Lecture 5: Fluid Balance

What percent of the body is water

60%

ICF is how much of body weight

40%

ECF is how much of body weight

20%

Primary regulators of fluid balance

Baroreceptors
Vasomotor center
Hypothalamus
Adrenal gland
Kidney

What does osmolality depend on

Number of dissolved solutes in fluid
-sodium, glucose, urea

Expected osmolality

275-295mOsm/kgH2O

How does dehydration affect osmolality

Increases it

How does overhydration affect osmolality

Decreases it

What is tonicity

relative measurement of IV fluid's osmolality

What does tonicity dictate

Movement of fluid btw compartments

IV fluid tonicity's main solutes

Sodium and dextrose

Isotonic fluids & osmolality

Same as plasma

Hypertonic fluids and osmolality

higher than plasma

Hypotonic fluids and osmolality

Lower than plasma

Describe colloid fluids

Supply proteins into ECF
Stay in circulation
Plasma expanders

What can colloid fluids treat

Hypovolemic shock

Examples of colloid fluids

plasbumin
alburex

Describe crystalloid fluids

Supply H2O and electrolytes and other solutes like glucose
Can move btw ICF and ECF

5% Albumin is what in the bag and what in the body

Bag - Isotonic
Body - hypertonic

D51/2NS is what in the bag and what in the body

Bag - mildly hypertonic
Body - can become isotonic or hypotonic

Fluid maintenance

Meeting body requirements
- Oral intake, IV fluids, SC infusion

Fluid resuscitation

Replacing deficits
-Oral if minor, IV if concerning
-Goal = adequate perfusion - rescue intravascular volume

Fluid restriction

Restricted fluid intake

NPO

nothing per oral, all fluids given IV

Routine fluid maintenance for a fully grown adult

35 ml/kg/day of water
-potassium, sodium and chloride
-50-100g/day of glucose to limit starvation ketosis

4/2/1 rule

4 ml/kg/hr for 1st 10kg of body weight
2 ml/kg/hr for 2nd 10 kg of body weight
1 ml/kg/hr for remaining kgs

Isotonic fluid examples

LR's
NS (0.9%)
5% albumin (colloid)
Dextran 40 (colloid)

Dextran 40 is what in the bag and what in the body

Bag - isotonic
Body - hypertonic

Contents of NS (0.9%)

154 mEq Na
154 mEq Cl

NS 0.9% Category

Isotonic

What is the #1 resuscitation fluid choice for adults

NS 0.9%
-500 mL bolus, reasses

Side affects of NS 0.9%

Hypokalemia
No dextrose!

LR Contents

Na - 130 mEq
Ca - 2.7 mEq
Cl - 128 mEq
K - 4 mEq
Lactate - 28 mEq

Side effects of LR's

Hyperkalemia
No dextrose
High lactate

Contraindications for LR's

pediatrics:
-high lactate
-high electrolyte for kids

Hypertonic fluid examples

D5NS
D5LR
D10W
D5 1/2 NS
3% NaCl
25% Albumin (colloid)

What does 3% NaCl treat

Head injury to lower ICP

What does 25% albumin treat

resuscitation, if low volume

Content of D51/2NS

77mEq Na
77mEq Cl
50mEq dextrose

Side effects of D51/2NS

Cellular dehydration, hyponatremia

Pediatric #1 choice for maintenance fluids

D51/2NS
-Check K

Osmolality of D51/2NS

405

25% Albumin Contents

25% albumin
Up to 160mEq Na

Why is there a caution with using 25% albumin

IV volume expander
3.5x its volume of additional fluid into the circulation within 15 minutes

Hypotonic fluid examples

0.45% NaCl
D5W
3.3% Dextrose, 0.3% sodium
D5 0.2% NaCl

TX of GI Bleed

NSAIDS
Blood thinners - antiplatelets, anticoagulants, thrombolytics
Fluids
Blood transfusion
PPI's
Endoscopy or colonoscopy?

If blood loss, what can we give?

RBC
Whole blood
Platelets
FFP

Electrolytes

positively or negatively charged inorganic molecules

What are electrolytes essential for

Nerve conduction, membrane permeability
Water balance, other critical body functions
Imbalances can be serious or fatal

What electrolytes are the most common for issues

Potassium and sodium imbalances

Hyponatremia

Most common cause of hyponatremia

Diuretic use, dehydration hyponatremic

TX of hyponatremia

D5NS

Hypernatremia

>145 mEq/L

Common cause of hypernatremia

Kidney failure
High Na intake
Dehydration hypernatremic

Tx of hypernatremia

Restrict salt intake
Diuretics to remove Na+ if IV fluid = low Na

Hyperkalemia

>5 mEq/L

Common cause of hyperkalemia

Potassium sparing diuretics
Renal disease

TX of hyperkalemia

Kayexalate PO, NG

Hypokalemia

Common causes of hypokalemia

Meds such as potassium wasting diuretics, N&V

TX of hypokalemia

KCL, IV or PO