Preoperative evaluation of a 58-year-old man for elective inguinal hernia repair shows the following values. Which result is an indication to postpone surgery and correct the abnormality first?

• A Serum potassium 3.0 mEq/L ✓
• B Serum sodium 133 mEq/L
• C Serum bicarbonate 23 mEq/L
• D Serum magnesium 1.8 mg/dL

Explanation

Elective surgery is generally deferred when serum potassium falls below about 3.5 mEq/L, because hypokalaemia potentiates arrhythmias, sensitises the myocardium to digoxin toxicity, and augments non-depolarising muscle relaxant effect. Mild hyponatraemia at 133 mEq/L, a normal bicarbonate, and borderline low magnesium at 1.8 mg/dL do not by themselves mandate postponement of a minor elective procedure. Potassium should be replaced and its cause addressed before anaesthesia.

Reference: Morgan and Mikhail's Clinical Anesthesiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.