Mastectomy it is a very aggressive surgery with a high level of tissues trauma. Cortisol is a corticosteroid hormone directly involved in all responses to stress independently of the etiology. Plasmatic lactate results from the anaerobic metabolism developed when hypoxia and hypoperfusion are presented at the tissues. The study aimed to evaluate the differences between the plasmatic cortisol(Cort) and lactate(Lact) levels in patients submitted to total unilateral mastectomy with a scalpel blade(GS), CO2 laser(GL), and a mix of both techniques(GSL). A sample of 60 bitches underwent a total unilateral mastectomy was divided into 3 groups according to the incision technique: GS,GL,GSL. Plasmatic Cort and Lact levels were measured at the pre-and post-surgical time. Patient pain level, was measured with Melbourne Pain Scale (MPS). Significant differences were registered for the surgical time (p=0.041), for the Cort variation between T0T1(p=0.002), Lact variation between T0T1(p=0.032) and time to remove all the stitches(p=0.018), with the GL presenting lower values than GS and GLS. Cortisol variation was lower in the GL than in GS and GSL being associated with a minor surgical tissues trauma and consequently with a lower inflammatory reaction response. Plasmatic Lact variation was lower in GL and GSL than in GS, and no differences were registered between GL and GSL. Lower lactatemia values are associated with a lower level of tissues trauma.Surgical time and healing time were also shorter in the GL. CO2 laser promotes a surgery less bleeding, with a minor inflammatory reaction and lower pain level associated, which can be traduced by the lower variation of plasmatic cortisol and lactate levels, and a faster healing process.