THERMOREGULATION

THERMOREGULATION

Instructor: Jessica Gay, PhD, RNC-MNN, CNE

INTRODUCTION

• Each individual in the room is deemed capable, qualified, and motivated to excel in nursing.

• We commit to treating all with respect and maintaining high standards for learning and practice.

• Participants are encouraged to engage openly, take risks, and embrace curiosity while respecting one another.

LESSON OBJECTIVES

By the end of this lesson, the learner will be able to:

• Utilize defining attributes to discuss the concept of thermoregulation and differentiate it from related concepts.

• Describe physiological changes related to hypothermia and hyperthermia.

• Identify methods of heat loss in the human body including examples in acute care, primary care, and community settings.

• Identify at-risk populations for thermoregulation problems and provide rationale.

• Discuss exemplars of thermoregulation, including etiology, nursing interventions, patient education, and how each exemplar illustrates the defining attributes of thermoregulation.

• Apply clinical judgment to develop appropriate nursing care plans for patients with thermoregulation issues.

CONCEPT DEFINITION

• Thermoregulation: The body’s process of balancing heat production and heat loss to maintain body temperature within the optimal physiological range.
     - Definition by Giddens: “The process of maintaining core body temperature at a near constant value.”

• Bacc Big 5 Domain: Nursing Across the Lifespan.

DEFINING CHARACTERISTICS

• Appropriate thermoregulatory controls consist of:
    - Sensory Receptors: Located in the skin and core.
    - Integrator: The hypothalamus.
    - Effectors: Actions such as vasoaction, epinephrine release, sweating, and shivering.
    - Chemical Mediators: Hormones involved in the thermoregulation process.
    - Intact, Functional Integumentary System: It utilizes radiation, conduction, convection, vaporization, evaporation, and vasodilation for thermoregulation.

THERMOREGULATION RANGE

• Normal Temperature Range: 36.2 – 37.6°C (97.6 – 100.0°F)

• Clinical Fever: Defined as 100.4°F (38.0°C) or higher.

• System Type: Negative feedback system with the main goal of achieving homeostasis.

THERMOREGULATION CONTINUUM

• Normothermia: 97.6 – 100.0°F (36.2 – 37.6°C)

• Severe Hyperthermia: 104.0°F (40.0°C) or greater (heatstroke).

• Hypothermia: 95.0°F (35.0°C) or lower.

THERMOREGULATION AND HEAT MANAGEMENT

• Body Temperature Regulation:   - Heat Preservation:
     - Blood vessels constrict to conserve heat.
     - Sweat glands do not secrete fluid.
     - Shivering (involuntary muscle contraction) generates heat.
    - Heat Loss:
     - Blood vessels dilate to release heat.
     - Sweat glands secrete fluid, aiding in heat loss through evaporation.

INTERRELATED CONCEPTS

• Key Concepts:
    - Fluid Balance
    - Intracranial Regulation
    - Thermoregulation
    - Tissue Integrity
    - Perfusion
    - Infection
    - Nutrition

INFECTION AND THERMOREGULATION

• Infection's Relationship to Thermoregulation: Fever serves as the body’s defense mechanism:
    - Enhances immune response.
    - Stimulates white blood cell production.
    - Reduces iron levels in blood to suppress bacterial growth.
    - Stimulates interferon, a natural virus-fighting substance.

HEAT PRODUCTION

• Key Points of Heat Production:
    - Basal Metabolic Rate (BMR): The heat produced at rest, primarily as a by-product of metabolism mainly occurring in the liver and muscles.
    - Heat production can increase due to:
      - Muscle contractions.
      - Chemical thermogenesis involving epinephrine.
      - Peripheral vasoconstriction.
      - Non-shivering thermogenesis (heat generated through metabolic processes, not shivering).

HEAT LOSS MECHANISMS

• Methods of Heat Loss:
    - Radiation: Heat loss from skin to air when exposed.
    - Conduction: Heat transfer through direct contact.
    - Convection: Heat loss through air currents across the body surface.
    - Vasodilation: Increases heat loss from the skin surface.
    - Evaporation: Loss of heat through sweat and respiratory processes (where water loss must be monitored).

FACTORS AFFECTING BODY TEMPERATURE

• Circadian Rhythm: Fluctuations in body temperature throughout the day.

• Stress: Leads to an increase in body temperature.

• Environmental Factors: Affect body temperature regulation significantly.

POPULATIONS AT RISK

• At-Risk Groups:
    - Highest Risk: Very young (newborns) and very old (elderly).
      - Newborns:
        - Larger surface area relative to body mass.
        - Little to no subcutaneous “brown” fat, increasing susceptibility.
      - Elderly Individuals:
        - Decreased function of sweat glands, reduced circulation, and activity levels.
        - Slower metabolic rate and reduction in vasoconstriction responses.
    - Low Socioeconomic Status:
      - Homeless population or those living in extreme climates.

INDIVIDUAL RISK FACTORS

• Specific Individual Risks Include:
    - Cognitive impairments.
    - History of traumatic brain injury (TBI).
    - Surgical patients.
    - Malnutrition or dehydration.
    - Genetic predispositions, such as malignant hyperthermia.
    - Specific occupational hazards linked to outdoor exposure, including:
      - Cardiovascular disease.
      - Thyroid disease.
      - Diabetes or alcoholism.
      - Medications: Phenothiazines, anticholinergics, diuretics, amphetamines, beta-adrenergic receptor antagonists.

ASSESSMENT METHODS

• Temperature Measurement Techniques:
    - Methods: Oral, axillary, temporal, rectal, core.
    - Observations:
      - Sweating and shivering.
      - Skin color and temperature.
      - Considerations based on age, health history, family history, environmental exposure, thyroid function, and neurological effects.

ASSESSMENT FINDINGS FOR HYPOTHERMIA

• Indicators:
    - Cool skin and slow capillary refill.
    - Skin color shifts from pale to cyanotic.
    - Signs include muscle rigidity and shivering, confusion, stupor, coma, dysrhythmias, and decreased urine output.

SEVERE HYPOTHERMIA SEQUELAE

• Progression of Symptoms:
    - Initial shivering leads to peripheral vasoconstriction and coagulation of microcirculation.
    - Transition to impaired tissue perfusion as hypothalamic function fails leading to vasodilation.
    - Increased heat loss can result in cardiovascular collapse, cellular damage, and potentially death.

ASSESSMENT FINDINGS FOR HYPERTHERMIA

• Indicators Include:
    - Warm, flushed skin appearance.
    - Sweating which can eventually stop, leading to dry skin and mucous membranes.
    - Symptoms of nausea/vomiting, syncope, muscle cramps, weakness, decreased urine output, signs of dehydration, confusion, visual changes, and seizures (particularly in children).

SEVERE HYPERTHERMIA SEQUELAE

• Progression of Symptoms:
    - Sweating leads to sodium loss and dehydration, resulting in hypotension and tachycardia.
    - Decreased cardiac output leads to reduced tissue perfusion and microcirculatory coagulation, which can result in cardiovascular collapse, cerebral edema, CNS damage, renal necrosis, and ultimately, death.

DIAGNOSTIC TESTS

• Importance of Accurate Temperature Measurements: Essential for evaluation and diagnosis.

• Tests for Malignant Hyperthermia: Muscle contraction test is critical for diagnosing susceptibility.

NURSING CLINICAL PROBLEMS

• Clinical Issues to Monitor:
    - Hypothermia or risk thereof.
    - Hyperthermia or risk thereof.
    - Chronic fever lasting more than 10 to 14 days.
    - Risk for perioperative hypothermia.

RELATED CLINICAL PROBLEMS

• Consideration of Related Issues:
    - Impaired cognition.
    - Fluid imbalance.
    - Socioeconomic challenges.
    - Infection or infection risk.
    - Altered blood pressure.
    - Impaired cardiac function.
    - Impaired tissue perfusion.
    - Risk for compromised tissue integrity.

PRIMARY PREVENTION: NURSING INTERVENTIONS

• Key Preventative Strategies:
    - Reduce exposure to extreme temperatures.
    - Provide adequate shelter and appropriate clothing.
    - Encourage physical activity to maintain body warmth (in cases of hypothermia).

SECONDARY PREVENTION: NURSING INTERVENTIONS

• Identifying At-Risk Populations:
    - Recognize and address risk factors in real-time to promote prevention.

TERTIARY PREVENTION: NURSING INTERVENTIONS FOR HYPERTHERMIA

• Immediate Actions:
    - Identify the cause of hyperthermia.
    - Remove excess clothing and hydrate the patient.
    - Use cool packs at axillae and groin areas.
    - Administer cooling blankets and tepid baths (not cold!).
    - Gastric lavage if needed.

TERTIARY PREVENTION: NURSING INTERVENTIONS FOR HYPOTHERMIA

• Key Interventions Include:
    - Provide dry, warm clothing and warm blankets.
    - Offer warm oral fluids and mild exercise.
    - Administer warmed IV fluids, heated and humidified O2, and utilize Bair hugger for forced air warming.
    - Continuous cardiac monitoring and warm fluid lavage as required.
    - Cardiac support may include cardiopulmonary bypass if necessary.

THERMOREGULATION EXEMPLARS

• Example Conditions:
    - Newborn hypothermia.
    - Traumatic injury.
    - Therapeutic hypothermia.
    - Environmental hypothermia.
    - Frostbite.
    - Heat stroke.
    - Malignant hyperthermia.
    - Fever.

FEATURED EXEMPLAR: NEWBORN HYPOTHERMIA

• Challenges:
    - Large surface area and minimal subcutaneous fat.
    - Newborns lack the ability to shiver for heat production and rely on non-shivering thermogenesis, stimulated by cellular respiration — this raises the oxygen and glucose consumptions.
    - The brown adipose tissue is the primary thermogenic source in full-term newborns, warming blood as it passes through this tissue.

NEWBORN HEAT LOSS MECHANISMS

• Heat Loss Can Occur Via:
    - Radiation
    - Convection
    - Conduction
    - Evaporation

COLD STRESS IN NEWBORNS

• Signs of Cold Stress:
    - Peripheral vasoconstriction leading to acrocyanosis and cold extremities (decreased blood flow).
    - CNS depression is observed through lethargy, bradycardia, apnea, and poor feeding.
    - Respiratory distress may appear as tachypnea; prolonged exposure results in long-term challenges like weight loss and failure to thrive.

NEUTRAL THERMAL ENVIRONMENT

• Defines the environmental temperature range within which an infant can maintain its normal body temperature with minimal basal metabolic rate and oxygen consumption.

NURSING INTERVENTIONS IN NEWBORNS

• Promotive Measures:
    - Encourage skin-to-skin contact.
    - Use radiant warmers during bathing, deferring bath for the first 24 hours.
    - Ensure infants wear hats, especially within the first 24 hours.
    - Educate parents on the risks of low birth weight (LBW) and preterm infants facing cold stress, hypoxia, metabolic acidosis, and hypoglycemia, as increased metabolism can lead to higher oxygen and caloric needs.

FEATURED EXEMPLAR: MALIGNANT HYPERTHERMIA

• Characteristics of Condition:
    - A potentially fatal, inherited disorder (autosomal dominant) triggered by certain general anesthetics, particularly inhalants or succinylcholine.
    - Underlying defect involves abnormally high cellular calcium levels in skeletal muscle, causing hypermetabolic response during anesthesia.

MALIGNANT HYPERTHERMIA SYMPTOMS

• Presenting symptoms include:
    - Muscle rigidity and stiffness.
    - Tachycardia.
    - Rapid increase in body temperature to 105°F (40.6°C) or higher.
    - Muscle breakdown, indicated by dark urine, and increased acid content in the blood which can occur during heavy exercise or heat exposure.

MALIGNANT HYPERTHERMIA DIAGNOSTIC TESTING

• Screening Approach:
    - Heavily dependent on family and surgical history.
    - Muscle contracture tests, such as the caffeine halothane contracture test (CHCT), are considered the gold standard.
    - This involves obtaining a skeletal muscle biopsy to assess contractile properties upon exposure to ryanodine receptor agonists like caffeine and halothane.
    - Must be conducted at a certified MH muscle biopsy center.
    - High levels of contractile force upon testing signal MH susceptibility with sensitivity nearing 100%, indicating rare false negatives.

MALIGNANT HYPERTHERMIA RESPONSE PROTOCOL

• Immediate Response Protocol During Events:
    - Cease administration of inhalants and succinylcholine while maintaining anesthesia with alternative methods (such as propofol).
    - Halt surgical procedures temporarily.
    - Administer dantrolene immediately.
    - Provide 100% oxygen and employ cooling blankets along with cool IV fluids.
    - Obtain blood gas analyses and correct dysrhythmias, hyperkalemia, and metabolic acidosis as necessary.
    - Diurese kidneys as required to aid recovery.

FEATURED EXEMPLAR: THERAPEUTIC HYPOTHERMIA

• Applications of Therapeutic Hypothermia:
    - Implemented post-events such as traumatic brain injury (TBI), pulmonary embolism stroke, myocardial infarction (MI), neonatal hypoxic-ischemic encephalopathy, and hemorrhagic shock.
    - Reduces ischemic tissue injury by lowering oxygen demand and minimizes inflammation effects.
    - Can be administered endovascularly or externally. Requirements for neonatal cases follow specific criteria and timelines, targeting blood temperatures of 33°C - 34°C for whole body cooling, or 34°C - 35°C for selective cooling of the brain.

THERAPEUTIC HYPOTHERMIA PRECAUTIONS

• Cooling Duration and Monitoring:
    - Maintain cooling for 72 hours with careful rewarming over 6 to 12 hours at a rate of 0.5°C every 1 to 2 hours.
    - Significant improvements in survival and neurological function have been documented through this intervention.

CLASS ACTIVITY

• In-Class Activity:
    - Case studies comparing hypothermia and hyperthermia. Collaborate in groups to answer provided questions.
    - Work collectively to enhance team learning, avoiding dividing questions for independent work.
    - Compile findings into a single document to submit to Dropbox with potential presentations in class to share conclusions found.