Effect of Dexmedetomidine on Lung Protection in Elderly Patients Undergoing Laparoscopic Surgery for Colorectal Cancer

The Second Affiliated Hospital of Chongqing Medical University64 enrolled

Overview

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.

Eligibility

Sex: ALLMin age: 60 YearsMax age: 85 Years

Medical Language ↔ Plain English

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.

Outcomes

Primary Outcomes

oxygenation index

oxygenation index is the ratio of partial pressure of O2 in arterial blood to fraction of inspired oxygen, namely PaO2/FiO2 ratio.

Time frame: When patients enter the operation room (T0), 5 minutes after completion of pneumoperitoneum and trendelenburg position (T1), 30 (T2) and 60 (T3) minutes after trendelenburg position, when extubate the endotracheal tube (about 30 min postoperatively, T4)

Secondary Outcomes

PaCO2

arterial carbon dioxide pressure assessed by arterial blood gas measurement.

EtCO2

end-tidal carbon dioxide pressure assessed by arterial blood gas measurement.

Time frame: 5 minutes after establishment of pneumoperitoneum and trendelenburg position (T1), 30 minutes after trendelenburg position (T2), 60 minutes after trendelenburg position (T3)

Pplat

plateau pressure (Pplat) is the end-inspiratory airway pressure and is measured just after airflow has ceased, which is displayed automatically on the anesthesia machine.

Time frame: 5 minutes after establishment of pneumoperitoneum and trendelenburg position (T1), 30 minutes after trendelenburg position (T2), 60 minutes after trendelenburg position (T3)

Ppeak

peak airway pressure is the highest pressure measured during the respiratory cycle and is a function of both the resistance of the airways and the compliance of the respiratory system, which is displayed automatically on the anesthesia machine.

Time frame: 5 minutes after establishment of pneumoperitoneum and trendelenburg position (T1), 30 minutes after trendelenburg position (T2), 60 minutes after trendelenburg position (T3)

lung compliance

lung compliance is defined as the change in lung volume for a unit change in transalveolar pressure, which is displayed automatically on the anesthesia machine.

Time frame: 5 minutes after establishment of pneumoperitoneum and trendelenburg position (T1), 30 minutes after trendelenburg position (T2), 60 minutes after trendelenburg position (T3)

Vd/Vt

Vd/Vt represents dead space ventilation, which is the volume of ventilated air that does not participate in gas exchange. Vd/Vt = 1.14 × (PaCO2-EtCO2) / PaCO2-0.005.

Time frame: 5 minutes after establishment of pneumoperitoneum and trendelenburg position (T1), 30 minutes after trendelenburg position (T2), 60 minutes after trendelenburg position (T3)

Qs/Qt

Qs/Qt is a measurement of pulmonary shunt. It describes the percentage of blood that reaches the left side of the heart without picking up oxygen. Qs/Qt = (CcO2 - CaO2) / (CcO2 - CvO2), where CcO2 = pulmonary end-capillary O2 content, same as alveolar O2 content, CaO2 = arterial O2 content, CvO2 = mixed venous O2 content.

PA-aO2

alveolar-arterial oxygen gradient measures the difference between the oxygen concentration in the alveoli and arterial system, which can be obtained from the arterial blood gas measurement.

SPO2

oxygen saturation refers to the amount of oxygen bound to hemoglobin in arterial blood.

Time frame: When patients enter the operation room (T0), 5 minutes after trendelenburg position (T1), 30 (T2) and 60 (T3) minutes after trendelenburg position, when extubate the endotracheal tube (about 30 min postoperatively, T4), postoperative day 1-3

Blood pressure

Systolic blood pressure, diastolic blood pressure, mean arterial pressure

hear rate

Lac

lactic acid in blood

Time frame: When patients enter the operation room (T0), 5 (T1), 30 (T2) and 60 (T3) min after trendelenburg position, and when the tracheal tube was extubated (T4)

WBC

White blood cell counting in blood