Vasoactive agents
Fluid resuscitation is the first strategy to restore mean arterial pressure in hemorrhagic shock. However, vasopressor agents also may be transiently required to sustain life and maintain tissue perfusion in the presence of
a persistent hypotension, even when fluid expansion is
in progress and hypovolemia has not yet been corrected.
This point is crucial, because tissue perfusion is directly
related to the driving pressure (the difference between
pressures at the sites of entry and exit of the capillary),
the radius of the vessel, and the density of capillaries;
additionally, tissue perfusion is inversely related to blood
viscosity. Thus, arterial pressure is a major determinant
of tissue perfusion.
Norepinephrine (NE), which often is used to restore
arterial pressure in septic and hemorrhagic shock, is
now the recommended agent of choice during septic
shock [ 14 ]. NE is a sympathomimetic agent with predominantly vasoconstrictive effects. NE exerts both arterial and
venous α-adrenergic stimulation [15 ]. In addition to its arterial vasoconstrictor effect, NE induces venoconstriction
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(especially at the level of splanchnic circulation), which
induces an increase in pressure in the capacitance vessels
and actively shifts the venous blood volume to the systemic
circulation [1 6]. This venous adrenergic stimulation
may recruit blood from the venous unstressed volume,
ie, the blood volume that fills the blood vessels without
generating an intravascular pressure. Moreover, stimulation of β
2
-adrenergic receptors decreases venous resistance and increases venous return [1 6]. Poloujadoff et al.
[ 17 ], in an animal study during uncontrolled hemorrhage,
suggested that NE infusion reduced the amount of fluid
required to achieve a given arterial pressure target and corresponded to lower blood loss and significantly improved
survival. We can therefore propose the early use of NE to
restore blood pressure as quickly as possible and limit fluid
resuscitation and hemodilution. However, the effects of NE
have not been rigorously investigated in humans who suffered traumatic hemorrhagic shock. An analysis performed
during a multicenter, prospective, cohort study designed to
evaluate the outcome of adults who suffered blunt injury
and who were in hemorrhagic shock proposed that the
early use of vasopressors for hemodynamic support after
hemorrhagic shock may be deleterious, compared with the
aggressive use of volume resuscitation, and should be
approached cautiously [ 18] .
This study has several limitations. First, this was a secondary analysis of a prospective, cohort study and was not
designed to answer the specific hypothesis tested; second,
the group that received vasopressors had a higher
incidence of thoracotomy. Thus, a prospective study to
define the effect of vasopressors used in patients with
hemorrhagic shock is required. In conclusion, vasopressors may be useful if they are used transiently to sustain
arterial pressure and maintain tissue perfusion during persistent hypotension, despite fluid resuscitation (Figure 1) .
Moreover, the early use of NE could limit fluid resuscitation and hemodilution. If we use NE at an early stage, we
must note the recommended objectives of arterial pressure (SAP 80–100 mmHg) [1 1] . Thus, the dose of NE
should be titrated until we reach the target SAP (Figure 1) .
Then, fluid resuscitation should be pursued and titrated
according to indicators of preload responsiveness, cardiac
output, and tissue oxygenation markers.
Because vasopressors may increase cardiac afterload
when there is excessive infusion rate or impaired left
ventricular function, it is essential to assess cardiac function during the initial ultrasound examination. Cardiac
dysfunction may be altered in the trauma patient after
cardiac contusion, pericardial effusion, or secondary to
brain injury with intracranial hypertension. The presence
of myocardial dysfunction requires treatment with an
inotropic agent, such as dobutamine or epinephrine. In
the absence of an evaluation of cardiac function or cardiac output monitoring, which often is observed in
Figure 1 Flowchart of initial management of traumatic hemorrhagic shock. In the acute phase of traumatic hemorrhagic shock, the
therapeutic priority is to stop the bleeding. As long as this bleeding is not controlled, the physician must manage fluid resuscitation, vasopressors,
and blood transfusion to prevent or treat acute coagulopathy of trauma. AP, arterial pressure; SAP, systolic arterial pressure; TBI, trauma brain
injury; Hb, hemoglobin; PT, prothrombin time; APTT, activated partial thromboplastin time.
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patients in the acute phase of hemorrhagic shock, we
should suspect cardiac dysfunction in the presence of a
poor response to fluid expansion and NE.
Which objectives of fluid resuscitation and blood
pressure?
The mean arterial pressure, which represents the perfusion pressure of all organs (except the heart), might
serve as a target that physicians must achieve by early
fluid administration. A critical element of the resuscitation of the patient with hemorrhagic shock is to prevent a
potential increase in bleeding by a resuscitative manoeuvre
that is overly aggressive. Fluid resuscitation may promote
coagulopathy by diluting coagulation factors and favoring
hypothermia. Moreover, an excessive level of mean arterial
pressure (MAP) can favor the bleeding by preventing clot
formation. Two concepts have emerged in past years: the
concept of “low-volume resuscitation” and the concept of
“hypotensive resuscitation.” Often, these two concepts are
merged. Several experimental studies have suggested that
the limited administration of fluids associated with a low
blood pressure level as an end point may limit bleeding
without the related increased risk of death [1 9] . Bickell
et al. [2 0] in 1994 tested this concept in hypotensive
patients with penetrating injuries to the torso. They compared immediate and delayed fluid resuscitation and
reported that aggressive administration of intravenous
fluids should be delayed until the time of operative intervention. Thus, Bickell et al. supported the concept of
bringing the patient as quickly as possible to the trauma
center and restricting fluid resuscitation until the time of
operative intervention. Recently, a retrospective cohort
study of patients from the American Trauma Data Bank
[ 21 ] suggested that there was no survival benefit for prehospital IV placement or IV fluid administration. This concept could be limited by factors, such as older patients,
severe brain injuries, or longer prehospital transport times
(rural trauma). Future studies are required to clarify the
volume and the timing of fluid resuscitation before surgical
or angiographic embolization bleeding control. Minimal
volume resuscitation is preferable to aggressive volume
resuscitation before active bleeding has been controlled. It
is critical to prevent hemodilution by limiting fluid resuscitation and using an aggressive transfusion strategy. Additionally, despite adequate fluid resuscitation, only blood
transfusion can improve tissue oxygenation [ 22 ]. Thus, one
key message is that we must consider blood transfusion
early during the management of hemorrhagic shock to improve microvascular oxygen delivery.
The optimal level of blood pressure during the resuscitation of the hemorrhagic shock patient is still debated.
The initial objectives are to control the bleeding as soon
as possible and to maintain a minimal arterial pressure
to limit tissue hypoxia. Restoration of arterial pressure
with uncontrolled bleeding exposes the patient to the
risk of increased bleeding or of prevented clot formation.
Dutton et al. [2 3] found that titrating the initial fluid
therapy to a lower-than-normal systolic blood pressure
(70 mmHg) during active hemorrhage did not affect the
mortality rate. The low number and the heterogeneity of
studied patients limit the conclusions of this study. For
example, the average systolic blood pressure was equal
to 100 ± 17 mmHg in the 70-mmHg group, because the
blood pressure had increased spontaneously toward normal in some patients. Recently, Morrison et al. [2 4] ,
while evaluating patients in hemorrhagic shock who
required emergent surgery, compared an intraoperative,
hypotensive, resuscitative strategy in which the target
MAP was 50 mmHg with a standard fluid resuscitative
strategy in which the target MAP was 65 mmHg. The
hypotensive, resuscitative strategy was a safe strategy
that resulted in a significant reduction in blood product
transfusions and overall IV fluid administration with a
decrease in postoperative coagulopathy. However, in this
study, there was no MAP difference between the two
groups (64.4 mmHg vs. 68.5 mmHg) despite the different MAP objectives. The authors attributed this absence
of a MAP difference to faster control of the bleeding in
the 50-mmHg group by inducing a spontaneous MAP
increase in this group. Thus, there is an insufficient
quality or quantity of evidence to determine an optimal
blood pressure level during active hemorrhagic shock.
However, European guidelines for the management of
bleeding trauma patients recommended a target systolic
blood pressure of 80 to 100 mmHg until major bleeding
has been stopped in the initial phase after trauma for
patients without brain injury [11 ] (Figure 1). When traumatic hemorrhagic shock is associated with severe brain
injury, cerebral perfusion pressure must be maintained
by increasing the arterial pressure to prevent secondary
brain injury. Before monitoring the intracranial pressure,
we must define the optimal level of arterial