This prospective, single-center, randomized controlled clinical trial aims to investigate the impact of intraoperative phrenic nerve stimulation (i.e., diaphragmatic neuromodulation) on postoperative complications in neurosurgical patients. The primary objective is to assess the effect on postoperative brain injury, including the development of delirium and changes in biomarkers. Additionally, the incidence of postoperative pulmonary complications will be investigated.

【Background】Postoperative complications, such as delirium and pulmonary complications, commonly occur in patients undergoing craniotomy. In preclinical studies, phrenic nerve stimulation (i.e., diaphragmatic neuromodulation) has been reported to effectively mitigate brain injury and pulmonary complications. However, its intraoperative administration and its impact on postoperative complications in this population are largely unknown.

【Method】In this prospective, single-center, randomized controlled clinical trial, patients receiving elective craniotomy will be screened. Eligible patients will be randomly divided into three groups: 1) Control group (without any interventions); 2) Intraoperative phrenic nerve stimulation (PNS) without total neuromuscular blockade (Train-of-Four (TOF) = 0); 3) Intraoperative PNS with partial neuromuscular blockade (TOF in the range of 1-2). Diaphragm ultrasound will be performed to assess diaphragm function before surgery and at 24 hours and 48 hours after surgery, respectively. Postoperative delirium will be assessed daily using the 3D-CAM and CAM-ICU within 3 days. Plasma biomarkers of brain injury will also be tested at baseline, 24 hours, and 48 hours after surgery. Pulmonary complications will be diagnosed by three independent clinicians based on laboratory tests, imaging, and clinical signs.

【Aims and Hypothesis】The primary aims are to investigate the impact of intraoperative diaphragmatic neuromodulation on brain injury, including the occurrence of delirium and changes in biomarkers. The secondary aims are the incidence of postoperative pulmonary complications and other clinical outcomes. We hypothesize that intraoperative diaphragmatic neuromodulation could reduce brain injury induced by craniotomy, as well as the incidence of postoperative delirium and pulmonary complications.

Inclusion Criteria:

• Age ≥ 18 years old;
• Body mass index ≤ 30 kg/㎡;
• American Society of Anesthesiologists Classification: I-II level;
• Patients who undergo elective supratentorial tumor resection surgery;
• Mechanical ventilation during operation ≥ 4h;
• Signed informed consent form;

Exclusion Criteria:

• With known respiratory diseases, such as chronic obstructive pulmonary disease, obstructive sleep apnea, asthma, etc.;
• History of respiratory infection within 6 months before surgery;
• Received invasive or non-invasive mechanical ventilation within 6 months;
• Contraindications to extracorporeal diaphragmatic pacemakers, such as pneumothorax, active pulmonary tuberculosis, and wearing a cardiac pacemaker;
• Diagnosis with neuromuscular dysfunction diseases such as Guillain-Barre syndrome, myasthenia gravis, muscle atrophy, etc.;
• Pregnant or lactating patients;
• Preoperative cognitive impairment, consciousness disorders.

During the study period, the investigator will set the intensity of the phrenic nerve stimulation, so the investigator will not be masked. However, patients who are enrolled in this study and assessors who assess the clinical outcomes will be masked.