Page 129 - Journal of Special Operations Medicine - Spring 2016

500mL/day to clear toxic solutes through the kidneys, despite extensive study and debate. In the operational
and another 500mL/day to replace sweat losses. Febrile environment, the main benefit of colloids is to provide
patients may lose an additional 100–150mL/day for resuscitative fluid in smaller and lighter volumes than
every degree over 38°C. Respiratory losses of approxi- crystalloids. This advantage makes colloids a more ideal
mately 500mL/day are generally offset by generation of “ruck” fluid. Examples of colloids include all blood
water from oxidation, unless the patient is hyperventi- products, freeze-dried plasma, albumin, and semisyn-
5
lating. Children are much more sensitive to fluid loss thetic colloid solutions, such as hetastarch. Currently,
than adults, because of larger insensible loss per kilo- only hetastarch is widely available to military medical
gram and decreased renal concentrating ability, so more providers in operational environments.
thought needs to be put into the content and amount of
maintenance fluid in children. Hetastarch. Semisynthetic colloid solutions are made of
large molecules that rarely cross capillary membranes.
The route of fluid administration takes on additional Giving 500mL of hetastarch to a patient will have the
importance in PFC because of resource limitations. For volume expansion effect of giving 2,000–2,500mL of
resuscitation and replacement, there is evidence that de- normal saline (NS), and the effect will last longer, since
scribes good outcomes with oral or enteral resuscitation only 20%–25% of crystalloids remain in the intravas-
of shock due to burns up to 40% total body surface area cular space at 1 hour compared with nearly 100% of
6–8
(TBSA), and dehydration from diarrheal illness. There colloids. Thus, a medic can carry 500mL of hetastarch,
are limited studies of successful resuscitation of hemor- instead 1,500mL of NS. As the SOF medic transitions
rhagic shock with fluids given PR. 9,10 We recommend a a PFC patient from the initial treatment and stabiliza-
trial of oral or enteral resuscitation be considered for tion (ruck phase) to the “truck” or “house” phase, the
burns less than 40% TBSA, and hypovolemic shock due weight advantage of starches becomes less important.
to dehydration. These routes should be considered for
patients with hemorrhagic and septic shock if blood or Starches, used in critically sick patients, can increase the
intravenous (IV) fluid are unavailable. incidence of kidney disease, contribute to coagulopathy,
and worsen patient outcome. Because of these risks,
Providers in the PFC environment should be trained in they should be used for initial resuscitation or replace-
the preparation (i.e., glucose and electrolyte content) ment fluids only. There is no role for their use as a main-
and administration of oral, enteral, and PR fluids for tenance fluid, since they contain none of the nutritional
resuscitation, replacement, and maintenance require- requirements (i.e., electrolyte and glucose) required.
ments. The PFC WG also recommends that oral or
enteral routes for maintenance fluids be encouraged in In summary, the recommended use of semisynthetic
PFC to conserve resources. colloids is as follows: (1) for initial volume expansion
in hemorrhagic shock while provision of blood is be-
Fluid given for resuscitation comprises only half of the ing arranged and (2) initial resuscitation of perfusion
therapy needed to manage the critically ill or injured pa- to dysfunctional organs or unstable hemodynamics in
tient. The other aspect of therapy is treatment of the un- nonhemorrhagic shock states until adequate volume of
derlying cause (e.g., hemostasis for hemorrhagic shock, crystalloids is available.
antimicrobials for septic shock). It is beyond the scope
of this paper to discuss the details of treating and re- Crystalloids
suscitating the various shock states, but an overview of Fluids in this category include NS and buffered or “bal-
fluids in PFC would be remiss if it did not remind the anced” solutions, such as lactated Ringer’s (LR) and
practitioner that resuscitation must be accompanied by Plasma-Lyte A (Baxter; http://www.baxter.com). These
treatment for the critically ill or injured patient to have electrolyte solutions expand intravascular volume; how-
the best chance of survival and recovery. ever, only 20%–25% of a volume of crystalloid infused
remains in the intravascular space. Crystalloids, when
given to improve organ perfusion or hemodynamics,
Overview of Fluid Types should be given as large-volume boluses (500mL to 1L
per bolus) to cause a physiologic effect on the organs
Colloids and vascular system.
Colloids refer to fluids that contain microscopic parti-
cles in suspension. The principal clinical effect of giving Crystalloids given as continuous infusions to critically
colloids is that they are less likely to cross membrane ill patients are more likely to diffuse out of the intravas-
barriers, specifically blood vessels, and thus remain cular space (“third space”) than when given as boluses.
in the intravascular compartment longer than crystal- For this reason, any continuous infusion in the critically
loids. Whether this has clinical benefit is uncertain ill or injured patient should be the minimum necessary to

Fluid Therapy Recommendations 113