Potassium (Hypo-hyperkalaemia)

What is Hypokalaemia?

Hypokalaemia refers to a serum potassium level < 3.5 mmol/L. It may be due to gastrointestinal loss, urinary loss, transcellular shift, or inadequate intake. Severe hypokalaemia (< 2.5 mmol/L) can cause life-threatening arrhythmias.

Primary Care Management

  • If potassium 3.0-3.4 mmol/L:
    • Recheck U&Es to confirm
    • Review symptoms: fatigue, cramps, palpitations
    • Start oral potassium (e.g. Sando-K 1-2 tablets BD/TDS)
    • Review in 3-7 days. Continue Sando-K for up to 2 weeks or until potassium normalises
    • Stop when potassium > 4.0 mmol/L and review the cause
    • Review medications (e.g. diuretics, steroids)
  • If potassium 2.5-2.9 mmol/L:
    • Urgent bloods including magnesium
    • If asymptomatic and well: start oral replacement + safety net
    • If symptomatic or comorbidities (e.g. heart disease): refer same day to secondary care
  • If potassium < 2.5 mmol/L or ECG symptoms (e.g. palpitations):
    • Same-day referral to hospital
    • Do not delay for oral replacement
    • Call ambulance if unwell, e.g. chest pain, collapse
  • Additional blood tests to consider in primary care:
    • Magnesium
    • Calcium
    • Renal function (U&Es)
    • Consider 9am cortisol if unexplained

Secondary Care Management

  • Repeat U&Es and check magnesium
  • Request ECG immediately (look for U waves, prolonged PR, flattened T)
  • Identify symptoms: weakness, cramps, arrhythmia, ileus, respiratory compromise
  • Review drug chart (diuretics, insulin, beta-agonists, amphotericin, steroids)
  • Monitor fluid balance and consider urinary potassium loss if unclear cause

Common Causes and Differentiation

  • Medications: diuretics (e.g. furosemide), steroids, insulin, beta-agonists
  • Hypomagnesaemia: impairs potassium reabsorption
  • GI loss (intestinal): vomiting, diarrhoea, NG suction
  • Renal loss: diuretics, hyperaldosteronism, tubular disorders
  • Increased intracellular uptake: insulin, alkalosis, refeeding, beta-agonists

Mild Hypokalaemia (3.0-3.4 mmol/L)

  • No ECG changes or symptoms
  • Start oral potassium replacement: e.g. Sando-K 2 tablets TDS
  • Aim for 40-60 mmol/day, titrate based on serum level
  • Recheck potassium in 1-2 days
  • Check and correct magnesium if low

Moderate Hypokalaemia (2.5-2.9 mmol/L)

  • Check ECG even if asymptomatic
  • If stable and tolerating oral meds: Sando-K 2 tablets QDS or liquid potassium
  • If unable to take orally or symptomatic: IV potassium via peripheral line 40 mmol in 1L NaCl over 4 hours
  • Monitor for burning/pain at IV site
  • Recheck potassium and ECG 4-6 hourly until stable

Severe Hypokalaemia (< 2.5 mmol/L or ECG changes)

  • Urgent senior review and ECG monitoring
  • Typical dose: potassium chloride in 1L of 0.9% saline over 4-6 hours
  • Consider continuous infusion (e.g. 60 mmol over 8-10 hours)
  • Always replace magnesium if low: IV MgSO4 20 mmol in 100 mL over 2 hours

Step 3: Monitor and Prevent Recurrence

  • Identify and treat the underlying cause (e.g. stop offending drug)
  • Maintain potassium with diet or supplements if needed
  • Repeat U&Es 4-6 hourly until stable, then daily
  • Monitor ECG if potassium < 3.0 or any cardiac symptoms

What is Hyperkalaemia?

Hyperkalaemia refers to a serum potassium level > 5.0 mmol/L. Levels > 6.0 mmol/L are considered moderate and > 6.5 mmol/L are severe. Immediate action is required to prevent life-threatening arrhythmias.

Stepwise Primary Care Approach

  • Step 1: Confirm diagnosis: repeat U&Es urgently to exclude spurious hyperkalaemia (e.g. haemolysis)
  • Step 2: Review medication: stop potassium-retaining drugs (e.g. ACE inhibitors, ARBs, spironolactone)
  • Step 3: Assess severity:
    • < 6.0 mmol/L: advise low-potassium diet, repeat U&Es in 2-3 days
    • 6.0–6.4 mmol/L: if well can repeat in 1 day or arrange urgent same-day review as they will an ECG (which may show peak T waves, wide QRS, VT or VF)
    • > 6.4 mmol/L or symptomatic: send to A&E via ambulance
  • Step 4: Safety netting: provide clear instructions on when to call 999 or return urgently (e.g. chest pain, dizziness)

Stepwise Secondary Care Approach

  • Step 1: Confirm diagnosis and ECG: check potassium urgently and repeat ECG
  • Step 2: Identify reversible causes:
    • Drugs: ACEi, ARB, spironolactone, trimethoprim, NSAIDs
    • Renal failure, metabolic acidosis, adrenal insufficiency
  • Step 3: Stabilise cardiac membrane (if ECG changes or K+ ≥ 6.5):
    • IV calcium (6.8 mmol): 30ml 10% Calcium Gluconate over 5mins, then rpt ECG then consider another dose if ECG changes persist (follow local guideline)
  • Step 4: Shift potassium into the cells and remove from body (after 15mins):
    • Start insulin-glucose IV: 10 units actrapid + 50 mL 50% dextrose over 15 min (follow local protocol)
    • if before treatment blood glucose is < 7.0 mmol/l > follow protocol or start 10% dextroze at 50ml/hr for 5hr after initial infusion
    • Then 10-20 mg salbutamol nebuliser stat
  • Step 5: Monitor:
    • Repeat U&Es every 1-2 hours
    • Continuous ECG monitoring until potassium < 6.0 mmol/L

Common Causes

  • Reduced renal excretion: AKI, CKD, ACE inhibitors, ARBs, spironolactone
  • Excess intake: potassium supplements, diet (rare unless renal impairment)
  • Cellular shift: metabolic acidosis, insulin deficiency, tissue breakdown (e.g. rhabdomyolysis)
  • Medications: potassium-sparing diuretics, NSAIDs, heparin, trimethoprim

Mild Hyperkalaemia (5.5-5.9 mmol/L)

  • Repeat sample to confirm
  • Stop any potassium-retaining medications
  • Consider loop diuretic (e.g. furosemide) if fluid overloaded
  • Dietary advice on potassium restriction
  • Monitor U&Es every 24-48 hours depending on risk

Moderate Hyperkalaemia (6.0-6.4 mmol/L)

  • Review for symptoms or ECG changes
  • If stable: administer oral calcium resonium 15 g TDS
  • Consider salbutamol nebulisers 10 mg stat
  • Recheck potassium 4-6 hours post-intervention
  • Refer to renal/acute medical team if persistent

Severe Hyperkalaemia (≥ 6.5 mmol/L or ECG changes)

  • Call medical registrar urgently
  • Administer IV calcium gluconate 10 mL of 10% over 5-10 mins
  • Follow with insulin-dextrose infusion (e.g. 10 units actrapid in 50 mL 50% glucose over 20 mins)
  • Add nebulised salbutamol 10 mg stat
  • Consider bicarbonate if acidotic and renal impairment
  • Monitor ECG and repeat U&Es hourly

Step 3: Monitor and Refer

  • Monitor U&Es closely (hourly if severe, then 4-6 hourly)
  • Review need for renal replacement therapy in refractory cases
  • Involve nephrology or critical care early if not responding
  • Always document medication changes and escalation steps
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