3. U and Es Flashcards
Which 5 concepts must be considered during an electrolyte disorder?
Concentrations ** Compartments Contents Volumes Rates of gain and loss
What is the result of increased excretion on the equilibrium of fluid in the ECF and ICF?
Decrease solute concentration
What is the result of haemorrhage on the equilibrium of fluid in the ECF and ICF?
Loss of isotonic solutions e.g. fistula fluid
Fluid is lost from ECF
No change in the {Na]
No fluid redistribution
What is the result of dehydration on the equilibrium of fluid in the ECF and ICF?
3L Loss of hypotonic fluid e.g. insensible loss
- ->
- Greater loss from ICF than ECF
- Small increase in [Na]
- Fluid redistribution ECF and ICF
What is the result of gain of isotonic solutions on the equilibrium of fluid in the ECF and ICF?
Gain of 2L of isotonic fluid e.g. saline drip --> Gain is to the ECF No change in [Na] No fluid redistribution
What is the result of gain of hypotonic fluid on the equilibrium of fluid in the ECF and ICF?
Gain of 3L of hypotonic fluid e.g. water, dextrose --> Greater gain to ICF than ECF Small decrease in [Na] Fluid redistribution between ECF and ICF
Name 3 physiological and therapeutic compensatory mechanisms to electrolyte and fluid imbalances?
Physiological: Thirst, ADH, RAAS
Therapeutic: Intravenous therapy, diuretics, dialysis
What is the relation of plasma and urine osmolality in ADH status testing?
If urine > plasma suggests ADH is active
What is the relation of plasma and urine urea in ADH status testing?
If urine»_space; plasma suggests water retention
Where is ADH produced?
The median eminence
Describe the activation and effects of the RAAS
Renin –> Angiotensin —> Aldosterone
Activated by reduced intra-vascular volume (IVV)
E.g. in Na depletion, haemorrhage
Results in renal Na retention
Test to ascertain R/A/A status?
– measure plasma & urine Na
– if urine < 10 mmol/L suggests R/A/A active
Sodium is mainly ______, potassium is mainly ____
Na= Extracellular K= Intracellular
2 methods of replacement of 2L loss of isotonic fluid?
- With isotonic fluid
- No change in [Na]
- No fluid redistribution - With hypotonic fluid
- Fall in [Na]
- Fluid redistribution
2 methods of replacement of 3L loss of hypotonic fluid?
- With isotonic fluid
- [Na] slightly increased
- No fluid redistribution - With hypotonic fluid
- [Na] restored
- Fluid redistribution
How is urea formed?
From protein metabolism
Where is an elevated urea found?
CCF
Shock
MI
Severe burns
What is creatinine?
Breakdown product of protein and muscle.
Reflects muscle mass and is higher in males
Relevance of urea and creatinine levels in urine?
• Loss of renal function and results in decrease
in filtered volume
• Results in increase in plasma concentrations of urea and creatinine
• Urea and creatinine used as markers of renal dysfunction
Factors which influence GFR?
Influenced by renal perfusion pressure, renal vascular resistance, glomerular damage, post-glomerular resistance.
Normal range of GFR?
90-150mL/min (Approx 170 L per day)
A larger healthy person has a higher GFR
Values fall with increasing age
What is eGFR?
Use?
Based on?
“e” is for ESTIMATED glomerular filtration rate
Use:
- To aid staging of kidney disease
- Flag up incipient Acute Kidney Injury (AKI)
Based on creatinine
How is hyponaturaemia caused by diuretics?
U&E presentation?
- Decrease in urine Na reabsorption –> Na diuresis
- Increase in renal loss of sodium > water.
- -> Increase in urine [Na]
- -> Decrease in plasma [Na]
- -> Decrease Intravenous volume.
- Decrease in GFR hence increase in plasma [creatinine] and [urea]
- Increase ADH release so increased water intake, hence decrease plasma [Na]
U&E:
- Low plasma [Na]
- High plasma [urea]
- High urine [Na]
How is hyponatraemia caused by SIADH?
U&E presentation?
SIADH= Sydrome of inappropriate ADH secretion
- Increase in ADH hormone release
- Increased renal water reabsorption
- -> Increase IVV
- Haemodilution (Decrease in plasma [Na] and [creat]/[urea]
- Decrease in renal [Na] absorption
- -> Increase in urine osmolality - Decrease in urine volume
- -> Increase urine [Na]
U&E:
- Low plasma [Na], [Urea] and osmolality.
- High urine [Na]
