Fluids and Electrolytes

What are the uses of water in the body?

• Metabolic reactions (enzymatic access, chemical reactions)

• Transport (molecules, blood products, waste products)

• Lubricant (joints and torso (organs slide against each other)

• Insulator

• body temperature (respiration and sweating)

Healthy individuals I&O

Roughly equal

Fluid Loss of the Kidney

Urine output of 1ml/kg/Hr

Fluid Loss of the Skin

sensible due to sweating and insensible due to fever, exercise, and burns

Fluid loss of lungs

300 ml everyday, greater with increased RR

Fluid losses of the GI Tract

Due to diarrhea and fistulas

Age and water balance

less lean muscle as we age

sex

females have more fat content

body habitus

fat doesn’t fold as much H2O as muscle tissue

Temperature

body is trying to cool, and may release fluid

what are the factors affecting water balance

• age

• sex

• body habitus

• temperature

• disease state

How much of the typical adult is fluid

60% (varies with age, body fat, gender)

Intracellular fluid

2/3 of body fluid, skeletal muscle mass

Extracellular fluid

intravascular: plasma, erythrocytes, leukocytes, thrombocytes

interstitial: lymph

transcellular: cerebrospinal, pericardial, synovial

Osmolality

concentration of solutes in body fluid

normal serum: 280-295

urine: 100-1300

Hypotonic

hypoosmolar

solutes are LESS concentrated than the cells

Hypertonic

Hyperosmolar

solutes are more concentrated than the cells

The movement of fluid through capillary walls depend on

hydrostatic pressure and osmotic pressure

Hydrostatic Pressure

BP generated by heart contraction

this increases the vascular hydrostatic pressure which pushes water from the vascular system into the interstitial space and can inhibit fluid from moving back into the vascular space

A pulse wave is a short increase in hydrostatic pressure

Osmotic Pressure

protein molecules (albumin) in plasma attract water, pulling fluid from the tissue spaces into the vascular space

colloids or hypertonic solutions increase osmotic pressure and draws fluid from interstitial space into plasma

what can cause fluid to shift from plasma spaces to interstitial

• increase in venous hydrostatic pressure

• increase in interstitial osmotic pressure

• decrease in plasma osmotic pressure

RESULTS IN SECOND OR THRID SPACING

How do you decrease interstitial shifts?

• Reducing hydrostatic pressure (lower BP), administer colloids mannitol and hypertonic solutions

  • increase tissue hydrostatic pressure (ted hose)

TED Hose

increase pressure on outside of vessel (tissue)

fluid then gets pushed

first spacing

normal distribution

second spacing

abnormal accumulation of interstitial fluid (edema)

third spacing

fluid is trapped where it is difficult or impossible for it to move back into cells or blood vessels (ASCITES)

colloids

stay in vascular space and increases osmotic pressure and pulls fluid INTO the vascular spaces

sometimes referred to as volume or plasma expanders

what are some examples of COLLOIDS?

human plasma products (albumin, fresh frozen plasma, blood)

semisynthetic (dextran and starches, bedpan)

Crystalloids

solutions (like saline) with small molecules which can move around easily when injected into the body

what are the purpose of IVF?

maintenance (MIV) and replacement

0.45% NaCl

HYPOTONIC (154)

contains more water than electrolytes. It moves water from ECF to ICF by osmosis.

monitor for changes in mentation

0.9% NaCl

Expands only ECF (no net loss or gain from ICF)

ideal to replace ECF volume deficit and can be used as MIV or replacement

0.9% NaCl, D5W*, and Lactated Ringer's solution (LR) are all

ISOTONIC (275-308)

3% Saline

Hypertonic

initially expands and raises the osmolality of ECF

Require frequent monitoring of

• blood pressure

• lung sounds

• serum sodium levels

D5 ½ NS; D10W; 3% saline are all

HYPERTONIC

Dehydration

Loss of water alone, with increased serum sodium

mild dehydration is corrected by oral consumption, sports drinks etc

common in:

• elderly

• children

• confused

• overexertion

FVD

hypovolemia

may occur alone or in combination with other imbalances

ECF loss > intake ratio of water

(electrolytes lost in the same proportion as they exist in normal body fluids)

FVE

Isotonic expansion of the ECF caused by abnormal retention of water and Na in approximately the same proportions in which they normally exist in the ECF

secondary to an increase in the total body sodium content

FVD Possible causes

• Abnormal fluid losses (Vomiting, diarrhea, sweating, GI suctioning)
• Decreased intake (Nausea, lack of access to fluids)
• Third-space fluid shifts (Due to burns, ascites)
• Additional causes (Diabetes insipidus, adrenal insufficiency, hemorrhage,
trauma)

Possible causes of FVE

• HF

• Renal injury or failure

• Liver failure

• excessive IV or transfusions

• excessive Na intake

• abnormal retention of fluids and sodium

• Fluid shift increasing intravascular volume (interstitial to plasma fluid shift)

what are electrolytes and what do they help regulate

substances whose molecules dissociate into ions when placed in water

help regulate:

• cardiac and neurological function

• fluid balance

• oxygen delivery

• acid-base balance

what are the mechanisms of electrolyte movement

• diffusion

• facilitated diffusion

  • active transport

facilitated diffusion

• use a carrier to move molecules

  • such as glucose and insulin

active transport

molecules are moving against a concentration gradient and energy is needed

ex.

Na and K pump (atp is used to move 3 Na+ out and 2 K+ into the cell)

functions of calcium

• Formation of teeth and bone

• Blood clotting

• Transmission of nerve impulses

• Myocardial contractions

• Muscle contractions

PTH

• production and release is stimulated by low serum Ca2+

  • PTH increases bone resorption, increases GI absorption of calcium, and increases renal reabsorption of calcium

Calcitonin

• produced by the thyroid gland

• stimulated by high serum calcium levels. It opposes the action of PTH

primary anion in ICF

phosphate

Fluid challenge

goal is to provide fluids rapidly enough to attain adequatee tissue perfusion without compromising the CV system.

a pt with FVD but has normal renal function is increased urine output and an increase in bp

second spacing rx

hypertonic fluid (mannitol, ds ½ ns)

plasma proteins (albumin) followed by diuretics

third spacing rx

thoracentesis

paracentesis

albumin

aquapheresis

ultrafiltration

removes excess salt and water from the body

diuretics for mild vs severe hypervolemia

mild: loop

severe/moderate: thiazide

what are the meds that can cause hyponatremia

• anticonvulsants

• SSRIs

• Desmpressin Acetate

meds that blocks ADH

conivaptan and tolvaptan