19- hypokalemia

• Potassium


  • Most of the body's potassium is intracellular
  • Serum levels are controlled by: uptake of K+ into cells, renal excretion (controlled mainly by aldosterone), and extrarenal losses (e.g. gastrointestinal)
• Hypokalemia


  Serum K concentration of <3.5 mmol/L
• Causes of hypokalemia


  • Renal loss (diuretic treatment, steroids, hyperaldosteronism, Mg deficiency, metabolic alkalosis, DKA, RTA)
  • GI loss (diarrhea, vomiting, intestinal fistula, laxative abuse)
  • Shift into cells (alkalosis, increased insulin, beta adrenergic stimulation)
• Hypokalemia


  • Leads to problems with muscular contraction and cardiac conduction
  • May be asymptomatic
  • Presents with weakness, paralysis, loss of reflexes (never presents with seizures)
  • Increases the risk of cardiac arrhythmias, especially in patients with cardiac disease
• ECG findings in hypokalemia


  • U waves (most characteristic)
  • Ventricular ectopy (PVCs)
  • Flattened T waves
  • ST depression
• Hypomagnesaemia


  • Makes it difficult to correct hypokalemia
  • Mg levels should be checked and normalized
• Mild hypokalemia


  K 3.1-3.5
• Treating mild hypokalemia


  1. Treat the underlying cause

  2. Withdrawal of laxatives

  3. Assessment of diuretic treatment

  4. Replacement with oral KCl supplements
• Oral administration of potassium for mild hypokalemia

  10 to 20 mEq of potassium given two to four times per day (20 to 80 mEq/day)
• Severe hypokalemia


  K <2.5-3.0 and symptomatic (arrhythmias, marked muscle weakness, or rhabdomyolysis)
• Treating severe hypokalemia


  1. KCl given orally in doses of 40 mEq, three to four times per day

  2. Close monitoring every 2-4 hours
• Indications for intravenous infusion of potassium chloride

  • Hypokalemic diabetic ketoacidosis
  • Severe hypokalemia associated with cardiac arrhythmias or muscle weakness not responsive to oral treatment
• There is no maximum rate of oral potassium replacement
• IV potassium replacement can cause a fatal arrhythmia if it is done too fast
• Replacement rates of >20 mmol/hr should only be done with ECG monitoring & hourly measurement of serum K
• The maximum amount of K that can be given by a peripheral line is 40 mmol/L
• High concentrations (>60 mmol/L) should not be given through peripheral veins as they cause local irritation
• Ampoules of potassium should be mixed in sodium chloride 0.9%, avoid glucose solutions as they make hypokalemia worse