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Hypokalemia: Periop mgmt

Hypokalemia is an electrolyte imbalance that may be present in elderly patients with salt-wasting alkalosis or in patients who chronically use diuretics. Risks associated with hypokalemia include hypomagnesemia, EKG changes including increased P wave height, prolonged PR intervals, QT prolongation, shortened or flattened T waves, T wave inversion, ST depression and U Waves (see figure below). By extension, patients with hypokalemia are at an increased risk of arrhythmias including Torsades De Pointes, ventricular tachycardia, ventricular fibrillation, weakness, ileus, metabolic alkalosis, and confusion.

To correct these abnormalities, the acuity or chronicity of the imbalance must be established. Patients with long-term use of diuretics or with salt-wasting syndromes have a more chronic abnormality and may not need immediate treatment. EKG changes in the above pattern can guide the physician regarding the necessity to correct the abnormality and how quickly to correct it. This would ideally be done in a pre-operative clinic, well ahead of any scheduled surgery along with other cardiac risk stratification and correction of other electrolyte abnormalities.

In patients who have no symptoms or other significant risk factors with a potassium level ≥ 3.0 mmol/mL and a magnesium level ≥ 0.5 mmol/mL, there should be no need for delays (with consideration of a level of 2.2 mmol/mL of potassium if patient has very limited risk factors). If magnesium level is ≤ 0.5 mmol/mL, then potassium levels should ideally be ≥ 3.3 mmol/mL. Rapid correction of the electrolyte is not recommended immediately pre-operatively in stable patients due to the associated risks of arrhythmia and arrest. However, in patients with a history of coronary artery disease, serum potassium level ≤ 3.5 mmol/L has been independently associated with perioperative mortality, and should be corrected, especially if EKG findings or other cardiac risks (or cardiac surgery) are planned or present.

Other References

  1. New guideline for perioperative management of people with inherited salt-wasting alkaloses Link
  2. Preoperative Serum Potassium Levels and Perioperative Outcomes in Cardiac Surgery Patients Link
  3. Image Credit: Reddy, P. June 20, 2014. Slideshare: Hypokalemia, Slide 32. Link