Effect of Low-flow CO₂ Insufflation on Hemodynamics in Gynecological Laparoscopic Surgery: A USCOM-based Randomized Controlled Trial

Technical Summary: Effect of Low-flow CO₂ Insufflation on Hemodynamics in Gynecological Laparoscopic Surgery

Problem Statement
Laparoscopic surgery is the standard approach for many gynecological procedures, relying on CO₂ pneumoperitoneum to create operative space. However, the resulting increase in intra-abdominal pressure (IAP) mechanically compresses major vessels (e.g., inferior vena cava), impairing venous return and reducing cardiac output (CO). While the impact of IAP levels is well-documented, the effect of the insufflation rate remains under-investigated. Current clinical practice often utilizes high insufflation rates (3–5 L/min) to expedite pneumoperitoneum establishment, but this may induce abrupt hemodynamic fluctuations, particularly in patients with limited cardiovascular reserve. Furthermore, traditional invasive monitoring methods pose risks (bleeding, infection) that limit their use in low-risk populations, creating a need for sensitive, non-invasive tools to capture dynamic hemodynamic changes during insufflation.

Methodology
This prospective, randomized, double-blind controlled trial was conducted at the Obstetrics and Gynecology Hospital of Fudan University.

• Participants: 50 patients (ASA physical status I–II, aged 18–45) scheduled for gynecological laparoscopic surgery under general anesthesia.
• Intervention: Patients were randomized into two groups (n=25 each):
  • Group A (Low-flow): CO₂ insufflation rate of 1 L/min.
  • Group B (Standard-flow): CO₂ insufflation rate of 5 L/min.
  • Control: Both groups maintained a target pneumoperitoneal pressure of 15 mmHg.
• Monitoring: The Ultrasonic Cardiac Output Monitor (USCOM) was used for non-invasive, real-time measurement of Cardiac Output (CO), Stroke Volume (SV), Systemic Vascular Resistance (SVR), and Heart Rate (HR).
• Time Points: Measurements were recorded at baseline (T0) and at specific IAP thresholds (3, 5, 7, 9, 11, 13, 15 mmHg), as well as upon positioning (T8) and at the end of surgery (T9).
• Analysis: Data were analyzed using two-way repeated-measures ANOVA to assess group-by-time interactions, with Holm–Šidák correction for multiple comparisons.

Key Results

• Hemodynamic Stability: Group A (1 L/min) demonstrated significantly better preservation of hemodynamic parameters compared to Group B (5 L/min).
  • Cardiac Output (CO) & Stroke Volume (SV): Group A maintained significantly higher CO and SV values at IAP levels of 9–15 mmHg (T4–T7) compared to Group B (all p < 0.05). At the end of surgery (T9), CO remained significantly higher in Group A (p = 0.043).
  • Systemic Vascular Resistance (SVR): Group A exhibited significantly lower SVR at T4–T7 compared to Group B, indicating reduced afterload stress.
  • Baseline Stability: In Group A, all hemodynamic parameters remained stable relative to baseline throughout the procedure. In contrast, Group B showed significant declines in CO and SV and significant increases in SVR at multiple time points.
• Heart Rate & Blood Pressure: No statistically significant differences were observed in Heart Rate (HR) or Mean Arterial Pressure (MAP) between the two groups at any time point.
• Surgical Efficiency & Safety: There were no significant differences between groups regarding operative duration, pneumoperitoneum duration, or intraoperative fluid volume. No serious adverse events occurred in either group, and the incidence of intraoperative hypotension, hypertension, or arrhythmia was comparable.

Key Contributions

1. Identification of Insufflation Rate as a Critical Variable: The study establishes that the speed of IAP elevation is a distinct physiological modifier, independent of the final pressure target. It demonstrates that a low-flow rate (1 L/min) mitigates the acute circulatory stress response associated with rapid insufflation.
2. Validation of USCOM in Laparoscopic Monitoring: The research successfully utilized USCOM to detect subtle, real-time hemodynamic differences (specifically in CO and SV) that conventional monitoring (HR, MAP) failed to reveal, highlighting the utility of non-invasive ultrasonic monitoring in gynecological anesthesia.
3. Clinical Optimization Evidence: The findings provide empirical support for adjusting insufflation protocols to prioritize hemodynamic stability without compromising surgical efficiency.

Significance and Claims
The paper concludes that a low CO₂ insufflation rate of 1 L/min effectively attenuates hemodynamic fluctuations during the establishment of pneumoperitoneum. Specifically, it preserves cardiac output and stroke volume while preventing excessive increases in systemic vascular resistance. The authors claim that this approach supports the individualized optimization of pneumoperitoneal parameters, aligns with Enhanced Recovery After Surgery (ERAS) principles, and enhances perioperative safety.

The study explicitly notes its limitations: the sample size was modest, and the population was restricted to healthy, young women (ASA I–II), limiting the generalizability of the findings to high-risk or elderly populations. Additionally, the study focused on intraoperative effects and did not assess long-term postoperative recovery outcomes. Consequently, the authors advocate for the adoption of low-flow insufflation in similar patient populations while calling for future research to validate these findings in broader, higher-risk cohorts.