💉 Mean Arterial Pressure (MAP): Formula, Physiology & Step 1 Clues

Whether it’s shock, organ perfusion, or cardiovascular physiology, mean arterial pressure (MAP) comes up everywhere. Understanding how to calculate MAP, what it reflects, and how it’s regulated is crucial for crushing cardio physiology on Step 1 and making sense of ICU cases on Step 2 CK.

💡 MAP Formula

MAP = (2 × Diastolic BP + Systolic BP) ÷ 3

• Why x2 for diastolic? Because diastole lasts longer than systole

• MAP < 60 mmHg → inadequate perfusion

• MAP ~70–100 mmHg is ideal in most stable patients

🧠 KOTC Tip: On Step 1, if they give systolic and diastolic but ask about perfusion → calculate MAP!

🧪 Physiology in Action

Situation	MAP Trend	Clinical Relevance
Hypovolemic Shock	↓ MAP	↓ preload → ↓ perfusion
Septic Shock	↓ MAP early	Vasodilation and leaky capillaries reduce resistance
Vasopressors (e.g., NE)	↑ MAP	Used to restore perfusion in shock
Renal Autoregulation	Holds MAP	Maintains constant GFR in MAP range 80–180 mmHg

🫀 Regulation of MAP

MAP = CO × TPR

• CO = HR × SV

• TPR = total peripheral resistance

So MAP is influenced by:

• Heart rate and stroke volume (CO)

• Vessel tone (α₁, angiotensin II, endothelin)

• Blood volume (aldosterone, ADH)

📌 This is a favorite Step 1 integration point for autonomics + renal!

🧠 Mnemonic: “MAP = Road to Organs”

• MAP is like pressure in a pipe feeding your organs

• Too low? Organs suffer.

• Too high? Damage over time.

Use “Roadmap” concept: brain → heart → kidneys → skin

📌 Before You Go…

Don’t just guess the pressure—map it.

✅ Call-to-Action (CTA)

Use KOTC’s physiology visuals, cardiovascular quizzes, and timed calculation drills to lock in MAP and dominate cardio-based questions.
👉 Start mastering with KOTC now

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