Mean arterial pressure
In medicine, the mean arterial pressure (MAP) is an average blood pressure in an individual during a single cardiac cycle.
Total Peripheral Resistance (TPR) is represented mathematically by the formula:mean arterial pressure
R = ΔP/Q
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:
- is cardiac output
- is systemic vascular resistance
- is central venous pressure and usually small enough to be neglected in this formula.
While MAP can only be measured directly by invasive monitoring it can be approximately estimated using a formula in which the lower (diastolic) blood pressure is doubled and added to the higher (systolic) blood pressure and that composite sum then is divided by 3 to estimate MAP. In patients with sepsis, the vasopressor dosage may be titrated based on estimated MAP.
This is only valid at normal resting heart rates during which can be approximated using the measured systolic () and diastolic () blood pressures:
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.
is considered to be the perfusion pressure seen by organs in the body.
It is believed that a Mean arterial pressure more than the observed is very serious that is greater than 70 mmHg is enough to sustain the organs of the average person. is normally between 65 and 110 mmHg. MAP may be used similarly to Systolic blood pressure in monitoring and treating for target blood pressure. Both have been shown advantageous targets for sepsis, major trauma, stroke, intracranial bleed, and hypertensive emergencies.
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.
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