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Mean arterial pressure

The mean arterial pressure (MAP) is a term used in medicine to describe an average blood pressure in an individual.[1] It is defined as the average arterial pressure during a single cardiac cycle.

Calculation

Total Peripheral Resistance (TPR) is represented mathematically by the formula:

R = ΔP/Q[2]

R is TPR. ΔP is the change in pressure across the systemic circulation from its beginning to its end. Q is the flow through the vasculature (equal to cardiac output)

In other words:

Total Peripheral Resistance = (Mean Arterial Pressure - Mean Venous Pressure) / Cardiac Output

Therefore, Mean arterial pressure can be determined from:[3]

<math>MAP = (CO \cdot SVR) + CVP</math>

where:

Estimation

At normal resting heart rates <math>MAP</math> can be approximated using the more easily measured systolic and diastolic pressures, <math>SP</math> and <math>DP</math>:[4][5][6]

<math>MAP \simeq DP + \frac{1}{3}(SP - DP)</math>

or equivalently

<math>MAP \simeq \frac{2}{3}(DP) + \frac{1}{3}(SP)</math>

or equivalently

<math>MAP \simeq \frac{(2 \times DP) + SP}{3}</math>

or equivalently

<math>MAP \simeq DP + \frac{1}{3}PP</math>

where <math>PP</math> is the pulse pressure, <math>SP-DP</math>

At high heart rates <math>MAP</math> is more closely approximated by the arithmetic mean of systolic and diastolic pressures because of the change in shape of the arterial pressure pulse.

Clinical significance

<math>MAP</math> is considered to be the perfusion pressure seen by organs in the body.

It is believed that a <math>MAP</math> that is greater than 60 mmHg is enough to sustain the organs of the average person. <math>MAP</math> is normally between 70 and 110 mmHg.[7] MAP may be used similarly to Systolic blood pressure in[clarification needed] for target blood pressure. Both have been shown advantageous targets for sepsis, trauma, stroke, intracranial bleed, and hypertensive emergencies.[8]

If the <math>MAP</math> falls below this number for an appreciable time, vital organs will not get enough Oxygen perfusion, and will become hypoxic, a condition called ischemia.

See also

References

  1. ^ Zheng L, Sun Z, Li J et al. (July 2008). "Pulse pressure and mean arterial pressure in relation to ischemic stroke among patients with uncontrolled hypertension in rural areas of China". Stroke 39 (7): 1932–7. PMID 18451345. doi:10.1161/STROKEAHA.107.510677. 
  2. ^ Total peripheral resistance, Wikipedia
  3. ^ Cardiovascular Physiology Concepts: Mean Arterial Pressure, Richard E. Klabunde, Ph.D
  4. ^ Physiology: 3/3ch7/s3ch7_4 - Essentials of Human Physiology
  5. ^ Cardiovascular Physiology (page 3)
  6. ^ http://www.clinicalreview.com Physiology Review
  7. ^ impactEDnurse (May 31, 2007). "mean arterial pressure". impactednurse.com. Retrieved 2013-12-12. 
  8. ^ Magder SA (2014). "The highs and lows of blood pressure: toward meaningful clinical targets in patients with shock.". Crit Care Med. 42 (5): 1241–51. PMID 24736333. 

External links

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