08 Assessment of volume status and fluid responsiveness in the emergency department

quickly obtainable technique include the
inability of the CXR to detect hypovolemia
[14], an accuracy of at best 70 % (leaving
a substantial 30 % of patients misclassified),
and missing data on the significance
of VPW and CTR in a spontaneously
breathing ED patient cohort. Despite
these limitations, we agree with Ely
et al. to “use the information already available
on the patient’s CXR to its maximum
potential” [37].
Central venous pressure
The implantation of a central line and the
measurement of CVP are among the invasive
procedures that can be performed
in the ED.
However, there are considerable differences
in the clinical practice of central venous
catheterization in the ED among different
countries [41, 42]. Whereas in specific
patient groups placement of a central
venous catheter seems to be routine clinical
ED practice in the USA and Australia
(e.g., treatment of the control group in
the ProCESS and ARISE studies [43, 44]),
central venous catheterization is rarely
performed in European ED settings.
In this context, it is questionable
whether ED patients benefit from the
placement of a central venous line with
regard to their hemodynamic management
as there is abundant evidence that
CVP is a poor predictor of cardiac preload
and fluid responsiveness [45–47]. Marik
and Cavallazzi performed a meta-analysis
including 43 studies that reported the
correlation coefficient or area under the
receiver operating characteristic curve
(ROC-AUC) between CVP and changes
in stroke volume index or cardiac index
following an intervention-related change
in cardiac preload [47]. The authors demonstrated
that the CVP is able to predict
fluid responsiveness with a ROC-AUC of
only 56 %. Therefore, CVP as a static measure
of cardiac preload should not be used
to guide fluid therapy and assess fluid responsiveness
[48].
Functional tests for
the assessment of fluid
responsiveness in the ED
The aforementioned tests may quickly
aid to determine a patient’s intravascular
volume status after his arrival in the
ED. However, they provide no information
on whether this patient will benefit
from fluid therapy or not. To come to
the crucial decision of whether to administer
fluid therapy or not, two functional
tests—the passive leg-raising test (PLR)
and the fluid challenge test—are available
and have been studied primarily in intensive
care unit patients. However, in the ED
setting, the clinical applicability of these
tests might be limited due to restraints
in hemodynamic monitoring modalities.
However, despite the limited availability
of advanced hemodynamic monitoring,
the ED physician might perform a PLR or
fluid challenge test using surrogate endpoints
available in the ED setting.
Passive leg-raising test
Lifting the legs of the patient passively
from the horizontal position recruits
venous blood volume and transfers it to
the intrathoracic compartment [49–51].
By using the PLR maneuver, a prediction
whether a patient will be fluid responsive
or not is possible without the need to
give a fluid bolus [49, 51]. PLR is applicable
even in arrhythmic and spontaneously
breathing patients [51]. As an endpoint
to define fluid responsiveness different
hemodynamic parameters have been
proposed. Although it has been shown
that changes in radial pulse pressure induced
by PLR can be used for the prediction
of fluid responsiveness in nonintubated
patients [52], for an optimal utilization
of this functional test, the immediate
hemodynamic effects of PLR on blood
flow (i.e., CO or stroke volume) should
be assessed 30–90 s after the onset of the
test [51, 53, 54] because the predictive value
of PLR-induced changes in CO is higher
compared with changes in arterial pulse
pressure [55]. Because usually invasive real-time
measurement of blood flow (e.g.,
using pulse contour analysis) is not possible
in the ED, in this setting, alternative
methods for the estimation of CO/stroke
volume or surrogate parameters might be
considered.
According to recent guidelines [56],
PLR maneuver-induced blood pressure
changes can be used as a surrogate marker
for the initial assessment of fluid responsiveness.
In this context, Lakhal et al.
demonstrated that PLR-induced changes
in systolic arterial pressure measured with
a brachial cuff are able to identify fluid responsive
patients [57]. Lamia and coworkers
described the assessment of PLR-induced
changes of stroke volume by echocardiography
in critically ill patients with
spontaneous breathing activity [58]. In
addition, it was suggested that changes
in the pulse oximetry plethysmographic
waveform amplitude might be used during
PLR in spontaneously breathing patients
[59].
Fluid challenge
In order to assess fluid responsiveness, a
fluid challenge test following a structured
protocol can be performed [60, 61]. During
a fluid challenge test a certain amount
of fluid is given intravenously over a predefined
period of time, and the induced
changes in hemodynamic parameters
are observed [62]. The best way to monitor
hemodynamic effects of a fluid challenge
is to continuously observe CO [60].
A fluid challenge-induced increase in
blood flow (i.e., stroke volume or CO) of
10–15 % indicates that the patient is in the
volume-dependent upward slope of the
Frank–Starling curve and thus fluid responsive
[60, 63]. Because the fluid challenge
maneuver directly assesses the actual
hemodynamic response to fluid loading,
it can be considered the standard criterion
method for the evaluation of fluid
responsiveness. Since only about 50 % of
critically ill patients are fluid responsive,
careful hemodynamic monitoring during
a fluid challenge is of utmost importance
to promptly identify “non-responders”
and avoid unnecessary fluid loading.
The fact that assessment of CO is not routinely
possible in the ED limits the clinical
applicability of the fluid challenge test
in this setting. Blood pressure can only be
considered as a surrogate marker for fluid
responsiveness. However, for the assessment
of fluid responsiveness based on a
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