Diuretic-induced hypokalaemia, pancuronium neuromuscular blockade and its antagonism by neostigmine.

The effect of hypokalaemia on a neuromuscular blockade induced by pancuronium and its antagonism by neostigmine was studied in the cat anterior tibialis-peroneal nerve preparation using the constant infusion of pancuronium technique. Hypokalaemia was induced by chronic administration of chlorothiazide. The infusion rate of pancuronium required to maintain a 90% depression of twitch tension was reduced from 0.72 +/- 0.06 microgram kg-1 min-1 in the cats with a normal serum concentration of potassium (K+ = 4.4 +/- 0.2 mmol litre-1; n = 7) to 0.41 +/- 0.07 microgram kg-1 min-1 in the hypokalaemic cats (K+ = 2.3 +/- 0.1 mmol litre-1; n = 8). The dose of neostigmine necessary for 50% antagonism of the pancuronium-induced depression of twitch tension (ED50) was 10.0 microgram kg-1 in the cats with a normal potassium concentration and 18.5 microgram kg-1 in hypokalaemic cats. We conclude that hypokalaemia decreases the dose of pancuronium required for neuromuscular blockade and increased the dose of neotigmine required for antagonism of the block.