Pseudocholinesterase activity and atracurium v. suxamethonium block

Serum pseudocholinesterase activity in pregnant women was assayed spectrophotometrically using either propionylthiocholine or suxamethonium as substrate. All patients had a normal phenotype as indicated by normal dibucaine and fluoride numbers. However, the mean cholinesterase activity was lower than in the general population. There was a negative correlation between cholinesterase activity and the duration of neuromuscular blockade following suxamethonium, but no correlation was observed between the cholinesterase activity and the duration of block following atracurium.