Serum potassium, catecholamine levels and ECG during field block for inguinal hernia surgery.

Abstract

The purpose of this study was to find out whether hypokalaemia and associated ECG changes occur as a result of field block for hernial repair, alone or in combination with surgery. We recorded the ECG and measured the serum potassium and the plasma catecholamine concentrations at 10-min intervals in three groups of patients. In Group 1 (n = 7) and in Group 2 (n = 7), the blockade was instituted with prilocaine 0.5% and adrenaline 1:250,000, while in Group 3 plain prilocaine 0.5% was used. In Group 1 surgery was withheld for 40 min, while in Groups 2 and 3 surgery started as soon as the blockade became effective. There was a prolonged 4 to 5-fold elevation of the plasma adrenaline level from the adrenaline-containing solutions, the peak being 2.44 +/- 0.48 nmol/l (mean +/- s.d.) 10 min after the blockade had been instituted. The S-K level was unchanged in Group 1, while in Group 2 it decreased from 4.14 +/- 0.33 mmol/l to 3.91 +/- 0.29 at 60 min (P less than 0.05). An ECG pattern consistent with hypokalaemia did not develop. In Group 3, with plain prilocaine, there was a significant increase in the S-K level from 3.86 +/- 0.21 mmol/l to 4.08 +/- 0.36 at 40 min (P less than 0.05).