Electrolyte Imbalances Flashcards
Hypercalcaemia diagnosis?
Serum calcium concentration of 2.6 mmol/L or higher, on two occasions, following adjustment (correction) for the serum albumin concentration.
- Mild: 2.6-3
- Moderate: 3.01-3.4
- Severe: >3.4
What 2 conditions account for 90% of cases of hypercalcaemia?
- primary hyperparathyroidism
- malignancy e.g. lung, myeloma
How does malignancy cause hypercalcaemia?
- bone mets
- PTHrP from tumour eg. squamous cell lung cancer
- myeloma (increased osteoclastic bone resporption caused by local cytokines eg. IL-1 tumour necrosis factor, released by myeloma cells
Less common causes of hypercalcaemia?
sarcoidosis, vit D intoxication, acromegaly, thyrotoxicosis, milk-alkali syndrome, drugs, dehydration, Addison’s, Paget’s
What drugs can cause hypercalcaemia?
Thiazides, calcium-containing antacids
What is the key diagnostic investigation for hypercalcaemia?
PTH levels
How does hypercalcaemia present?
- bones, stones, groans and psychic moans
- corneal calfication
- HTN
- Bone pain
- Abdominal pain
- Renal stones
- Depression
- Drowsiness
- Confusion
- Muscle weakness
How is hypercalcaemia managed?
- IV Saline (3-4 L/day)
- IV Bisphosphonates
Referral if required. Consider stopping certain causative drugs and monitor response. Monitor symptoms. Lifestyle measures. ?monitor serum Ca, eGFR, creatinine, BMD, renal imaging if specialist advises.
What would you see on blood test results for hypercalcaemia secondary to malignancy?
- Raised calcium
- low PTH
- low phosphate
- raised PTHrP
Most common cause of hypercalcaemia in outpatients?
Primary hyperparathyroidism
What are plasma potassium levels regulated by?
Aldosterone, acid-base balance and insulin levels.
What causes hyperkalaemia?
- AKI
- ACE/Spironolactone
- Addisons
- Rhadbomyolysis
- Massive blood transfusion
- Metabolic acidosis
What drugs cause hyperkalaemia?
Potassium sparing diuretics eg. spironolactone, ACE in, angiotension 2 receptor blockers, ciclosporin, heparin
What can potentially cause hyperkalaemia in renal failure patients?
Beta blocks- interfere with potassium transport into cells.
How does heparin cause hyperkalaemia?
Inhibition of aldosterone secretion
Why is metabolic acidosis associated with hyperkalaemia?
Hydrogen and potassium ions compete with each other for exchange of sodium ions across cell membranes and in the distal tubule.
Foods high in potassium?
Bananas, oranges, kiwi, avocado, spinach, tomatoes. Salt substitutes (contain K instead of Na).
What is the classification for hyperkalaemia?
Plasma potassium level:
Mild - 5.5 - 5.9
Moderate: 6 - 6.4
Severe: >6.5
How does hyperkalaemia show on ECG?
- Tall T waves
- Absent p waves
- broad QRS
- Sinusoidal pattern
Untreated hyperkalaemia may cause what?
Life-threatening arrhythmias.
Precipitating factors eg. AKI and aggravating drugs eg. ACE i should be stopped in what?
Hyperkalaemia
What patients for hyperkalaemia should have emergency treatment?
All patients with severe hyperkalaemia (≥ 6.5 mmol/L) or with ECG changes
Overview of hyperkalaemia management
- Emergency management
- Then further management: TUC, stop exacerbating drugs eg. ACE in
- Then LOWER total body potassium
How is hyperkalaemia managed initially?
- IV Calcium gluconate (stabilise myocardium- does NOT lower K)
- Insulin/Dextrose solution (short term shift in K from ECF to ICF)
- Nebulised salbutamol