Hyperlactacidemia in Major Abdominal Surgery and Monocarboxylate Receptors

The goal of this clinical trial is to identify those situations in which the increase of lactate levels is not clinically relevant since it is associated with altered genetic polymorphism of the genes involved in the membrane proteins acting as carriers for lactate (mainly monocarboxylate transporters, MCTs) patients undergoing major abdominal surgery. The main questions it aims to answer are: 1. Is there a relationship between the lactate levels in the immediate post-operative period and the presence of some lactate receptor polymorphisms? 2. Can hyperlactacidemia related to lactate receptor polymorphisms affect length of stay in the recovery room and/or in intensive care unit, postoperative hospital stay, postoperative complications? - Which are the risk factors for hyperlactacidemia in the immediate post-operative period in addition to the presence of lactate receptors polymorphisms? Participants will undergo pre-operative genomic assay testing.