Hypokalemia from intercostal nerve block

Hypokalemia may arise from adrenergic stimulation during regional anesthesia. The authors studied the effects of adding epinephrine to the local anesthetic solution and of upper abdominal surgery on the hypokalemia following intercostal nerve block.

Intercostal block was induced with bupivacaine 0.5% in 10 female volunteers. Bupivacaine 0.5% with epinephrine 1:200,000 was used for another intercostal nerve block in the same volunteers and in eight women who had just undergone cholecystectomy. Plasma concentrations of potassium, epinephrine, glucose, and bupivacaine were measured and the ECG was recorded.

The decrease in the plasma potassium level during the experiment with plain bupivacaine was 0.10 +/- 0.09 mmol/L (mean +/- SEM). With bupivacaine and epinephrine, the decrease was 0.26 +/- 0.06 mmol/L in the volunteers and 0.58 +/- 0.07 mmol/L in the patients. After surgery the drug absorption was facilitated and the concentration-response relationship between epinephrine and potassium was maintained. The epinephrine-containing local anesthetic was associated with minor ECG changes.

The hypokalemic effect of intercostal nerve block with bupivacaine 0.5% and epinephrine 1:200,000 is doubled after upper abdominal surgery performed under general anesthesia.