Fluid Compartments IV Fluid Selection PHR927

Where are the two main compartments TBW is distributed

ICF and ECF

How to calculate peds TBW

first 10kg: 100ml/kg/day

second 10kg: 50ml/kg/day

Other kg above 20kg: 20ml/kg/day

How to calculate adult TBW

30-35ml/kg/day

1.5 x BSM

How much does ICF take up of TBW

2/3

How much does ECF take up in the TBW

1/3

ECF components

Intersitial and intravascular

How much does the Intravascular TBW take up in the ECF

1/4

How much does the interstitial volume take up in the ECF

3/4

What is the cascular to intersitial regulation of TBW among compartments

Hydrostatic pressure

Oncotic pressure

Capillary integrity pressure

Hydrostatic pressure:

Pressure on the vessel wall

Oncotic pressure

Proteins trying to keep fluid in the blood (albumin)

Capillary inegrity:

“leaky” channels

Regulation of water from interstitial to intracellular compartments

• Na/K+ ATPase pump

• Serum osmolarity

• Various other voltage and ligand gated channels

Regulation of TBW btwn the interstital and intracellular compartments are not what?

In equilibrium

Water sparing/adding:

• Vasopressin/antidiuretic hormone

• Aldosterone

• Thirst

Water depleting:

• Diuresis

• Insensible losses (sweating, breathing, diarrhea, fever)

• Bleeding

• Burn

• Third spacing

What is third spacing

When vascular volume leaks into the intersitial space (lack of capillary integrity)

What is osmolarity primarily dependent on

Sodium

How is osmolarity restricted into the ICF

Na+/K+ ATPase pump

Water moves from how in osmolarity

High to low

Forces that try to push fluid out of the vessel

Hydrostatic

Forces (proteins) that work to keep fluid in

Oncotic

Effect of hydrostatic pressure on blood pressure

Increases BP due to pressure on the vessel wall making the fluid want to leave

Effect of oncotic pressure on blood pressure

Lowers BP due to causing causing water to go to the proteins

Signs and Symptoms of fluid loss

• Thirst

• Dry membranes

• Decreased skin turgor

• Increase in sodium and osmolarity

• Changes in urine output

• Changes in BP

• Confusion

What populations are very sensitive to fluid loss?

Peds and elderly

Crystalloids

Water + electrolytes

What is free water

Water with no salt content

Where does free water distribute to

ICF and ECF

Where does water with electolytes distribute to

ECT only due to the Na+/K-ATPase pump

Colloids:

Large solutes like proteins or sugars that do not eradi

D5W components

Dextrose: 5mg/dl

Na: 0mEq/L

K: 0mEq/L

Cl: 0mEq/L

.45% NaCl components

Dextrose: 0

Na: 77mEq

Cl: 77mEq

.9% NaCl components

Dextrose: 0gm/dl

Na: 154mEq/L

Cl: 154mEq/L

3% NaCl components

Na: 513nEq/L

Cl: 513mEq/L

Lactated Ringers components

Na:130mEq/L

K: 4mEq/L

Cl: 105mEq/L

Why do we never inject sterile water

Makes RBC burst

What do we use D5W for

Dehydration

NPO diet

What do we use .2% NaCl for

Hyperatremia, usually combined with D5 or added K+ to avoid hemolysis

What do we use .45% NaCl for

Dehydration, hypernatremia, maintenance IV fluid

What do we use .9% NaCl for

Fluid rescuscitation, maintnance IV fluid

What do we use 3% NaCl for

Cerebral edema, hyponatremia, rarely for fluid resuscitation

What do we use lactated ringers for

Fluid resuscitation

If you add a NaCl bolus to any fluids, where does the NaCl go?

ECF ONLY do not add it to the ICF, it does not enter the ICF

When using a 3% hypertonic solution, what space does it go into ONLY

Vasculature

Sodium containing crystalloids expand the plasma volume (intravascular volume) and is good for what

Resuscitation

More free water =

More distribution into the ICF

When more free water enters the ICF what can occur?

Exacerbation of swelling and edema due to water going into the cells and intersitial space

Most fluids given affect what areas more than the intravascular

ICF and Intersitial space

Volume is depleated, what crystalloid do we choose

Something with sodium

Dehydrated and hemo-concentrated, what fluid do we pick

Something with free water

Giving massive amounts of fluid, what fluid do we pick?

Something balanced like plasmolyte/ringers

What is the most dominant colloid in clinical practice

Albumin

Where is albumin made

Endogenously produced by liver

What is the primary determinant of plasma oncotic pressure

Albumin

Hypoalbuminemia leads to what

Third spacing

How much of the 5% albumin injection (25gm/500mL) goes into the intravascular volume

~450mL

What does the 25% albumin injection do

Pulls from interstitial and ICF space

Do we use Hetastarch or dextran as a colloid?

NO

When to choose crystalloid fluids

Agent of choice in nearly every situation

• Fluid resuscitation to restore intravascular homeostasis

• Maintenance IV fluids

• Inexpensive and rarely on short supplly

When do we use colloids (Albumin)?

• When excessive fluid is too harmful (brittle heart failure, renal dysfunction)

• Extreme edema (lung/bowel)

• Obvious low oncotic pressure: Malnutrition, cirrhosis, hepato-renal syndrome