The primary change in aging lung tissue among older people is atrophy, leading to a significant decline in ventilatory function. Intraoperative mechanical ventilation further decreases lung compliance and ventilatory function in elderly patients, making them more susceptible to respiratory dysfunction and postoperative pulmonary complications, which severely affects patient safety and postoperative recovery. Dexmedetomidine is a highly selective α2-adrenergic receptor agonist, and several studies have found that intravenous infusion of dexmedetomidine exerted lung protective effects during single-lung ventilation thoracic surgery. However, one study found that continuous intravenous dexmedetomidine infusion during low-temperature cardiac arrest aortic surgery did not improve perioperative respiratory mechanics and oxygenation. Therefore, this project aims to investigate the lung protective effects of continuous intravenous infusion of dexmedetomidine during laparoscopic surgery for elderly patients with rectal or sigmoid colon cancer.

As the body ages, all organs and tissues gradually undergo aging. Research has found that aging becomes increasingly significant after age 60, with the main change in pulmonary tissue aging being atrophy and a substantial decrease in ventilatory function. In elderly patients undergoing surgery, mechanical ventilation during surgery further reduces lung compliance, leading to an increased risk of respiratory dysfunction and postoperative pulmonary complications, which severely affect patient safety and postoperative recovery. Furthermore, due to its advantages, such as minimal trauma, less postoperative pain, and faster wound recovery, laparoscopic surgery has gradually become an essential surgical approach. However, during surgery, pneumoperitoneum and head-down position can cause diaphragmatic elevation, increased thoracic pressure, increased airway pressure, decreased lung compliance, and further aggravation of respiratory dysfunction and postoperative pulmonary complications. Therefore, exploring effective measures to protect the lungs during the perioperative period has always been a critical research direction for anesthesiologists.

Dexmedetomidine is a highly selective α2-adrenergic receptor agonist that mainly functions as a sedative and hypnotic, often used as an adjuvant in anesthesia. In recent years, some studies have found that intravenous infusion of dexmedetomidine during single-lung ventilation in thoracic surgery can play a lung-protective role by reducing the inflammatory response, improving oxidative stress, improving respiratory mechanics, increasing oxygenation, and reducing postoperative pulmonary complications. In obese patients undergoing laparoscopic sleeve gastrectomy, continuous intravenous infusion of dexmedetomidine can improve respiratory mechanics and increase oxygenation. However, some studies have also found that constant intravenous infusion of dexmedetomidine during chest aortic surgery with low-temperature cardiac arrest does not improve perioperative respiratory mechanics and oxygenation. In addition, it is unclear whether dexmedetomidine also has a lung-protective effect in elderly patients undergoing laparoscopic surgery in the head-down position.

According to the latest data statistics, the incidence and mortality of colorectal cancer rank among the top five malignant tumors globally, making it one of the primary cancers that endanger life and health. Although colorectal cancer is showing a trend toward younger age, it is still predominantly seen in elderly patients. Laparoscopic surgery for tumor resection is the primary treatment method, and during the surgery, a head-down position is required to expose the surgical field fully. As the head-down angle is the same for rectal cancer and sigmoid colon cancer laparoscopic surgery, this project focuses on elderly patients undergoing laparoscopic rectal or sigmoid colon cancer surgery. It explores the lung-protective effect of continuous intravenous infusion of dexmedetomidine during surgery, providing guidance for anesthesia management in this patient population.

Inclusion Criteria:

1. Patients undergoing elective laparoscopic surgery for rectal or sigmoid colon cancer.
2. American Society of Anesthesiologists (ASA) physical status classification I-III.
3. Age ≥60 years and <85 years.
4. Voluntary participation and ability to understand and sign the informed consent form.

Exclusion Criteria:

1. Patients with obesity (BMI>28 kg/m2)
2. Grade 3 hypertensive patients (systolic blood pressure ≥180 mmHg and/or diastolic blood pressure ≥110 mmHg)
3. Patients with acute coronary syndrome, sinus bradycardia (heart rate <45 beats/minute), II or III degree atrioventricular block, or NYHA heart failure class III or IV
4. Patients with a history of severe chronic obstructive pulmonary disease (COPD) (GOLD stage III or IV), severe or uncontrolled bronchial asthma, lung infections, bronchiectasis, thoracic deformities, and chest diseases (such as mediastinal tumors and thoracic tumors)
5. Pulmonary artery pressure ≥ 60 mmHg
6. Patients with Child-Pugh Class B or C liver function
7. Patients with stage 4 or 5 chronic kidney disease
8. Patients with hyperthyroidism, pheochromocytoma
9. Patients with hearing, intellectual, communication, or cognitive impairments
10. Patients who cannot cooperate with the study for any reason, or whom the investigator deems unsuitable for inclusion in this trial.

Individual participant data (IPD) will be available with the corresponding author when required.

The data will be available when published and kept for 5 years.

Researchers who provide a methodologically sound proposal.