What is the improvement in blood pressure during a fluid responsiveness test?

From the Guidelines

Blood pressure typically improves by 10-15% during a fluid responsiveness test in patients who are truly fluid responsive, with a positive response generally defined as an increase in systolic blood pressure by at least 10 mmHg, or an increase in mean arterial pressure (MAP) by 7-10 mmHg, as supported by recent guidelines 1.

Key Points to Consider

• The improvement in blood pressure occurs due to the increase in venous return to the heart, enhancing cardiac preload, which leads to increased stroke volume and cardiac output according to the Frank-Starling mechanism.
• The test is most useful in patients with hypotension or signs of inadequate tissue perfusion, particularly in critical care settings, as emphasized in the surviving sepsis campaign guidelines 1.
• Not all patients are fluid responsive, and those with heart failure or volume overload may not show improvement or could even deteriorate with additional fluid administration, highlighting the need for careful patient selection and monitoring 1.
• Dynamic measures, such as passive leg raises or fluid challenges against stroke volume measurements, have been proposed to improve fluid management and predict fluid responsiveness, with a sensitivity of 0.72 and a specificity of 0.91 for pulse pressure variation 1.

Clinical Application

• The blood pressure response typically occurs within minutes of fluid administration if the patient is truly fluid responsive, allowing for rapid assessment and adjustment of treatment.
• Initial fluid resuscitation should begin with 30 mL/kg of crystalloid within the first 3 hours, as recommended by the surviving sepsis campaign guidelines 1, with further fluid administration guided by functional hemodynamic measurements.
• The use of CVP alone to guide fluid resuscitation can no longer be justified, and dynamic measures should be used to assess fluid responsiveness and guide treatment 1.

From the Research

Fluid Responsiveness and Blood Pressure Improvement

• The improvement in blood pressure during a fluid responsive test is not directly quantified in the provided studies, but the changes in cardiac output and other hemodynamic parameters are reported 2, 3, 4, 5, 6.
• A study published in Critical Care Medicine in 2017 found that the proportion of responders increased from 20% in the group receiving 1 mL/kg of crystalloid to 65% in the group receiving 4 mL/kg, with a predicted minimal volume required for a fluid challenge between 321 and 509 mL 5.
• Another study published in Anesthesiology in 2017 reported that changes in stroke volume index induced by 100 mL of crystalloid predicted fluid responsiveness with a sensitivity of 93% and a specificity of 85% 4.
• A study published in Intensive Care Medicine in 2013 found that the correlation between a fluid-induced increase in pulse pressure and fluid-induced increase in cardiac output was weak, but a high increase in invasive pulse pressure (>23%) or non-invasive pulse pressure (>35%) reliably detected a response to fluid 6.

Hemodynamic Effects of Fluid Challenge

• The hemodynamic effects of different doses of fluids for a fluid challenge were investigated in a quasi-randomized controlled study, which found that the doses of fluids used for a fluid challenge modify the proportions of responders in postoperative patients 5.
• A study published in Critical Care in 2014 reported that the variation of cardiac output and aortic velocity time index after the administration of 50 mL of crystalloid solution over 10 seconds can accurately predict fluid responsiveness 3.
• The use of transthoracic echocardiography to guide a 10-second fluid challenge was found to be effective in predicting fluid responsiveness in critically ill patients 3.

Predicting Fluid Responsiveness

• The prediction of fluid responsiveness using changes in stroke volume index, cardiac output, and pulse pressure variations has been investigated in several studies 3, 4, 6.
• A study published in Anesthesiology in 2017 reported that changes in stroke volume index induced by 100 mL of crystalloid predicted fluid responsiveness with a high degree of accuracy 4.
• The area under the receiver operating curve of changes in stroke volume index induced by 100 mL was found to be 0.95, indicating excellent predictive value 4.