Renal 3) Acid-base and electrolyte disturbances Flashcards
What is urea?
Produced by liver from excretion of ammonia and breakdown products of amino acids
Excreted in urine
What can increase urea levels?
Intravascular depletion
Blood
Food
Renal failure
What are the normal serum urea levels?
1.7-8.3mmol/L
What symptoms occur when urea is above 20?
Nausea Decreased appetite Itchiness Tiredness Smelly breath Metallic taste in mouth
What symptoms occur when urea is above 60?
Extreme uraemia frost
Uraemic pericarditis
Encephalopathy
What is creatinine?
Breakdown product of creatinine phosphate in muscle
What are normal creatinine levels?
62-106umol/L depending on muscle mass
What is the MDRD formula for eGFR?
186 x (creatinine /88.4)^-1.154 x (age)^-0.203 x (0.742 if female) x (1.210 if black)
What is the normal eGFR?
> 90mls/min
What is the eGFR in CKD stage 1?
> 90mls/min
What is the eGFR in CKD stage 2?
> 60mls/min
What is the eGFR in CKD stage 3a?
> 45mls/min
What is the eGFR in CKD stage 3b?
> 30mls/min
What is the CKD stage if eGFR is >15mls
Stage 4
What is the CKD stage if eGFR is <15mls?
Stage 5
What is the average eGFR when starting dialysis in UK?
8
What are the 3 factors that can cause hyponatraemia?
Intra-renal factors
Defect with NaCl transporter out of thick ascending limb / distal convoluted tubule
Continued secretion of ADH stimulated by non-osmotic mechanisms
What can decrease glomerular filtration?
Age Renal disease Congestive heart failure Cirrhosis Nephrotic syndromes Volume depletion
What can reduce NaCl reabsorption in the TAL and DCT?
Loop diuretics Osmotic Diuretics Interstitial disease Thiazide diuretics (DCT only)
What can increase permeability of the collecting duct?
Vasopressin
Drugs
What are normal serum K levels?
3.2-5.1mmol/L
What are the causes of hypokalaemia?
Redistribution
Non-renal loss
Poor diet
Renal loss >20mmol/L
What can cause a renal loss of potassium?
Drugs - diuretics, ahminoglycosides, amphotericin
Renal tubular acidosis or metabolic acidosis
Low BP in Bartter’s or Gitelman’s
High BP
High /low aldosterone
What are the complications of chronic hypokalaemia?
Cardiovascular - hypertension - ventricular tachyarrhythmias Endocrine - impairs insulin activity and sensitivity Muscular - impairs muscle contraction Renal - mild tubulointerstitial fibrosis - renal cyst formation - metabolic alkalosis - polyuria Liver - increases renal ammonia production
What are the causes of hyperkalaemia?
Impaired renal excretion - drugs impairing secretion - increased K load Increased intake Pseudohyperkalaemia + haemolysis
What drugs can impair renal excretion of K?
Spironolactone
Amiloride
ACEi
ARB
What can increase K load?
Rhabdomyolysis
Haemolysis
GI bleed
What is the treatment of hyperkalaemia?
Put K back into cells: - salbutamol - insulin and dextrose - sodium bicarbonate Stabilisation - calcium gluconate Removal - IV fluids and diuretics, dialysis
What are the causes of metabolic alkalosis?
Excess alkali
K+ depletion
Cl- depletion
What are the normal levels of serum calcium?
2.2-2.6mmol/L
Where in the kidneys is calcium reabsorbed?
Loop of Henle
Distal tubule
What hormone controls calcium levels?
Parathyroid hormone
What are the normal levels of phosphate?
0.85-1.6mmol/L
Describe electrolyte levels in an AKI
Normal Na High K Low bicarb Low pH High urea High creatinine Normal Ca, phosphate, PTh
Describe electrolyte levels in CKD
Normal Na High K Low Bicab Normal pH High urea High creatinine High calcium, phosphate and PTH levels
