Hypokalaemia

Introduction
Identification
Severity assessment
Management based on severity
Relevant history, examination
Investigations
Referral criteria
Discharge criteria
Treatment Algorithm

Introduction/ Description

Potentially life-threatening decrease in extracellular K⁺ concentration

Identification/recognition/diagnosis of problem

HypoK⁺ is often only retrospectively diagnosed.  Where prospectively diagnosed the cues were taken from the history and examination that pointed to the underlying cause.  Cause include:

• Excessive losses (Non-renal)
  • Vomiting, diarrhoea, laxative abuse
  • Gastro-intestinal fistula
  • Excessive sweating in dry environments with prolonged exertion
• Redistribution from extra- to intracellular:
  • Treatment of DKA (acute insulin administration)
  • Drugs: ß₂ Agonists, theophylline, caffeine, Amphotericin B, insulin overdose, decongestants, chloroquine overdose
  • Hyperaldosteronism – Primary or Secondary hyperaldosteronism (CCF, Hepatic insufficiency, Nephrotic Syndrome)
  • Hypokalaemic periodic paralysis
• Renal Potassium losses
  • Drugs: Diuretics - Thiazide diuretics > loop and osmotic diuretics
  • Distal Renal Tubular acidosis
  • Magnesium deficiency
  • Rare: Barrter, Gitelman and Liddle syndromes

Differential Diagnosis

• Bartter Syndrome
• Cushing Syndrome
• Hyperthyroidism
• Hypocalcaemia
• Hypochloraemic Alkalosis
• Hypomagnesaemia
• Metabolic Alkalosis

Severity assessment (Triage)

Management based on severity

Immediate action:

Non-drug treatment

• Stabilise using ABCs, perform blood glucose, apply oxygen if hypoxic and establish IV access
• Address acidosis and treat hypovolaemia or volume deficits with Isotonic fluids if present
• Discontinue all drugs that may cause or worsen HypoK⁺
• Look for underlying cause of HypoK⁺

Drug treatment

• Safe replacement rate = 10 mmol per hour.
• 20 - 40 mmol Potassium Chloride in 200 ml Saline 0.9% at 20 mmol/h (1 ampoule = 20mmol).  ALWAYS label fluid bag when adding K⁺

Note:High concentrations or more rapid administration should be done very carefully(preferably through a central line) with continuous cardiac monitoring. 

Maximum dose 40mmol/hour in arrest/ peri-arrest situation (usually given as 20mmol over30 minutes followed by review of K⁺ level)

• In suspected or proven Hypomagnesaemia states and refractory Hypokalaemia replace Magnesium as well. Give 1-2 g Magnesium Sulphate over 20 minutes in 50-200ml Normal Saline.  Don’t mix KCl and MgSO₄ in same bag
• Oral replacement:
  • Natural food sources: Dried fruit, Nuts, avocado, bananas, orange juice, white mushrooms, broccoli, spinach, French fries
  • Oral K⁺ preparations: Potassium Chloride 40-100 mmol/day for treatment and 20 mmol/day for prevention of HypoK⁺ (other preparations: Potassium Bicarbonate, Potassium Citrate, Potassium Phosphate)

Relevant history, examination

• May present with: fatigue, weakness, progress to paralysis, ileus. Usually unremarkable examination and any findings made will depend on the underlying cause.  General and systemic examination should be done to look for causes/ precipitants

Investigations

• Blood gas: the K⁺ level can usually be seen on the gas.  Look for a metabolic alkalosis as well
• ECG
• T waves flattened
• U waves
• Non-specific ST changes and T-wave inversion
• Cardiac arrest: PEA, Asystole

• Renal function: Look for HypoK⁺ and pre-renal failure
• Other investigations to be guided by the suspected underlying cause

Referral criteria

• Uncomplicated HypoK⁺ and HypoK⁺ due to reversible causes should be managed where presented.  Stabilisation and initial correction of HypoK⁺ is also required whilst awaiting transfer to referral unit when indicated.  Referral criteria include:
• Persistent HypoK⁺ despite optimal management
• Investigations as part of work-up not offered at current facility
• Conditions causing HypoK⁺ than can’t be manage at current facility
• If unsure whether to refer or not contact the Physician at your closest referring facility

Discharge criteria/checklist

• K⁺ Corrected
• Underlying cause found and treated/ corrected
• Drugs causing/ aggravating HypoK⁺ discontinued/ decreased
• Appropriate outpatient follow-up arranged
• Advise given on K⁺ containing foods: e.g. dried fruit, nuts, avocado, bananas, orange juice, white mushrooms, broccoli, spinach, French fries, etc.
• Consider oral K+ supplement for patients with very high risk of cardiac dysfunction/ arrhythmia

Treatment algorithm for the acute presentation of Hypokalaemia

References

Weiner DI, Wingo C. Hypokalemia – Consequences, causes and correction. J Am Soc of Neph 2012: 1179-1186

Cohn JN, Kowey PR, Whelton PK, Prisant M. New guidelines for Potassium Replacement in Clinical Practice. Arch Intern Med 2000;160:2429-2436

Rossiter D, Blockman M (eds.). South African Medicines Formulary. 11^th Ed. Cape Town: Health and Medical Publishing Group; 2014

Cameron P, Jelinek G, Kelly A, et al. Textbook of Adult Emergency Medicine. 4^th Ed. Elsevier; 2015

For further information on the drugs listed in the above guidelines, click on the drug name and you will be directed to the EMGuidance drug monograph.

Amphotericin B

Chloroquine

Magnesium Sulphate

Potassium Chloride

Theophylline