What are the acceptable ranges for mean arterial pressure (MAP) and heart rate during an operative procedure?

From the Guidelines

During operative procedures, the acceptable mean arterial pressure (MAP) should be maintained at 60 mmHg in at-risk patients, as recommended by the most recent consensus statement 1.

Key Considerations

• Heart rate should generally be maintained between 60-100 beats per minute.
• These parameters may need adjustment based on the patient's baseline values, with hypertensive patients potentially requiring higher MAP targets.
• For cardiac, neurosurgical, or vascular procedures, more specific targets may be necessary.
• If hypotension occurs, initial management includes fluid boluses, followed by vasopressors if needed.

Management of Hypotension

• Initial management of hypotension includes fluid boluses (500-1000 mL crystalloid).
• Vasopressors such as phenylephrine, norepinephrine, or ephedrine may be used if needed.

Importance of Continuous Monitoring

• Continuous monitoring via arterial line provides the most accurate blood pressure measurements during surgery.
• This is crucial because inadequate perfusion can lead to organ ischemia, while excessive pressures may increase bleeding or cardiac strain.

Recent Guidelines

• The 2024 POQI international consensus statement on perioperative arterial pressure management recommends maintaining intraoperative mean arterial pressure at 60 mmHg in at-risk patients 1.
• The 2024 EACTS/EACTAIC/EBCP guidelines on cardiopulmonary bypass in adult cardiac surgery recommend maintaining MAP between 50 and 80 mmHg during cardiopulmonary bypass 1.

From the Research

Acceptable Mean Arterial Pressure and Heart Rate

• The acceptable mean arterial pressure (MAP) and heart rate (HR) during operative procedures can vary depending on the specific context and patient population 2, 3, 4, 5.
• Studies have shown that the use of vasopressors such as phenylephrine and ephedrine can help maintain MAP and HR within acceptable ranges during anesthesia-induced hypotension 2, 3, 4.
• For example, a study published in 2010 found that phenylephrine increased MAP from 51 +/- 12 to 81 +/- 13 mmHg, but reduced frontal lobe oxygenation by 14% 2.
• In contrast, ephedrine increased MAP from 53 +/- 9 to 79 +/- 8 mmHg and preserved frontal lobe oxygenation 2.
• Another study published in 2022 found that a heart rate-dependent phenylephrine/ephedrine protocol resulted in a lower mean HR and better control of systolic blood pressure compared to an ephedrine-only protocol 3.
• The study also found that the incidence of abnormal HR was comparable between the two groups, but the phenylephrine/ephedrine protocol resulted in a lower mean HR and better control of systolic blood pressure 3.

Factors Affecting Mean Arterial Pressure and Heart Rate

• HR can affect the calculation of MAP, and studies have shown that the proportion of systole in the cardiac cycle changes with HR 6.
• A study published in 1995 found that the fraction of systole from the heart cycle was related to HR and could be described mathematically as: St = 0.01exp(4.14-40.74/HR) 6.
• The study also found that MAP could be calculated from diastolic blood pressure and pulse pressure adjusted for the proportion of systole 6.
• Other factors that can affect MAP and HR include the type of vasopressor used, the dose and duration of administration, and the patient's underlying medical condition 2, 3, 4, 5.

Clinical Implications

• The choice of vasopressor and the target MAP and HR can have important clinical implications, including the risk of organ dysfunction and mortality 2, 3, 4, 5.
• Studies have shown that ephedrine may be superior to phenylephrine in restoring uterine blood flow and fetal oxygenation during ritodrine infusion and epidural anesthesia-induced hypotension 4.
• However, the optimal MAP and HR targets may vary depending on the specific patient population and clinical context, and further research is needed to determine the best approach 2, 3, 4, 5.