Normal map BP
Blood pressure is considered normal when systolic is less than 120 mmHg and diastolic is less than 80 mmHg (written as <120/<80 mmHg). Values from 120-129/<80 are "elevated," 130-139/80-89 is Stage 1 hypertension, and ≥140/≥90 is Stage 2 hypertension.
Here is a quick reference map of BP categories:
| Category | Systolic (mmHg) | Diastolic (mmHg) | |
|---|---|---|---|
| Normal | < 120 | AND | < 80 |
| Elevated | 120 - 129 | AND | < 80 |
| Stage 1 HTN | 130 - 139 | OR | 80 - 89 |
| Stage 2 HTN | ≥ 140 | OR | ≥ 90 |
| Hypertensive Crisis | > 180 | AND/OR | > 120 |
Key points:
- Measured in mmHg, recorded as systolic/diastolic (e.g., 115/75)
- Normal pulse pressure (difference between systolic and diastolic) is roughly 40 mmHg
- Mean Arterial Pressure (MAP) = Diastolic + 1/3 (Pulse Pressure); normal MAP is 70-100 mmHg
- Hypotension is generally defined as systolic < 90 mmHg or MAP < 65 mmHg
These thresholds are based on the 2017 ACC/AHA hypertension guidelines, which lowered the definition of hypertension from 140/90 to 130/80 mmHg.
MAP
Mean Arterial Pressure (MAP)
Definition
MAP is the average arterial pressure throughout one cardiac cycle. It reflects the true perfusion pressure driving blood to vital organs.
Formula
MAP = DBP + 1/3 (SBP - DBP)
Or equivalently:
MAP = (SBP + 2×DBP) / 3
DBP is weighted more (2/3) because diastole lasts longer than systole at normal heart rates.
Example
BP = 120/80 mmHg
MAP = 80 + 1/3 (120 - 80) = 80 + 13.3 = 93.3 mmHg
Normal & Clinical Ranges
| MAP Value | Interpretation |
|---|---|
| 70 - 100 mmHg | Normal |
| < 60 mmHg | Critical - inadequate organ perfusion |
| ≥ 65 mmHg | Minimum target in septic shock (ICU goal) |
| > 110 mmHg | Hypertensive range |
| < 65 mmHg | Defines hypotension / shock threshold |
Clinical Importance
- Cerebral perfusion pressure (CPP) = MAP - ICP; must keep MAP adequate in head injury
- Renal perfusion requires MAP ≥ 65-70 mmHg to maintain urine output
- Sepsis/septic shock: Surviving Sepsis Campaign targets MAP ≥ 65 mmHg with vasopressors
- Autoregulation of the brain maintains constant CBF between MAP 60-150 mmHg; outside this range, flow becomes pressure-dependent
Why Not Just Use Systolic BP?
MAP better represents true circulatory driving pressure because it accounts for the time spent in each phase of the cardiac cycle - diastole occupies roughly 2/3 of the cycle at rest.
Normal MAP
Normal MAP
Normal MAP = 70 - 100 mmHg
The most commonly cited minimum acceptable value is ≥ 65 mmHg.
Quick Reference
| MAP | Status |
|---|---|
| 70 - 100 mmHg | Normal |
| 65 - 70 mmHg | Low-normal / borderline |
| < 65 mmHg | Hypotension / shock |
| > 100 mmHg | Elevated |
Verify with Normal BP (120/80)
MAP = (120 + 2×80) / 3 = (120 + 160) / 3 = 280 / 3 = 93.3 mmHg ✓
Falls within 70-100 mmHg range.
Key Clinical Anchor
65 mmHg is the universal critical threshold - below this, organ perfusion (kidneys, brain, heart) becomes compromised.The image shows a clinical question from Grace Abuga asking about MAP computation and whether to increase Norepinephrine (NE) for a patient with chronic hypertension (HPN), with a target MAP of 70-75 mmHg.
How to Answer Grace
1. MAP Formula
MAP = (SBP + 2×DBP) / 3
or
MAP = DBP + 1/3 (SBP − DBP)
2. Example — Compute Your Patient's MAP
You need your patient's current BP reading. Plug it in:
| Patient BP | MAP Calculation | MAP Result |
|---|---|---|
| 100/60 | (100 + 120) / 3 | 73.3 mmHg ✓ |
| 90/60 | (90 + 120) / 3 | 70 mmHg ✓ |
| 85/55 | (85 + 110) / 3 | 65 mmHg ✗ too low |
| 80/50 | (80 + 100) / 3 | 60 mmHg ✗ too low |
3. Target for Chronic HPN Patients
Grace is correct - for patients with chronic hypertension, the MAP target is 70-75 mmHg (higher than the standard sepsis target of ≥65 mmHg), because their cerebral and renal autoregulation is shifted to a higher baseline.
4. Should You Increase NE?
| Patient's MAP | Action |
|---|---|
| ≥ 70-75 mmHg | No need to increase NE - target met |
| 65-70 mmHg | Consider uptitrating NE |
| < 65 mmHg | Increase NE - below safe threshold |
General rule: Uptitrate NE if MAP is consistently below 70 in a chronic hypertensive patient, titrating in small increments (e.g., 0.02-0.05 mcg/kg/min) and reassessing response.
To give Grace a direct answer, you need to share your patient's current BP values so the MAP can be calculated precisely.
How to compute map
How to Compute MAP
Formula
MAP = (SBP + 2 × DBP) ÷ 3
That's it. You only need 2 numbers from the BP reading.
Step-by-Step
Given BP = 110/70 mmHg
| Step | Action | Result |
|---|---|---|
| 1 | Multiply DBP × 2 | 70 × 2 = 140 |
| 2 | Add SBP | 140 + 110 = 250 |
| 3 | Divide by 3 | 250 ÷ 3 = 83.3 mmHg |
MAP = 83.3 mmHg ✓
More Examples
| BP Reading | Calculation | MAP |
|---|---|---|
| 120/80 | (120 + 160) ÷ 3 | 93.3 mmHg |
| 110/70 | (110 + 140) ÷ 3 | 83.3 mmHg |
| 100/60 | (100 + 120) ÷ 3 | 73.3 mmHg |
| 90/60 | (90 + 120) ÷ 3 | 70 mmHg |
| 80/50 | (80 + 100) ÷ 3 | 60 mmHg ✗ low |
Memory Trick
"1 SBP + 2 DBP, divide by 3" DBP counts twice because the heart spends more time in diastole than systole.
Normal Target
- Normal: 70-100 mmHg
- Chronic HPN patients: target 70-75 mmHg
- Critical minimum: ≥ 65 mmHg
Map of 110/50 mmHg PX and do we need to inc ne
MAP for BP = 110/50 mmHg
Calculation
| Step | Action | Result |
|---|---|---|
| 1 | DBP × 2 | 50 × 2 = 100 |
| 2 | Add SBP | 100 + 110 = 210 |
| 3 | Divide by 3 | 210 ÷ 3 = 70 mmHg |
MAP = 70 mmHg
Do We Need to Increase NE?
| Patient Type | Target MAP | Patient's MAP | Action |
|---|---|---|---|
| General/Sepsis | ≥ 65 mmHg | 70 mmHg | ✅ No need |
| Chronic HPN | 70-75 mmHg | 70 mmHg | ⚠️ Borderline - monitor closely |
Clinical Decision
If patient is NOT chronic hypertensive:
MAP 70 mmHg = target met. No need to increase NE.
If patient HAS chronic HPN (as Grace mentioned):
MAP 70 mmHg = at the lower end of target (70-75).
- If stable and no signs of hypoperfusion → hold NE, monitor
- If showing signs of poor perfusion (↓ urine output, altered sensorium, rising lactate) → consider uptitrating NE
Watch for Signs of Hypoperfusion
- Urine output < 0.5 mL/kg/hr
- Rising serum lactate (> 2 mmol/L)
- Altered mental status
- Cold, mottled extremities
Bottom line: MAP of 70 is acceptable but borderline for a chronic HPN patient. Clinical picture matters more than the number alone.
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