Week 4 - Lecture 1a - Altered Electrolyte Balance Flashcards
cells function depends on what
continuous supply of nutrients
removal of waste products
physical and chemical homeostasis of surrounding fluids
Water
universal solvent
solutes
what is dissolved in water
- classified as non electrolytes and electrolytes
non electrolytes
most organic
- do not dissolve in water: glucose, lipids, creatinine, and urea
- no charged particles created
electrolytes
dissociate into ions in water
e.g. inorganic salts, all acids and bases, some proteins
ions conduct electrical current
electrolytes have a greater osmotic power than non-electrolytes
greatest ability to cause fluid shifts
electrolyte concentration
expressed in miliequivalents per litre (mEq/L)
mEq/L = ion concentration *mg/L) / atomic weight of ion (mg/mmol) x
extracellular and intracellular fluids
each fluid compartment has distinctive pattern of elctrolyte
extracellular fluid
major cation : Na+
major anion : Cl-
intracellular fluid
Low Na+ and Cl-
Major cation : K+
Major anion : HPO 4^2-
electrolyte balance
electrolytes are salts, acids, bases, some proteins
electrolyte balance usually refers only to salt balance
- salts control fluid movements
- provide minerals for excitability
- secretory activity
- membrane permeability
salts enter body by ingestion and metabolism
lost via perspiration, feces, urine, vomiting
altered sodium balance
most abundant cation in the extracellular fluid
only cation exerting significant osmotic pressure
- controls extracellular fluid volume and water distribution
- changes in Na+ levels
- affects plasma volume
- blood pressure
- extracellular and intracellular fluid volumes
Sodium balance altered
Na+ leaks into cells
- pumped out against electrochemical gradient
Na+ moves back and forth between the extracellular fluid and body secretions (eg. digestive secretions)
Concentration of Na+
- determines osmolality of extracellular fluid
- influences excitability of neurons and muscles
- Remains stable due to water shifts out of or into intracellular fluid
Content of Na+
- total body content of Na+ determines extracellular fluid volume and therefore blood pressure
Hyponatraemia (low sodium)
serum sodium <135mEq/L cause - vomiting - diarrhoea -sweating
manifestations are related to cellular swelling
- muscle twitching, weakness
- hypotension
- tachycardia
- oliguria
- anuria (no urine output)
- altered neuronal function (nausea, vomiting, lethargy)
Hypernatraemia (high sodium)
serum sodium > 145mEq/L
cause
- related to sodium gain or water loss
- excessive dietary intake
- water movement from the intracellular to the extracellular compartment
- intracellular dehydration
manifestations of hypernatraemia
intracellular dehydration agitation, restlessness, decreased level of consciousness hypertension tachycardia edema weight gain
Importance of potassium
extracellular fluid has higher concentration of Na+ than intracellular fluid
- balanced chiefly by chloride ions (Cl-)
Intracellular fluid has higher concentrations of K+ than the extracellular
- balanced negatively charged proteins
K+ plays most important role in membrane potential
What is hypokalaemia
low potassium(<3.5 mEq/L)
Manifestations of hypokalaemia (low potassium)
dizziness, muscle weakness, and leg cramps
cardiac arrhythmia, hypotension, thirst, nausea, anorexia, poorly concentrated urine, polyuria
What is hyperkalaemia
high potassium (>5mq/L)
manifestations of hyperkalaemia
cardiac arrest
abdominal cramping, flaccid paralysis
what is hypochloremia
low chlorine (<98mEq/L)
manifestations of hypochloremia (low chlorine)
increased muscle tone, twitching, weakness, and tetany
shallow, depressed breathing
respiratory arrest
mental confusion
what is hyperchloremia
high chlorine (>108mEq/L)
manifestations of high chlorine (hyperchloremia
hyperchloremic metabolic acidosis rapid breathing
deep, rapid breathing
weakness, headache, and diminished cognitive activity
cardiac arrest
