Electrolytes And Fluid Balance

Question 1

What usually causes hypernatraemia?

Answer 1

Water deficit

Question 2

What is the effects of water deficit on the cells?

Answer 2

Cellular dehydration (osmotic drag)
Creates vascular shear stress which leads to bleeding and thrombosis

Question 3

What are the symptoms of hypernatraemia?

Answer 3

Thirst, apathy, irritability, weakness, confusion, reduced consciousness, seizures, hyperreflexia, spasticity and coma

Question 4

What are the types of hypovolaemic high Na?

Answer 4

Renal free water losses such as osmotic diuresis (NG feed), loop diuretics, intrinsic renal disease
Non renal free water losses such as excess sweating, burns, diarrhoea, fistulas

Question 5

What can cause euvolemic high Na?

Answer 5

Renal losses - Diabetes insipidus, hypodipsia

Extra renal losses - insensible, respiratory losses

Question 6

What can cause hypervolaemic high Na? (sodium gains)

Answer 6

Primary hyperaldosteronism 
Cushings syndrome
Hypertonic dialysis
Hypertonic sodium bicarbonate
Sodium chloride tablets

Question 7

What is a differential for diabetes insipidus?

Answer 7

Psychogenic polydipsia

Question 8

What is the urine osmolality of dilute urine?

Answer 8

urine osmolality <300

Question 9

What is cranial DI?

Answer 9

Impaired release of ADH

Question 10

What can cause cranial DI?

Answer 10

Trauma/post-op, tumours, cerebral sarcoid/TB, infection (meningitis/encephalitis), cerebral vasculitis (SLE/Wegeners)

Question 11

What is nephrogenic DI?

Answer 11

Resistance to ADH?

Question 12

What can cause nephrogenic DI?

Answer 12

Congenital, drugs (lithium, amphoterecin, demeclocycline), hypokalaemia, HYPERCALCAEMIA, tubulointerstitial disease

Question 13

What is the treatment for hyponatraemia?

Answer 13

Free water

Question 14

What are some symptoms of low Na?

Answer 14

Decreased perception and gait disturbance, yawning, nausea, reversible ataxia, headache, apathy, confusion, seizures, coma

Question 15

What is a cause of hyponatraemia and when would it occur?

Answer 15

Psuedohyponatraemia occurs with high lipids, myeloma, hyperglycaemia, uraemia

Question 16

What investigations should be done for hypponatraemia?

Answer 16

Plasma osmolality, potassium and magnesium, urine sodium, TSH, 9am cortisol, calcium, albumin, glucose, LFT, CT head or chest

Question 17

Why may you do a CT head or chest to investigate low Na?

Answer 17

Suspect SIADH

Question 18

What plasma osmolality suggests psuedohyponatraemia?

Answer 18

Normal or raised

Question 19

Why should you measure potassium and magnesium when patient has low Na?

Answer 19

Low K and low Mg potentiates ADH release

Question 20

What is the relevance of urine sodium when a patient has low Na?

Answer 20

if <20 then non renal salt losses

if >40 then SIADH

Question 21

What are some risk factors for AKI?

Answer 21

Diabetes
CKD
IHD/CCF
Elderly >75
Sepsis
Medications: ACEi, ARBs, NSAIDs, antibiotics

Question 22

Define stage 1 AKI

Answer 22

Serum creatinine 1.5-1.9 x baseline or >26.5 micromol/l increase
Urine output <0.5ml/kg/h for 6-12 hours

Question 23

Define stage 2 AKI?

Answer 23

Serum creatinine 2.0-2.9x baseline

Urine output <0.5/kg/hr for >12 hours

Question 24

Define stage 3 AKI

Answer 24

Serum creatinine 3x baseline or increase >353.6micromol/l or initiation of renal replacement therapy
Urine output <0.3 ml/kg/h >24hours or anuria for >12 hours

Question 25

What are the 3 broad categories of causes of AKI?

Answer 25

Pre renal

Intrinsic Postrenal

Question 26

Name some causes of pre renal AKI

Answer 26

Hypovolemia, Decreased CO, decreased effective circulating volume (congestive HF, liver failure), Impaired renal auto regulation (NSAIDs, ACEi/ARB, cyclosporine)

Question 27

What are intrinsic causes of AKI and group them into categories?

Answer 27

Glomerular: Acute glomerulonephritis
Tubules and interstitium: Ischaemia, Sepsis/Infection, Nephrotoxins
Vascular: vasculitis, malignant hypertension, TTP-HUS

Question 28

Name some nephrotoxins and group them

Answer 28

Exogenous: iodinated contrast, aminoglycosides, cisplatin, amphotericin B
Endogenous: Haemolysis, rhabdomyolysis, myeloma, intratubular crystals

Question 29

Name some causes of post renal AKI

Answer 29

Bladder outlet obstruction

Bilateral pelvoureteral obstruction or unilateral obstruction if only have single kidney

Question 30

What is a vital investigation in AKI and what are you looking for?

Answer 30

Urine dipstick looking for abnormal protein and blood

Question 31

If rhabdomyolysis is suspected then what is an important blood to do?

Answer 31

CK

Question 32

What blood tests should be performed in AKI?

Answer 32

FBC, U&E, LFT, bone profile, CRO, serum bicarb

Question 33

What investigations other than urine dipstick and bloods should be performed in AKI?

Answer 33

Urine PR, urine MC+S, US KUB

Question 34

Why is US KUB useful in AKI?

Answer 34

To rule out obstruction

Question 35

What should be done if protein and blood are found on urine dipstick and why?

Answer 35

c-ANCA and pANCA for vasculitis
anti-GBM, ANA, C3, C4 for lupus nephritis
serum immunoglobulins and electrophoresis to look for myeloma

Question 36

What should you do if you suspect post-streptococcal GN?

Answer 36

Anti streptolysin O titres

Question 37

How should AKI be managed?

Answer 37

Stop nephrotoxic agents
Ensure volume status and perfusion pressure 
Beware 3rd space losses 
Consider funciona haemodynamic monitoring with CVP line/arterial line 
monitor UO and daily bloods 
Avoid hyperglycaemia 
Look for changes in drug dosing
Treat underlying cause

Question 38

What are some indications for RRT?

Answer 38

High K refractory to medical therapy
Metabolic acidosis refractory to medical therapy
Fluid overload due to diuretics (anuric)
Uraemic pericaridits
Uraemic encephalopathy
Intoxication: ethylene glycol, methanol, salicylates, lithium

Question 39

What are some symptoms of uraemia encephalopathy?

Answer 39

Vomiting, confusion, drowsiness, reduced consciousness