From the Guidelines
MAP stands for Mean Arterial Pressure, which is the average blood pressure in a person's arteries during one cardiac cycle, and is calculated using the formula: MAP = [(2 × diastolic pressure) + systolic pressure] ÷ 3, with a normal range of 70-100 mmHg in adults. This measurement is clinically important because it represents the perfusion pressure experienced by organs in the body. Healthcare providers use MAP to assess tissue perfusion, especially in critical care settings, as it provides a more comprehensive picture of circulatory function than standard blood pressure readings 1.
Importance of MAP in Critical Care
When MAP falls below 60 mmHg, organs may not receive adequate blood flow, potentially leading to organ damage. Therefore, maintaining an optimal MAP is crucial, especially in patients with shock, sepsis, or during surgery. The optimal MAP target may vary depending on the individual patient's condition, but a target MAP of 65 mmHg is generally recommended in septic shock and general ICU patients 1.
Factors Influencing MAP Targets
However, some studies suggest that the optimal MAP target may be higher in patients with atherosclerosis and/or previous hypertension, and lower in young patients without cardiovascular comorbidity 1. Additionally, the use of vasopressors, such as norepinephrine, should be titrated to maintain a MAP of 65 mmHg, while also monitoring other markers of systemic and organ perfusion, such as lactate, mixed or central venous oxygen saturations, urine output, skin perfusion, renal and liver function tests, and mental status 1.
Clinical Application of MAP
In clinical practice, the most recent and highest quality study recommends targeting a MAP of 65 mmHg in patients with septic shock 1. This recommendation is based on the findings of a large RCT that demonstrated no difference in 90-day mortality between patients with a MAP target of 60-65 mmHg and those with a higher MAP target 1. Therefore, targeting a MAP of 65 mmHg is a reasonable approach in clinical practice, while also considering individual patient factors and monitoring other markers of perfusion.
From the Research
Definition of MAP
- Mean Arterial Pressure (MAP) is a common characteristic of the cardiac cycle, usually evaluated by assuming that the left ventricular ejection time (systole) constitutes a constant proportion of the cardiac cycle 2.
- MAP is calculated from the diastolic blood pressure (dBP) and the pulse pressure (PP) adjusted for the fraction of systole (St) as follows: MAP = dBP+St.PP; (mmHg) 2.
Clinical Significance of MAP
- The Surviving Sepsis Campaign targets central venous pressure, mean arterial pressure, and central venous oxygen saturation as guides for resuscitation 3.
- In patients resuscitated after cardiac arrest, a higher mean arterial pressure (MAP) may increase cerebral perfusion and attenuate hypoxic brain injury 4.
- Vasopressors are indicated to maintain mean arterial pressure of <65 mm Hg, both during and following adequate fluid resuscitation 5.
Measurement and Management of MAP
- An arterial catheter should be placed as soon as possible in patients with septic shock to measure mean arterial pressure 5.
- Norepinephrine or dopamine are the vasopressors of choice in the treatment of septic shock to maintain mean arterial pressure 5.
- Vasopressin may be considered for salvage therapy in patients with vasodilatory shock that is unresponsive to fluid resuscitation and catecholamine administration 6.