Clinical Trial Details
— Status: Completed
Administrative data
| NCT number |
NCT01681251 |
| Other study ID # |
B2009:135 |
| Secondary ID |
|
| Status |
Completed |
| Phase |
Phase 1
|
| First received |
May 18, 2011 |
| Last updated |
November 7, 2013 |
| Start date |
August 2010 |
| Est. completion date |
October 2013 |
Study information
| Verified date |
November 2013 |
| Source |
University of Manitoba |
| Contact |
n/a |
| Is FDA regulated |
No |
| Health authority |
Canada: Ethics Review Committee |
| Study type |
Interventional
|
Clinical Trial Summary
The management and delivery of intravenous fluids during surgical operations is one of the
important duties for anesthesiologists.
The goal of this study was to determine if goal directed fluid therapy, titrated using the
FloTrac monitor's measurement of stroke volume variation results in a decrease in the length
of stay of patients undergoing open abdominal aneurysm repair.
Description:
The management and delivery of intravenous fluids during surgical operations is one of the
important duties for anesthesiologists. There is a growing body of evidence that fluid
overload in surgical patients is associated with decreased wound healing, slower return of
gut function, anastomotic breakdown, pulmonary edema and post-operative visual changes.
In the United States, abdominal aortic aneurysms are diagnosed in 190,000 people per year,
and over 50,000 of those have the aneurysm repaired5. Recent advances in endovascular
techniques have allowed many of these patients to forego an open repair. However, because of
technical difficulties, many patients still require an open repair.
The most common cause of morbidity in these patients is related to post-operative
gastrointestinal tract dysfunction. This usually involves an adynamic ileus that the
patients develop on the fourth post-operative day. This delays their tolerance of enteral
foods and lengthens their hospital stay and hospital costs. It also has the potential of
causing more morbidity in that patients may require total parenteral nutrition while
awaiting return of bowel function.
There are several causes of this gastrointestinal morbidity including direct mechanical
trauma to the bowel during surgery and activation of the inflammatory cascade. These factors
are unfortunately not modifiable by the team caring for the patient. One factor that is
modifiable is the amount and type of intravenous fluids administered to the patient.
Typically, anesthesiologists decide on the amount of fluid to administer to patients based
on parameters such as heart rate, blood pressure and urine output. These are unfortunately
unreliable in determining a patient's volume status, as these parameters can be within the
normal range, and a patient might still have inadequate perfusion to their vital organs.
Further, clinician's reliance on blood pressure as a target for fluid administration ignores
the fact that organs require blood flow as well as pressure to function optimally. Until
recently, the only way to measure blood flow was with the insertion of a pulmonary artery
catheter. Based on several studies showing a lack of benefit of this invasive procedure, it
has fallen out of favor in the non-cardiac arena. Newer monitors of cardiac output that can
be attached to a patients arterial catheter (commonly placed for major surgical procedures)
offer an alternative method for clinicians to measure cardiac output.
One of these monitors, the FloTrac system (Edwards Life Sciences, Irvine CA), utilizes the
arterial pulse contour to calculate cardiac output (CO) and the stroke volume variation
(SVV) as a monitor of volume status. In patients who are mechanically ventilated there is a
phasic variation in CO and stroke volume based on the ventilatory cycle. Large changes in
stroke volume during the ventilatory cycle may indicate hypovolemia in patients. The
administration of intravenous fluid to these patients results in a decrease in the SVV.
Thus, the SVV can be use a volume monitor and used to titrate intravenous therapy. There
have been several trials (mostly in colonic resection surgery) that have looked at such goal
directed therapy with this and similar devices and have found a decrease in patient
morbidity and length of stay.
All of these studies have in common the use of a minimally invasive CO monitor and a
reliance on colloids as the predominant fluid utilized during the case.
The utilization of SVV to determine volume status is a novel approach to fluid management in
surgical patients. As stated above, clinicians' historical reliance on pressures (such as as
blood pressure and central venous pressure) to estimate intravascular volume status is based
on an incomplete understanding on the factors that govern organ blood flow. To this end, the
investigators will also assess several parameters during this study in an attempt to
ascertain which is the best at predicting fluid responsiveness. Fluid responsiveness is
defined as the ability to predict if a given patient will increase their CO to a fluid
bolus. To date this has not been looked at in a systematic fashion.
There is also evidence to suggest that such goal directed therapy reduces the degree of
inflammation that invariably occurs after operations of this magnitude. It is hypothesized
that by resuscitating the endothelium more effectively with intravenous fluids that remain
in the intravascular space longer, there is less endothelial damage and thus less
inflammation.
