Mean arterial pressure

The mean arterial pressure is calculated as the sum of the diastolic blood pressure plus the difference of the systolic pressure to the diastolic pressure, with the difference divided by three, as shown in the equation below. For example, a diastolic pressure of 70 mm Hg and a systolic pressure of 100 mm Hg would yield by means of the calculator below a MAP of 80 mm Hg. == Testing ==

Mean arterial pressure can be measured directly or estimated from systolic and diastolic blood pressure by using a formula. ==Estimating==

While MAP can only be measured directly by invasive monitoring, there are several formulas for estimating MAP in terms of easy-to-measure quantities such as systolic and diastolic blood pressure. One common formula is to double the lower (diastolic) blood pressure, add it to the higher (systolic) blood pressure, and divide the resulting sum by 3 to estimate MAP: MAP \approx DP+1/3(SP-DP) where: • DP = diastolic pressure • SP = systolic pressure • MAP = mean arterial pressure Systolic pressure minus diastolic pressure equals the pulse pressure which may be substituted in. MAP \approx CO \cdot SVR This is only valid at normal resting heart rates during which MAP can be approximated using the measured systolic (SP) and diastolic (DP) blood pressures. Elevated heart rate At high heart rates MAP 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 more accurate formula of MAP for elevated heart rates use: : MAP \simeq DP + 0.01 \times \exp(4.14 - 40.74 / HR) \times PP Where • HR = heart rate. • DP = diastolic pressure • MAP = mean arterial pressure • PP = pulse pressure which is systolic minus diastolic pressure Most accurate The version of the MAP equation multiplying 0.412 by pulse pressure and adding diastolic blood pressure is indicated to correlate better than other versions of the equation with left ventricular hypertrophy, carotid wall thickness and aortic stiffness. It is expressed: MAP=DBP +(0.412\times PP) where: • DBP = diastolic pressure • MAP = mean arterial pressure • PP = pulse pressure Young patients For young patients with congenital heart disease a slight alteration to the factor used found to be more precise. This was written as: MAP=DBP +(0.475\times PP) where: • DBP = diastolic pressure • MAP = mean arterial pressure • PP = pulse pressure This added precision means cerebral blood flow can be more accurately maintained in uncontrolled hypertension. Neonates For neonates, because of their altered physiology, a different formula has been proposed for a more precise reading: MAP=DBP +(0.466\times PP) where: • DBP = diastolic pressure • MAP = mean arterial pressure • PP = pulse pressure It has also been suggested that when getting readings from a neonates radial arterial line, mean arterial pressure can be approximated by averaging the systolic and diastolic pressure. Other formula versions Other formulas used to estimate mean arterial pressure are: MAP=DBP+ (0.33 PP) +5 or MAP=DBP+[0.33+(0.0012 \times HR)]\times PP or MAP=DAP + PP/3 or MAP = DAP+(PP/3)+5mmHg • MAP = mean arterial pressure • PP = pulse pressure • DAP = diastolic aortic pressure • DPB = diastolic blood pressure ==Clinical significance==

Mean arterial pressure is a major determinant of the perfusion pressure seen by organs in the body. MAP levels greater than 90 mmHg increase the risk stepwise of having higher risk of cardiovascular diseases, such as stroke, and mortality. Even one minute at a MAP of 50 mmHg, or accumulative effects over short periods, increases the risk of mortality by 5%, and can result in organ failure or complications. In people hospitalized with shock, a MAP of 65 mmHg lasting for more than two hours was associated with higher mortality. In people with sepsis, the vasopressor dosage may be titrated on the basis of estimated MAP. Hypertension In younger people, elevated MAP is used more commonly than pulse pressure in the prediction of stroke. However in older people, MAP is less predictive of stroke and a better predictor of cardiovascular disease. == See also ==