DIURETIC-INDUCED HYPOKALAEMIA, PANCURONIUM NEUROMUSCULAR BLOCKADE AND ITS ANTAGONISM BY NEOSTIGMINE

The effect of hypokalaemia on a neuromuscular blockade inducedby pancuronium and its antagonism by neostigmine was studiedin the cat anterior tibialis-peroneal nerve preparation usingthe constant infusion of pancuronium technique. Hypokalaemiawas induced by chronic administration of chlorothiazide. Theinfusion rate of pancuronium required to maintain a 90% depressionof twitch tension was reduced from 0.72 ±0.06 µgkg^–1 min^–1 in the cats with a normal serum concentrationof potassium (K⁺ = 4.4±0.2 mmol litre^–1; n = 7)to 0.41±0.07 µg kg^–1 min^–1 in the hypokalaemiccats (K⁺ = 2.3±0.1 mmol litre^–1; n = 8). The doseof neostigmine necessary for 50% antagonism of the pancuronium-induceddepression of twitch tension (ED₅₀) was 10.0 µg kg^–1in the cats with a normal potassium concentration and 18.5 µgkg^–1 in hypokalaemic cats. We conclude that hypokalaemiadecreases the dose of pancuronium required for neuromuscularblockade and increases the dose of neostigmine required forantagonism of the block.