Background: A cyclic relationship exists, between; arginine, citrulline, and ornithine. Arginase is a specific enzyme that plays a role in this relationship. This study aimed to elucidate the role of surgical trauma and anesthesia on plasma levels of the previous acids and nitric oxide (NO) and to determine whether the changes in these levels can be correlated to the duration of surgery and anesthesia exposure. Patients and methods: The study included: group A 41 patients who underwent coronary bypasses and group B 17 patients who underwent lung cancer surgery. The amino acid analyzer was used for the detection of amino acids, while NO was estimated by a Spectro-photometric method. Results: The study revealed a significant decrease in the intra-operative levels of arginine, citrulline, ornithine, and NO compared to their pre-operative levels in both groups. Conclusion: Depletion of these basic amino acids is possibly multifunctional and can be associated with an increase in arginase, surgical trauma, anesthesia, and stress.