Fluid, Electrolyte and Acid-Base balance Flashcards
the body’s three major homeostatic mechanisms for managing hydrogen ions (acidity).
- chemical buffer systems (carbonic acid/bicarb, phosphate, protein buffer)
- respiratory mechanism
- renal mechanism
Normal serum phosphate
2.5-4.5 mg/dL
or
1.8-2.6 mEq/L
Effect of hypernatremia on cells
Increase in tonicity of ECF pulls fluid from cells (ICF). This leaves cells depleted.
Type of solution that can be used emergently to expand volume when blood products or cross-matching are not available
Colloid “volume expanders”
Hypertonic solution
Greater osmotic pressure than serum. Pulls fluid into vasculature and out of cells.
The major intracellular electrolyte
Potassium
the chemical buffer systems and lungs are short term solutions to pH disturbances. What organ is needed for long term adjustment?
the kidneys
Sometimes, pts getting blood or blood products are prescribed ___ ___ to prevent fluid overload
Loop diuretics
in the presence of alkalosis, the kidneys respond by…
retaining H+ ions and excreting bicarbonate ions to lower pH
Do colloids have oxygen carrying properties?
No, colloids only expand volume, they don’t have the ability to carry oxygen
Which kind of crystalloid fluid can cause hypotension due to decreased intravascular volume?
Hypotonic solution
Hypermagnesemia causes
Renal failure, excessive mag intake (use of antacids or laxatives containing magnesium)
Most abundant electrolyte in ECF
Sodium
plasma bicarb concentration is regulated by
the kidneys
Dextrose solutions > 10% must be given via…
Central vein (central line or PICC line)
Type of solution known as “plasma expander a” because particles do not pass through capillary walls
Colloids
IV potassium should never be administered as a…
IV bolus
Resp alkalosis =
Low PaCO2 due to alveolar hyperventilation
Respiratory acidosis is caused by
Any decrease in alveolar ventilation that results in retention of carbon dioxide.
Two principles of fluid and electrolyte balance
- Anions and cations must be balanced in each compartment and remain electrically neutral.
- Compartments must remain in osmotic equilibrium
Maximum infusion rate for IV KCL solution
10 mEq/HR
HCO3-
Bicarbonate
A primary excess of carbonic acid in the ECF
Respiratory acidosis
normal serum pH
7.35-7.45
S/s of hypernatremia
Neurological impairment, weakness, confusion, delusions, hallucinations
Cause of hyponatremia
Loss of sodium or gain of water (vomiting, diarrhea, sweating, diuretics)
urine pH
4.5-8.2
In respiratory and most metabolic acidosis the kidneys excrete ____ ions and conserve ____ ions to increase pH.
Excrete hydrogen and conserve bicarbonate
Solution that contains fluid and electrolytes and can freely cross semi-permeable capillary walls
Crystalloid solutions
acid-base regulation by the kidneys may take as long as
three days
Normal pH
7.35-7.45
How do you measure respiratory acidosis or alkalosis with ABGs?
PaCO2
how does the phosphate buffer system work?
converts the weak base sodium phosphate into the acid sodium phosphate in the kidneys.
Causes of hyperkalemia
Renal failure, hyperaldosteronism, use of: KCl, heparin, ACE inhibitors, NSAIDs, potassium-sparing diuretics
Normal ionized calcium
4.5-5.1 mg/dL
Chvostek’s sign
Tap over facial nerve approx 2 cm anterior to tragus of ear. Watch for twitching. May indicate hyperactive nerves due to hypocalcemia
Causes of hypernatremia
Excess water loss or excess of sodium. Fluid deprivation or lack of fluid consumption.
the two fluid compartments in the body
ECF and ICF (extracellular fluid and intracellular fluid)
Isotonic solution
Osmolality is the same as ECF/plasma. Fluid does not enter or leave the cell (no fluid shift)
Type of crystalloid solution used to treat increased ICP due to cerebral edema
Hypertonic solution
H2CO3
Carbonic acid
Normal bicarbonate
22-26 mEq/L
what percent of weight loss caused by fluid volume deficit is considered life threatening?
15%
IV solution that is made from the components of blood that can be processed through centrifugation methods
Blood products: Packed RBCs (PRBCs) Plasma Platelets Cryoprecipitate
If decreasing the resp rate does not fix respiratory alkalosis after approx 6 hrs…
The kidneys begin retaining hydrogen and increasing excretion of bicarbonate.
s/s of hypokalemia
Muscle weakness, leg cramps, paresthesias and dysrhythmias
Effects of hyponatremia on cells
Decrease in ECF sodium causes fluid to shift into cells since ICF is now hypertonic. This causes swelling and possible rupture of cells
Minimum urinary output
0.5-1 mL/kg/hour
35-70 mL/h for a 70 kg pt (154 lbs)
50-100 mL/h for a 100 kg pt (220 lbs)
Largest fluid loss route
Urine ~ 1400 mL/day
ECF is composed of…
- intravascular fluid (plasma)
- interstitial fluid (surrounding cells)
- transcellular fluid (third space) -mucus, GI, cerebrospinal, pericardial, synovial, etc.
s/s of hyperkalemia
Muscle weakness, paralysis, dysrhythmias and cardiac arrest
common anions in the body
Chloride Cl-
Bicarbonate HCO3-
Phosphate PO4-
Sulfate SO4-
Normal serum potassium range
3.5-5.3 mEq/L
major cation in the ECF
sodium (Na+)
ECF has a bicarbonate to carbonic acid ratio of
20:1
20 parts bicarb to 1 part carbonic acid
Affect if hypokalemia on cells
ECF loses potassium and potassium moves from cells to replace ECF potassium.
This creates an intracellular deficit.
Cells then retain sodium and hydrogen to maintain isotonic fluids.
if the blood level of CO2 decreases, resp rate and depth decreases. This allows CO2 retention so that ___ ___ can be formed in the blood
carbonic acid
s/s of hyponatremia
Confusion, hypotension, edema, cramps, weakness, dry skin
*cerebral edema can lead to seizures
Maximum (longest acceptable) rate of infusion for blood/blood products
4 hrs from the time it leaves the refrigerator
Respiratory alkalosis is the result of…
Alveolar hyperventilation and increased elimination of CO2
how do the lungs assist the carbonic acid/bicarb system?
carbonic acid is formed in the lungs (CO2+H2O) and bicarb is formed in the kidneys.
ICF is located…
inside the cells
the most important buffer system of the body
carbonic acid-bicarb system
Hypertonic solutions should be very closely monitored for?
Circulatory overload
a substance that prevents body fluids from becoming too acidic or too alkaline.
buffer
Which crystal loud solution causes cell shrinkage?
Hypertonic solutions
Summary of metabolic acidosis
Deficit of bicarbonate or excess of hydrogen ions in ECF. This causes low pH and low plasma bicarbonate.
A primary deficit of carbonic acid in the ECF
Respiratory alkalosis
Hypotonic solution
Osmolality is less than ECF/plasma. Causes water to shift out of vasculature and into cells
Normal potassium
3.5-5.3 mEq/L
Normal chloride range
96-106 mEq/L
the body’s three chemical buffer systems
- carbonic acid/sodium bicarb
- phosphate buffer system
- protein buffer system
what organ is the primary controller of the body’s carbonic acid supply?
the lungs
IV lipid emulsions are indicated for patients…
Who are unable to tolerate oral or enteral feedings for seven days or more
How do colloids increase intravascular volume?
Pulls fluid into the vasculature from interstitial space because large particles can’t pass through semipermeable membranes
Hypomagnesemia causes
NG suction, diarrhea, alcohol withdrawal, parenteral feeding, sepsis or burns
PRBCs
Concentrated red blood cells with most of the plasma and platelets removed.
Approx volume of PRBCs is 350 mL/unit vs 500 mL/unit for whole blood.
Hypomagnesemia s/s
Weakness, tremors, tetany, Sz, heart block, AMS, hyperactive deep tendon reflexes, respiratory paralysis
carbonic acid yields ___ and ___
carbon dioxide and water
Osmolality vs tonicity
Osmolality- concentration of particles in body fluid
Tonicity- concentration of particles in IV solution compared to the osmolality of body fluids
Mechanisms of K+ loss
Vomiting, diarrhea, gastric suction, diuretic use
as CO2 is exhaled, the levels of ___ in the blood decreases causing a rise in pH
carbonic acid
ECF is ___% of Total body weight
20%
Respiratory acidosis=
High PaCO2 due to alveolar hypoventilation.
major cation in ICF
potassium (K+)
Normal serum magnesium
1.5-2.5 mEq/L
The cells of what body system are most affected by hypernatremia fluid shift from ICF to ECF?
Cells of the CNS.
Summary of metabolic alkalosis
Excess bicarbonate or a decrease in hydrogen ions causes high pH and high plasma bicarbonate concentration.
Insensible fluid loss
Loss that can’t be measured. Respiration, sweat and feces. Totals approx 1000 mL/day
Hypermagnesemia s/s
N/V, weakness, flushing, lethargy, loss of deep tendon reflexes, resp depression, coma, cardiac arrest
What electrolyte should be closely monitored when pt is receiving multiple blood transfusions?
Serum calcium
Infusing packed red blood cells allows for increased __ ___ ___ with smaller volume than whole blood.
O2 carrying capacity
ICF is ___ % of total body weight
40%
common cations in the body
potassium K+
Sodium Na+
Calcium Ca++
Magnesium Mg++
Perioheral IV sites should be changed every
72-96 hrs
IV fluid that contains proteins or other large molecules that increase osmolality without dissolving in the solution
Colloid solutions
CO2 is a potential acid. When dissolved in water it becomes ____ ____.
Carbonic acid
CO2 + H2O = H2CO3
Three types of IV solution
Crystalloid
Colloid
Blood/blood products
Normal sodium range
135-145 mEq/L
in the presence of acidosis, the kidneys respond by…
excreting H+ ions and forming and conserving bicarbonate ions to raise pH
If the increased resp rate is not effective in reducing CO2 in respiratory acidosis, next…
The kidneys increase elimination of H+ ions (acids) and conserve bicarbonate and sodium ions. The NaHCO3 acts as a buffer and reduces CO2 levels.
How are crystal loud solutions classified?
By their osmolality compared to serum (hypertonic, hypotonic or isotonic)
Normal PaCO2
35-45 mmHg
Par enteral nutrition formulas can only be administered through…
A central line or a PICC line
how does the protein buffer system work?
plasma proteins and hemoglobin can combine with or liberate H+ ions as needed to adjust pH. It can work both inside or outside the cell.
Normal serum calcium
8.9-10.1 mg/dL
condition of loss of H+ ions or increase of base ions (bicarb) causing plasma pH to increase above 7.45
alkalosis
condition of excess H+ ions or a loss of base ions (bicarbonate) which decreases plasma pH below 7.35
acidosis
Crystalloid solution used to treat DKA
Hypotonic solutions because is corrects cellular dehydration by pulling fluid into cell.
