🩺 Vital Signs — What You Need to Know

Vital signs reflect how well the body is maintaining basic life functions.

They are often the first sign that something is going wrong.

🔢 Core Vital Signs

🌡 Temperature

What it reflects: metabolic activity & infection

Normal (Adult):

• Oral: 36.5–37.5°C (97.7–99.5°F)
• Rectal: +0.3–0.6°C higher than oral
• Axillary: ~0.5°C lower than oral

Key thresholds:

• Fever: ≥38°C (100.4°F)
• Hypothermia: <35°C (95°F)

Conversion:

• °F = (°C × 9/5) + 32
• °C = (°F − 32) × 5/9

📌 Fever increases HR and oxygen demand.

❤️ Heart Rate (Pulse)

What it reflects: cardiac output & perfusion

Normal (Adult):

• 60–100 bpm

Abnormal:

• Bradycardia: <60 bpm
• Tachycardia: >100 bpm

Important notes:

• Athletes may have lower resting HR
• Pain, fever, anxiety ↑ HR
• Hypoxia ↑ HR

📌 Always assess rhythm + strength, not just the number.

🫁 Respiratory Rate

What it reflects: oxygenation & acid–base balance

Normal (Adult):

• 12–20 breaths/min

Abnormal:

• Bradypnea: <12
• Tachypnea: >20

⚠️ Critical nursing rule:

Respiratory rate is the most commonly missed abnormal vital sign.

📌 A rising RR is often an early sign of deterioration.

🩸 Blood Pressure

What it reflects: circulation & organ perfusion

Normal:

• <120 / <80 mmHg

Ranges:

• Elevated: 120–129 / <80
• Hypertension: ≥130 / ≥80
• Hypotension (general): <90 systolic

Key concepts:

• Systolic: pressure during heart contraction
• Diastolic: pressure during relaxation

📌 Trends matter more than one reading.

🫀 Mean Arterial Pressure (MAP)

Why it matters: organ perfusion (especially brain & kidneys)

Formula:

• MAP = (SBP + 2×DBP) ÷ 3

Normal target:

• ≥65 mmHg

📌 MAP <65 = poor organ perfusion risk.

🩸 Oxygen Saturation (SpO₂)

What it reflects: oxygen bound to hemoglobin

Normal:

• 95–100%

Acceptable (some chronic conditions):

• 88–92%

⚠️ Important:

• Normal SpO₂ does NOT always mean adequate oxygen delivery
• Always assess breathing effort and mental status

📏 Conversions You Must Know

Weight

• 1 kg = 2.2 lb
• lb ÷ 2.2 = kg

Height

• 1 inch = 2.54 cm
• 1 ft = 12 in

Fluids

• 1 mL = 1 cc
• 1000 mL = 1 L

📌 Medication dosing often depends on kg.

🧠 High-Yield Nursing Connections

• Fever → ↑ HR → ↑ oxygen demand
• Hypotension + tachycardia → possible shock
• Increased RR → early respiratory or metabolic problem
• Low SpO₂ + confusion → urgent assessment

Vital signs never stand alone — interpret them with the patient.

⚠️ Quick Note

Values and measurement methods may vary slightly by facility. Always follow your school or clinical guidelines.

✅ What to Remember (Cheat Sheet)

• RR is the earliest warning sign
• MAP ≥65 is critical for perfusion
• Trends > single numbers
• Treat the patient, not the number
• Always convert units correctly