fever and infection

NURS 3325 Health Care Pathophysiology

Presenter Information

  • Slides by: Michael D. Moon PhD, MSN, RN, CNS-CC, CEN, FAEN

  • Presented by: Julio Lujano, DNP, APRN, FNP, ENP

Temperature Regulation

Influencing Factors

  • Location

  • Activity

  • Environment

  • Circadian Rhythm

  • Gender

  • Age

  • Medications

  • Reference Pages: 342-344

Mechanisms of Temperature Regulation

  • Thermoreceptors:

    • Peripheral and Central thermoreceptors

    • Hypothalamic Control

  • Hormonal Response:

    • Thyroid Stimulating Hormone-Releasing Hormone (TSH-RH) → Thyroid Stimulating Hormone (TSH) → Thyroxine → Epinephrine

  • Heat Production and Conservation Mechanisms:

    • Chemical reactions of metabolism

    • Skeletal muscle contraction

    • Chemical thermogenesis

    • Vasoconstriction

    • Voluntary mechanisms

Heat Loss Mechanisms

  • Types of Heat Loss:

    • Radiation

    • Conduction

    • Convection

    • Vasodilation

    • Evaporation

    • Decreased muscle tone

    • Increased respirations

Age Considerations in Temperature Regulation

Pediatrics

  • Capable of producing sufficient body heat but are unable to conserve heat produced. Factors include:

    • Small body size and high body surface-to-weight ratio

    • Thin subcutaneous layer

Aging

  • Slower blood circulation, vasoconstrictive response, and decreased metabolic rate.

  • Decreased ability to sweat, shiver, and perceive temperature changes.

Fever

Definition

  • Fever: A temporary resetting of the hypothalamic thermostat that triggers heat production and conservation measures to a new set point.

  • Associated with exogenous pyrogens and endogenous pyrogens.

  • Fever of Unknown Origin (FUO): Lasting three weeks with no identifiable cause.

Fever Mechanism Diagram

  • Exogenous Pyrogens:

    • Sources include bacteria (endotoxins), viruses, or fungi.

  • Activation Pathway:

    • Monocyte-macrophage and T cell activation

    • Release of IL-1, IL-6, IFN, TNF leads to increased PGE2 production

    • This results in a raised thermostatic set point in the hypothalamus

  • Physiological Response:

    • Heat conservation via cutaneous vasoconstriction and decreased sweating

    • Heat generation via increased muscle contraction (shivering reflex)

Benefits of Fever

  • Kills many microorganisms.

  • Alters microorganism replication by decreasing serum levels of iron, zinc, and copper.

  • Promotes lysosomal breakdown and auto-destruction of cells, preventing viral replication.

  • Increases lymphocyte transformation and phagocyte motility, enhancing immune response.

  • Augments antiviral interferon production and phagocytosis.

Caution on Fever Management

  • Eliminating a fever is counterproductive unless it reaches dangerous levels (greater than 104 degrees Fahrenheit).

  • The goal is to maintain a “therapeutic fever.”

Hyperthermia

Characteristics

  • Not mediated by pyrogens; no resetting of the hypothalamic set point.

  • High temperatures:

    • At 41°C (105.8°F): Nerve damage and convulsions occur.

    • At 43°C (109.4°F): Death can result.

Forms of Accidental Hyperthermia

  • Heat Cramps:

    • Severe spasmodic cramps in abdomen/extremities following prolonged sweating and sodium loss.

    • Normal sodium levels: 135-145 mEq/L.

    • Symptoms may include fever, rapid pulse, and increased blood pressure.

  • Heat Exhaustion:

    • Result of prolonged high core or environmental temperatures due to vasodilation and excessive sweating.

    • Symptoms: Dizziness, weakness, nausea