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Potassium

For hypokalaemia click here

Hyperkalaemia in Primary Care

Click here for the full hyperkalaemia guideline

Definition

  • Mild          Hyperkalaemia 5.5 – 5.9 mmol/L: Needs review

  • Moderate Hyperkalaemia 6.0- 6.4 mmol/L: Needs urgent review or treatment

  • Severe     Hyperkalaemia ≥6.5 mmol/L or if ECG changes present: Severe, potentially life threatening - needs emergency treatment

Renal patients may be more tolerant of hyperkalaemia but in general if K ≥ 6.5 mmol/L urgent action is needed. Acute changes >0.5mmol/L in 6-12 hours may be more significant than absolute values.

Causes

The causes are often multifactorial and can include:

Factitious

  • Delay in reaching laboratory

  • Contamination with EDTA (FBC) in tube

  • Refrigeration

  • Haemolysis during venipuncture or excess cuff time

  • Drip arm

  • Thrombocytosis

  • Leukocytosis

 

Renal

  • Acute or chronic renal failure

  • Interstitial nephritis or tubular disease

  • Lack of aldosterone e.g. Addison’s disease, Congenital adrenal hyperplasia, RTA type 4

  • Drugs: ACE inhibitors, ARB, NSAIDs, Spironolactone

  • Advanced CCF

 

Redistribution

  • Acidosis

  • Diabetic ketoacidosis

  • Drugs: Beta blockers, digoxin

 

Excess potassium

  • Excess diet/ K supplements

  • Cell tissue breakdown e.g. rhabdomyolysis, haemolysis, tumour lysis, transfusion.

Investigations & Management in Primary Care

1. Assess severity and urgency

• Urgent referral to secondary care is recommended for patients with:

K ≥6.5mmol/L

Acute ECG changes and K ≥5.5mmol/L

Acute increase >0.5mmol/L in 6-12 hours

There is a risk of cardiotoxicity and sudden death with severe hyperkalaemia or those with ECG changes.

• All those with K ≥6.0mmol/L should have an ECG.

 

ECG may show bradycardia, P waves absent or PR prolongation, peaked T waves, widened QRS, VT or VF

 

Renal patients may be more tolerant of high potassium levels but if unsure about the need for admission in this group it is best to discuss with Renal Registrar (or Medical SpR out of hours).

 

2. Assess trend

Pseudohyperkalaemia is a common cause when there is an isolated rise in K or unexpected potassium result, especially where there are no ECG changes, symptoms or kidney disease.

• Discuss with Acute GP if uncertain but causes are listed below.

• An urgent repeat should be arranged when K ≥ 6.0mmol/L with an ECG (NB this can be done in the community if possible and doesn't in itself necessitate admission unless there is no way to obtain a repeat at a safe timescale)

• If there is a possibility of fragile blood cells (e.g. in CLL, thrombocytosis, leucocytosis, vasculitis) discuss with the lab (via ERCH switchboard) to send a whole blood potassium in lithium heparin tube.

• Check previous K results but if there is a rapid rise (K >0.5mmol/L in 6-12 hrs) an urgent referral to secondary care should be arranged as this is associated more strongly with conduction abnormalities.

3. Assess clinical situation

• Assess for any symptoms which include lethargy, nausea, muscle weakness or paraesthesia.

• ECG when K>6.0mmol/L

• Look for any possible causes of hyperkalaemia such as acute or chronic renal failure, DKA, oliguria (see below).

• Review diet for high K intake: banana, nuts, dried fruit, avocado.

• Review medications

Most commonly hyperkalaemia is due to medications so that the most common course of action is to withhold the likely drug and repeat potassium.

The following drugs are common causes: ACE inhibitors, ARB’s, NSAID’s, Aspirin, K sparing diuretics, Beta blockers and K containing laxatives (Movicol and Fybogel).

 

4. Investigations

Review recent results or organise appropriate tests:

• Look for evidence renal impairment (U&E)

• Look for evidence of acidosis (venous bicarbonate)

• Look for possible diabetes (Fasting glucose)

• If relevant consider DKA (urine ketones)

• Consider Addison’s if hyponatraemia and hyperkalaemia (9am Cortisol)

• Look for evidence of tissue damage (CK, LDH)

• Look for underlying condition that may increase cell fragility (FBC)

7. Monitoring

Mild Hyperkalaemia 5.5 – 5.9 mmol/L:

If eGFR has not increased >10% or no acute increase in K can repeat in 1-2 weeks

Review medications & diet for causes

Moderate Hyperkalaemia 6.0- 6.4 mmol/L

Recheck ASAP

If ECG changes admit

Stop medications that may elevate K

Severe Hyperkalaemia ≥6.5 mmol/L or if ECG changes present

Urgent repeat: Admit

 

The urgency of assessment and frequency of potassium monitoring will depend on individual circumstances.

 

 

References

1. North Bristol NHS Trust Blood Sciences: Dept of Biochemistry. Hyperkalaemia in primary care. Q Pulse Reference No: BS/CB/DCB/PROTOCOLS/40 Version NO: 9

2. Pathogenesis, diagnosis and management of Hyperkalaemia, Lehnhardt and Kemper. 2010

3. CREST Guideline for treatment of hyperkalaemia in adults. 2005.

4. Best practice in primary care; review. Smellie. J Clinical Pathology. 2007

5. A primary care approach to Na & K imbalance 2011. Kyle . BPAC

6. Patient Safety Alert – Resources to support safe and times management of hyperkalaemia, NHS Improvement, NHS/PSA/RE/2018/006; 2018

Patient.co.uk has a clear summary on hyperkalaemia

 

Hypokalaemia

 

Discuss with AGP if:

K+ <2.5 mmol/L.

 

Advice on management of mild-moderate hypokalaemia in primary care.