Crystalloid fluids
- principal component: NaCl
- Distributes uniformly throughout ECF, which is 75-80% interstitial, 25%
intravascular.
- Therefore, giving crystalloid
predominantly fills interstitium.
- (side note: D10 = 10 grams dextrose per 100 mL)
Isotonic Saline:
- 0.9% NaCl has 9 g NaCl/L (154 mEq of Na and Cl each)
- is actually hypertonic to
ECF, and therefore 1000 mL of NS will result in 1100 mL volume expansion as
some volume is drawn from ICF.
- pH < plasma pH (is more acidic
than plasma)
- very high chloride vs plasma levels mean
if replacing with lots of NS, may get
a hyperchloremic metabolic acidosis. Hyperchloremia has been reported.
Acidosis is rare.
- ("Normal Saline" is a misnomer, since "Normal" solution has 1equivalent
(to counter OH-) per liter. e.g. 1 N NaCl has 58 g of NaCl (the combined MW of
Na and Cl).
| meq/L |
pH |
Na+ |
Cl- |
K+ |
Ca++ |
Lactate |
Glucose |
Osmolality |
Other |
| .9% NS |
5.0 |
154 |
154 |
0 |
0 |
0 |
0 |
308 |
0 |
| LR |
6.5 |
130 |
109 |
4 |
3 |
28 |
0 |
275 |
0 |
Lactated Ringers LR:
- No evidence that it provides any
benefit over isotonic saline. No evidence that the lactate provides any buffer
effect.
- Con: Calcium can bind drugs e.g if using donor blood, can bind citrate
anticoagulant and promote clotting. LR IS
CONTRAINDICATED AS DILUENT FOR BLOOD
XFUSIONS.
- Sydney Ringer: designed it to promote contraction of isolated from hearts.
Contained Ca++ and K+ (approximates free ionic concentrations in plasma), in
NaCl solution. To maintain electrical neutrality, had to decrease Na+.
- Alex Hartman added lactate (28 mEq/L) cuz he thought it could act as a
buffer in metabolic acidosis. To maintain elecrtrical neutrality, had to
decrease Cl-
- A frequent alternative to normal saline is LR, which more closely mimics
the electrolyte concentration of human plasma as well as having a small amount
of lactate included.
Normosol/PlasmaLyte:
- added buffer capacity (therefore
pH is closer to plasma pH)
- Mg added (many hospitalized
pts are Mg-depleted)
- Con: hypermagnesemia can promote
renal insufficiency, and, in low flow states, counteract compensatory
vasoconstriction and promote hypotension.
Dextrose Solutions:
- originally intended to supply calories. Not indicated for calories anymore
(use Total Par/Enteral Nutrition)
- not an effective volume expander
- 3.4 kcal/g dextrose
- 5% Dextrose-in-water
- = 0.05 kg dextrose in 1 L water
- = 50 g in 1 L
- = 170 kcal
- Cons:
- 50 g dextrose adds 278 mOsm. If
used with LR or NS, hypertonic infusion results. If glucose use
impaired (e.g. in critically ill), can promote cell dehydration
- enhanced CO2 production
(burden in those on ventilator)
- enhanced lactic acid production
5% of glucose becomes lactate in nl people; 85% in critically ill)
- aggravation of ischemic brain injury
- ABANDON USE OF D5W IN CRITICALLY ILL PATIENTS