What is in each bag (US labels), osmolarity, pH and the point that matters
Per liter, from the labels
0.9% saline (normal saline)
Na 154, Cl 154 mEq/L; 308 mOsm/L; pH 5.0. Chloride load: hyperchloremic acidosis with volume; first choice in TBI and with blood
Lactated Ringer’s (LR)
Na 130, K 4, Ca 2.7, Cl 109, lactate 28 mEq/L; 273 mOsm/L; pH 6.5. Mildly hypotonic (not for TBI); calcium clots blood in a shared line
Plasma-Lyte A
Na 140, K 5, Mg 3, Cl 98, acetate 27, gluconate 23 mEq/L; 294 mOsm/L; pH 7.4. No calcium; labeled compatible with blood
Normosol-R, Isolyte S
Same electrolytes as Plasma-Lyte A within 1 mEq/L; 294–295 mOsm/L; pH 6.6–7.4 depending on the product
D5W
Dextrose 50 g/L, no electrolytes; 252 mOsm/L; pH 4.0; 170 kcal/L. Free water once the glucose is used: never for volume
D5½NS
Dextrose 50 g/L, Na 77, Cl 77 mEq/L; 406 mOsm/L in the bag; pH 4.0. Hypotonic once the glucose is used; adult maintenance with KCl
0.45% saline (½NS)
Na 77, Cl 77 mEq/L; 154 mOsm/L; pH 5.0. Hypotonic: free water for hypernatremia; worsens hyponatremia and brain swelling
Plasma for comparison: Na 135–145, K 3.5–5.0, Cl 98–107 mEq/L; osmolality 275–295 mOsm/kg. The lactate in LR (in the liver) and the acetate in Plasma-Lyte (in most tissues) become bicarbonate.
Albumin and other colloids
Albumin 5% and 25%, why starches are avoided, and why plasma is not for volume
Albumin (human)
Albumin 5%
12.5 g in 250 mL; iso-oncotic: expands plasma by about its own volume; Na 130–160 mEq/L. Hypovolemia 250–500 mL, repeat in 15–30 min
Albumin 25%
12.5 g in 50 mL; hyperoncotic: draws about 3.5 times its volume from the tissues within 15 min (label); a dry patient needs crystalloid too
Albumin uses
Paracentesis over 5 L: 6–8 g per liter removed; SBP: 1.5 g/kg day 1 and 1 g/kg day 3; hepatorenal AKI with a vasoconstrictor
Albumin in sepsis
SSC 2026 suggests crystalloids alone; may fit after large crystalloid volumes or in cirrhosis; avoid in TBI (SAFE)
Albumin handling
Start within 4 h of spiking; dilute only with 0.9% saline or D5W; slow or stop for dyspnea, JVD or rising BP
Not for volume
Hydroxyethyl starch (Hespan, Hextend)
FDA boxed warning (2021): more death, kidney injury and bleeding; do not use unless no adequate alternative exists (6S 2012)
Dextran 40, gelatins
Dextran: label warns of fatal anaphylactoid reactions, kidney failure and bleeding. Gelatins: not sold in the US; SSC advises against
Plasma (FFP)
Not a volume expander (Circular of Information): 10–15 mL/kg for bleeding with factor deficiency; risks TRALI, TACO, allergy
Hypertonic and concentrated fluids
Strength per mL, osmolarity and which line
3% saline
513 mEq/L Na (0.513 mEq/mL); 1,027–1,030 mOsm/L. Label: slowly into a large vein; many ICU protocols allow a good peripheral IV
3% saline doses
Severe symptomatic hyponatremia: 100–150 mL over 10–20 min, repeat to raise Na about 5 mEq/L; raised ICP: 150–250 mL or 2.5–5 mL/kg
23.4% saline
4 mEq/mL; 8,008 mOsm/L. Label: additive only, must be diluted; the neuro bolus of 30 mL over 10–20 min is off-label, central line only
Sodium bicarbonate 8.4%
1 mEq/mL (50 mEq in 50 mL); 2,000 mOsm/L. Vesicant: large or central vein; flush; never in a line with calcium, norepinephrine or dobutamine
Sodium bicarbonate 150 mEq/L
Isotonic drip: premixed bag (about 300 mOsm/L), or 150 mEq added by pharmacy to 1 L of sterile water or D5W; a peripheral IV is fine
Dextrose 50% (D50)
0.5 g/mL (25 g in 50 mL); 2,525 mOsm/L. Label: 10–25 g for hypoglycemia into a central or large peripheral vein; necrosis if it leaks
Dextrose 10% (D10)
0.1 g/mL (25 g in 250 mL); 505 mOsm/L; 340 kcal/L. A peripheral IV is fine; bolus, or infusion to prevent repeat lows
Dextrose labels: consider a central vein at 900 mOsm/L or more. Check sodium every 4–6 h on hypertonic saline; in chronic hyponatremia raise it no more than 8 mEq/L in 24 h.
Choosing and dosing fluid
Balanced vs saline, albumin trials, fluid responsiveness, de-resuscitation
Trials
SMART 2018
15,802 ICU adults, balanced vs saline: major kidney events 14.3% vs 15.4%; 1,641 with sepsis: 30-day in-hospital death 26.3% vs 31.2%
BaSICS 2021
11,052 ICU adults, Plasma-Lyte vs saline: 90-day death 26.4% vs 27.2%, no difference; the TBI subgroup fared worse with Plasma-Lyte
PLUS 2022
5,037 ICU adults, Plasma-Lyte vs saline: 90-day death 21.8% vs 22.0%, no difference
SAFE 2004
6,997 ICU adults, 4% albumin vs saline: 28-day death 20.9% vs 21.1%; more deaths with albumin in TBI
ALBIOS 2014
1,818 with severe sepsis, 20% albumin to keep 3 g/dL: 90-day death 41.1% vs 43.6%, no difference
Bottom line
Balanced crystalloid for most (SSC 2026 in sepsis); saline for TBI, hypochloremic alkalosis and blood lines; albumin not routine
Will more fluid raise cardiac output?
Passive leg raise (PLR)
From 45° head-up, trunk flat and legs up 45°: SV or CO up 10% or more within 1–2 min means responsive. Judge by CO or VTI, not BP
Pulse pressure variation (PPV)
Over about 12–13% (gray zone 9–13%); valid only if passive on the vent, regular rhythm, Vt 8 mL/kg PBW or more, closed chest
Stroke volume variation (SVV)
Over about 12% on a pulse contour monitor; same limits as PPV: spontaneous breaths, arrhythmia or low Vt void it
Mini-bolus
100 mL over 1 min (Muller 2011): VTI or SV up 10% predicts response to the full bolus; changes this small sit near echo noise
CVP
Does not predict fluid response (Marik 2008); a high or rising CVP warns of venous congestion
After resuscitation
De-resuscitation
Once shock resolves: stop maintenance, concentrate drips, then diurese or ultrafilter to negative balance (FACTT 2006: more vent-free days)
Fluid creep
Diluents, flushes and keep-open lines: median 645 mL/day, a third of ICU intake (Van Regenmortel 2018). Burns: fluid beyond the formula
Fluid overload
Weigh daily and track cumulative balance; over 10% weight gain from fluid is linked to death in AKI (observational)
Maintenance fluids
Adult daily needs, why hypotonic maintenance is avoided, the pediatric 4-2-1 rule
Adult needs per day (NICE CG174)
Water
25–30 mL/kg/day, about 73–88 mL/h at 70 kg; 20–25 mL/kg/day if old, frail, malnourished, or in kidney or heart failure
Na, K and Cl
About 1 mmol/kg/day each (70 mmol at 70 kg); add potassium once K and urine output are known
Glucose
50–100 g/day to limit starvation ketosis; D5 at 100 mL/h gives 120 g (about 400 kcal), which is not nutrition
Obesity
Base the volume on ideal body weight
Why not hypotonic
Pain, nausea, opioids, surgery and lung or brain disease release ADH, so free water is kept and sodium falls
D5W and D5½NS act as free water once the glucose is used, whatever the bag osmolarity says
Hospital-acquired hyponatremia can cause brain swelling, seizures and death; children and young women are most at risk
Isotonic maintenance prevents it in children (AAP 2018); in adults, check sodium daily and give no more than needed
Stop IV maintenance once the patient eats, drinks or is fed enough; count drug diluents and flushes
Children: 4-2-1 rule (Holliday-Segar)
First 10 kg
4 mL/kg/h (100 mL/kg/day)
Next 10 kg
2 mL/kg/h (50 mL/kg/day)
Each kg over 20
1 mL/kg/h (20 mL/kg/day)
Example, 25 kg
40 + 20 + 5 = 65 mL/h
Fluid (AAP 2018)
Isotonic with KCl and dextrose, 28 days to 18 years; excludes neonates and heart, liver, kidney or neurosurgical disease, DI, burns
In adults
4-2-1 gives 110 mL/h at 70 kg, above the NICE range of about 73–88 mL/h
For education and exam preparation only. Follow your institution’s protocols. Typical adult values for study. Follow the order, the label and your institution's protocols.