Electolytes Flashcards
Anion gap
(Sodium+potassium)-(chloride+bicarbonate)
Normal range 10-18
Metabolic acidosis - normal anion gap
renal tubular acidosis,
GI bicarbonate loss(diarrhoea, fistula, ureterosignoidostomy), drugs,
ammonium chloride injection,
Addison’s disease
Metabolic acidosis -raised anion gap
Lactate - type A: shock, hypoxia, burns - type B: metformin Ketones - DKA, alcohol Urate- renal failure Acid poisoning - salicylates, methanol
Metabolic alkalosis causes
Loss of hydrogen or gain of bicarbonate (Kidney/ GI tract)
- vomiting/ aspiration
- diuretics
- liquorice, carbenlxolone
- hypokalemia
- primary alderosteronism
- congential adrenal hyperplasia
- cushing’s syndrome
- bartter’s syndrome
Metabolic alkalosis mechanism
Activation of renin-angiotensin II- aldosterone system
Causes reabsorption of sodium in exchange for H+ in distal convoluted tubule
ECF depletion (vomiting, diuretics) -> na and cl loss -> activation RAA system -> Raised aldosterone levees
In hypokalemia, K shift into cells -> ECF. Shift of H into cells to maintain neutrality
Hyponatraemia
Due to water excess or sodium depletion
Psuedo hyponatriemia - hyperlipidemia or drip arm sample
Every 100mg/dL increase of blood glucose will lower Na 1.6meq
Hypertonic hyponatriemia
Plasma osmolality >290
Hyperglycaemia
Hypertonic mannitol
Isotonic hyponatriemia
Plasma osmolality 275-290 Pseudo hyponatriemia Sodium free irrigate solutes - hysterectomy - TURP
Hypotonic hyponatriemia (hypervolaemic)
Plasma osmolality <275 High ECF Interstitial fluid shift -congestive HF - cirrhosis - nephrotic syndrome - renal failure - sepsis - anaphylaxis - pregnancy
Hypotonic hyponatriemia (euvolaemic)
SIADH
- CNS disorders: haemorrhage, surgery, trauma, mass lesions, stroke
- pulmonary: infection, acute resp failure, positive pressure ventilation
- drugs
Hypothyroidism Malignancy Primary poly dips is Decreased Na intake (tea and toast, beer potomania) Secondary adrenal insufficiency
Hypotonic hyponatriemia (hypovolaemic)
- Cerebral salt wasting: haemorrhage, surgery, trauma
- Hypokalemia
- Renal sodium loss: diuretics, osmotic diuretics, primary adrenal insufficiency, salt wasting nephropathy, bicarbonaturia, ketonuria
- Extra renal sodium loss: diarrhoea, vomiting, blood loss, excess sweating, fluid sequestration (bowel obstruction, peritonitis, pancreatitis, muscle trauma, burns)
Hypernatremia
Dehydration
Osmotic diuretics Eg Hyperosmolar non ketotic diabetic coma
Diabetes insipidus
Excess IV saline
Potassium regulation
Aldosterone
Acid base balance
Insulin levels
Hyperkalaemia ECG changes
Tall tented t waves
Small p waves
Widened QRS
Sinusoidal pattern and asystole
Hyperkalemia
Metabolic acidosis (hydrogen and potassium compete for exchange with sodium across cell membrane in distal tubule)
Acute renal failure Drugs: K sparing diuretic, ace-I, cyclosporin Addisons Rhabdomyolosis Massive blood transfusion
Nb - beta blockers interfere with K transport into cells, potential cause in renal failure
Management hyperkalemia
IV calcium gluconate (stabilise cardiac membrane)
Insulin/dextrose, salbutamol men’s (shift extra cellular to intracellular)
Calcium resinous, loop diuretic, dialysis (remove potassium from body)
Hypokalemia with alkalosis
Vomiting
Diuretics
Cushing’s syndrome
conn’s syndrome (primary hyperaldosteronism)
Hypokalemia with acidosis
Diarrhoea
Renal tubular acidosis
Partially treated DKA
Acetazolamide
ECG features hypokalemia
U waves Small or absent T waves Prolong PR interval ST depression LoNg QT
Hypomagnesemia causes
Diuretics TPN Diarrhoea Alcohol Low K/Ca Cisplatin (NSCLC)
Hypomagnesemia features
Paraesthesja Tetany Seizures Arrhythmia Low PTH secretion -> low calcium ECG features similar to hypokalemia Exacerbates digoxin toxicity
Hypophosphatemia causes
Alcohol excess Acute liver failure DKA Refeeding syndrome Osteomalacia Primary hyperparathyroidism
Hypophosphatemia consequences
Red cell hemolysis
White cell and platelet dysfunction
Muscle weakness and rhabdo
CNS dysfunction
Hypocalcemia ecg
Prolonged QT
Trousseau’s sign
Hypocalcemia
Carpal spasm in brachial artery occluded
95% of people with low Ca
1% normal
Chvostek’s sign
Hypocalcemia
Less sensitive than Trousseau’s - 70%
10% normal Ca
Tapping over parotid causes facial muscles to twitch
Treat severe hypocalcemia
IV calcium gluconate 10ml of 10% solution over 10mins
ECG monitoring
Hypercalcemi
Most common malignancy (bone nets, myeloma, PTHrP from squamous lung)
Primary hyperparathyroidism
Differentiating MGUS and myeloma
Absence of complications -
Immune paresis, hypercalcemia and bone pain
Treatment hypercalcemia
Fluids
Bisohosphonates if malignancy, take 2-3days to work with maximal effect at 7days
Corticosteroids in sarcoidosis
