Electrolytes Flashcards
Electrolytes
Saltsthat dissociate in solution and will carry an electric current; clinically used to mean the mineral salts of blood plasma and other body fluids.
Common Electrolytes
Sodium, potassium, calcium,
magnesium , chloride, phosphorous
Electrolytes function
help regulate kidney function and the retention of water.
% of body weight that is water
Women: 45-50%
Men: 50 - 65%
Daily fluid and electrolyte requirements:
2-3L water
50-100 mmol sodium
40-80 mmol potassium
Daily fluid and electrolyte Requirements vary with
Age
Sex
Body fat content
Normal urine output
> 1400 ml/day
Water turnover
~ 5-10% in adults
3. 3L sedentary men 4. 5L active men
Water requirements vary depending on
Dietary factors
Physical activity level
Environmental conditions
Metabolism
Health statusUK Water intake recommendation
1.2L/ day for men & women
Disease risk of unsafe water/poor sanitation
3.7 % of global burden of disease
6th cause of death) (1. 73m death
Reduced availability of fresh water
783 million people lack access to drinking water.
2 billion people lack adequate sanitation.
By 2050 more than half the world will face water shortages
Functions of water in the body
Maintaining cell structure
~ Forming a solvent within which chemical reactions in the body can take place
~ Physically transporting other nutrients and oxygen through the body via the bloodstream
~ Transporting white blood cells to fight infection via the lymphatic system
~ Enabling the body to get rid of waste products via the excretory systems, such as through the formation of urine.
~ Lubricants – synovial fluid in joints
~ Temperature regulation - sweating
Distribution of body water
Total body water 45L
Extracellular fluid (outside cell) 15L Blood or intravascular fluid 3L Intracellular fluid (inside cell) 30L
Intercellular, interstitial or extravascular fluid 12L –>
–> Carries nutrients to the cells/ Collects waste products/ Changing water content
Intracellular and extracellular electrolytes
extracellular: Na+ , Cl-, Ca++, HCO3-
Intracellular: K+, Mg++, PO4 ^3- , [protein]
Body water gains
Food and drink
Metabolic water, by-product from oxidation of carbohydrates, protein and fats:
- 1g of carbohydrate produces 0.60g water
- 1g of protein produces 0.41g water
- 1g of fat produces 1.07g water
Body water losses
Insensible water loss:
- Transepidermal water loss i.e lost through the skin and lungs
- Skin – occurs independently of sweating (350 ml/day)
- Lungs - Expired air saturated with water vapour (350 - 650 ml/d)
Water loss in sweat :
Perspiration: 100 – 5000 ml/day
Hot climates: 500-2500ml per hour
Water loss in urine:
Highly controlled by the kidneys ( 500-1400 ml/day)
Water loss in faeces (100 ml/day)
Regulation of fluid balance
slide 14
Anti-diuretic hormone (ADH)
- Secreted by the hypothalamus
- Causes the insertion of water channels into the membranes of cells lining the kidney collecting ducts, allowing water re-absorption to occur
- Without ADH, little water is reabsorbed in the kidney collecting ducts and dilute urine is excreted
Anti-diuretic hormone (ADH) Secretion influenced by:
Receptors in the hypothalamus that are sensitive to increasing plasma osmolarity .
–> Increase ADH secretion
Stretch receptors in the atria of the heart - activated by a larger than normal volume of blood returning to the heart from the veins.
–> increase ADH secretion
Stretch receptors in the aorta and carotid arteries, which are stimulated when blood pressure falls.
–> decrease ADH secretion
Abnormal water states
Hypotonic –> Water enters the cell; Cell expands and may finally burst.
hypertonic –> Water moves out of the cell. Cells shrink (crenation).
Isotonic - balanced
Increased extracellular volume
Peripheral oedema:
Expansion of the extracellular volume by at least 2 L
Hyponatremia: cell swelling
Cause of peripheral oedema:
Renal Sodium chloride retention
Heart failure
Hepatic cirrhosis
Nephrotic syndrome
Cause of hyponatremia
# Loss of sodium from the extracellular fluid # Addition of excess fluid to the extracellular fluid
The brain can’t increase its volume more than ~ 10% without causing brain injury and death.
Protective mechanism against hyponatremia
If changes occur slowly the brain can transport electrolytes and organic solutes from cells into the extracellular compartments to prevent osmotic flow of water into the cells.
Hypernatremia & cause
cell shrinking
# Loss of water from the extracellular fluid which concentrates sodium – dehydration # Excess sodium in the extracellular fluid
Protective mechanism against Hypernatremia
promote intense thirst to protect against large increases in plasma and extracellular fluid sodium.
mineral water
# clean water # must have at least 250 parts per million total dissolved solids.
Traditional diet:
10-20 mmol/day Na, up to 200 mmol/day K
Diet high in fruit and vegetables and no processed food.
Fewer incidents of high blood press and cardiovascular disease
Modern diet:
140-180 mmol/day Na, 30-70 mmol/day K
Increases risk for hypertension, cardiovascular and kidney disease
High potassium diet can protect against high sodium intake
Sweat
[regulation/ problem/ solution]
contains sodium chloride
Increased aldosterone secretion –> Increased re-absorption of sodium chloride from sweat
Problem: Increased secretion of aldosterone causes increased potassium loss in urine and sweat.
Athletes drinks contain enhanced sodium and potassium concentrations.
