Sodium and Water Homeostasis Flashcards
U and Es measure
Na, K, Cl-, H2CO3, urea, creatinine
estimate water
Abnormal electrolytes due to
Primary disease state, secondary consequence of a multitude of disease, iatrogenic problems
Clinical examples
Haemorrhage, D and V, Poor intake (elderly), Increased loss (pyrexia and heat), Diabetes insipidus, Diabetes mellitus, Diuretic therapy, Endocrine disorders (ADH, aldosterone)
Important concepts
Concentrations, compartments, contents, volumes, rates of gain and loss
Na+ concentrations
Intracellular - 10mmol/L
Plasma - 140mmol/L
K+ concentrations
Intracellular - 150mmol/L
Plasma - 5mmol/L
Lose isotonic fluid
No change
Lose hypotonic
Increase loss ICF, Increase Na, cells shrink
Gain hypotonic
Dilute, decrease Na, water > cells
Severe lack of sodium can lead to
Death by stroke (dextrose dip)
Physiological compensatory mechanisms
Thirst, ADH, Renin-angiotensin system
Therapeutic compensatory mechanisms
IV, diuretics, dialysis
ADH
Produced by median eminence and release increases when osmolality rises, decreases renal water loss, increases thirst
Tests for ADH
Measure plasma and urine osmolality, high ADH high in plasma high urine osmolality
Renin-angiotensin system
Renin (kidney) > angiotensin > aldosterone
Activated by reduced intravascular vol, low sodium, haemorrhage
Causes renal Na retention
