IV Fluids & Management Flashcards
Adult human body male and female water content
60% water in men and 55% water in women
Why is there a total body weight difference between men and women? muscle mass
Intracellular fluid(ICF)
All fluid enclosed in cells by plasma membranes
~2/3 of thetotal body water
The fluid volume tends to be very stable because the amount of water in living cells is closely regulated
Extracellular fluid(ECF)
Extracellular fluid(ECF)
Fluid outside the cells
~1/3 of the total body water
2 primary constituents:
Intravascular fluid (plasma) - the fluid component of the blood
Interstitial fluid(IF) surrounding all cells
Fluid Spacing
definition
Term that describes thedistribution of water present in a body
breaks down into first second and third spacing.
First spacing
Normal distribution of fluid in the intracellular compartment and extracellular compartment
Extracellular fluids are distributed between the interstitial compartment (tissue) and intravascular compartment (plasma) in an approximately 75%-25% ratio
Second spacing
Abnormal accumulation of interstitial fluid in the body (edema); able to move back into first spacing
Third spacing
Mobilization of body fluid to a non-contributory space rendering it unavailable to the circulatory system (ascites)
Osmosis
- Spontaneous movement of water across a semipermeable membrane
- Water moves from a region of ↓ solute concentration → a region of ↑ solute concentration
- Tends to equalize the solute concentrations on either side of the membrane
Osmotic pressure
What does it depend on
- Hydrostatic pressurenecessary to counteract the process of osmosis
- Depends on the solute concentration
↑ osmotic pressure with high solute concentration - NOT dependent on the mass or size of the molecules
Tonicity
The capability of a solution to modify the volume of cells by altering their water content
On the first day in the hospital, a medical resident administers 100% water to a patient instead of normal saline. What are the consequences?
A. RBCs will shrink
B. RBCs will swell and burst
C. Serum Na concentration will increase
D. Total body sodium will decrease
E. Increase in serum pH
B. RBCs will swell and burst
water is hypotonic
Osmolality andosmolarity
Osmolar concentration of a solution = How much solute is present
In medicine, osmolarity and osmolalitycan be used interchangeably
Normal range: 275–295 mOsm/kg
Calculation of plasma/serum osmolality =2 x (Na+) + (Glucose mg/dL /18) + (BUN/2.8)
80% of the totalosmolarity of IF andplasma is due to Na+ and Cl-ions
50% of the totalosmolarityofICFis due to K+ ions; the remainder is due to other intracellular substances
~osmalarity is talking about amount of solute in volume (L)
~osmolality is amount in weight
Plasma/serum osmolality
iso/hyper/hypo-tonic
57-year-old male patient with Hyponatremia (Plasma Na+ < Cell Na+)
So, is the plasma osmolality high or low in this patient?
What type of fluid would we NOT want to give this patient? Why?
Low
Hypotonic, they are always deficient in sodium
hypertonic solution to replenish
Water Balance is influenced by
Water intake = Water output
Influenced by:
Dietary intake
Physical activity level
Age
Environmental conditions
Majority of intake = GI tract
Majority of output = Urine
Regulation of Water Intake & Loss
Hypothalamic Thirst Center
Stimulated when osmoreceptors
Increase in plasma osmolality (2-3%)
Decrease in blood volume or pressure (10-15%)
Patient will experience:
Dry mouth
Sensation of thirst
Drinking water → inhibition of the thirst center
Inhibitory feedback signals include:
Relief of dry mouth
Activation of stomach and intestinal stretch receptors
Regulation of Water Intake & Loss
Antidiuretic hormone (ADH)
Hypothalamus will stimulate the releases (ADH) from the posterior pituitary gland in a patient with dehydration
ADH works at the level of the kidneys to recover water from urine
Regulation of Water Intake & Loss
Aldosterone
Kidneys have a renin-angiotensin hormonal system that increases the production of angiotensin II → stimulate thirst and stimulate the release of the hormone aldosterone from the adrenal glands
Increases the reabsorption of sodium in the distal tubules of the nephrons in the kidneys, and water follows the reabsorbed sodium back into the blood
IV fluids
Common indications (4)
- Fluid resuscitation
- Correction of electrolyte imbalances
- Maintenance of fluids for patients that cannot take fluids enterally
- IV medication delivery
IV fluids
2 categories with differing compositions
Crystalloid solutions
Contain small molecular weight solutes (minerals, dextrose) and sterile water
Colloid solutions
Contain large molecular weight solutes (albumin, blood pr oducts) and sterile water
Crystalloid Solutions
general
Most commonly used IV fluids
Consist of aqueous electrolyte solutions with varying concentrations
DO NOT readily cross plasma membranes, but
DO cross capillary membranes
Will this fluid be distributed to the interstitial space?
Will this fluid be distributed to the intracellular space?
Isotonic, Hypotonic, Hypertonic, Mixed, or Concentrated
Isotonic crystalloid solutions
Normal Saline (0.9% NaCl)
Contains equal mEq/L of Na+ and Cl-
↑ extracellular volume
No change in intracellular volume
Indications:
Fluid resuscitation
Maintenance fluid therapy
Solvent for IV drugs
Isotonic crystalloid solutions
Normal Saline (0.9% NaCl)
RISKS
Hyperchloremic non-anion gap metabolic acidosis
Seen with large volume administration; Cl- can have negative effects on kidney function
Fluid overload
Isotonic crystalloid solutions
Lactated Ringer’s Solution (LR)
Contains Na+, Cl-, K+, Ca2+, and lactate
↑ extracellular volume
Minimally ↑ intracellular volume
Mild buffering action to prevent acidosis
Indications:
Fluid resuscitation
Maintenance fluid therapy
