Brief Summary This clinical trial aims to evaluate whether perioperative goal-directed fluid therapy (GDFT) targeting a venous excess ultrasound (VExUS) score of 1 can reduce postoperative pulmonary complications (PPCs) in elderly patients undergoing McKeown minimally invasive esophagectomy (MIE). The study will also assess postoperative organ microcirculatory perfusion and quality of recovery.

Key research questions the trial seeks to answer include:

Does VExUS score-guided GDFT reduce the incidence of PPCs in elderly patients following McKeown MIE? Do participants receiving VExUS-guided GDFT achieve better clinical outcomes? Investigators will compare VExUS score-targeted GDFT with fluid therapy guided by the standard Vigileo-FloTrac™ system, to determine if the VExUS-guided approach reduces the occurrence of postoperative pulmonary complications in elderly patients.

Participant assessments and data collection include:

VExUS score assessment at four time points: preoperatively, after thoracic phase of surgery, after abdominal phase of surgery, and at the end of surgery. Concomitant measurements will include capillary refill time (CRT, in minutes), perfusion index (PI), blood lactate level (Lac, in mmol/L), and central venous oxygen saturation (ScvO₂, in percent).

Postoperative lung ultrasound score assessment. Recording of clinical outcomes including length of intensive care unit (ICU) stay (in days), postoperative hospital length of stay (in days), 30-day postoperative readmission rate due to pulmonary complications (in percent), and in-hospital postoperative mortality rate (in percent).

1. Background In China, esophageal cancer (EsC) is a common malignancy of the digestive tract, and surgery remains the primary treatment modality . Currently used esophageal tumor resection approaches include McKeown esophagectomy, Ivor Lewis esophagectomy, and Sweet esophagectomy, among others. Among these, thoracoscopic three-incision McKeown minimally invasive esophagectomy (McKeown MIE) offers advantages in lymph node dissection and is therefore one of the commonly used surgical approaches for esophageal cancer. Postoperative pulmonary complications (PPCs) are the most frequent type of complication following esophagectomy, accounting for 28.9%-50% of all complications , and have been demonstrated to be associated with in-hospital mortality , prolonged hospital stay, and increased medical costs .

   With the implementation of enhanced recovery after surgery (ERAS) protocols, perioperative fluid management in esophageal cancer surgery has become increasingly important. Inappropriate perioperative fluid volume is an independent risk factor for lung injury . Veelo et al. emphasized that goal-directed hemodynamic therapy can significantly reduce the incidence of postoperative pneumonia . In the absence of continuous hemodynamic monitoring, total intraoperative fluid infusion exceeding 5000 mL should be avoided in patients without ongoing blood loss . Inappropriate intraoperative blood transfusion increases the incidence of PPCs, elevates postoperative mortality, and leads to poorer long-term prognosis due to higher tumor recurrence rates .

   Therefore, perioperative fluid management is particularly critical in McKeown MIE. In patients undergoing this procedure, perioperative fluid overload can lead to: (a) increased capillary hydrostatic pressure, and (b) accumulation of excess fluid in the alveolar space, causing alveolar compression, collapse, and exudation, resulting in increased dead space ventilation and intrapulmonary shunt, which in turn induces pulmonary venous congestion and interstitial pulmonary edema. Conversely, inadequate fluid resuscitation may lead to insufficient organ perfusion, exacerbating organ injury such as acute kidney injury (AKI). The traditional "empiric fluid therapy" approach is gradually being replaced by goal-directed fluid therapy (GDFT). Thus, GDFT has become an important target for preventing PPCs in elderly patients undergoing McKeown MIE.

   GDFT aims to optimize end-organ perfusion and improve tissue oxygen delivery through precise fluid administration, thereby reducing the risk of PPCs. Existing GDFT strategies include fluid therapy based on dynamic hemodynamic parameters (Vigileo-FloTrac™), central venous pressure (CVP)-guided fluid therapy , perfusion index-guided therapy, and transesophageal echocardiography (TEE)-guided fluid therapy. However, compared with the Venous Excess Ultrasound (VExUS) score, these monitoring modalities cannot accurately and real-time reflect overall venous congestion, nor can they provide integrated monitoring of the matching between venous return driving pressure and right ventricular function.

   The VExUS score is an emerging bedside ultrasound-based volume quantification tool that evaluates important capacitance veins, including the inferior vena cava diameter, and the hepatic, portal, and renal veins. By comprehensively monitoring their vessel diameter, resistance indices, and Doppler waveforms, it provides a real-time, non-invasive, and direct reflection of the match between fluid therapy and patient status .

   Elevated venous pressure is associated with poor prognosis and prolonged intensive care unit (ICU) stay . This non-invasive assessment of venous congestion may become an important bedside tool for clinicians. This novel technique has several potential applications in the ICU , including guiding diuretic therapy in patients with cardiogenic shock and individualizing fluid resuscitation in patients with septic shock . Studies have demonstrated that VExUS-guided fluid therapy reduces circulation-related complications in patients undergoing major abdominal surgery and in those with heart failure. However, evidence regarding its application in elderly patients undergoing esophageal cancer surgery remains lacking. Elderly patients are characterized by reduced vascular elasticity, diminished renal functional reserve, and poor tolerance to fluid fluctuations. In elderly patients undergoing McKeown MIE, extensive surgical wounds, prolonged one-lung ventilation, and impaired pulmonary venous return increase the risk of pulmonary congestion. Fluid responsiveness and lung-protective strategies are closely related to fluid therapy. Therefore, the application of the VExUS score - a "cardiac congestion score" - in this patient population may effectively prevent PPCs.

   This randomized controlled trial aims to investigate the effect of perioperative GDFT targeting a VExUS score of 1 on postoperative PPCs in elderly patients undergoing McKeown MIE, with the goal of providing a more precise and safer fluid management strategy for this patient population. This study holds important clinical significance for reducing postoperative pulmonary complications, improving prognosis, and advancing perioperative fluid management concepts.

2. Objectives and Expected Outcomes 2.1 Objectives Primary Objective: To verify whether GDFT based on the VExUS score can reduce the incidence of PPCs in elderly patients after McKeown MIE, compared with classic Vigileo-FloTrac™ system-guided fluid therapy.

   Secondary Objectives: To explore the effects of VExUS score-based GDFT on postoperative lung ultrasound score (LUS), duration of postoperative mechanical ventilation, length of ICU stay, total length of hospital stay, 30-day readmission rate due to pulmonary complications, and in-hospital postoperative mortality in elderly patients undergoing McKeown MIE. Additionally, to identify important risk factors affecting postoperative pulmonary complications in this population within the framework of GDFT-based perioperative management.

   2.2 Expected Outcomes Through clinical intervention, data analysis, and synthesis, this study aims to clarify the efficacy of VExUS score-based GDFT in preventing pulmonary complications in elderly patients after McKeown MIE, and to develop a comprehensive understanding of the associated risk factors. These findings will provide an optimized perioperative fluid management strategy for this patient population, improve postoperative recovery and overall prognosis, offer a reference for early screening and future rational intervention in this high-risk group, and ultimately enhance the quality of postoperative recovery.

3. Study Design and Methods 3.1 Study Design This randomized controlled clinical trial strictly adheres to the Declaration of Helsinki [19] and employs a randomized, controlled, prospective design, following the ethical principles of clinical trials and the CONSORT guidelines for the conduct and reporting of randomized controlled trials. The study will be registered with the Chinese Clinical Trial Registry.

3.2 Study Population Ethical approval for this study will be submitted to the Ethics Committee of the First Affiliated Hospital of Chongqing Medical University. Patients scheduled to undergo thoracoscopic three-incision McKeown MIE will be recruited from the Department of Anesthesiology, the First Affiliated Hospital of Chongqing Medical University, from February 2026 to July 2026. An estimated total of 126 patients will be enrolled.

3.3 Allocation, Randomization, and Blinding Enrolled subjects will be allocated in a 1:1 ratio to the VExUS score-guided GDFT group (Group V) and the control group (Group C). Randomization will be performed using a permuted block design (block size of 4) by an independent researcher not involved in patient management, using SAS version 9.4 (SAS Institute Inc., Cary, NC, USA). Allocation concealment will be achieved using sequentially numbered, opaque, sealed envelopes. On the day of surgery, a research nurse not involved in anesthesia management or data collection will open the next envelope before induction and inform the attending anesthesiologist of the group assignment. All VExUS assessments will be performed by the same senior ultrasonographer to ensure procedural consistency. To preserve internal validity, the anesthesiologists managing intraoperative care, the postoperative outcome assessors, and the data analysts will all remain blinded to group allocation.

3.4 Study Methods and Procedures 3.4.1 Anesthesia Management All enrolled patients must provide written informed consent, and the study protocol must be approved by the hospital ethics committee. One day before surgery, the attending anesthesiologist will conduct a preoperative visit to assess the patient's baseline condition. Patients will undergo standard preoperative fasting for 6-8 h and abstain from clear liquids for 2 h. All patients will receive routine preoperative preparation with complete preoperative examinations. Blood pressure and blood glucose levels in patients with comorbidities such as hypertension and diabetes will be controlled within ranges appropriate for surgery.

Both groups will receive standardized anesthesia management as follows:

Anesthesia induction: Midazolam (0.03 mg/kg), etomidate (0.3 mg/kg), sufentanil (0.5 μg/kg), and rocuronium (0.6 mg/kg).

After induction, a double-lumen endotracheal tube or bronchial blocker will be placed for one-lung ventilation (OLV), and correct positioning will be confirmed by fiberoptic bronchoscopy. After the patient is repositioned to the left lateral decubitus position, a paravertebral nerve block (T4-T6) will be performed using 20 mL of 0.25% ropivacaine. All nerve block procedures will be performed by the same group of senior anesthesiologists.

Anesthesia maintenance: Remifentanil (0.05-0.2 μg/kg/min), propofol (4-6 mg/kg/h), sevoflurane (1-2%), with cisatracurium added as needed. Doses will be adjusted according to depth of anesthesia, with the bispectral index (BIS) maintained at 40-60.

At the time of transition from OLV to two-lung ventilation and at the end of surgery, thorough tracheal suctioning will be performed, followed by an alveolar recruitment maneuver (ARM) (30 cmH₂O for 30 s).

Patient-controlled analgesia (PCA): Sufentanil 2 μg/kg diluted with normal saline to a total volume of 100 mL, administered at a background infusion rate of 2 mL/h, with a bolus dose of 2 mL and a lockout interval of 15 min.

At the end of surgery, the double-lumen endotracheal tube will be exchanged for a single-lumen tube in the operating room, and patients will be transferred to the thoracic surgery ICU intubated. Spontaneous breathing will be allowed to recover, and tracheal extubation will be performed according to extubation criteria. The same anesthesiologist will be responsible for perioperative anesthesia management for all patients in this study; another staff member will collect all perioperative data. Postoperative pulmonary complications will be assessed by thoracic surgeons not involved in the surgery or anesthesia.

Lung-protective ventilation strategy: OLV tidal volume (VT): 4-6 mL/kg; respiratory rate (RR): 12-18 breaths/min; fraction of inspired oxygen (FiO₂): 50%-100% . The lowest driving pressure (ΔP) will be targeted at 10-15 cmH₂O: PEEP will be increased from 1 cmH₂O to 10 cmH₂O, with each PEEP level maintained for 10 respiratory cycles. The ΔP of the last respiratory cycle at each level will be recorded, and the PEEP associated with the lowest ΔP will be selected and maintained throughout OLV . PETCO₂ will be maintained at 35-45 mmHg, and SpO₂ > 95%.

3.7.2 Study Interventions

1. Control Group (Group C): GDFT guided by the Vigileo-FloTrac™ system (Edwards Lifesciences, USA). The radial artery will be cannulated and connected to the Vigileo-FloTrac™ system to monitor stroke volume variation (SVV) and cardiac index (CI). Maintenance fluids will be administered at 2-3 mL/kg/h. Targets: SVV: 10%-12%; CI: 2.5-4.0 L/min/m²; systemic vascular resistance index (SVRI): 1900-2400 dyn·s/cm⁵; CVP: 8-12 cmH₂O.

   When SVV > 12% and CVP < 12 cmH₂O, a colloid bolus of 3 mL/kg will be infused over 10 min for volume expansion. If, after volume expansion, SVV decreases to < 12% or CI fluctuation ≤ 10%, CI will be assessed: if CI > 2.5 L/min/m², reassessment will be performed after 5 min; if CI ≤ 2.5 L/min/m², dopamine will be infused at 3 μg/kg/min until CI > 2.5 L/min/m². If urine output < 0.5 mL/kg/h, 150-200 mL of fluid will be administered; if after 30 min urine output remains < 0.5 mL/kg/h, furosemide 10 mg will be administered intravenously until urine output reaches 0.5-1 mL/kg/h .

2. Experimental Group (Group V): VExUS scoring will be performed by an ultrasonographer proficient in ultrasound techniques (experience with > 100 cases and certified by the Chinese Medical Doctor Association Ultrasound Branch). Assessment time points: before surgery, after thoracic manipulation, after abdominal manipulation, and at the end of surgery.

Inclusion Criteria:

• Age between 65 and 80 years old
• Scheduled for elective McKeown MIE
• ASA physical status classification I to III
• Body mass index (BMI) between 18 kg/m² and 30 kg/m² (exclusive of 18 kg/m²)

Exclusion Criteria:

• Respiratory failure (SaO₂ < 60 mmHg and/or PaCO₂ > 50 mmHg)
• Severe cardiac dysfunction (NYHA class III-IV)
• Angina pectoris within the past 3 months or acute myocardial infarction (STEMI/NSTEMI) within the past 6 months
• Pulmonary hypertension (pulmonary artery systolic pressure, PASP > 35 mmHg)
• Moderate to severe tricuspid stenosis/regurgitation (valve orifice area < 1.5 cm² / vena contracta width ≥ 0.3 cm)
• Decompensated cirrhosis (Child-Pugh class ≥ B)
• Chronic kidney disease (CKD stage ≥ 3a) (estimated glomerular filtration rate, eGFR < 45 mL/min/1.73 m²)
• Cognitive impairment (Mini-Mental State Examination, MMSE < 27) and inability to cooperate with follow-up

The study protocol has been submitted for ethical approval to the Ethics Committee of the First Affiliated Hospital of Chongqing Medical University. A total of 126 patients scheduled for elective thoracoscopic three-incision radical esophagectomy (McKeown MIE) will be recruited from the Department of Anesthesiology, First Affiliated Hospital of Chongqing Medical University between February 2026 and July 2026.

Access to de-identified individual participant data (IPD) will be considered only when receiving legally valid, ethically approved requests that are in compliance with applicable data protection regulations and trial protocols.