In medicine, the mean arterial pressure (MAP) is an average calculated blood pressure in an individual during a single cardiac cycle.[1] Although methods of estimating MAP vary, a common calculation is to take one-third of the pulse pressure (the difference between the systolic and diastolic pressures), and add that amount to the diastolic pressure.[2][3] A normal MAP is about 90 mmHg.[4]
| Mean arterial pressure | |
|---|---|
 Representation of the arterial pressure waveform over one cardiac cycle. The notch in the curve is associated with closing of the aortic valve. | |
| MeSH | D062186 |
Mean arterial pressure = diastolic blood pressure + (systolic blood pressure - diastolic blood pressure)/3
MAP is altered by cardiac output and systemic vascular resistance.[5] It is used clinically to estimate the risk of cardiovascular diseases, where a MAP of 90 mmHg or less is low risk, and a MAP of greater than 96 mmHg represents "stage one hypertension" with increased risk.[3][4]
Testing
edit
Mean arterial pressure can be measured directly or estimate from systolic and diastolic blood pressure by using a formula.[5] The least invasive method is the use of a blood pressure cuff which gives the values to calculate an estimate of the mean pressure. A similar method is to use a oscillometric blood pressure device that works by a cuff only method where a microprocessor determines the systolic and diastolic blood pressure.[6] Invasively, an arterial catheter with a transducer is placed and the mean pressure is determined by the subsequent waveform.
Estimating MAP
edit
While MAP can only be measured directly by invasive monitoring, it can be estimated by 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.[2]
Thus, a common way to estimate mean arterial pressure is to take one-third of the pulse pressure added to the diastolic pressure:[2][3][7]
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.[5]
Another way to find the MAP is to use the systemic vascular resistance equated ( ), which is represented mathematically by the formula
where is the change in pressure across the systemic circulation from its beginning to its end and is the flow through the vasculature (equal to cardiac output).
In other words:
Therefore, MAP can be determined by rearranging the equation to:
where:
- is cardiac output
- is systemic vascular resistance
- is central venous pressure and usually is small enough to be neglected in this formula.[8]
This is only valid at normal resting heart rates during which can be approximated using the measured systolic ( ) and diastolic ( ) blood pressures.[9][10]
Elevated heart rate
editAt 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 more accurate formula of for elevated heart rates use:
Where
- HR = heart rate.
- DP = diastolic pressure
- MAP = mean arterial pressure
- PP = pulse pressure which is systolic minus diastolic pressure[11]
Most accurate
editThe version of the MAP equation multiplying 0.412 by pulse pressure and adding diastolic blood is indicated to correlate better than other versions of the equation with left ventricular hypertrophy, carotid wall thickness and aortic stiffness.[12] It is expressed:
where:
- DBP = diastolic pressure
- MAP = mean arterial pressure
- PP = pulse pressure
Young patients
editFor young patients with congenital heart disease a slight alteration to the factor used found to be more precise. This was written as:
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.[13]
Neonates
editFor neonates, because of their altered physiology, a different formula has been proposed for a more precise reading:
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.[14]
Other formula versions
editOther formulas used to estimate mean arterial pressure are:
or
![{\displaystyle MAP=DBP+[0.33+(0.0012\times HR)]\times PP}](https://wikimedia.org/api/rest_v1/media/math/render/svg/10395a9b18d545145bb5528f4fe91fb5c31b2b0b)
or
or
- MAP = mean arterial pressure
- PP = pulse pressure
- DAP = diastolic aortic pressure
- DPB = diastolic blood pressure
Clinical significance
edit| 24 hr. MAP category | 24 hr. MAP |
|---|---|
| Normal | < 90 mmHg |
| Elevated blood pressure | 90 to < 92 mmHg |
| Stage 1 hypertension | 92 to < 96 mmHg |
| Stage 2 hypertension | > 96 mmHg |
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.[3]
Hypotension
editWhen assessing hypotension, the context of the baseline blood pressure needs to be considered. Acute decreases in mean arterial pressure of around 25% put people at increased risk for organ damage and potential mortality.[19] 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.[20][21]
In people hospitalized with shock, a MAP of 65 mmHg lasting for more than two hours was associated with higher mortality.[22] In people with sepsis, the vasopressor dosage may be titrated on the basis of estimated MAP.[2]
MAP may be used like systolic blood pressure in monitoring and treating target blood pressure. Both are used as targets for assessing sepsis, major trauma, stroke, and intracranial bleeding.[23]
Hypertension
editIn 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.[24][25]
See also
editReferences
edit- ^ Zheng L, Sun Z, Li J, Zhang R, Zhang X, Liu S, 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): 1932–1937. doi:10.1161/STROKEAHA.107.510677. PMID 18451345.
- ^ a b c d "Calculating the mean arterial pressure (MAP)". Nursing Center. 8 December 2011.
- ^ a b c d e Melgarejo JD, Yang WY, Thijs L, et al. (January 2021). "Association of Fatal and Nonfatal Cardiovascular Outcomes With 24-Hour Mean Arterial Pressure". Hypertension. 77 (1): 39–48. doi:10.1161/HYPERTENSIONAHA.120.14929. PMC 7720872. PMID 33296250.
- ^ a b "Understanding Blood Pressure Readings". American Heart Association. 2023. Retrieved 3 June 2023.
- ^ a b c DeMers D, Wachs D (2022). "Physiology, Mean Arterial Pressure". StatPearls. Treasure Island (FL): StatPearls Publishing. PMID 30855814. Retrieved 2022-05-22.
- ^ Lewis PS (May 2019). "Oscillometric measurement of blood pressure: a simplified explanation. A technical note on behalf of the British and Irish Hypertension Society". Journal of Human Hypertension. 33 (5): 349–351. doi:10.1038/s41371-019-0196-9. PMC 8076036. PMID 30926901.
- ^ "Mean arterial pressure calculator". PhysiologyWeb. 2023. Retrieved 3 June 2023.
- ^ Klabunde RE. "Mean Arterial Pressure". Cardiovascular Physiology Concepts. Marian University College of Osteopathic Medicine.
- ^ Nosek TM. "Section 3/3ch7/s3ch7_4". Essentials of Human Physiology. Archived from the original on 2016-03-24.
- ^ "Cardiovascular Physiology (page 3)". World of Anesthesia. Nuffield Dept.of Anaesthetics, University of Oxford. 12 September 2006. Archived from the original on 2006-12-11.
- ^ Moran D, Epstein Y, Keren G, Laor A, Sherez J, Shapiro Y (November 1995). "Calculation of mean arterial pressure during exercise as a function of heart rate". Applied Human Science. 14 (6): 293–295. doi:10.2114/ahs.14.293. PMID 8591100.
- ^ Papaioannou TG, Protogerou AD, Vrachatis D, et al. (September 2016). "Mean arterial pressure values calculated using seven different methods and their associations with target organ deterioration in a single-center study of 1878 individuals". Hypertension Research. 39 (9): 640–647. doi:10.1038/hr.2016.41. PMID 27194570. S2CID 11382793.
- ^ Meaney E, Alva F, Moguel R, Meaney A, Alva J, Webel R (July 2000). "Formula and nomogram for the sphygmomanometric calculation of the mean arterial pressure". Heart. 84 (1): 64. doi:10.1136/heart.84.1.64. PMC 1729401. PMID 10862592.
- ^ Gevers M, Hack WW, Ree EF, Lafeber HN, Westerhof N (1993). "Calculated mean arterial blood pressure in critically ill neonates". Basic Research in Cardiology. 88 (1): 80–85. doi:10.1007/BF00788533. PMID 8471006. S2CID 27547225.
- ^ Chemla D, Hébert JL, Zamani K, Coirault C, Lecarpentier Y (August 1999). "Estimation of mean aortic pressure". Lancet. 354 (9178): 596. doi:10.1016/S0140-6736(05)77948-4. PMID 10470724. S2CID 20720814.
- ^ Razminia M, Trivedi A, Molnar J, Elbzour M, Guerrero M, Salem Y, et al. (December 2004). "Validation of a new formula for mean arterial pressure calculation: the new formula is superior to the standard formula". Catheterization and Cardiovascular Interventions. 63 (4): 419–425. doi:10.1002/ccd.20217. PMID 15558774. S2CID 25022922.
- ^ Chemla D, Nitenberg A (June 2005). "A call for improving mean aortic pressure estimation". American Journal of Hypertension. 18 (6): 891. doi:10.1016/j.amjhyper.2004.10.025. PMID 15925755.
- ^ Chemla D, Hébert JL, Aptecar E, Mazoit JX, Zamani K, Frank R, et al. (July 2002). "Empirical estimates of mean aortic pressure: advantages, drawbacks and implications for pressure redundancy". Clinical Science. 103 (1): 7–13. doi:10.1042/cs1030007. PMID 12095398.
- ^ Jones D, Francesco L (2017). "Hypotension". In McKean SC, Ross JJ, Dressler DD, Scheurer DB (eds.). Principles and Practice of Hospital Medicine (2nd ed.). McGraw Hill. ISBN 978-0-07-184313-3.
- ^ Nicklas JY, Beckmann D, Killat J, Petzoldt M, Reuter DA, Rösch T, Saugel B (February 2019). "Continuous noninvasive arterial blood pressure monitoring using the vascular unloading technology during complex gastrointestinal endoscopy: a prospective observational study". Journal of Clinical Monitoring and Computing. 33 (1): 25–30. doi:10.1007/s10877-018-0131-6. PMID 29556885. S2CID 4025532.
- ^ Maheshwari K, Khanna S, Bajracharya GR, Makarova N, Riter Q, Raza S, Cywinski JB, Argalious M, Kurz A, Sessler DI (August 2018). "A Randomized Trial of Continuous Noninvasive Blood Pressure Monitoring During Noncardiac Surgery". Anesthesia and Analgesia. 127 (2): 424–431. doi:10.1213/ANE.0000000000003482. PMC 6072385. PMID 29916861.
- ^ Vincent, Jean-Louis; Nielsen, Nathan D.; Shapiro, Nathan I.; et al. (2018-11-08). "Mean arterial pressure and mortality in patients with distributive shock: a retrospective analysis of the MIMIC-III database". Annals of Intensive Care. 8 (1): 107. doi:10.1186/s13613-018-0448-9. ISSN 2110-5820. PMC 6223403. PMID 30411243.
- ^ Magder SA (May 2014). "The highs and lows of blood pressure: toward meaningful clinical targets in patients with shock". Critical Care Medicine. 42 (5): 1241–1251. doi:10.1097/ccm.0000000000000324. PMID 24736333. S2CID 39745357.
- ^ Wong ND, Franklin SS (2017). "Epidemiology of hypertension.". In Fuster V, Harrington RA, Narula J, Eapen ZJ (eds.). Hurst's The Heart (14th ed.). McGraw Hill. ISBN 978-0-07-184324-9.
- ^ Verdecchia P, Schillaci G, Reboldi G, Franklin SS, Porcellati C (May 2001). "Different prognostic impact of 24-hour mean blood pressure and pulse pressure on stroke and coronary artery disease in essential hypertension". Circulation. 103 (21): 2579–84. doi:10.1161/01.cir.103.21.2579. PMID 11382727. S2CID 13521935.