Predicting Volume Response Study

The administration of intravenous fluid and blood products for treatment of hypovolemia is
common in the ICU setting. Static resuscitation endpoints such as heart rate, blood
pressure, and CVP are frequently used to guide this therapy, despite compelling evidence
they are unreliable in predicting patient response to therapeutic volume administration or
as an endpoint for ongoing therapy. Dynamic parameters such as continuous stroke volume and
cardiac output (index) monitoring, along with pulse pressure and stroke volume variance
measures are more reliable in predicting and measuring response to fluid challenge and
therapeutic volume administration. The purpose of this study is to observe changes in stroke
volume (SV) and cardiac output (CO) during a passive leg raise maneuver (PLR) as a surrogate
to volume challenge, and to determine if these changes can predict changes in the same
parameters with fluid or blood product administration in surgical patients. The PLR maneuver
involves positioning the patient to the supine position and elevating the legs to 45
degrees. The PLR moves blood from the capacitance vessels of the legs to the heart,
potentially improving stroke volume (SV) and cardiac output (CO), without the administration
of intravenous fluids. PLR may predict whether SV or CO would improve with administration of
fluids, and guide decisions on whether fluid administration would be beneficial. Stroke
volume and cardiac output (index) will be calculated by a commercial pulse power arterial
pressure cardiac output system (LIDCORapid), using the patients' measured heart rate and
blood pressure imported from the bedside monitor. By using the combination of a reversible
volume challenge (PLR) and a minimally invasive monitoring system, it is hoped that a more
reliable method will emerge to both predict a response and guide therapeutic volume
administration, while reducing the risk associated with fluid volume overload.

Inclusion Criteria:

- Patients 18 years or older admitted to the Surgical Intensive Care Unit, anticipated
to receive IV fluid boluses or blood products, with the presence of an arterial
pressure line.

Exclusion Criteria:

- patients under 18 years of age,

- pregnancy,

- prisoners,

- inability to lay in the supine position,

- conditions of the lower extremities,

- pelvis or spine that preclude elevation of the legs