Decrease in serum potassium concentration during epidural anaesthesia

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Abstract
A mean decrease in the arterial serum potassium concentration (S‐K) of 0.40 mmol/1 (range 0–1.0) was found in 45 elderly men who were studied before and after induction of epidural anaesthesia (using mepivacaine 2% with adrenaline). The decrease was similar in patients who received acetated Ringer solution or dextran 40 in normal saline as intravenous fluid supplementation. No difference in S‐K change was found between patients with a normal (< 115 μmol/l) or elevated serum creatinine concentration. The decrease in S‐K prevailed at the end of surgery except in patients with an elevated serum creatinine. Corrections of S‐K for changes in arterial blood pH and rectal temperature during induction of anaesthesia did not explain the decrease in S‐K. Correlations of clinical parameters such as the extension of anaesthesia, amount of intravenous fluid given and blood pressure changes gave conflicting results. A smaller decrease or no change in S‐K was usually seen in arterial (n = 7) and venous (n = 7) samples when no intravenous fluid was given, as well as in venous samples when acetated Ringer solution was given (n = 6).