cytokines interleukin 1 (IL)-1 and IL-6, tumor necrosis factor-α (TNF-α), interferon (IFN)-β , IFN-γ & (PG)E2.

Exogenous pyrogens :Infectious pathogens and drugs.

2.Heat production exceeding loss, and 3.Defective heat loss.

Causes of Fever

1. Infectious,2. Inflammatory, 3. Neoplastic, 4. Miscellaneous.

• The pattern of the fever can provide clues to the underlying etiology.

• Viral infections typically associated with a slow decline of fever over a week, whereas Bacterial infections are associated with a prompt resolution of fever after effective antimicrobial treatment is employed.

• Although administration of antimicrobial agents can result in a very rapid elimination of bacteria, if tissue injury has been extensive, the inflammatory response and fever can continue for days after all microbes have been eradicated.

Types of Fever

• Intermittent fever: Temperature fluctuation is more than 1 C and fever

present only few hours in a day. Eg:filaria • Septic or hectic fever: Extremely wide fluctuations .• Sustained fever : Persistent and does not vary by more than

0.5°C/day. • Remittent fever : Persistent and varies by more than 0.5°C/day.

• Relapsing fever :           Characterized by febrile periods that are

separated by intervals of normal temperature. • Tertian fever:  Occurs on the first and third days (malaria

caused by Plasmodium vivax)• Quartan fever :Occurs on the first and fourth

days (malaria caused by Plasmodium malariae).

• Biphasic fever: A single illness with 2 distinct periods (camelback fever pattern); poliomyelitis is the classic example,also characteristic of other enteroviral infections, leptospirosis, dengue fever, yellow fever, Colorado tick fever, spirillary rat-bite fever (Spirillum minus), and the African hemorrhagic fevers (Marburg, Ebola, and Lassa fevers).

• Factitious fever or self-induced fever: May be caused by intentional manipulation of the thermometer or injection of pyrogenic material.

Fever Without Localizing signs

• Etiology & Evaluation of fever without localizing signs depends upon age of the child

• Neonates-1 month: Challenge to evaluate because of difficulty to clinically distinguish between serious bacterial & self limiting viral illness.

- Immature immune response in this period increases the significance of illness.

• Neonates without sick look & with fever have 7% risk of serious bacterial infection.

i.e. occult bacteremia, meningitis (Caused by E.Coli, Listeria monocytogenes, Herpis simplex, enterovirus) , pneumonia, osteomyelitis, septic arthritis, enteritis & UTI.

Management

• Admit• CBC, Blood culture, CSF studies, Urine analysis Stool C/s, Chest X ray etc.• Combination of antibiotics such as Ampicillin &

Cefotaxime.• Acyclovir for suspected HSV infection (CSF

pleocytosis), maternal H/O genital HSV during delivery.

1- 3 Months

• Mostly viral origin• May be vaccine induced, if recent immunization

done in recent past.• But can be serious bacterial infections such as: Gr. B streptococcus, L. monocytogenes,

Salmonella enteritis, E.Coli, S. Pneumoniae, HIB , Staph aureus

• Otitis media, pneumonia, omphalitis, mastitis, skin & soft tissue infections.

• In contrast to bacterial infections, viral diseases have seasional pattern.

- Winter : RSV, Influenza A- Summer & Fall: Enterovirus.

Management

• Sick/ Toxic looking febrile infants should be admitted

• CBC, Blood culture, CSF studies, Urine analysis Stool C/s, Chest X ray etc.• Combination of antibiotics such as Ampicillin

(to cover L.monocytogenes & Enterococcus)& Cefotaxime/ Ceftriaxone.

• This regimen is effective against usual bacteria causing sepsis, UTI & Enteritis in infants.

• If meningitis is suspected, VANCOMYCIN should be added to t/t possible Penicillinase resistant S. Pneumoniae until C/S reports come.

• A well looking infant with no clinical focus of infection (TC < 15000, Band form< 20%, CRP neg, urine WBC <10HPF) can be observed at home without antibiotics.

LOW RISK CRITERIA IN 1-3 MONTHS OLD WITH FEVER

Boston Criteria

3-36 Months

• Risk of serious bacterial infections is 5%.• Detailed Immunization H/O• Sick contacts in family.

Management

• Sick looking babies – Admit.• Prompt administration of antibiotics after

collecting Urine, blood, CSf Samples.• HiB bacteremia is characteristically associated

with higher risk of localized serious infection than S. Pneumoniae.

• .

• Empirical antibiotic therapy is recommended for well appearing children < 36 months who have not received HiB & Conj. pneumococcal vaccine& who have rectal temp > 39 C with TC > 15000

Management of Fever without localizing signs.

THANK YOU

• Nelson 18th ed