Crystalloids, colloids, blood product ratios, the traps, and the logistics limits of prehospital/transport/combat environments. Verified against standard fluid composition references, CHEST/6S, PROPPR, Bickell, PAMPer/COMBAT/RePHILL, and TCCC guideline data. July 2026.
0.9%, Na 154, Cl 154, isotonic
| Preferred | Avoid / caution |
|---|---|
| Head injury, metabolic alkalosis, hypercalcemia, with blood transfusion | Large-volume resuscitation, hyperchloremic acidosis |
Not actually "normal": its chloride sits far above plasma (plasma Cl is roughly 100-106 mEq/L). The harm from large volumes is dose-dependent, driven by chloride load causing a non-anion-gap metabolic acidosis.
Na 130, K 4, Ca 3, lactate 28 mEq/L, mildly hypotonic
| Preferred | Avoid / caution |
|---|---|
| Resuscitation, surgery/trauma, burns, GI losses | Head injury, same line as blood, liver failure |
Its potassium content is not a reason to withhold it in hyperkalemia; the added potassium is small relative to the volume given and does not meaningfully worsen hyperkalemia in practice.
Avoid running LR through the same line as a blood transfusion because its calcium can theoretically overcome the citrate anticoagulant in stored blood and promote clotting in the line, though the clinical significance of this is debated; avoid in significant liver failure because lactate metabolism to bicarbonate depends on hepatic function.
Na 140, K 5, acetate 27, lactate-free, calcium-free
| Preferred | Avoid / caution |
|---|---|
| Resuscitation, liver failure, renal transplant, with blood | Head injury, cost/access |
Calcium-free, so it can safely run with blood products, and it buffers via acetate metabolized peripherally in muscle rather than lactate metabolized in the liver, so it needs no liver to buffer.
50 g/L glucose, becomes free water
| Preferred | Avoid / caution |
|---|---|
| Hypernatremia, hypoglycemia, free-water deficit, drug diluent | Resuscitation, hyponatremia, cerebral edema |
Not a resuscitation fluid. Once the glucose is metabolized, almost none of the water stays in the intravascular space; it distributes across total body water, making it a poor choice whenever intravascular volume is the goal.
Na 77, Cl 77, hypotonic
| Preferred | Avoid / caution |
|---|---|
| Maintenance, hypernatremia, free-water replacement | Resuscitation, raised ICP, hyponatremia risk |
A maintenance fluid. Never use it to resuscitate; its low effective tonicity means much of it moves out of the vascular space quickly.
Na 513, Cl 513, hypertonic
| Preferred | Avoid / caution |
|---|---|
| Symptomatic hyponatremia, raised ICP/edema | Rapid correction, volume overload |
Lift sodium no faster than 8 mEq/L in 24 hours, or risk osmotic demyelination syndrome. This is the standard limit for patients at elevated risk (severe hyponatremia, liver disease, alcoholism, malnutrition); some guidelines allow up to 10-12 mEq/L/24h in average-risk patients, but 8 is the safer number to default to.
5% iso-oncotic, 20-25% hyperoncotic
| Preferred | Avoid / caution |
|---|---|
| Large-volume paracentesis, SBP, hepatorenal syndrome | Head injury, routine resuscitation |
A targeted drug, not a routine resuscitation fluid. Its role is specific: replacing oncotic pressure lost with large-volume paracentesis, preventing renal impairment after spontaneous bacterial peritonitis, and treating hepatorenal syndrome, not general-purpose volume expansion.
Side-by-side composition, then side-by-side indications/contraindications/best setting
| Fluid | Na | K | Ca | Cl | Buffer | Tonicity |
|---|---|---|---|---|---|---|
| Normal saline (0.9%) | 154 | 0 | 0 | 154 | none | Isotonic |
| Ringer's lactate | 130 | 4 | 3 | 109 | lactate 28 | Mildly hypotonic |
| Plasma-Lyte | 140 | 5 | 0 | 98 | acetate 27, gluconate 23 | Isotonic |
| 5% dextrose | 0 | 0 | 0 | 0 | none | Isotonic in bag, hypotonic in vivo |
| Half-normal saline (0.45%) | 77 | 0 | 0 | 77 | none | Hypotonic |
| Hypertonic saline (3%) | 513 | 0 | 0 | 513 | none | Hypertonic |
| Albumin 5% | ~130-160* | 0 | 0 | ~130-160* | none | Iso-oncotic |
*Albumin's electrolyte content varies by manufacturer and carrier solution — check the specific product's label rather than assuming a fixed number. All values in mEq/L except where noted.
| Fluid | Best-use setting | Absolute contraindication |
|---|---|---|
| Normal saline | TBI/raised ICP resuscitation; diluent for blood products; correcting metabolic alkalosis | None absolute; relative caution with large-volume use (hyperchloremic acidosis) and pre-existing hyperchloremia |
| Ringer's lactate | General trauma/surgical resuscitation, burns, GI-loss replacement | Severe hepatic failure (can't metabolize lactate); avoid same line as blood (calcium/citrate interaction) |
| Plasma-Lyte | Resuscitation when calcium-free/blood-compatible fluid is needed; hepatic or renal transplant recipients | None absolute; cost/formulary access is the practical limiter, not physiology |
| 5% dextrose | Free-water deficit, hypernatremia correction, hypoglycemia, drug vehicle | Resuscitation for volume/hemorrhage; cerebral edema/raised ICP; will worsen hyponatremia |
| Half-normal saline | Maintenance fluid, gradual free-water replacement | Any acute resuscitation indication; raised ICP; risk of overly rapid sodium drop if over-used |
| Hypertonic saline 3% | Symptomatic hyponatremia, refractory raised ICP | Correction faster than 8 mEq/L/24h in at-risk patients (ODS risk); avoid as a routine resuscitation fluid |
| Albumin | Large-volume paracentesis, SBP prophylaxis, hepatorenal syndrome | Routine resuscitation (cost/no outcome benefit over crystalloid in most populations); TBI (worse outcomes vs. saline) |
The TBI/sepsis reversal, quantified: a 2020 network meta-analysis across sepsis, surgical, and trauma populations found the "best" fluid actually reverses by population. In sepsis, balanced crystalloids reduced mortality more than saline (OR 0.84) and more than hydroxyethyl starch (OR 0.81). In traumatic brain injury specifically, that flips: saline and starch achieved lower mortality than albumin and balanced crystalloids, with saline significantly outperforming albumin (OR 0.55). This is the trial-level evidence behind the "avoid balanced fluid in head injury" trap in section 13.
The practical read: "always use balanced crystalloid" is a sepsis-shaped default that doesn't transfer to TBI, where saline's higher effective tonicity may matter more than a balanced solution's acid-base profile. Fluid choice is population-specific, not universal.
Bickell et al., NEJM 1994 — the foundational trial: 598 adults with penetrating torso trauma and prehospital SBP ≤90 mmHg, randomized to immediate prehospital/ED fluid resuscitation vs. delayed resuscitation withheld until operative control. Survival to discharge was significantly higher in the delayed group (70% vs. 62%, p=0.04).
The theory: aggressive crystalloid before hemorrhage control raises blood pressure enough to dislodge a forming clot ("popping the clot"), while also driving dilutional coagulopathy, dilutional anemia, and hypothermia — the same lethal triad damage control resuscitation is built to avoid.
| Real limitations of the founding trial | Why it matters |
|---|---|
| Single center, single EMS system, penetrating torso trauma only | Limited external validity to blunt trauma or systems with different transport times |
| Used crystalloid, not modern hemostatic/blood-component resuscitation | The comparison being tested has moved on since 1994 — predates the blood-ratio evidence in section 10 |
| Blood pressure was actually similar between groups regardless of allocation | A frequently overlooked methodologic detail — raises the question of what, mechanistically, actually drove the mortality difference |
Current practice generally applies permissive hypotension (targeting SBP ~80–90 mmHg or MAP ~50 in pure hemorrhagic shock per EAST guidance) until hemorrhage is controlled — with an important carve-out for concurrent traumatic brain injury, where SBP <90 is independently associated with worse outcomes and small aliquots (100–200 mL) to maintain SBP above 90 are favored instead.
PROPPR (Holcomb et al., JAMA 2015): in-hospital massive transfusion trial comparing plasma:platelets:RBC ratios of 1:1:1 vs. 1:1:2. No statistically significant difference in 24-hour or 30-day mortality between ratios, though more patients in the 1:1:1 group achieved hemostasis and fewer died from exsanguination in the first 24 hours.
Despite PROPPR not reaching significance on its primary mortality endpoint, balanced-ratio transfusion (approximating whole blood composition) has been widely adopted as practice — built substantially on observational data with real survivorship-bias risk (patients have to survive long enough to receive the later components of a ratio). A smaller earlier RCT (Nascimento 2013) comparing a 1:1:1 target to standard care actually found higher, though not statistically significant, mortality in the balanced-ratio group — a reminder that the observational enthusiasm for balanced ratios outran the randomized evidence for some time.
This is the section most relevant to evaluating any new plasma product's real-world promise (freeze-dried or otherwise), and it's considerably messier than "prehospital plasma saves lives."
| Trial | Design | Result |
|---|---|---|
| PAMPer (NEJM 2018) | Cluster-randomized, air-medical transport, 2 units thawed plasma vs. standard care | Positive — reduced 30-day mortality with prehospital plasma |
| COMBAT (2018) | 2 units thawed AB plasma prehospital vs. standard crystalloid care, ground EMS | Negative — stopped early for futility; no outcome difference; groups imbalanced at baseline (plasma arm sicker) |
| RePHILL (Lancet Haematology 2022) | UK phase 3 RCT, PRBC + lyophilized plasma vs. saline, prehospital | Negative — did not demonstrate improved survival or lactate clearance; stopped early (COVID-19 disruption) |
Worth sitting with: RePHILL is the trial that actually tested lyophilized plasma in the prehospital setting, and it was negative on both primary outcomes. This doesn't mean freeze-dried plasma products won't help; RePHILL tested one specific product (Lyoplas) in one health system with its own transport times, and was underpowered by early stopping. But it's a directly relevant data point that a clean "freeze-dried plasma saves lives" framing skips entirely.
A post hoc analysis pooling PAMPer and COMBAT found the prehospital plasma survival benefit was concentrated in patients with transport times longer than 20 minutes — suggesting the effect, where real, may be distance/time-dependent rather than universal. A second lyophilized-plasma trial, PREHO-PLYO (France, 2022, 134 patients), was also negative: median admission INR was 1.21 with lyophilized plasma versus 1.20 with saline.
The "right" fluid on paper isn't always the fluid you can actually carry, keep stable, or afford the weight of
The doctrine has already moved past crystalloid for combat hemorrhagic shock. TCCC Guidelines Change 21-01 (2021) designated cold-stored low-titer group O whole blood (CS-LTOWB) as the preferred resuscitation fluid, with fresh LTOWB as the first alternate — and explicitly removed crystalloids and Hextend as recommended options for hemorrhagic shock. The question below isn't really "which crystalloid to carry" at the point of injury anymore; it's "how far down the evacuation chain can a blood product realistically travel before logistics force a fallback to something else."
| Echelon | Storage reality | What that means for fluid choice |
|---|---|---|
| Ground ambulance | Cabin temperatures logged as low as −13.2°C and as high as +50.6°C in real-world services; the vehicle interior exceeded the recommended 25°C storage ceiling for roughly half of total transport time in one study. | Bagged crystalloid (saline) held up chemically even under sustained 70°C or cyclic 70/22°C stress testing for a month — sodium/chloride stayed within label range, no precipitation. The bigger unresolved risk is sub-freezing exposure (bag/tubing integrity, IV catheter function), not chemical breakdown from heat. Many progressive EMS systems now carry a small cooler of RBCs/plasma alongside crystalloid, accepting the added cold-chain burden for the survival benefit. |
| Civilian HEMS (helicopter EMS) | Typically a climate-controlled cabin, but payload is constrained by aircraft performance margins — weight and cube compete directly with fuel, crew, and equipment. | Increasingly carries low-titer O whole blood or a plasma/RBC combination under dedicated air-medical transfusion programs, precisely because the climate control removes the ambulance's temperature problem — the limiting factor here is payload weight and programmatic cost, not thermal stability. |
| Military rotary-wing MEDEVAC/CASEVAC | Faces the ambulance's thermal extremes and the civilian aircraft's payload limits simultaneously, often without the benefit of a fully climate-controlled cabin, plus genuine tactical constraints on dwell time at the landing zone. | CS-LTOWB is doctrine-preferred per TCCC 21-01 where the cold chain can be maintained; when it can't, room-temperature- stable freeze-dried plasma and reduced breakage risk (section 11) become the more realistic fallback than frozen components. |
| Foot / dismounted / light transport (combat medic aid bag) | The most severe constraint of all: doctrine explicitly requires equipment be "simple, light, and rugged," carried in a backpack over body armor, often under hostile fire. There is no cold chain at this echelon, full stop. | Whole blood is essentially impossible to carry here — no refrigeration, no practical shelf life. This is the exact gap freeze-dried plasma is built to close: no freezer, no thaw cycle, plastic packaging that survives being carried and dropped, reconstituted in about a minute. Crystalloid remains the lightest option by weight but is no longer TCCC's preferred choice for hemorrhagic shock specifically. |
Warming matters at every echelon. TCCC recommends a battery-powered warming device delivering fluid at 38°C; ATLS guidance for in-hospital use targets 39°C. In practice, a single 2 L bolus of room-temperature (21°C) crystalloid drops core body temperature by only about 0.3°C in healthy adults — a real but modest effect — so active warming is about avoiding the cumulative, multi-liter scenario and the added hypothermia risk of fluid that has equilibrated to a cold ambient environment (a winter ambulance cabin, a cold LZ), not a single small bolus in isolation.
The throughline across every echelon: the fluid that wins on paper (whole blood, or a balanced crystalloid) isn't always the fluid that survives the storage conditions, fits the weight budget, or can be resupplied at that point in the evacuation chain. Matching fluid choice to the environment is as real a clinical decision as matching it to the patient's physiology in sections 1-8.
Match the fluid to the patient — and to the environment you're actually operating in.
| Fluid | One-line reminder |
|---|---|
| Normal saline | Preferred in head injury; large volumes cause hyperchloremic acidosis |
| Ringer's lactate | Good general resuscitation fluid; avoid in head injury and severe liver failure |
| Plasma-Lyte | Calcium-free, runs with blood, no hepatic buffering needed |
| 5% dextrose | Free water once metabolized; never for resuscitation |
| Half-normal saline | Maintenance and free-water replacement only |
| Hypertonic saline 3% | Symptomatic hyponatremia/raised ICP; cap correction at 8 mEq/L/24h |
| Albumin | Targeted use: paracentesis, SBP, hepatorenal syndrome |
| Starch (HES) | Avoid; kidney injury and mortality signal, CHEST/6S trials |
| Blood product ratio | ~1:1:1 widely adopted; PROPPR itself didn't reach mortality significance |
| Fluid before hemorrhage control | Permissive hypotension (SBP ~80-90) outside TBI |
| Prehospital plasma | Contradictory trial record — positive, negative, and negative-for-lyophilized-specifically |
Primary sources checked for this guide: