APEX Fluids, Electrolytes, & Acid-Base

Total Body Water accounts for what percentage? Liters?

60%

42 Liters

intracellular fluid accounts for what percentage? Liters?

40%

28 L

The major ions found in intracellular fluid are?

potassium

phosphate

mag

Extracellular Fluid accounts for what percentage? Liters?

20%

14 L

The major ions found in the extracellular fluid are?

sodium

chloride

calcium

bicarbonate (HCO3-)

What two things comprise extracellular fluid?

plasma volume

interstitial fluid

Plasma volume accounts for what percentage? Liters?

4% TBW

3L

Interstitial fluid accounts for what percentage? Liters?

16%

11L

What population has the higher TBW%?

neonates

What population has the lower TBW%?

elderly

females

obese

What is plasma?

the non-cellular fraction of circulating blood volume

What determines the movement of fluid between the intravascular space and the interstitial space?

Starling forces

Glycocalyx

Net Filtration Pressure =

(Pc-Pif) - (piec-pieif)

NFP > 0 =

filtration (fluid exits capillary)

NFP < 0 =

reabsorption (fluid is pulled into capillary)

What forces move fluid from the capillary to the interstitium?

Pc and pie if

Pc

capillary hydrostatic pressure (pushes fluid out of capillary)

pie if

interstitial oncotic pressure (pulls fluid out of capillary)

What forces move fluid from the interstitium into the capillary?

Pif and pie c

Pif

interstitial hydrostatic pressure (pushes fluid into capillary)

pie c

capillary oncotic pressure (pulls fluid into capillary)

glycocalyx

a protective layer on the interior wall of the blood vessel that can be viewed as the gatekeeper that determines what can pass from the vessel into the interstitial space

anticoagulant properties

What conditions impair the integrity of the glycocalyx?

DM

ischemia

sepsis

vascular surgery

Blood volume is the sum of what two things?

plasma volume (60%) and blood cell volume (40%)

hematocrit

the fraction of blood volume that is occupied by the erythrocytes

What is hematocrit increased by?

increased number of RBCs (polycythemia)

decreased plasma volume (hypovolemia)

What is hematocrit decreased by?

decreased number of RBCs (anemia)

increased plasma volume (hemodilution)

interstitium

the space between the cells

What does the lymphatic system do?

"Fluid scavenger"

removes fluid, protein, bacteria, and debris that has entered the interstitium through a pumping mechanism that propels lymph through a vessel network lined with one-way valves creating a net negative pressure in the interstitial space.

How is lymph returned to the venous circulation?

By way of the thoracic duct at the juncture of the IJ and subclavian vein.

What can you injure during venous cannulation?

The thoracic duct especially on the LEFT side --> greater risk of chylothorax.

When does edema occur?

When the rate of interstitial fluid accumulation exceeds the rate of removal by the lymphatic system.

Effusion

Fluid that accumulates in a potential space.

What is osmosis?

The net movement of water across a semipermeable membrane.

What is the direction of water movement driven by during osmosis?

The difference in solute concentration on either side of the membrane.

Which direction does water tend to move?

From areas of lower solute concentration to areas of higher solute concentration.

What is osmotic pressure?

the pressure of a solution against a semipermeable membrane that prevents water from diffusing across that membrane.

What is osmotic pressure a function of?

The number of osmotically active particles in a solution (amount of ionization).

NOT molecular weight

What are two measures of concentration?

osmolarity and osmolality

What does osmolarity measure?

The number of osmoles per liter of solution

What does osmolality measure?

The number of osmoles per kilogram of solvent.

What is the normal plasma osmolarity?

280 - 290 mOsm / L

Plasma osmolarity =

2 [Na+] + glucose / 18 + BUN / 2.8

What is the most important determinant of plasma osmolarity?

Sodium

What two conditions can increase plasma osmolarity?

Hyperglycemia

Uremia

Tonicity

Compares the osmolarity of a solution relative to the osmolarity of the plasma

What does a hypotonic solution do to a cell?

Enters a cell and swells.

What are some examples of HYPOTONIC solutions?

D5W, 0.45% NaCl

What are some examples of isotonic fluids?

0.9% NaCl, LR, plasmalyte A,Albumin 5%, voluven 6%, hespan 6%

What does a hypertonic solution do to a cell?

Water exits and the cell shrinks

What are some examples of hypertonic solutions?

NaCl 3%, D5NaCl 0.9%, D5NaCl 0.45%, D5LR, Dextran 10%

What patient population should hypotonic solutions never be given to?

A patient with increased ICP

How long do crystalloids tend to remain in the intravascular space?

30 minutes

What can be caused if large amounts of sodium chloride is given?

hyperchloremic metabolic acidosis

What is hypertonic saline useful in treating?

cerebral edema

correcting hyponatremia

What can result if sodium is replaced too quickly?

Myelinolysis

What is the replacement ratio for colloids?

1:1

How long do colloids increase plasma volume for?

3-6 hours

What causes more peripheral edema: crystalloids or colloids?

crystalloids

Name two unique characteristics about albumin?

1) anti-inflammatory properties

2)binds calcium -> hypocalcemia

What colloid reduces blood viscosity?

Dextran 40

What is the replacement ratio for crystalloids?

3:1

Name the natural colloids?

Albumin

Name synthetic colloids?

Dextran, Hetastarch, Hextend, Voluven

Which colloids have a black box warning? What is the black box warning?

Synthetic colloids.

Risk of renal injury.

Which colloids can cause coagulopathy?

Dextran > Hetastarch > Hextend

Don't exceed 20 mL / kg

What colloid has the highest risk for anaphylactic potential?

Dextran

What is the only colloid derived from human blood products?

Albumin.

It does not contain antibodies.

How long does crystalloids increase plasma volume for?

20 - 30 minutes

What is the lab value for hypokalemia?

< 3.5 mEq / L

What is the most abundant intracellular cation?

Potassium

fxn of K

regulates RMP in nervous tissue, skeletal muscle, and cardiac muscle

hypok=hyperpolaizes membrane

hyperk= depolarizes membranes

most imortant ion for repolarization of neural tissue and muscle cells

Potassium

most important regulator of  K homeostasis

kidneys (think real failure with decreased gfr and high K)

What is the etiology of hypokalemia?

Poor intake: diet

GI loss: vomiting, diarrhea, NG suction, kayexalate, malabsorption

Renal loss: diuretics, metabolic alkalosis, licorice

Intracellular shift: Beta 2 agonists, insulin/d50, alkalosis, hyperventilation, bicarb

How does hypokalemia present?

skeletal muscle cramps -> weakness -> paralysis

worsens digoxin toxicity

What EKG changes are seen with hypokalemia?

LOW K+-->

PR interval -> LONG

QT interval -> long

T wave -> flat

U wave

What is the treatment for hypokalemia?

potassium supplementation UNLESS etiology is redistribution

What is the lab value for hyperkalemia?

> 5.5 mEq / L

etiology of hyper k

Increased K intake: K admin, banked blood

impaired k excretion: renal dx, hypoaldosteronism, drugs tha impair k excretion (NSAIDS, spirnolactone)

redistribution: acidosis, succs, beta blocker, 

cellular injury: rhabdomyolysis, tumor lysis syndrome, hemolysis, burns,crush injury

How does hyperkalemia present?

cardiac rhythm disturbances

What EKG changes are seen with hyperkalemia?

5.5-6.5: T wave -> peaked,

6.5-7.5: P -> flattening,PR- LONG

7-8: QRS -> LONG

>8.5: QRS -> sine wave -> VF

What is the treatment for hyperkalemia?

Calcium (stabilizes cardiac membranes)

Insulin + D50

Hyperventilation

Bicarbonate

Albuterol

Potassium wasting diuretics, kayexalate

Dialysis

replace k slow

peripheral 10 mEq/hr

central 20meq

primary determinant of serum osmo and regulates ECF volume through osmotic forces?

Sodium

Most abundant ECF cation

NA

Most important iiond uring depolarization of neurla tissues and muscle cells

Sodium

consider cancelling sx if na <

130

What is the lab value for hyponatremia?

< 135 mEq / L

What is the etiology of hyponatremia?

May exist in various states of hydration (hypovolemic, isovolemic, and hypervolemic) - you must evaluate plasma osmolarity to determine the cause

Ex: SIADH, CHF, cirrhosis, TURP syndrome, Cushings, Diuretics, hypoaldosteronism

How does hyponatremia present?

125-129 N/V, malaise

115-124 HA, lethargy, altered LOC

<115 -> seizures -> coma, Cerebral edema (cell swelling), respiratory arrest

What is the treatment for hyponatremia?

Depends on the specific cause.

The goal is to restore Na+ balance by manipulating serum osmolality and fluid balance with H2O restriction, IVF selection based on tonicity, and diuretics.

What is the lab value for hypernatremia?

> 145 mEq / L

What is the etiology of hypernatremia?

May exist in various state of hydration so you must evaluate plasma osmolarity and ECF volume to determine cause.

Ex: osmotic diuresis, N/V, adrenal insufficiency

DI, renal failure, diuretics

Hyperaldosteronism, increased NA+ intake (3% NS)

How does hypernatremia present?

Based on Serum osmolarity

350-375 HA, agitation, confusion

376-400 weakness, tremors, ataxia

401-430 hyperreflexia, mm twitching

>431 seizures, coma, death

What is the treatment for hypernatremia?

Depends on specific cause.

The goal is to restore Na+ balance by manipulating serum osmolality and fluid balance with H2O restriction, IVF selection based on tonicity, and diuretics.

Replace Na slow

1-2 meq/L/hr

Tx hypoNa too quickly causes fluid to shift from ICF to ECF —> central pontine myelinolysis

Tx hyperna too quickly causes fluid to shift from ECF to ICF —> cerebral edema

Normal Ca and ICal levels

Ca= 8.5-10.5

Ical= 4.5-5.6 mg/dL

Most abundant electrolyte in the body

Calcium- nearly all stored in bone

Fxn Ca

second messenger systems, NT release, muscle contraction (skeletal, cardiac, vascular muscle, bronchial muscle)