Intravenous Fluid Management
and Monitoring
The use of pulmonary artery catheters (PACs) in critically
ill patients has dramatically decreased. Most studies
have failed to show efficacy or have demonstrated harm.
The best known of these investigations is the Study to
Understand Prognoses and Preferences for Outcomes
and Risks of Treatments (SUPPORT), which was a retrospective,
observational study involving 5735 critically ill
patients.114 In those patients, the use of a PAC was associated
with increased mortality and cost. Richard and
coworkers completed a prospective, observational trial of
PACs versus central venous catheters (CVCs) in patients
with ARDS or shock.115 Clinical management was left
to the discretion of the treating physician. In 36 French
ICUs, no difference was observed in any of the outcome
variables measured in 676 patients.
The Fluids and Catheters Treatment Trial (FACTT),
conducted by the National Heart, Lung, and Blood Institute
(NHLBI) ARDSnet, compared hemodynamic management
guided by a PAC with hemodynamic management
guided by a CVC in 1000 patients with established ALI.116
Patients were treated at select academic ICUs by clinicians
who were trained in interpreting hemodynamic data and
who were following a specific management protocol.
Although serious catheter-related complications were
rare, the PAC group had a higher incidence of arrhythmias
and conduction blocks. The investigators were
unable to demonstrate prevention or reversal of organ
failure, reduced need for support (e.g., vasopressors,
assisted ventilation, renal replacement therapy), faster
discharge from the ICU, or decreased 60-day mortality in
the PAC group versus the CVC group. Possibly because of
this growing evidence, the use of the PAC has decreased
by 65% during the last decade in the United States.117
The interesting result from FACTT was that a conservative
fluid management plan appeared more effective
in patients with established ALI.118 Although the 60-day
mortality was similar in both groups, patients in the conservative
fluid management group had improved lung
function; improved central nervous system function;
and a decreased need for sedation, mechanical ventilation,
and intensive care. In addition, the patients in the
conservative fluid management group did not have an
increased incidence of complications, such as nonpulmonary
organ failure or shock.
For the past decade, the emphasis has been less on
the measurement of pulmonary capillary wedge pressure
or central venous pressure and more on the assessment
of fluid responsiveness. The belief is that this dynamic
measurement based on physiologic responses would be
better than a static indicator.119 The measurements can
be derived from an arterial pressure waveform (systolic
pressure variations [SPVs] and pulse pressure variations
[PPVs]), are minimally invasive, allow beat-to-beat monitoring,
and permit assessment of heart-lung interactions
in patients who are mechanically ventilated