Pneumoperitoneum, the use of carbon dioxide, presents some disadvantages, including a risk of hypercarbia and respiratory acidosis during surgery in the respiratory system, and of an increased mean arterial pressure and systemic vascular resistance due to sympathetic excitation in the cardiovascular system. 10~15 mmHg intra-abdominal pressure is required in order to achieve a pneumoperitoneum, and increased abdominal pressure following a pneumoperitoneum causes hemodynamic changes leading to a reduced cardiac function by increasing the left ventricular end systolic wall stress and the right and left ventricular filling pressure, while decreasing the stroke volume and cardiac index. The author compared the intra-abdominal pressure necessary to achieve a pneumoperitoneum under deep muscle relaxation and medium muscle relaxation in ten patients undergoing laparoscopic surgery for colorectal cancer as part of preliminary research. The results showed that deep muscle relaxation, compared to medium muscle relaxation, was able to lower the intra-abdominal pressure by an average of 5.6 mmHg (13.2 ± 0.8 vs 7.6 ± 1.1) and the inspiratory pressure by an average of 8. Above all, even after lowering the intra-abdominal pressure with deep muscle relaxation, the surgeon was able to maintain a view almost identical to the one afforded by medium muscle relaxation. However, up until now, no reports have clearly indicated the change in pneumoperitoneum pressure, the patient's hemodynamic change, post-operative recovery, and surgical prognosis depending on the depth of muscle relaxation.Against this background, this study aims to identify the degree to which intra-abdominal pressure in laparoscopic colorectal surgery can be reduced by deep muscle relaxation, and the corresponding advantages this method presents in terms of physiological changes such as hemodynamic and respiratory system changes. In addition, the study intends to examine the difference between deep muscle relaxation and medium muscle relaxation in terms of surgical prognosis, including their effects on post-operative pain and on the patient's recovery of intestinal mobility.

Inclusion Criteria:

• Patients aged 19 to 80 scheduled to undergo laparoscopic colorectal or rectal surgery below the ASA class 3

Exclusion Criteria:

• Patients with neuromuscular disease/patients with a personal history or family history of malignant hyperthermia/patients with a serious heart, kidney (GFR < 60) or liver condition (ALT/AST > 100)/ patients who have had colorectal or rectal surgery/obese patients (BMI ≥35)