Postoperative hyperamylasaemia in cardiac surgery.

The mechanism of postoperative hyperamylasaemia was studied in 48 patients undergoing coronary artery bypass grafting (CABG). Mild hyperamylasaemia developed in 87% of the patients, and in 10% the serum amylase activity was > 1000 U/l. Serial measurements of serum salivary (S-) and pancreatic (P-) isoamylases indicated that hyperamylasaemia was highest 24 hours after CABG and consisted mainly of P-amylase component. Serum creatinine, creatinine clearance and urinary albumin concentration remained normal after CABG, excluding severe renal damage. The fractional clearance (i.e. relative to creatinine clearance) of P-amylase decreased more than of S-amylase (from 3.6 to 0.9% vs 1.3 to 0.8%). Decreased rate of excretion into urine, rather than pancreatic cellular damage, is the main source of hyperamylasaemia after CABG.