Permissive Hypotension: What’s New in Fluid Resuscitation in the Management of
Istanbul Research and Training Hospital, Department of Emergency Medicine, Turkey
Submission: May 29, 2018; Published: July 19, 2018
*Corresponding author: Ozgur Karcioglu, Emergency Physician, Istanbul Research and Training Hospital, Department of Emergency Medicine, Istanbul, Turkey.
How to cite this article: Ozgur Karcioglu. Permissive Hypotension: What’s New in Fluid Resuscitation in the Management of Hemorrhagic Shock?.
J Anest & Inten Care Med. 2018; 7(2): 555708. DOI: 10.19080/JAICM.2018.07.555708
This review addresses up-to-date recommendations on evaluation and management of the patient with hemorrhagic shock in the emergency setting. The endpoints recognized to monitor perfusion and oxygenation status of the victim are presented. Although it is traditionally recommended that patients should be `filled in` using crystalloid and even colloids, numerous complications secondary to such policy has led to a current trend towards permissive hypotension in trauma patients as opposed to over resuscitation. Day by day, the policy of judicious fluid administration to maintain the mean arterial pressure with lower-than-usual mean arterial pressures (around 65 mmHg) is set as the standard of care.
It is not a prophecy that there will be much more mass casualties affecting human being in this century. Additionally, hi-tech mass transportation using imported technologies are known to cause much more frequent incidents in developing countries, along with other man-made disasters. Therefore, it is not surprising to see that trauma resuscitation is a hot debate again nowadays. Primary care and emergency physicians should be well prepared to encounter a higher toll of victims with blood loss and Hemorrhagic Shock (HS) resulting from mass casualties as well as from individual accidents and suicides.
In brief, shock is a condition caused by inadequate blood flow to meet the metabolic demands of tissues to maintain basic processes for life. Shock is the final common pathway of many kinds of insults, classically including hypovolemic, septic, cardiac, or neurologic impairment. In the recent decades, the term `distributive` shock is used more commonly to comprise anaphylactic, septic and neurogenic subtypes, while `obstructive` shock is used to depict the low-perfusion state in conditions such as tension pneumothorax, cardiac tamponade, and massive pulmonary embolism. Among all, HS is one of the commonest causes of death in victims of trauma following Traumatic Brain Injury (TBI) [1,2]. Therefore, the key principle in the primary survey is to evaluate the oxygenation and ventilation, followed by the hemodynamic status and tissue perfusion of the victim.
Another rule of thumb involves continuous monitoring for hemorrhage and efficacy of resuscitation .
Markers and endpoints of fluid resuscitation in HS
Roughly, monitoring adjuncts in shock management can be classified as hemodynamic vs. oxygenation parameters, and can also be divided as non-invasive and invasive tools as summarized in Table 1. Besides heart rate and Blood Pressure (BP), clinical assessment for blood loss should employ capillary refill, skin temperature and color, mental status, and urine output . Unfortunately, these parameters are not sensitive or specific to identify early hemorrhage . Among many tools proposed to evaluate severity of shock and resuscitation. efficacy so far (Table 1), few proved practical and routinely feasible in the Emergency Department (ED) setting. BP is known to be a poor predictor for tissue O2 delivery (DO2). A decrease in BP only occurs in Class III shock in the classification employed in ATLS that heralds impending multiorgan failure and consequently, a grave outcome. Thus, it is a rather late sign to screen for a proper trauma management strategy. Besides the `classical` vital signs, lactate and Base Deficit (BD) can be regarded practical and useful in the acute setting. Lactate and BD are the most commonly utilized indicators which yield accurate information on anaerobic glycolysis. Lactate is a measure of O2 debt, which is an important characteristic of shock states. BD is a rough measure of global tissue acidosis which is an indirect indicator of tissue perfusion. It was pointed out
that BD could remain abnormal despite improvements in Mean
Arterial Pressure (MAP), CO, mixed venous O2 saturation, and
oxygen extraction in an animal model of HS .
Known or suspected injuries, vital signs, extent of
hemorrhage, available resources, and need for transfer guide the
management in the ED and trauma bay. The search for the source
of hemorrhage should occur simultaneously with the institution
of volume infusion. A minimum of two 16-gauge intravenous
catheters should be established in adults . New and practical
venous access options such as intraosseous devices supplanted
the `traditional` venous cut-down. Resuscitation of patients with
HS traditionally consisted of large volumes of fluids in order to
restore tissue perfusion. Most respected protocols i.e. Advanced
Trauma Life Support (ATLS) recommend to begin with infusing
2 L of crystalloid followed by packed Red Blood Cells (RBC) and
plasma tailored for the patient’s general response and blood
pressure (BP) . However, there is virtually no scientific evidence
proving the need for prompt Fluid Resuscitation (FR) in HS . If
the patient responds to the initial volume adequately and rapidly,
one can say that the injury was not very severe and blood loss
was relatively small. In these cases an infusion of a balanced saline
solution can be sufficient treatment.
If resuscitation of all critically ill patients is taken into
account, researchers point out that the choice of fluid has a
small or no effect on mortality [7,8]. In contrast, when only
resuscitation of trauma patients is considered, the results are
very similar and suggest that resuscitation with colloids carries
an increased mortality. Crystalloids therefore should remain the
fluid of choice for the resuscitation of trauma patients in HS.
ATLS guidelines recommend administration of an aggressive FR
with an initial 2-L bolus of crystalloids. Resuscitation continues
with repeated boluses of Lactated Ringer’s (LR) solution, blood
(if necessary), along with a thorough search of reversible sources
of blood loss . NS solution is also a reasonable choice for
resuscitation of hypovolemic patients. Previous concerns about
inducing hypernatremic, hyperchloremic metabolic acidosis
with massive resuscitation volumes have not been borne out by
further investigation with NS and the hypertonic saline solutions.
Resuscitation with crystalloid solutions requires a volume
administration ratio of 3 : 1 to 4 : 1 over volume lost .
Blood is the optimal agent to replace losses in victims of
trauma with substantial hemorrhage. IV crystalloid resuscitation
in HS boosts coagulopathy due to dilution of clotting factors and
platelets, and hypothermia. Therefore, treatment with IV fluid
should be avoided. In mandatory situations these fluids should be
administered via small volumes, and should be halted when blood
products can be infused. In the acute management of the victim in
shock, blood products (i.e., red blood cells, plasma, and platelets)
should be given in a ratio of 1:1:1. This approach will alleviate the
untoward effects such as coagulopathy.
Early or large-volume resuscitation in severe hemorrhage has
not been supported by randomized controlled trials so far .
Increased hemorrhage volume and markedly higher mortality
may ensue following ‘classical’ high-volume, normotensive
resuscitation in case of major vascular injury [9,10]. In a study
of uncontrolled hemorrhage, infusion of only enough fluid
to maintain a MAP of 40 mm Hg improved survival rates and
decreased hemorrhage  withholding of intravenous fluids in
severe shock resuscitation still needs to be studied .
Brown et al.  cited that infusions of more than 500 mL
of crystalloid in the prehospital setting led to worse outcomes in trauma victims without hypotension . This finding indicated
that resuscitation should be goal directed based on the blood
pressure and hemodynamics. Infusion of crystalloids are to be
replaced by blood as soon as possible in the hypotensive trauma
cases. Crystalloid infusion (ie, ratio of crystalloid to PRBCs >1.5:1)
was shown to result in worse outcomes in patients with ongoing
hemorrhage [14,15]. Aggressive fluid infusion was blamed as
potentially harmful in many reports [6,14,16,17] [7,9,21,22]. The
algorithm known as permissive hypotension adopts a strategy of
fluid infusion only to maintan the systolic BP at a minimum of 70
In the study by Bickell et al. , patients who did not receive
the `usual` amounts of fluids reached to the ED with BP readings
equivalent to those received the expected doses . One of
the major advantages of SVR is believed to be its allowance to
homeostatic mechanisms to play their roles freely with resultant
diminution of hemorrhage [19,20]. Accordingly, withholding FR
has been shown to cause a significant decrease (62.5%) in ARDS
and renal failure . Aggressive volume replacement in the
shocky patient is known to cause pulmonary edema, exacerbation
of hemorrhage and increased intracranial pressure . In a, RCT
by Dutton et al.  patients with HS were assigned to either a
protocol with target systolic BP>100 or 70 mmHg and gauged the
FR as needed for these endpoints. The study failed to show any
detrimental effect of a low systolic BP endpoint on mortality.
In another study, SVR with HHS (7.5% NaCl plus 6% of
dextran-70) substantially improved systemic and splanchnic
hemodynamic and oxygen transport, without an increase in
pulmonary artery pressure . In a clinical study of 230 patients
after penetrating torso injuries, Wade et al.  demonstrated that
HSD could result in favorable prognosis, especially if surgery is
contemplated . PH encompasses the strategy of maintenance
of BP infranormal levels in order to sustain optimal or acceptable
perfusion of vital organs without exacerbating bleeding due
to injury. In well, designed animal studies of uncontrolled
hemorrhage, it was shown that the survival rate of the animals
left hypotensive and of the animals receiving fluid resuscitation
was similar . Most trauma surgeons advocate a policy of
judicious fluid administration to maintain the MAP between
60 and 80 mmHg. Permissive hypotension is not proposed as a
definitive therapy; in fact it can only be a temporizing measure
before definitive control of blood loss is accomplished . Initial
fluid resuscitation for shock should comprise 500 cc boluses of NS
via the largest and shortest gauge as possible peripheral IV route.
Infusion of NS will cease with commencement of blood products
or a normalized systolic blood pressure of 90 mmHg is noted with
improvement of clinical status.
Hypovolemia resulting from hemorrhage is the leading
etiology of shock in victims of multiple trauma. Although crystalloid
solutions are chosen as the initial treatment to expand the volume
and prevent cellular hypoxia, hemodynamically, unstable patients
deserve treatment with blood products. Although aggressive
FR is the mainstay therapy in trauma management, permissive
hypotension should also be considered as a temporizing measure
before definitive control of blood loss is accomplished. “A little
goes a long way” in severely injured patients, that is, crystalloid
administration is to be minimized while being cautious of
significant hypotension. Limited volume resuscitation or PH is
recommended to maintain minimally adequate organ perfusion
to increase survival rates after trauma.