Vital Signs

The Four Traditional Vital Signs

1. Body Temperature

• Normal range: 97.7°F - 99.1°F (36.5°C - 37.3°C); average 98.6°F (37°C)
• Measured orally with an electric thermometer in adults. Tympanic (ear) thermometers are less reliable in hospitalized patients due to variability.
• Abnormal: Fever (>38°C / 100.4°F) or hypothermia (<35°C / 95°F)

2. Pulse (Heart Rate)

• Normal range: 60-100 beats per minute (bpm) in adults
• Assessed for both rate and rhythm
• Abnormal: Tachycardia (>100 bpm) or bradycardia (<60 bpm)

3. Respiratory Rate

• Normal range: 12-18 breaths per minute in adults
• Should be assessed with the patient unaware they are being observed, as awareness can alter the rate
• Clinicians should note whether the patient can complete sentences without pausing and observe for increased work of breathing
• Abnormal: Tachypnea (rapid) or hypopnea (slow/shallow)

4. Blood Pressure (BP)

• Normal: 120/80 mmHg (systolic/diastolic)
• Should be measured with an appropriately sized cuff; if abnormal, should be repeated
• Due to variability and phenomena like "white coat hypertension," confirmation outside the clinical setting is now recommended
• Abnormal: Hypertension (>130/80 mmHg) or hypotension (<90/60 mmHg)

Additional Vital Signs (5th and 6th)

Why Vital Signs Matter

• They serve as the critical first step in any clinical evaluation
• Used in triage to determine the severity of a patient's condition in emergency and urgent care settings
• Enable early detection of clinical deterioration - whether in the ER or on a hospital floor
• Reflect response to treatment and guide ongoing management
• Normal values vary with age, sex, weight, fitness level, and overall health - pediatric normal ranges differ significantly from adults

Quick Reference: Normal Adult Vital Signs

Interpreting Abnormal Vital Signs

Core Principle: Context Is Everything

• The patient's baseline (an athlete may normally have HR of 40 bpm)
• Medications (beta-blockers mask tachycardia; stimulants cause it)
• Trends over time - a single reading can mislead; trends reveal the true picture

1. Abnormal Heart Rate

Tachycardia (HR > 100 bpm)

• Fever causes sinus tachycardia - if a febrile patient has NO tachycardia, suspect drug fever, typhoid fever, or central neurogenic fever
• In sepsis, early tachycardia with bounding pulses reflects high cardiac output and low vascular resistance; later, pulses become weak as cardiac output falls
• Unexplained tachycardia at discharge is a red flag - it predicts adverse outcomes and repeat visits

Bradycardia (HR < 60 bpm)

• Hypothermia reduces metabolic demands and typically accompanies bradycardia
• A pacemaker or cardioactive medications will alter the heart rate's ability to respond to new physiological stress

Heart Rhythm

• An irregular pulse suggests atrial fibrillation or flutter - always confirm by auscultating the apical pulse
• The apical rate is often higher than the peripheral rate (pulse deficit) due to nontransmitted beats; a larger deficit means more severe disease

2. Abnormal Blood Pressure

Hypotension (BP < 90/60 mmHg)

• In distributive shock (e.g. sepsis), cardiac output may actually be elevated, but BP is low due to very low systemic vascular resistance (SVR)
• Orthostatic vital signs (checking BP lying vs. standing) are key for detecting hypovolemia: a drop of >20 mmHg systolic or >10 mmHg diastolic on standing indicates significant volume depletion

Hypertension (BP > 130/80 mmHg)

• Confirm with repeat measurement; rule out white coat hypertension
• Hypertensive urgency/emergency if accompanied by end-organ signs (headache, vision changes, chest pain, confusion, oliguria)

3. Abnormal Respiratory Rate

Tachypnea (RR > 20 breaths/min)

• Tachypnea is NOT the same as hyperventilation - hyperventilation is defined by increased alveolar ventilation causing a low PaCO2
• A patient who cannot complete sentences without pausing to breathe and shows increased work of breathing is in respiratory distress

Hypopnea / Bradypnea (RR < 12 breaths/min)

• Opioid/sedative overdose, CNS depression, severe hypothyroidism

4. Abnormal Temperature

Fever (> 38°C / 100.4°F)

• Relative bradycardia with fever (no tachycardia despite high temperature): classic for typhoid fever, drug fever, or central neurogenic fever

Hypothermia (< 35°C / 95°F)

• Environmental exposure, sepsis (late), hypothyroidism, adrenal insufficiency
• Causes bradycardia and can trigger arrhythmias

5. Abnormal SpO2

Putting It All Together: A Clinical Framework

1. Measure correctly - Wrong cuff size, patient position, or device can give false readings. Repeat abnormal values.
2. Look at all vitals together - Tachycardia + hypotension + tachypnea = shock until proven otherwise
3. Consider medications - Beta-blockers mask tachycardia; steroids cause leukocytosis but can suppress fever
4. Trend over time - A single reading is a snapshot; serial measurements show the trajectory
5. Explain or correct before discharge - Unexplained abnormal vital signs on discharge predict worse outcomes