From the Guidelines
Mean arterial pressure (MAP) is a critical parameter in assessing tissue perfusion, and a target MAP of 65 mmHg is recommended in septic shock and general ICU patients, as evidenced by the Surviving Sepsis Campaign Guidelines 1 and recent practice guidance on acute-on-chronic liver failure 1.
Definition and Measurement of MAP
MAP is the average blood pressure in a person's arteries during one cardiac cycle, representing the average pressure driving blood through the systemic circulation. It's calculated using the formula: MAP = [(2 × diastolic pressure) + systolic pressure] ÷ 3. MAP can be measured directly through an arterial catheter connected to a pressure transducer, which is the most accurate method used in critical care settings. Alternatively, it can be estimated non-invasively using automated blood pressure cuffs that calculate MAP after measuring systolic and diastolic pressures.
Significance of MAP
The significance of MAP lies in its role as a better indicator of tissue perfusion than systolic pressure alone. A normal MAP ranges from 70-100 mmHg in adults, with values below 60 mmHg potentially causing inadequate blood flow to vital organs, while sustained elevations above 100 mmHg may indicate hypertension requiring treatment. MAP is particularly important in critical care medicine for managing patients with shock, trauma, or during surgery, as it helps clinicians ensure adequate perfusion to vital organs like the brain, heart, and kidneys. Maintaining appropriate MAP is essential for cellular function and preventing organ damage from hypoperfusion.
Key Considerations
- The optimal approach is to use an individualized MAP target based on frequent assessment of end-organ perfusion (mental status, capillary refill, urine output, extremity perfusion, lactate, central venous oxygen saturation, and end-organ function) 1.
- Norepinephrine (0.01–0.5 μg/kg/min) is recommended as the first-line vasopressor agent to maintain adequate organ perfusion pressure in patients with septic shock 1.
- Recent studies suggest that targeting a MAP of 65 mmHg may be beneficial in certain patient populations, such as those with septic shock or cirrhosis 1.
From the Research
Definition of Mean Arterial Pressure (MAP)
- Mean Arterial Pressure (MAP) is defined as the average of the arterial blood pressure through a single cardiac cycle 2, 3.
- It is a critical hemodynamic factor that plays a significant role in maintaining proper blood flow to organs and preventing pathophysiological consequences such as syncope, shock, and end-organ damage 4.
Measurement of Mean Arterial Pressure (MAP)
- MAP can be calculated using the diastolic blood pressure (dBP) and the pulse pressure (PP) adjusted for the fraction of systole (St) from the heart cycle: MAP = dBP + St.PP 2.
- The fraction of systole (St) from the heart cycle can be related to heart rate (HR) and described in mathematical terms as: St = 0.01exp(4.14-40.74/HR) 2.
- In neonates, MAP can be approximated by adding 46.6% of the pulse pressure to the diastolic arterial pressure (DAP) 3.
Significance of Mean Arterial Pressure (MAP)
- MAP is a significant predictor of cardiovascular events, including heart failure and all-cause mortality 5.
- Greater visit-to-visit MAP variability is associated with a higher risk of all-cause mortality and heart failure, indicating that MAP variability may be a potential risk factor for these conditions 5.
- MAP may be a more beneficial and accurate index for identifying the cerebrovascular impact of hypertension than using either systolic or diastolic blood pressure measurements alone 6.
- The arterial baroreflex system, which regulates MAP, is a complex system that plays a critical role in maintaining proper blood pressure and preventing pathophysiological consequences 4.