fluid 1 Flashcards
What is a mole (mol)?
A unit in chemistry that represents a specific quantity of particles, approximately 6.022 x 10^23 particles per mole.
This number is known as Avogadro’s number.
Define millimole (mmol).
1/1,000 of the molecular weight in grams or 1/1,000 of a mole.
What is a milliequivalent (mEq)?
Represents the amount, in milligrams (mg), of a solute equal to 1/1,000 of its gram equivalent weight, taking into account the valence of the ions.
How is mEq calculated?
mEq = mmole X valence
1 mEq = MW in mg/valence.
What is Total Body Weight (TBW)?
The weight of the patient when weighed on a scale.
How is Ideal Body Weight (IBW) calculated for males?
IBW (males) = 50 kg + (2.3 kg)(number of inches over 5 feet).
How is Ideal Body Weight (IBW) calculated for females?
IBW (females) = 45.5 kg + (2.3 kg)(number of inches over 5 feet).
What is Adjusted Body Weight (AdjBW)?
Calculated when patients are obese or overweight: AdjBW = IBW + 0.4 (TBW - IBW).
What is the formula for Body Mass Index (BMI)?
BMI = Weight (kg) / Height (m)².
What is the normal range for BMI?
A BMI of 18.5 - 24.9 kg/m² is considered normal.
When should Total Body Weight (TBW) be used for drug dosing?
Use TBW for all medications when TBW > 120% IBW.
When should Adjusted Body Weight (AdjBW) be used for drug dosing?
Use AdjBW for aminoglycosides in obese patients.
What does a BUN:SrCr ratio > 20:1 indicate?
Indicates dehydration.
What is the normal range for serum creatinine?
Approximately 0.6 - 1.3 mg/dL.
What is the Cockcroft-Gault equation used for?
To estimate renal function (CrCl).
What is the primary buffering system of the body?
The bicarbonate/carbonic acid system.
What condition is indicated by a pH < 7.35?
Acidosis.
What condition is indicated by a pH > 7.45?
Alkalosis.
How is osmolality defined?
A measure of the osmoles of solute per kilogram of solvent (Osm/kg).
How is osmolarity defined?
A measure of osmoles of solute per liter of solution (Osm/L).
What is the difference between ionic and non-ionic solutes?
Ionic solutes dissociate in solution (e.g., NaCl), while non-ionic solutes do not (e.g., glucose).
What is tonicity?
A measure of osmotic pressure gradients between fluids.
What is the formula for calculating the flow rate in mL/hour?
Flow rate = (Desired rate in units/hour) / (Concentration in units/mL).
How long will it take to infuse an entire bag if the order is for 1,000 units/hour?
It will take 25 hours to infuse the entire bag.
What is the effect of dehydration on serum creatinine levels?
Dehydration can cause serum creatinine levels to increase.
Fill in the blank: The formula for calculating Adjusted Body Weight is _______.
AdjBW = IBW + 0.4 (TBW - IBW).
True or False: The lungs help maintain a neutral pH by controlling bicarbonate reabsorption.
False.
What are the signs of dehydration?
- Decreased urine output
- Tachycardia
- Tachypnea
- Dry skin/mouth/mucous membranes
- Possibly fever.
What is osmolality (Osm/L)?
Total number of particles (or solutes) per liter of solution.
What are the two types of solutes?
- Ionic (e.g., NaCl)
- Non-ionic (e.g., glucose, urea)
How is osmotic pressure related to the total number of particles in a solution?
The total number of particles in a given solution is directly proportional to its osmotic pressure.
Define tonicity in biological terms.
Tonicity is a measure of osmotic pressure gradients between fluids.
What happens to a cell in an isotonic solution?
There will be no net flow of water into or out of the cell, and the cell’s volume will remain stable.
What occurs when a cell is placed in a hypotonic solution?
There will be a net flow of water into the cell, causing it to gain volume (swell).
What happens to a cell in a hypertonic solution?
There will be a net flow of water out of the cell, causing it to lose volume (shrink).
What is the normal range of plasma osmolality in the human body?
275-290 mOsm/kg.
What regulates plasma osmolality?
Thirst and secretion of arginine vasopressin (ADH) from the posterior pituitary.
What is the primary determinant of plasma osmolality?
Sodium salts.
What occurs when plasma osmolality increases?
An osmotic shift of fluid into the plasma, resulting in cellular dehydration and shrinkage.
What are the effects of decreased plasma osmolality?
An osmotic shift of fluid into cells, resulting in cellular overhydration and swelling.
What type of intravenous fluid does not result in a fluid shift?
Isotonic fluid (e.g., 0.9% NaCl).
What can hypertonic fluid cause?
Fluid to shift from the intracellular to extracellular compartment, leading to cellular dehydration and shrinkage.
What can hypotonic fluid cause?
Fluid to shift from the extracellular to intracellular compartment, leading to cellular overhydration and swelling.
What is the distribution of Total Body Water?
- Intracellular Fluid: 2/3 TBW
- Extracellular Fluid: 1/3 TBW
What percentage of extracellular fluid is interstitial fluid?
3/4 of ECF.
What is a sign of intravascular volume depletion?
- Tachycardia (HR > 100 beats/minute)
- Hypotension (SBP < 80 mm Hg)
- Increased BUN/SCr ratio > 20:1
- Dry mucous membranes
- Decreased skin turgor
- Reduced urine output
- Dizziness
What is the estimated adult fluid requirement?
30 - 40 ml/kg/day.
What is the most common electrolyte disorder?
Hyponatremia.
What is the reference range for serum sodium concentration?
135 - 145 mEq/L.
What are the symptoms of mild hyponatremia?
- Anorexia
- Nausea
- Vomiting
- Headache
- Lethargy
- Disorientation
- Blurred vision
- Muscle cramps
- Hyporeflexia
What are the symptoms of severe hyponatremia (Na < 120 mmol/L)?
- Seizures
- Encephalopathy
- Cerebral edema
- Herniation
What is the treatment for severe hyponatremia?
Increase serum sodium by 0.75-1 mEq/L/hour, not exceeding 10-12 mEq in 24 hours.
What is the mechanism of hypertonic saline?
Creates an osmotic gradient that drives fluid from the interstitial space into the intravascular space.
What are the major causes of hypernatremia?
- Loss of water (e.g., fever, burns, infection, renal loss)
- Retention of Na+ (e.g., hypertonic saline administration)
What is the treatment approach for hypernatremia?
Identify and treat the underlying cause and replace water deficit slowly.
What are the pharmacological options for treating hyponatremia?
- Isotonic saline
- 3% Hypertonic saline
- Loop diuretics
- Vasopressin antagonists (Vaptans)
- Urea
- SGLT2 inhibitors
What is the daily sodium requirement?
1-2 mEq/kg.
