Human Physiology: Fever and Heat Regulation

Vital Signs

• Vital signs include temperature, pulse, respiratory rate, blood pressure, oxygen saturation, and pain.
• Pain is sometimes called the fifth vital sign.
• Measuring vital signs provides baseline data on a patient's health.
• Vital signs monitor a patient's condition, identify potential problems, and evaluate responses to interventions.

Objectives

• Identify the appropriate time to assess each vital sign.
• Evaluate the patient's disease process, cognition, age, and other factors in choosing assessment sites.
• Select nursing measures to promote heat loss and conservation.
• Summarize physiological changes associated with fever.
• Analyze a patient's body temperature.
• Analyze the patient's radial and apical pulse.
• Evaluate the significance of a pulse deficit.
• Analyze a patient's respirations.
• Explain strategies for self-monitoring of blood pressure, including benefits and precautions.
• Analyze a patient's blood pressure.
• Explain factors impacting SpO2 values.
• Analyze a patient's SpO2 using pulse oximetry.
• Summarize factors influencing body temperature, pulse, oxygen saturation, capnography, respirations, and blood pressure measurements.
• Discuss the importance of clinical judgment to identify when to measure vital signs.
• Determine when vital sign measurement can be delegated to assistive personnel.
• Evaluate the effectiveness of nursing interventions in promoting or maintaining normal vital signs.
• Explain accurate recording and reporting procedures of vital sign measurements.

Guidelines for Measuring Vital Signs

• Measuring vital signs is the responsibility of the nurse.
• Clean all devices between patients.
• Assess equipment functionality to ensure it is working accurately for the patient.
• Select the proper equipment for the patient based on their condition.
• Know the patient's normal baseline vital signs.
• Know the patient's medical history, therapies, and medications (prescription & over-the-counter).
• Control environmental factors which may impact measurements.
• Use a systematic and organized assessment approach.
• Collaborate on assessment frequency.
• Use vital sign measurements to guide medication administration.
• Evaluate results according to the patient's condition.
• Document and report any significant changes.
• Provide patient teaching.

Body Temperature

• Normal range is 98.6°F to 100.4°F (36°C to 38°C).
• Use Fahrenheit or Celsius scales.
• Temperature measurements should ideally be taken using electronic or disposable thermometers.
• Temperature sites include oral, rectal, axillary, tympanic membrane, temporal artery, esophageal, and pulmonary artery.
• Rectal temperatures are closest to core temperature.
• Surface readings are less accurate because they measure further from the core.

Thermoregulation

• The physiological and behavioral mechanisms regulate the balance of heat loss and heat production in the body.
• Heat loss is transfer of heat between objects (direct contact, air movement, or liquid to gas transformation).
• Heat production occurs through basal metabolic rate and shivering.
• The hypothalamus plays a key role in maintaining a constant body temperature, establishing a "set point" via neural and vascular control.
• Skin, subcutaneous tissue, and fat contribute to conserving heat within the body.
• Behavioral control, allowing for adjusting clothing or physical activity, also regulates body temperature.

Factors Affecting Body Temperature

• Age: Newborns have immature temperature control until puberty. Older adults may have lower temperatures.
• Hormonal levels: Women usually experience greater temperature fluctuations.
• Exercise: increases heat production.
• Circadian rhythm: body temperature varies predictably over 24 hours.
• Environment: stress, increases metabolic rates and therefore heat production.

Temperature Alterations (Fever, Heatstroke, Heat Exhaustion)

• Pyrexia (fever) is an important defense mechanism.
• Mild elevations in temperatures can enhance the immune system, while elevations above a certain point can be harmful.
• Heart rate & respiratory rates may increase to meet the body's metabolic needs and heat production.
• Prolonged fever can weaken patients because of the high energy expenditure required to cope with it.
• Heatstroke (more than 104°F) happens through prolonged high environmental temperatures.
• Symptoms include hot, dry skin; confusion, dizziness, excessive thirst, nausea, muscle cramps, visual disturbances, elevated body temperature, and lower blood pressure.
• Heat exhaustion happens when profuse sweating (and water/electrolyte loss) surpasses the body's ability to maintain balance.

Pulse Physiology and Regulation

• Pulse is the palpable bounding of blood flow in peripheral arteries.
• It indicates circulatory status.
• Sites include temporal, carotid, apical, brachial, radial, ulnar, femoral, popliteal, posterior tibial, and dorsalis pedis.
• Pulse character includes rate, rhythm, strength, and equality.

Pulse Character (Rate, Rhythm, Strength, Equality)

• Rate: Radial rate is the number of pulsing sensations in a minute. Normal range is 60-100 BPM.
• Rhythm: Regular or irregular pulsing. Dysrhythmias are irregular patterns that impact the heart's ability to adequately circulate blood.
• Strength: The amplitude of the pulse reflects the volume of blood ejected each heart contraction (bounding, full, normal, diminished, absent).
• Equality: Pulse strength should be similar in each extremity; any discrepancies may indicate a problem.

Respiration

• Respiration includes ventilation, diffusion, and perfusion.
• Ventilation is the movement of gases into and out of the lungs.
• Diffusion is the exchange of gases (oxygen and carbon dioxide) between alveoli and red blood cells.
• Perfusion is the distribution of red blood cells to and from the pulmonary capillaries.
• Factors affecting respirations include activity, age, illness, position, medications, smoking, and neurological injury.
• Respiratory rate, depth, and rhythm should be assessed.

Assessment of Ventilation

• Respiratory rate (breaths/minute): normal range in adults is 12-20.
• Depth, including normal, shallow, deep and labored depth.
• Rhythm: regular or irregular

Assessment of Diffusion and Perfusion

• Measure arterial oxygen saturation (SaO2)- usually normal range is 95%-100%.
• Pulse oximetry indirectly measures oxygen saturation.
• Assess arterial oxygen saturation (SaO2) to determine the level of oxygen and the efficiency of gas exchange, using pulse oximetry.

Arterial Blood Pressure

• Pressure exerted on artery walls by pulsing blood under pressure from the heart.
• An artery is a blood vessel that carries blood away from the heart, to deliver oxygen & nutrients to tissues.
• Normal adult range is <120/<80.
• Systolic pressure is the maximum peak pressure during ventricular contraction.
• Diastolic pressure is the minimum pressure during ventricular relaxation.
• Pulse pressure is the difference between systolic & diastolic pressure.

Factors Influencing Blood Pressure

• Age - Increased blood pressure with age throughout lifespan.
• Ethnicity: Higher rate of hypertension in people of African descent.
• Gender - Higher blood pressure in males, especially after puberty, but a higher risk in women after menopause.
• Stress - causes sympathetic stimulation, increasing heart rate, cardiac output, and vascular resistance and therefore blood pressure.
• Daily variation - Highest during the day (1000-1800 hours), lowest during sleep (0300 hours).
• Daily variation - BP is highest between 1000 and 1800 hours. Blood pressure is lowest between hours of sleep and 0300. As the person wakes up, the blood pressure will rise.
• Activity/weight: Exercise can reduce blood pressure temporarily. Inactivity and weight gain may increase it.
• Medications: Antihypertensives can lower blood pressure. Some others raise it.
• Smoking: Smoking can increase blood pressure.

Hypertension vs. Hypotension

• Hypertension is more common than hypotension.
• Features of hypertension include thickening of artery walls, a decrease in elasticity, with a risk history for development, and risk factors.
• Hypotension is typically associated with systolic pressure less than 90, dilation of arteries, loss of blood volume, and decrease in blood flow to vital organs, including postural orthostatic hypotension.

Case Study (Ms.TS)

• Ms.TS is a 26-year-old schoolteacher with a history of maternal grandparents from Brazil, smoking, and slightly overweight.
• She presented with headaches and fatigue and was found to have a temperature of 98.6°F.
• Additional vital sign measurement (pulse, respiratory rate, blood pressure) is needed.
• Her blood pressure was 164/98 mmHg, which is outside of normal limits.