PHRM 825: Fluids and Electrolytes - Fluids Flashcards
IBW meaning
Ideal body weight
LBW meaning
Low body weight (same as IBW)
IBW calculation for males
50kg + (2.3 X inches over 60”)
IBW calculation for females
45.5kg + (2.3 X inches over 60”)
DBW meaning
Dosing body weight
DBW calculation
IBW + 0.4 (actual weight - IBW)
When should you use DBW?
Use if DBW is greater than 130% of IBW and you are dosing drugs
NBW meaning
Nutritional body weight
NBW calculation
IBW + 0.25 (actual weight - IBW)
When should you use NBW?
Use if DBW is greater than 130% of IBW and you are calculating fluid, electrolyte, and nutrition parameters
What fraction of the body’s fluid is intracellular?
2/3
What percentage of the body’s weight is intracellular fluid?
40%
What fraction of the body’s fluid is extracellular?
1/3
What percentage of the body’s weight is extracellular fluid?
20%
What is transcellular fluid?
Fluid in the cerebrospinal column, pleural cavity, lymphatic system, joints, eyes
What type of fluid is not subject to daily gains/losses?
Transcellular
What percentage of an adult male’s body weight is water?
50-60%
What percentage of an adult female’s body weight is water?
45-55%
What percentage of neonates/infants body weight is water?
75-90%
Why does the amount of water in the body decrease with age?
Skeletal muscle mass declines and proportion of fat may increase
What are the 2 categories of fluid losses
Sensible (measurable) and insensible (immeasurable)
Sensible fluid losses include
Urine, defecation, and wounds
Average fluid lost each day in urine
400-1500 mL
Average fluid lost each day in feces
100-200 mL
Insensible fluid losses include
Fluid lost from the skin and lungs (breathing)
What are 2 ways solutes move across the cell membrane
Diffusion and active transport
What are 3 ways fluids move across the cell membrane
Osmosis, Capillary filtration, and oncotic pressure
What 3 things regulate the volume of water in the body?
Kidneys, thirst, hormonal changes
What 3 hormones regulate the volume of water in the body?
ADH, RAAS, ANP
ADH meaning
Antidiuretic hormone; aka vasopressin
RAAS meaning
Renin-angiotension-aldosterone system
ANP meaning
Atrial natriuretic peptide
What does ADH do?
Reduces diuresis and increases water retention
What does RAAS do?
Controls renin secretion, sodium/water regulation, and active transport of sodium
What does ANP do?
Decreases ADH release and counteracts effect of RAAS
Concentration of a solution isotonic to fluids the human body in mOsm/L
275-290 mOsm/L
Concentration of a solution hypotonic to fluids in the human body in mOsm/L
<275 mOsm/L
Concentration of a solution hypertonic to fluids in the human body in mOsm/L
> 290 mOsm/L
Osmolarity definition
Measure of solute concentration
What 2 things is osmolarity dependent on?
pH and temperature
IV fluids of hypotonic or hypertonic solutions can result in _______, ________, and ______
Hemolysis of RBCs, renal failure, and death
Total osmolarity equation
Total osmolarity = osmolarity of IV solution + osmolarity of added electrolytes
Crystalloids tonicity
Isotonic, hypotonic, hypertonic
Colloids tonicity
Hypertonic
Crystalloid examples
NS, 1/2 NS, D5W, LR, Balanced salt solutions
Colloid examples
Albumin, Hetastarch (Hepsan), Tetrastarch (Voluven), Blood, Plasmanate
What does a crystalloid solution provide to the patient?
Water and/or sodium
Crystalloid solutions maintain _____ gradient between _____ and ____ compartments
osmotic, intravascular and extravascular
Normal Saline is used for
Intravascular fluid replacement (resuscitation, hypotension, septic shock, etc.); sodium and/or chloride replacement
1/2 Normal Saline is used for
Maintenance fluids
LR is used for
Replacement of blood loss; resuscitation (trauma, burn, intravascular repletion IF SYMPTOMATIC)
What crystalloid approximates human plasma
Lactated Ringers (LR)
D5W is used for
Free water replacement if dehydrated
D5W is NOT a ______ or ______
resuscitative fluid; maintenance IV fluid (MIVF)
Balanced Salt solution definition
Crystalloid solutions containing physiologic levels of chloride and buffer solutions
NS contains ___% higher ___ and ____% higher _____ than normal plasma
10% higher Na+ and 50% higher Cl-
Examples of balanced salt solutions
- Lactated ringers
- Normosol-R
- Plasma-lyte
How many mEq/L of Na+ are in crystalloid fluid
154
How many mEq/L of Cl- are in crystalloid fluid
154
Colloid solutions are used to
-Increase plasma oncotic pressure and move fluid from the interstitial compartment to the intravascular (plasma) compartment
What is the 2, 3, 4 rule?
We want:
- Mg+2: >2 mEq/L
- P-3: >3 mEq/L
- K+: >4 mEq/L
NS is _____
hypertonic
Plasma expanders include
Colloid fluids
What are characteristics of plasma expanders
- Increased molecular weight
- Corresponds to increased intravascular retention time (half-life) compared to crystalloids
Colloids are used selectively for _______, __________
Volume expansion, intravascular repletion in symptomatic patients
Colloids may be used in _____ shock
hemorrhagic (blood is a colloid)
Colloids are considered second-line therapy for _______ shock
hypovolemic
What is albumin
A human derived blood product
Albumin is used as supportive/symptomatic treatment unless the patient has ______
hypoproteinemia
Adverse effects of albumin
Hypervolemia, azotemia, infusion related reaction/anaphylaxis
Substitution ratio (SR) of synthetic colloids definition
number of hydroxyethyl groups per glucose molecule
High Substitution ratio (SR) of synthetic colloids results in
Prolonged intravascular expansion
Numeric value of high substitution ratio (SR)
> 0.5
High molecular weight (MW) of synthetic colloids does what
alters coagulation
Numeric value for high Molecular weight of synthetic colloids
> 200 kDa
High molecular weight (MW) and substitution ratio (SR) in synthetic colloids are associated with what
Increased mortality and toxicities
Synthetic colloids should be used ______
with caution
1 unit of RBCs = _____ mL
230-350
When should blood be used in therapy?
- Acute blood loss (30-40% of blood volume)
- Inadequate resucitation from fluids alone
- Preoperatively
- Low hemoglobin
What is the numeric value for low hemoglobin
<7-8 g/dL
1 unit of RBCs increases hemoglobin by _____ g/dL
1
What is the most common MIVF?
D5W + 1/2 NS + 20 mEq KCl/L
Why is D5W + 1/2 NS + 20 mEq KCl/L the most common MIVF?
It most closely resembles normal fluid losses and has a similar composition to urine
What BUN/SCr ratio may mean dehydration?
> 20
Shock definition
Hypotension that is refractory to fluid resuscitation
Effect of shock on heart
Tachycardia hypotension
Effect of shock on brain
Altered mental status
Effect of shock on kidneys
Decreased urine output
Effect of shock on Liver
Increased INR
Effect of shock on skin
Cool, cyanotic
Goal for resucitation of shock
Increase perfusion throughout the patient via fluid resuscitation and/or vasopressor support
CVP meaning
Central venous pressure
MAP meaning
Mean arterial pressure
UOP
Urinary output
CVP, MAP, and UOP goals following shock
8-12, 65, 0.5