Body fluids Electrolytes

Electrolytes form IONS when in H2O (ions are electrically charged particles) (Non electrolytes are substances which do not split into ions, e.g. glucose) CATIONS = Positively charged particles (e.g. Na+, K+, Ca++) ANIONS = Negatively charged particles (e.g. HCO3- Cl-) E.g. NaCl Na+ + Cl-

Major body electrolytes What are the body’s major electrolytes? Sodium (Na + )Potassium (K + ) Chloride (Cl - )Calcium (Ca + ) Magnesium (Mg ++ )Bicarbonate (HCO3 - ) Phosphate (PO4 --) Sulphate (SO4 -- ) (Urea and Creatinine are not electrolytes) You should be familiar with the chemical symbols: Na +, K +, Cl -, Ca +, Mg ++, HCO3 -

Importance of electrolyte balance Electrolytes are critical for cellular reactions They are found in all fluid compartments Essential in: Muscle co-ordination Heart function Fluid absorption and excretion Nerve function

Sodium (Na+) Na+ is the main Extra- cellular fluid Cation Normal range for Na+ = 135 – 145 mmol/L The hormone that regulates Na+ levels? = Aldosterone Adrenal Cortex Aldosterone Nephron reabsorption of Na+ = H20

Sodium (Na+) Functions of Na + Maintaining volume and concentration of extra-cellular fluid * Involved in nerve conduction When is a sodium test requested? * Part of a routine laboratory evaluation Na +

Sodium (Na+) What is Hyponatraemia? Low blood sodium levels (less than 135mmol/L) May occur in: Excessive sweating Symptoms of Hyponatraemia Muscle cramps & Weakness Fatigue & Nausea, Apathy & Headache Confusion  Seizures Treatment = Replacement therapy

Sodium (Na+) What is Hypernatraemia ? High sodium in the blood (more than 145mmol/L) Normally occurs because of inadequate fluid intake Signs and symptoms include Intense thirst Decreased urine output Confusion  Seizures Treatment =IV or oral water replacement

Potassium (K+) Primary intra-cellular cation Necessary to maintain nerve conduction Necessary for normal cardiac function Normal range for Potassium (K+) = 3.5 – 5.3 mmol/L (K+)

Potassium (K+) What type of muscle is particularly sensitive to K+ levels? Cardiac muscle E.g. High K+ level  Abnormal heart rhythm Potassium testing * Routinely measured * Also specifically measured in diuretic therapy

Potassium (K+) Hypokalaemia = An abnormally low level of blood potassium (less than 3.5mmol/L) Causes: Inadequate intake Loss of K + from the body (e.g. diuretics or gastric losses) Signs and symptoms Skeletal muscle weakness ECG changes Treatment = Replacement - foods (e.g. bananas, spinach) or K+ supplements

Potassium (K+) Hyperkalaemia = serum potassium concentration greater than 5.5mmol/L Caused by: Decreased excretion of K + Movement of K + out of the cells in trauma IV potassium infusion Signs of hyperkalaemia: Include ECG changes Treatment Depends on the blood K + level

Calcium (Ca++) 99% is stored in the skeleton and teeth (huge reserve) 50% of blood calcium is ionized, the rest is protein bound. * Only the ionized calcium is used in functions such as: muscle contractioncardiac nerve impulse functiontransmission

Phosphate (PO 4 ) 85% of body’s total phosphorus is contained in the bones, The remainder is in the cells. Phosphate is required for: Generation of bony tissue, Metabolism, Maintenance of acid base balance

Bicarbonate (HCO3 - ) What is the normal range for Bicarbonate (HCO3-) 22 – 30 mmol/L What is the ‘job’ of bicarbonate? Prevents body getting too acidic (i.e. acid-base balance)

Urea Nitrogen containing waste product from metabolism (protein breakdown) kidneys Excreted through the kidneys Good indicator of renal function Serum urea = 2.5 – 6.6 mmol/L

Creatinine A metabolic waste product produced by breakdown of muscle protein (creatine). Why is creatinine measured? To determine kidney function Serum Creatinine concentration is a more accurate indicator of renal function than urea

Laboratory Results Is an abnormal test always a sign of a real problem? Not always, but should be further investigated Are reference ranges specific to the laboratory that produces? Yes Final point All the above points are clinically relevant and it is important that you have a good understanding of fluid and electrolyte balance by the time you qualify.