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]
where:
- is cardiac output
- is systemic vascular resistance
- is central venous pressure and usually small enough to be neglected in this formula.
Estimation
At normal resting heart rates can be approximated using the more easily measured systolic and diastolic pressures, and :[4][5][6]
or equivalently
or equivalently
or equivalently
where is the pulse pressure,
At high heart rates is more closely approximated by the arithmetic mean of systolic and diastolic pressures because of the change in shape of the arterial pressure pulse.
For a generalized formula of :
Where HR is the heart rate.[7]
Clinical significance
is considered to be the perfusion pressure seen by organs in the body.
It is believed that a that is greater than 60 mmHg is enough to sustain the organs of the average person. is normally between 65 and 110 mmHg.[8] MAP may be used similarly to Systolic blood pressure in for target blood pressure. Both have been shown advantageous targets for sepsis, trauma, stroke, intracranial bleed, and hypertensive emergencies.[9]
If the 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
- ↑ 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. doi:10.1161/STROKEAHA.107.510677. PMID 18451345.
- ↑ Total peripheral resistance, Wikipedia
- ↑ Cardiovascular Physiology Concepts: Mean Arterial Pressure, Richard E. Klabunde, Ph.D
- ↑ Physiology: 3/3ch7/s3ch7_4 - Essentials of Human Physiology
- ↑ Cardiovascular Physiology (page 3)
- ↑ http://www.clinicalreview.com Physiology Review
- ↑ Calculation of mean arterial pressure during exercise as a function of heart rate.
- ↑ impactEDnurse (May 31, 2007). "mean arterial pressure". impactednurse.com. Retrieved 2013-12-12.
- ↑ 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. doi:10.1097/ccm.0000000000000324. PMID 24736333.
External links
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