Electrolyte Abnormalities Flashcards
What is K normally excreted for
Exchange for Na
What is a fatal level of K
Sequelae [4]
> 7
Cause fatal arrhythmias - asystole / VF / cardiac arrest
What can cause hyperkalaemia? [3]
Decreased excretion
Increased release of intracellular K
Endocrine
What causes decreased excretion? [4]
Renal failure - AKI or CKD
ACEI / ARB
NSAID
Spironolactone (K sparing diuretic)
What causes increased K out of cells? [4]
Tumour lysis
Rhabdomyolysis
Metabolic acidosis
BB
What are endocrine causes?
Addison’s (hypo adrenal)
- Increased K as decreased excretion
- Low Na as decreased reabsorption
- Low BP as low Na
What are other causes? Hyperkalaemia
Massive blood transfusion
Type 4 renal tubular acidosis seen with DM or CKD
What are symptoms of hyperkalaemia? [3]
Weakness, Dizzy
Fast irregular pulse
Chest pain, SOB, palpitations
What do you need if symptomatic [2]
U+E
Urgent dialysis / haemofiltration
How do you investigate [4]
DRABC
Bloods - U+E
ABG / VBG for K - repeat
ECG for arrhythmia
What does ECG show [5]
Sinus brady or slow AF Tall tented T waves P wave widens then disappears Broad QRS AV block
What should you do if haemodynamically unstable
Dialysis
Haemofiltration
When do you treat [2]
K >6.5
ECG + K>6
How do you treat [4]
Stop cause / drugs
Calcium gluconate / chloride
Insulin dextrose
Salbutamol
What dose calcium gluconate
10% 10 mls IV injection
What does calcium gluconate do
Stabilise myocardium if ECG changes
Gives 30-60 minute protection
What dose of insulin dextrose
50ml 50%10 units insulin dextrose
Then infusion
What does insulin do
Shift K internally
Dextrose counteract sugar loss
Must monitor for hypo
What dose of salbutamol
5-10mg neb
Tachy can limit use
What can you use if K not that high [2]
Calcium resonium
Used more in CKD to bring down over a few days
What do you do if this fails [2]
Dialysis / anion exchange
Need to cure cause by getting patient to diuresis potassium out of body
Why are diuretics not really used
Hypovolaemia
DO NOT use unless overloaded as well
How do you prevent [3]
Low K
Stop ARB / spironolactone
Treat underlying cause
How do you treat renal tubule acidosis [2]
HCO3
Fludrocortisone
What is emergency hypokalaemia
<2.5
What is most common causes of hypokalaemia (usually associated alkalosis but can be due to acidosis) [3]
D+V
Diuretic
Incorrect IV fluid replacement
What causes increased loss [4]
Diuretic
D+V
Laxatives
Pyloric stenosis
What are endocrine causes [2]
Cushing’s
Conn’s
What are other causes [7] hypokalemia
Alkalosis Insulin / salbutamol excess Steroid use Type 1 and 2 renal tubular acidosis Tubular defect - Barter Mg deficiency Hypokalamic periodic paralysis
What are the symptoms of hypokalaemia [6]
Weakness, Cramps Hypotonia, Hyporeflexia Tetany Palpitations Light headed Constipation
What does hypokalaemia predispose you too [2]
Digoxin toxicity
Careful if on diuretic
What does ECG show? [4] hypokalemia
U wave
Prolonged QT and PR
ST depression
Absent T
What will urine potassium show
If renal loss = high
If extra renal e.g. D+V then low
What should you do if renal loss
BP
If BP high
Endocrine
Renin-angiotensin ratio
Measure cortisol / creatinine
If BP normal
HCO3 levels
Acidosis
Tubular acidosis
Alkalosis
Tubular defect
Diuretic
How do you treat [5] hypokalemia
Correct cause Oral K if mild IV K if severe Monitor in cardiac area Consider K sparing diuretic
When would you not give K [2]
If oligouria
Or as fast bolus - no more than >20mmol / hour
What is best indication of long standing low K on diuretic
HCO3
What is most common cause of hypernatraemia [4]
Other causes [3]
Water loss > Na loss
Dehydration
Fluid loss with no replacement - D+V / burns
Incorrect IV fluids
Others:
- DI - decreased ADH so increased water loss
- Osmotic diuresis in diabetic coma
- Primary aldosteronism as increased reabsorption
What are symptoms of hypernatraemia [6]
Lethargy, Irritable Weakness Thirst, Dehydration Confusion Coma Seizure
What is important in bloods [4]
Increased Na
Increased albumin
Increased urea
Urine osmolarity
What else should you do
Water deficit calculator to work out
What will dehydration have
High urine osmolality as trying to conserve water
What will DI have
Low osmolarity
How do you treat hypernatraemia [2]
Oral rehydration
Glucose 5% slow IV guided by output and plasma Na
0.9% saline if hypovolaemia
What should you avoid
Hypertonic
What do you need to do with regards to fluid and how fast do you go and why [3]
Replace deficiency
Replace ongoing loss and insensible
Replace slowly no > than 0m5 as risk of cerebral oedema (seizure / coma / death)
When would you suspect primary aldosteronism [3]
K down
BP up
Alkalosis
What does dehydration always have [2]
High Na
Not the same as hypovolemia
What is most common
Hyponatraemia <130mmol
Either water excess or sodium depletion
What is important with regards to hyponatraemia? [2]
FLUID STATUS
Doesn’t mean Na depletion
Can just be overloaded so dilutes
What causes hypovolaemic (dehydrated) hyponatraemia ? [4]
Urine Na >20
Diuretic
Addison’s
Renal failure
Osmolar diuresis -hyperglycaemia
What causes hypovolaemic (Dehydrated) but urine Na <20 so lost other than kidney as kidney tried to hold on to Na / osmolarity high
D+V Fistula Burn, Trauma Obstruction - 3rd space loss CF Heat in extra sport = ongoing ADH release
What can D+V cause
Low or high Na
What drugs should you consider stopping in hyponatremia [4]
Diuretic
SSRI
PPI - omeprazole
ACEI
What causes hypervolaemic hyponatraemia - diluted NA [5]
Nephrotic HF Liver cirrhosis Renal failure Polydipsia
What causes euvolaemic hyponatremia [3]
SIADH
Severe hypothyroid
Glucose-corticoid insufficiency
What suggests SIADH
High urine osmolality
Think known cancer
What are symptoms of hyponatremia [6]
Confusion, Headache Anorexia Nausea Malaise, Irritable Weakness, CNS distubrance Seizure, Encephalopathy
What is a medical emergency
Rapid changes or acute
How should you investigate [3]
Fluid balance
Urine osmolarity
Serum osmolarity
What are baseline bloods for cause of hyponatremia [7]
Glucose Lipids TFT LFT Cortisol for Addison Urine Na+K Urine osmolality
How do you test for Addison [2]
Cortisol low
Short synacthen
How do you treat hyponatraemia [2]
Correct cause
Replace Na and water at same rate
What do you do for asymptomatic and chronic hyponatremia [4]
Fluid restriction
ADH antagonist
Diuretic
Hypertonic saline
What do you do for acute severe symptomatic [4]
Cautious rehydration
Hypertonic 3% saline or Hartman
150ml over 15 min
Repeat if no improvement
What should you not do
Correct more than 10mmol/l in 24 hours
When would you consider furosemide
Not hypovolaemic
If hypovolaemic
0.9% saline
If hypervolaemic [2]
Treat cause- CF / liver /r renal
Have fluid intake < output if oedema / SIADH / renal failure
What do you do if seizure or coma [2]
Hypertonic (1.8%) saline + furosemide
Aim for gradual increase to 125
What may happen if Na corrected rapid [3]
HF
Central pontine myelinolysis
Osmotic demyelination syndrome
What does ADH antagonist do (Tolvaptan) [3]
Promote water excretion
No loss of electrolyte
Effective if hypervolaemic or euvolaemic but expensive
What can cause inappropriate ADH secretion
Tumour - SCLC / pancreas / gut Empyema CF Pneumonia / TB Drugs CNS - meningitis / encephalitis / abscess / haemorrhage / stroke Head trauma
How do you Dx
Assess fluid balance - euvolaemic Hypotonic hyponatraemia Urine osmolarity high - high urine Na CXR CT head CAP Bronchoscopy
What is Furst formula
Used to see if fluid restriction would be helpful in Rx
<1 = restrict
How does metabolic acidosis cause hyperkalaemia
K and H ions fight to be exchanged for Na in distal tubule
What is hypokalaemia associated with [2]
Alkalosis
So K loss
What can hypokalemia be associated with
Acidosis e.g. renal tubular
Symptoms of osmotic demyelination syndrome [6]
Dysthria Dysphagia Paresis Seizure Confusion Coma
When should fluid intake be less than output in treatment of hyponatraemia [4]
Oedematous states
SIADH
Renal failure
Psychogenic polydipsia
Why should you replace fluid slowly in hypernatremia
Risk of cerebral oedema (seizure / coma) as brain loses electrolytes quickly whilst lowering of other electrolytes and water occurs more slowly
What causes hypo phosphate [6]
Alcohol Acute liver failure DKA Refeeding Primary hyperparathyroid Osteomalacia
What are the consequences of hypophosphate [5]
RBC haemolysis WBC / platelet dysfunction Muscle weakness Rhabdomyolysis CNS dysfunction
What causes raised ALP physiological [3]
Growing child
Pregnancy
Healing fracture
What causes pathological raised [6]
Liver Osteomalcia Bone mets Pagets Renal failure Hyperparathyroid
What causes high Ca [2]
Bone mets
Hyperparathyroid
What causes with low Ca [2]
Osteomalacia
Renal failure
What are causes of hypocalcaemia
Vit D deficiency (osteomalacia) CKD Renal failure Hypoparathyroid (surgery / thyroiditis) Pseudohypoparathyroid (insensitive) Rehabdomyolysis Mg deficiency Massive blood transfusion Acute pancreatitis
What is calcium needed for
Muscle and nerve function
What does hypoca cause [5]
Tetany Parathesia Increased QT Trosseau Chvostek's
What is tetany [3]
Twitching
Cramping
Spasm
If chronic hypoca[2]
Depression
Cataracts
What is trousseau [2]
Carpal spasm when brachial artery occluded when BP cuff above systolic
Wrist flexion and fingers drawn in
What is Chvostek
Tapping facial nerve causes facial muscles to twitch
How do you treat hypoercalcaemia [3]
IV calcium gluconate 10ml 10% 10 minutes if severe
ECG
Treat cause
How do you treat hypercalcaemia [3]
Rehydration
Normal saline
3-4l per day
What can be used after [2]
Biphosphonates
Calcitonin - works quicker
What do you give if caused by sarcoid
Steroids
What can be used but careful
Loop diuretics if can’t tolerate fluid but may worsen other electrolyte imbalances
