Page 132 - JSOM Winter 2021

use of hetastarch solutions. A subsequent 2016 meta-analysis Plasma-Lyte A has a neutral pH (7.4), an osmolarity of
found that even low-molecular-weight HES products reduced 295mOsm/L, and no calcium. This is in contrast to LR, which
coagulation competence when compared to crystalloids and has a lower pH, is slightly hypotonic with an osmolarity of
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albumin. A 2018 paper from Germany found that severely 273mOsm/L and contains calcium. Plasma-Lyte A was com-
injured patients receiving more than 1000mL of synthetic col- pared with NS in a study of 46 trauma patients and was associ-
loid solutions (predominantly hetastarch) had a higher rate of ated with improved acid-base status and less hyperchloremia at
renal and multiple organ failure but did not find any effect on 24 hours postinjury, although no improvement in survival was
70
mortality. 55 found. In a separate observational study of 30,994 patients
who received NS during major surgery compared with 926 pa-
The FDA issued a safety communication on HES solutions in
November 2013 that noted an increased risk in mortality and tients who received Plasma-Lyte A, the patients who received
renal replacement therapy associated with the use of HES to Plasma-Lyte A had a lower incidence of post operative infec-
treat critically ill patients. A further Cochrane Review con- tion, renal failure requiring dialysis, and the need for blood
7
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cluded that HES slightly increased the need for blood transfu- transfusion. Plasma-Lyte A may have a physiological advan-
sion and renal replacement therapy while albumin or FFP had tage over NS and LR, but like all crystalloids, does not have the
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minimal impact. Hextend had previously remained the TCCC- intravascular volume expansion properties of colloids or FFP.
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recommended resuscitation fluid when blood products were not Recent evidence, however, has demonstrated the superiority
available, and represented the best available colloid based on of whole blood or blood components over crystalloid solu-
available evidence in 2014. However, as noted by more recent tions. 2–4,73,74 Further, other studies have shown that large vol-
reviews, both high- and low-molecular HES products adversely umes of crystalloid are associated with poorer outcomes in
affect coagulation competence, increase kidney injury, and in- resuscitating trauma patients. 75,76
crease the incidence of subsequent surgeries. 54,57
In summary, the currently available evidence indicates that
neither crystalloids nor Hextend are acceptable options for
Crystalloids – General the prehospital fluid resuscitation of trauma patients in hem-
Once considered the prehospital standard of care, early and
aggressive administration of crystalloid fluid has fallen out of orrhagic shock.
favor in hemorrhagic shock. This approach was replaced by
damage control resuscitation, which for the casualty in hem- (3) What is the optimal target SBP for resuscitation of
orrhagic shock, focuses on not increasing the blood pressure hemorrhagic shock casualties, and does this change when
to the point where hydrostatic pressure may interfere with the traumatic brain injury is also present?
body’s attempts at hemostasis, on avoiding dilutional coagu- Isolated Hemorrhagic Shock Without TBI
lopathy, and on providing an increased ratio of plasma admin- Over the past decade and a half, resuscitation strategies for
istered with RBCs and the use of platelets when available, in military trauma have shifted from liberal fluid administration
a 1:1:1 ratio. 58 toward a controlled hypotensive resuscitation with various SPB
goals between 70 and 100mmHg. Bickell et al. demonstrated
Crystalloids are distributed throughout the interstitium as that delaying aggressive fluid resuscitation until after surgical
well as the intravascular space, resulting in the expansion control of noncompressible hemorrhage in penetrating trauma
of the entire interstitial space instead of the desired effect of patients significantly decreased mortality. The primary aim
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intravascular expansion. For example, an infused volume of of hypotensive resuscitation is to maintain SBP (or mean ar-
1L of 0.9% sodium chloride adds 275mL to the plasma vol- terial pressure) in order to sustain organ perfusion. It was
78
ume and 825mL to the interstitial volume after equilibration. proposed that permissively moderate SBP goals would avoid
This can lead to clinical complications like acute respiratory further hemorrhage due to dilution coagulopathy, reduce hy-
distress syndrome, hypoxemia, and abdominal compartment pothermia and avoid dislodging hemostatic blood clots. 79,80
syndrome. 59–64
Two recent meta-analyses were published that evaluated con-
Current clinical practice guidelines for damage control resus-
citation highlight that crystalloid fluids should be reserved for trolled hypotension vs. aggressive fluid resuscitation in trau-
81,82
specific clinical uses, such as carrier fluid for intravenous med- matic hemorrhagic shock. While both studies found a
ication or other nonresuscitative uses. The minimization of survival benefit in the controlled hypotension strategy, several
16
crystalloids is part of balanced resuscitation of patients with confounding factors need to be addressed. First, the various
hemorrhagic shock that avoids worsening the coagulopathy studies included in these meta-analyses had a wide variation of
of trauma. 65,66 target SBPs in the controlled hypotension arms ranging from
50mmHg to 100mmHg. Additionally, many of the studies that
met inclusion criteria were performed prior to the era of blood
Crystalloids – Lactated Ringer’s and Plasma-Lyte A product use in initial fluid resuscitation. Finally, both groups
The crystalloid solutions currently recommended in TCCC are
lactated Ringer’s solution (LR) and Plasma-Lyte A. LR appears of authors also note that many of the included studies were
to be better than Normal Saline (NS) in traumatic resuscita- insufficiently powered to find statistical significance and they
tion because it does not produce the degree of hyperchloremic were of poor-to-moderate quality due to insufficient protocol
acidosis that large volume NS resuscitation does. LR, NS, reporting and lack of blinding.
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Plasma-Lyte A, and Plasma-Lyte R were compared in a trans-
lational animal model where LR produced the highest 2-hour Hemorrhagic Shock With Concurrent TBI
survival rate among the four crystalloids studied. LR for The evaluation of a military trauma patient in hemorrhagic
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fluid replacement during vascular surgery has trended toward shock is complicated by the ever-present risk of either occult
less acidosis and less intraoperative blood loss, but with no or obvious concurrent TBI. High-energy kinetic weapons, ex-
decrease in mortality when compared to NS. 69 plosions, vehicle accidents, and falls from heights all contrib-
ute to the likelihood of concurrent brain injury. Management

130 | JSOM Volume 21, Edition 4 / Winter 2021