Fluid and Electrolyte Imbalances Flashcards
Calculation of Fluid Gain or Loss
One liter of water weighs 2.2 lb (1 kg)
Body weight change is an excellent indicator of overall fluid volume loss or gain
Electrolyte Composition
ICF
Prevalent cation is K+
Prevalent anion is PO43-
ECF
Prevalent cation is Na+
Prevalent anion is Cl-
Movement of electrolytes and particles
Passive Transportation
Diffusion
Facilitated Diffusion
Active Transportation
Endocytosis
Exocytosis
Na+/K+pump
Movement of water
Osmosis –
Movement of water from an area of low solute concentration to an area of high solute concentration through a semi-permeable membrane.
Measurement of Osmolality
Calculate the plasma osmolality using the following formula
Plasma Osmolality = (2 x Na) + (BUN / 2.8) + (glucose / 18)
Normal plasma osmolality is between 275and 295 mOsm/kg
Osmotic Movement of Fluids
The osmolality of the fluid surrounding cells affects them
Isotonic
Hypotonic
Hypertonic
Fluid Shifts
Edema – Accumulation of fluid in the interstitial space
Fluid Spacing
First spacing- Normal distribution
Second spacing- Abnormal (edema)
Third spacing- Fluid is trapped where it is difficult or impossible for it to move back into cells or blood vessels
Regulation of Water Balance
Hypothalamus – Releases ADH (main hormone in fluid balance) Aldosterone is secondary
Kidneys – Reabsorption or release of water and electrolytes in response to plasma levels
Cardiac – Heart cells can produce a hormone that suppresses ADH, aldosterone and renin in response to increased arterial pressure
Gastrointestinal – Oral intake accounts for most water. Small amounts of water are eliminated in feces. Diarrhea and vomiting can lead to significant fluid and electrolyte loss
Extracellular Fluid Volume Imbalances
Interprofessional Care
Correct the underlying cause and replace water and electrolytes
Orally
Blood products
Balanced IV solutions
Sodium
Imbalances typically associated with parallel changes in osmolality
Plays a major role in
ECF volume and concentration
Generation and transmission of nerve impulses
Muscle contractility
Acid-base balance
Hypernatremia
Elevated serum sodium occurring with inadequate water intake, excess water loss or sodium gain
Causes hyperosmolality leading to cellular dehydration
Primary protection is thirst from hypothalamus
Manifestations
Thirst
Alterations in mental status, ranging from agitation, restlessness, confusion and lethargy to seizures and coma
Symptoms of fluid volume deficit
Nursing and Interprofessional Management
Nursing Implementation
Treat underlying cause
Primary water deficit—replace fluid orally or IV with isotonic or hypotonic fluids
Excess sodium—dilute with sodium-free IV fluids and promote excretion with diuretics
Potassium
Major ICF cation
Necessary for
Transmission and conduction of nerve and muscle impulses
Cellular growth
Maintenance of cardiac rhythms
Acid-base balance
ources
Fruits and vegetables (bananas and oranges)
Salt substitutes
Potassium medications (PO, IV)
Stored blood
Regulated by kidneys
Hyperkalemia
High serum potassium caused by
Impaired renal excretion
Shift from ICF to ECF
Massive intake
Most common in renal failure
Manifestations
Cardiac dysrhythmias
Cramping leg pain
Weak or paralyzed skeletal muscles
Abdominal cramping or diarrhea
