Clinical Problem Solving: Renal failure and Electrolytes

Question 1

How can haemoglobin distinguish acute from chronic renal injury?

Answer 1

Kidneys secrete erthropoieitn.

Hg has life of about 120 days, if haemoglobin is lower, likely due to chronic as longer standing

Question 2

What can be said about pre renal AKI?

Answer 2

Low kidney perfusion, typically due to fluid loss (dehydration, diarrhoea, sepsis, bleeding)
Can cause ATN (renal injury)

Question 3

What are the types of renal AKI?

Answer 3

ATN: usually from pre reanl causes, however can be due to some drugs such as NSAIDs, aminoglycosides and contrast and rhabdomyolysis
RPGN: glomerular inflammation, crescents in glomeruli in biposy, due to SLE, vasculitis

Question 4

What is the best test for post renal AKI?

Answer 4

Ultrasound but bladder palpation is also useful etc

e.g hydronephrosis

Question 5

What are signs of hypervolaemia?

Answer 5

edema; high BP; orthopnea; crackles on auscultation; high JVP; strong rapid pulse

Question 6

What are some clinical signs of CKD?

Answer 6

malnutrition; fluid overload; rash (uraemic toxins); pericardial rub

Question 7

What is the best way to treat CKD?

Answer 7

treat the high BP.

Can treat the anaemia and can chuck in dialysis (won’t heal the kidneys)

Question 8

What BP treatments work best?

Answer 8

Mainly ACE inhibitors/ ARB’s but will be on Beta blockers and diuretics
reduce glomerular pressure to reduce damage to them!

Question 9

What are some ways to assess volume status?

Answer 9

Hypervolaemia: rapid weight gain, puffy eyes/ankles; high BP and breathlessness

Hypovolaemia: weight loss; dry mouth; low BP; dizziness

Question 10

When does a patient need IV fluid?

Answer 10

NOT when drinking enough, is on enteral feeding or is overloaded
Typically when fluid is being lost or not drinking.

Used for -maintenance; replacement of losses; resuscitation

Question 11

How do we lose fluid throughout the day?

Answer 11

Sweat, urination, defaecation and breathing.

maintenance fluid (about 2-3 L/day) if no eating or drinking

4 2 1 rule (4mL/kg/hr for first 10 kilos, then 2 for next 10, then 1 for the remainder of body weight)
Used in paediatrics and sometimes adults

Question 12

When might you need fluid replacement?

Answer 12

Fluid drainage; diarrhoea; vomiting.

Must be careful to replace fluid and do maintenance fluid

Question 13

What are some isotonic fluids used?

Answer 13

Plasma-lyte and saline
Safest is generally isotonic
generally give isotonic unless maintenance fluid and overloaded or high Na

Question 14

When would you use hypotonic fluids?

Answer 14

typical example is dextrose, starts isotonic but is metabolised to give free water.
overload or high sodium

Question 15

When do you use a hypertonic solution/

Answer 15

With extreme hyponatraemia.

Don’t chart as junior doctor

Question 16

What are causes of hyponatraemia?

NB symptoms include disorientated and drowsy

Answer 16

Sodium loss; GI loss. hypo aldosteronism, sweat, diuretics( thiazide will cause low sodium)
Water excess; cirrhosis, HF, nephrotic syndorme, SIADH, polydipsia. (can be euvolaemic due to bad ADH?)
pseudohyponatraemia: hypertriglyceridemia or hyperproteinemia (will show normal osmolality)

Question 17

What can cause water excess hyponatraemia?

*diuretics graph pg 146

Answer 17

No evidence of fluid overload (euvolaemic)
-SIADH, polydipsia; over hydration (hypotonic IVF), diuretics( as osmolality drops (sodium loss, ECF vol loss) the ADH switches so an increase will cause ADH secretion continually keeping water)

Question 18

How do you treat hyponatraemia?

Answer 18

Dehydrated with sodium loss- Saline IVF
Water excess- fluid restriction

Don’ think low sodium so hypertonic solution, may cause osmotic demyelination in the brain