Intravenous fluids
Composition and uses
إعداد
د
.
رافع
عالوي الفياض
كلية طب الفلوجة
\
2016
Electrolyte Physiology
Primary intravascular/ECF cation is Na
+
. Very small contribution
of K
+
, Ca
2+
, and Mg
2+
.
Primary intravascular/ECF anion
is Cl
-
. Smaller contribution from
HCO
3
-
, SO
4
& PO
4
, organic acids, and protein.
Primary ICF cation
is K
+
. Smaller contribution from Na and Mg.
1
Crystalloid
: Balanced salt/electrolyte solution; forms
a true solution and is capable of passing through
semipermeable membranes. May be isotonic,
hypertonic, or hypotonic.
Examples:
Normal Saline (0.9% NaCl), Lactated Ringer’s,
Hypertonic saline (3, 5, & 7.5%).
Types of IV fluids
1
Colloid
: High-molecular-weight solutions, draw fluid
into intravascular compartment via oncotic pressure.
It is plasma expanders, as they are composed of
macromolecules, and are retained in the intravascular space.
Examples:
Albumin, Hetastarch, Pentastarch (Pentaspan
®
),
Plasma, Dextran.
Types of IV fluids
1
Free H2O solutions
: provide water that is not
bound by macromolecules or organelles, free to pass
Through cell membrane.
Examples:
D5W (5% dextrose in water), D10W,
D20W, D50W, and
Dextrose/crystalloid mixes.
1
Blood products
: whole blood, packed RBCs,
FFP, cryoprecipitate, platelets, albumin. Essentially
all colloids.
Types of IV fluids
TABLE 61-5 -- Fluids Used for Resuscitation
NaCl
(0.9%)
RINGER'S
LACTATE
NaCl
(3%)
ALBUMIN
(5%)
HETASTARCH
(6%)
DEXTRAN 70 +
NaCl
Na(mEq/L)
154
130
513
130–160
154
154
Cl (mEq/L)
154
109
513
130–160
154
154
K(mEq/L)
0
4
0
0
0
0
Osmolarity
(mOsm/L)
308
275
1025
310
310
310
Oncotic P
(mm Hg)
0
0
0
20
30
60
Lactate
(mEq/L)
0
28
0
0
0
0
Maximum
Dose
(mL/kg/24 hr)
None
None
Limited
by serum
Na
+
None
20
20
Cost (L)
$1.26
$1.44
$1.28
$100
$27.30
$35.08
2
IVF can supply 3 things: fluid, electrolytes, & calories.
2
The most common uses for IVF:
1. Acutely expand intravascular volume in hypovolemic states
2. Correct electrolyte imbalances
3. Maintain basal hydration
Normal Saline (0.9% NaCl): Isotonic salt water.
154 mEq/L
Cheapest and most commonly used resuscitative
crystalloid.
Common used IV fluids
2- Lactated Ringer’s (RL): Isotonic, 273 mOsm/L.
Contains 130 mEq/L Na
+
, 109 mEq/L Cl
-
, 28 mEq/L
lactate, and 4 mEq/L K
+
. Lactate is used instead of bicarb
because it’s more stable in IVF during storage. Lactate is
converted readily to bicarb by the liver.
Has minimal effects on normal body fluid composition
and pH. More closely resembles the electrolyte
composition of normal blood serum. Does not provide
calories.
Common used IV fluids
3-D5W/¼NS: Hypertonic, 406 mOsm/L. Provides
170 calories/L from 5% dextrose. Provides free water for
insensible losses and some Na
+
to promote renal
K
+
function and excretion. With added
Common used IV fluids
4-Hypertonic Saline (3% NaCl): 1026 mOsm/L &
513 mEq/L Na. Increases plasma osmolality and thereby
acts as a plasma expander, increasing circulatory volume
via movement of intracellular and interstitial water into the
intravascular space. Risk of hypernatremia thus careful
neuro-monitoring and VS.
Common used IV fluids
Volume deficits are best estimated by acute changes in weight.
1. Mild deficit represents a loss of ~ 4% body wt.
2. Moderate deficit --- a loss of ~ 6-8% body wt.
3. Severe deficit --- a loss of ~ >10% body wt.
Volume deficit may be a pure water deficit or combined water
and electrolyte deficit.
Combined water and electrolyte deficit is commonly
associated with GIT losses, diuretic therapy, adrenal
insufficiency, excessive sweating, burns.
These combined water and electrolyte deficits are
corrected by choosing the appropriate IVF for the pt’s
electrolyte imbalance.
Crystalloids vs Colloids for Resuscitation
Colloids offer the theoretical advantage of expanding the
intravascular space with less volume, and have been
shown to increase blood pressure more rapidly than
crystalloids.
1 L of dextran increases intravasc vol by 800ml;
1 L 5% albumin by 500ml;
1 L NS by 180 ml.
Monitoring endpoints for IVF therapy
Endpoints:
normalization
of
VS,
UO>0.5ml/kg/hr
(1ml/kg/hr for a child) and restoration of normal mental
status and lack of clinical signs of deficit.