Changes in middle cerebral artery blood flow velocity during the early phase of fluid resuscitation in septic intensive care patients

Sepsis remains a major challenge for the Intensive Care Unit (ICU) with high
morbidity and mortality rates. Initial aggressive fluid resuscitation is
recommended as first treatment step for septic patients. However, it should be
strictly guided to prevent subsequent overzealous fluid therapy. It would be
beneficial to have the ability to predict whether a patient will respond to
fluid therapy (responder) or not (non-responder). Currently there is no such
non-invasive accurate parameter with the ability to predict fluid
responsiveness. In this study we aim to investigate whether the blood flow
velocity in the middle cerebral artery (MCA) measured by Transcranial Doppler
(TCD) can be used for this purpose. This choice is based upon the fact that the
brain is the first organ to be affected by sepsis, often preceding dysfunction
of other organ systems.

Primary we aim to investigate whether the MCA blood flow velocity measured by
TCD changes after initial fluid resuscitation in septic ICU patients, and
secondly whether this MCA blood flow velocity has the ability to accurately
predict fluid responsiveness in this population. Furthermore, we hope to gain
more insight into the influence of sepsis on the cerebral hemodynamics.

This prospective observational single centre study will take place at the ICU
in the Martini hospital Groningen. After the diagnosis sepsis is confirmed,
initial fluid resuscitation is started as soon as possible. This generally
implies fluid challenges of 500 mL colloid / hour. Before and after each fluid
challenge a TCD measurement of the blood flow velocity of both MCA*s will be
performed. This procedure will be repeated until the patient does not respond
anymore on the fluid challenges, with a maximum of five consecutive fluid
challenges. Furthermore, the blood pressure, heart rate, CO2 level and fluid
responsiveness are documented.

The participating subjects are exposed to additional measurements. However,
these are non-invasive and the associated burden is considered to be minimal.
They are only subjected to a maximum of six bilateral TCD measurements (taking
10 minutes each) during the early and critical phase of fluid resuscitation.
These measurements are non-invasive, safe and painless. Therefore it could be
stated that the risks associated with participation are considered to be
negligible and the study associated burden as minimal. The study will include
temporarily incapacitated septic ICU patients, as all patients admitted to the
ICU with severe sepsis or septic shock are mechanically ventilated and sedated.
In order to investigate changes in MCA blood flow velocity during the early and
critical phase at ICU admission, it is thus impossible to conduct the study
without participation of these temporarily incapacitated septic ICU patients.