In an intubated patient, do you adjust Tidal Volume or Positive End-Expiratory Pressure (PEEP) to increase both Mean Arterial Pressure (MAP) and Central Venous Pressure (CVP)?

From the Guidelines

In an intubated patient, neither tidal volume nor PEEP should be adjusted primarily to increase Mean Arterial Pressure (MAP) and Central Venous Pressure (CVP). These ventilator parameters should be set based on lung mechanics and oxygenation needs, not hemodynamic goals. Increasing PEEP typically decreases venous return and can lower both MAP and CVP by increasing intrathoracic pressure, while excessive tidal volumes can have similar negative hemodynamic effects 1.

Key Considerations

• If a patient needs hemodynamic support, the appropriate interventions would be fluid administration (to increase preload and therefore CVP) and/or vasopressors like norepinephrine (starting at 0.05-0.1 mcg/kg/min) to increase MAP.
• Mechanical ventilation settings should focus on lung-protective strategies (tidal volumes of 6-8 mL/kg ideal body weight and appropriate PEEP based on oxygen requirements) while minimizing hemodynamic compromise 1.
• The fundamental principle is that ventilator management and hemodynamic management are separate but interconnected concerns, and adjusting ventilator settings specifically to improve hemodynamics often leads to suboptimal respiratory care and potential lung injury.

Evidence-Based Recommendations

• The most recent and highest quality study suggests that tidal volume should be titrated according to the patient's condition, with a focus on driving pressure (ΔP = Pplat – PEEP) as a predictor of outcomes in patients with ARDS 1.
• The use of lower tidal volumes and higher PEEP levels may be necessary to maintain oxygenation and reduce hospital mortality in patients with ARDS 1.
• It is essential to monitor hemodynamics and adjust treatment accordingly, using tools such as echocardiography and pulse pressure variation to assess fluid responsiveness and cardiac output 1.

From the Research

Adjusting Parameters to Increase Mean Arterial Pressure and Central Venous Pressure

To increase both Mean Arterial Pressure (MAP) and Central Venous Pressure (CVP) in an intubated patient, the parameter that should be adjusted is Positive End-Expiratory Pressure (PEEP).

• The studies 2, 3, 4, 5 consistently show that increasing PEEP leads to an increase in CVP.
• Specifically, a 5 cmH2O increase in PEEP is associated with a 2.47 ± 1.53 cmH2O increase in CVP 5.
• Additionally, increasing PEEP can also lead to an increase in MAP, although this effect is not as consistent across studies.
• In contrast, there is limited evidence to suggest that adjusting Tidal Volume has a significant impact on both MAP and CVP.

Effects of PEEP on CVP and MAP

The effects of PEEP on CVP and MAP are as follows:

• CVP increases gradually with the increment of PEEP 2, 3, 4, 5.
• MAP may also increase with PEEP, although this effect is not as consistent across studies.
• The relationship between PEEP and CVP is direct, with a 5 cmH2O increase in PEEP leading to a 2.5 cmH2O increase in CVP 5.

Clinical Implications

The clinical implications of these findings are:

• Adjusting PEEP can be an effective way to increase both CVP and MAP in intubated patients.
• However, the effects of PEEP on MAP and CVP can vary depending on the individual patient and the specific clinical context.
• Therefore, careful monitoring of these parameters is necessary to ensure that the desired effects are achieved without causing adverse consequences 6.