Exam 1: Fluid and electrolytes, acid/base Flashcards
intracellular fluid
contained w/in the cell. 2/3 of total body water
higher concentrations:
potassium, magnesium, and phosphorus
extracellular fluid
fluid outside of the cells. 1/3 of total body water
higher concentrations:
sodium, calcium, chloride, bicarbonate
interstitial fluid
fluid b/t cells, outside of blood vessels
intravascular fluid
blood plasma or fluid w/in the blood vessels
osmolality
the # of particles of a solute in a unit of solution. Serum osmolality is 280-310 mOsm/kg
Starling’s law of capillary forces
the movement of fluid that occurs at every capillary bed using hydrostatic pressure and osmotic pressure (which includes oncotic pressure)
filtration
a form of passive transport
movement of both water and smaller molecules through a semi-permeable membrane from an area of high pressure to low pressure
occurs due to hydrostatic pressure being balanced with osmotic
reabsorption
fluid shifting back into the capillary from the interstitial space
hydrostatic pressure
pressure exerted by fluid within a closed system such as intravascular space. leads to movement of water through the capillary membranes into the interstitial space (greater pressure to lesser pressure)
osmotic pressure
Power of a solution to attract or draw water due to concentration. The concentration is through solutes in the solution. In the bloodstream, the concentration is created by electrolytes, nutrients and proteins.
oncotic pressure (colloidal)
Also called colloidal oncotic pressure. Refers to the force exerted specifically by albumin in the bloodstream. Good fact to know is that albumin is indicative of the protein nutritional status of the body so low albumin means poor nutritional status
edema
Accumulation of fluid within the interstitial space and intercellular fluid causes:
^ hydrostatic pressure
decreased oncotic pressure
increased membrane permeability
lymphatic channel obstruction (lymphedema)
generalized vs localized edema
Generalized edema: Palpable swelling produced by expansion of the interstitial fluid volume; when massive and generalized, the excess fluid accumulation is called anasarca
Localized edema: Increased interstitial fluid at a specific sight, generally due to trauma
tonicity (hyper-,hypo-,isotonic)
Hypertonic solution: More particles (solutes) than the blood, less water
Hypotonic solution: Fewer particles (solutes) than the blood, more water
Isotonic solution: Same tonicity of the blood. We use 0.9% normal saline or 305 mOsm/kg
regular fluid intake and output values
Intake: The amount of fluid a person takes into their body within a day is about 2400-3200ml, generally >1500mL for normal kidneys to function and 500-1000mL from food.
Output: The amount of fluid that leaves the body within a day. Obligatory output should be 300-500mL/day or around 30-40mL/hr. Insensible water loss is about 100mL/day more if you have a fever (through kidneys, lungs, GI, & skin)
blood pH
normal is 7.35 - 7.45
reflects acidity or alkalinity in the blood
regulated by lungs and kidneys
PaO2
The pressure of oxygen in the arterial blood (90 to 100 mm Hg)
PaCO2
The pressure of carbon dioxide in arterial blood (35 to 45 mm Hg)
HCO3-
The amount of bicarbonate ion in the blood (22 to 25 mEq/liter)
diffusion
passive transport
movement of solute AND solvent through permeable cell membrane from high conc to low conc
third spacing
excessive accumulation of fluid w/in body tissue or body cavity (ex. pleural effusion)
cations
positive
sodium
potassium
magnesium
calcium
anion
negative
chloride
bicarbonate
phosphate
sulfate
sodium (Na+)
normal serum sodium: 135-145 mEq/L
most plentiful in ECF compartment
function to maintain ECF volume through maintaining osmolarity
stimulates conduction of nerve impulses
potassium (K+)
normal serum K: 3.5 - 5 mEq/L
most plentiful in ICF
regulated throguh diet, kidneys, and Na/K pump
functions: electrical impulse transmit (cardiac ex.) and controls H+ ion conc.
calcium
8.5 - 10.5 mg/dl
most abundant electrolyte in body
99% in bones and teeth
The other 1% circulates in the blood and affects system function
Necessary for cardiac and muscle contraction
Promotes transmission of nerve impulses
Converts prothrombin to thrombin, necessary for formation of a clot
magnesium
Normal Range
1.3 - 2.1 mEq/L
Second major cation in the ICF
Main source of Magnesium is through the diet
Regulates neuromuscular activity
Facilitates transport of Sodium and Potassium across cell membranes
Maintains normal intracellular levels of potassium
Helps with carbohydrate and protein
metabolism
Produces vasodilation peripherally
phosphate
Normal serum phosphorus level
2.5-4.5 mEq/L
Most abundant intracellular anion
Phosphate in the ECF is referred to as “Phosphorus”
Most phosphate is bound with calcium in teeth and bones
Inverse relationship to calcium
Requires dietary intake
Functions include
* Major role in bone formation
* Promotes normal neuromuscular action
* Assists in acid base balance
* Important for cell division
arterial blood gas (ABG)
shows:
1. amt of O2
2. amt of CO2
3. % of H+ (pH)
normal values:
pH 7.35-7.45
pCO2 35 - 45
HCO3 22 - 26
pO2 90 - 100
base excess -2 - +2
aldosterone
causes sodium to be retained by the body which subsequently retains fluid
chief mineralcorticoid secreted by adrenal glands
renin-angiotensin system
- renin (kidneys) released in response to low renal blood flow & low BP
- Renin stimulates the production of Angiotensin I from Angiotensinogen
- Angiotensin I is converted to Angiotensin II by the “Angiotensin Converting Enzyme”
- Angiotensin II acts in two ways: potent vasoconstrictor and stimulates the release of Aldosterone
Ultimately:
low renal blood flow and low BP trigger hormonal cascade that results in release of aldosterone and vasoconstriction
Chvostek’s Sign
hypocalcemia facial sign
Trousseau’s sign
Carpopedal spasm w/ blood pressure
acid base balance
7.35 - 7.45 arterial blood pH
inverse b/t pH and H+ ion conc
(higher H+ the lower the pH and vice versa)
pCO2 ABG levels
35 - 45
indicator of respiratory acidosis or alkalosis
HCO3 ABG levels
22 - 26
indicator of metabolic acidosis or alkalosis
antidiuretic hormone
Secreted from the Posterior Pituitary Gland
Promotes water reabsorption from the kidney tubules
Maintains water balance in the body fluids
– Is also a potent vasoconstrictor
Pressure sensors in the vascular system stimulate or inhibit the release of ADH
– ADH will also be released in response to serum osmolality, fever, pain, stress and some opioids
Hyper- & hypokalemic impacts on EKG
Hyperkalemia: Peaked T, loss of P, widened QRS (leads to irregular pulse and V Fib
Hypokalemia: Flattened/Inverted T waves, ST depression, Prolonged QRS; Peaked P Wave; U wave present
calcium - phosphorus relationship
Calcium and phosphorus have an inverse relationship
One has high serum osmolality then the other will be low
renin
A hormone released from the kidneys when low renal blood flow and low BP
Stimulates the production of Angiotensin I from Angiotensinogen
Angiotensin I
A hormone in the middle of the renin-angiotensin system
transforms into angiotensin II with the help of “angiotensin converting enzyme”
Angiotensin II
Byproduct of angiotensin I after “angiotensin converting enzyme” acts on it
the final step in the renin-angiotensin system
potent vasoconstrictor
stimulates the release of aldosterone
Sodium-potassium pump
a form of active transport
located on the cell membrane and acts to balance Na and K in ICF and ECF (sodium diffuses into ICF and pump brings back out to ECF)
** relies on ATP that needs adequate oxygen to be produced - so someone hypoxic will have electrolyte imbalance
Naturietic peptides (NPs)
- Hormones secreted by special cells that line the atria and the ventricles of the heart
- Secreted in response to increased blood volume and blood pressure (this will stretch the heart tissue)
- NP’s bind to receptor sites in the kidneys, and oppose the renin- angiotensin system
Chemical buffer systems
Bicarbonate Buffer System
Transcellular Hydrogen-Potassium Exchange System
Protein Buffer System
Transcellular Hydrogen-Potassium Exchange System
Both H+ and K+ are positively charged
Both H+ and K+ move freely between the ICF and ECF compartments
When excess H+ is present in the intravascular space, it moves into the ICF in exchange for K+
When excess K+ is present in the intravascular space, it moves into the ICF in exchange for H+
Thus, potassium levels will influence acid-base balance…
And acid-base balance will influence potassium levels
How do kidneys regulate acid-base balance?
Bicarbonate reabsorption and formation
along with excreting H+ ions
Hyponatremia
Low Na+ ( <135 mEq/L)
Causes: sweating, vomiting diarrhea, decrease aldosterone levels, syndrome of inappropriate antidiuretic hormone (SIADH), Heart failure, liver disease, renal disease
Clinical manifestations:
Neurological symptoms (HA, Irritability, Confusion, Seizures to coma), lethargy, nausea, vomiting, diarrhea, muscle cramps & spasms (most often occur with severe hyponatremia - fewer than 125 mEq/L)
Hypotonic dilutional hyponatremia
water and Na both lost
Causes: sweating, vomiting diarrhea, decrease aldosterone levels
Euvolemic or normovolemic hypotonic hyponatremia
retention of water with dilution of Na
Causes: syndrome of inappropriate antidiuretic hormone (SIADH)
Hypervolemic hypotonic hyponatremia
low Na with edema disorders
Causes: Heart failure, liver disease, renal disease
Hypernatremia
High Na+ ( >145 mEq/L)
Causes:
- excess intake of sodium (PO or IV or hypertonic tube feedings)
- “Relative” Hypernatremia - water deprivation/ water loss (sodium is concentrated in low H2O)
Clinical manifestations:
Due to decrease ECF volume:
*Restlessness, agitation, lethargy, seizures, coma, intense thirst, dry swollen, tongue, dry mucous membranes, orthostatic hypotension, weight loss, oliguria, tachycardia
Specific to increase in sodium w/normal ECF volume:
*Twitching, weight gain, peripheral and pulmonary edema, increased BP
Hyperkalemia
High K+ ( >5.0 mEq/L)
Etiology:
* Renal failure, high K+ intake, certain meds, acidosis, hypoaldosteronism (decreased aldosterone causing K+ and H+ exchange places)
Clinical manifestations:
*Weakness, fatigue, confusion, cardiac dysrhythmias (irregular or Vfib)
– ECG Changes - peaked T waves, loss of P wave, widened QRS
*Neuromuscular (Restlessness, irritability, weakness, paresthesia, muscle (leg) cramps, respiratory muscle weakness)
*GI (N/V/D)
*Metabolic acidosis
Hypokalemia
Low K+ ( <3.5 mEq/L)
Etiology:
* Certain meds (diuretics, corticosteroids), GI fluid losses (V/D), hyperaldosteronism, anorexia nervosa
Clinical manifestations:
* Cardiac ECG Changes and Dysrhythmias (Flattened/Inverted T waves, ST depression, Prolonged QRS; Peaked P Wave; U wave present)
* Neuromuscular: Weakness, muscle cramping, hypoactive reflexes
* GI: Decreased motility, hypoactive bowel sounds, constipation, ileus, N/V, anorexia
* Metabolic Alkalosis, Weakness of respiratory muscles, Hyperglycemia (impairs insulin secretion)
Hypercalcemia
Etiology: Hyperparathyroidism, malignant bone disease, prolonged immobilization, excess calcium supplements, certain meds (thiazide diuretics, lithium)
Clinical manifestations:
GROANS (constipation or Anorexia, N/V)
MOANS (psychic moans = fatigue, lethargy, depression)
BONES (bone pain)
STONES (kidney stones - nephrolithias)
Psychiatric OVERTONES (including depression, memory issues and confusion)
Can’t pick up the PHONE! (muscle weakness, lack of coordination)
Hypocalcemia
Etiology: Hypoparathyroidism, malabsorption, vitamin D deficiency, liver or kidney disease
Clinical manifestations:
CATS go numb
C = Convulsions
A = Arrhythmias
T = Tetany (+Trousseau and +Chvostek’s)
S = Spasms, Seizures, & Stridor
Numbness in the fingers
Hypermagnesemia
Etiology: renal failure, excessive replacement (typically IV)
Clinical manifestations: Lethargy or drowsiness, N/V, depressed reflexes, muscle weakness/ paralysis, bradycardia, hypotension, respiratory depression, cardiac arrest
Hypomagnesemia
Etiology: chronic alcoholism, malabsorption, prolonged gastric suction
Neuromuscular (increased nerve impulse transmission, hyperactive deep tendon reflexes, muscle cramps, tremors, seizures) and cardiac dysrhythmias
Respiratory acidosis
PH <7.35
PCO2 >45mmHG
Bicarbonate: 22-26 mEq/L NORMAL
Etiology: hypoventilation which leads to CO2 retention
Patho: Retention of CO2 lowers the arterial pH
Respiratory alkalosis
PH > 7.45
PCO2 < 35 mmHG
Bicarbonate: 22-26 mEq/L NORMAL
Etiology: hyperventilation which leads to CO2 elimination
Patho: Elimination of CO2 raises the arterial pH
Metabolic acidosis
PH < 7.35
PCO2 35 -45 mmHG NORMAL
Bicarbonate: < 22 mEq/L
Etiology: accumulation of lactic acids or ketoacids, excess ingestion of acids, excessive loss of bicarbonate by the kidneys or GI tract (diarrhea), hyperkalemia (due to potassium / H+ relationship)
Metabolic alkalosis
PH > 7.45
PCO2 35 -45 mmHG NORMAL
Bicarbonate: > 26 mEq/L
Etiology: sodium retention (bicarb often accompanies sodium), excess intake of antacids, loss of stomach acids, hypokalemia (H+ is excreted instead of K+)
