The Impact of Ventilator Synchrony on Muscle Relaxant Consumption and Surgeon Satisfaction During Laparoscopic Cholecystectomy.

Laparoscopic cholecystectomy creates significant physiological challenges due to CO₂ pneumoperitoneum, including 25-50% reduction in lung compliance, increased airway pressures, and cephalad diaphragm displacement [1,2]. Effective intraoperative management of mechanical ventilation is crucial in laparoscopic surgeries. These procedures often require adequate neuromuscular blockade to ensure optimal surgical conditions, minimize patient movement, and maintain a steady operative field (3). Pressure-Controlled Volume-Guaranteed (PCV-VG) mode of Ventilations is our institutional standard for laparoscopic cholecystectomy. PCV-VG is an innovative mode of ventilation that uses consistent tidal volume in a decelerating flow, without increasing airway pressures. PCV-VG offers the benefits of both VCV and PCV, while reducing the incidence of barotrauma, making it a safe ventilatory mode of choice in surgeries involving changes in respiratory dynamics. (4). However, during pneumoperitoneum, unsynchronized spontaneous breathing efforts provoke diaphragmatic movements that surgeons misinterpret as inadequate neuromuscular blockade, triggering unnecessary relaxant requests (5) which increase the risk of residual neuromuscular blockade, delayed recovery, and high healthcare costs (6,7). Adding synchronized ventilation modes, such as SIMV (Synchronized Intermittent Mandatory Ventilation), may mask partial paralysis by aligning with patient effort, reducing visible chest or diaphragmatic movements and enhance both patient safety and surgical access [5,8].

This study aims to investigate the Impact of adding SIMV Synchronization to our standard PCV-VG mode of ventilation on muscle relaxant consumption, the frequency of relaxant top-ups and surgeon satisfaction during Laparoscopic Cholecystectomy.

Laparoscopic cholecystectomy presents unique anesthetic challenges due to pneumoperitoneum-induced changes in respiratory mechanics. Recent literature has explored the role of ventilator modes, in influencing the need for neuromuscular blockade and surgeon satisfaction. Kim et al. (2020) demonstrated that PCV-VG improved gas exchange and respiratory compliance compared to traditional volume-controlled ventilation during laparoscopic surgery [1]. Similarly, Sukriti et al. (2023) found PCV-VG superior to both pressure-controlled and volume-controlled modes in maintaining better respiratory dynamics in laparoscopic cholecystectomy patients [4]. Furthermore, Park et al. (2022) highlighted how pneumoperitoneum alters thoracic compliance and increases the work of breathing. Their findings underscore the importance of tailored ventilator strategies that optimize patient-ventilator synchrony during laparoscopy [2].

A systematic review by Bruintjes et al. (2017) confirmed that deep NMB enhances laparoscopic surgical conditions and may improve surgeon satisfaction [3]. However, Brull and Murphy (2010) emphasized that deeper paralysis may increase the risk of residual neuromuscular blockade postoperatively if not properly monitored and reversed.[6] Ventilator-patient asynchrony may increase the requirement for both sedatives and neuromuscular blockers. De Wit et al. (2011) demonstrated that ineffective triggering during mechanical ventilation was associated with increased use of neuromuscular blockers [7]. Thus, synchronized modes that accommodate patient effort might reduce the need for deep muscle relaxation.

The most recent narrative review by Santana et al. (2024) reinforces the importance of individualized ventilator strategies during laparoscopic and robotic surgeries. The authors argue for the use of lung-protective ventilation and synchronization to enhance both patient safety and surgical access [5].

In summary, literature supports the concept that synchronized ventilator modes may reduce muscle relaxant consumption and improve surgeon satisfaction by optimizing respiratory mechanics and minimizing patient-ventilator asynchrony. Combined with appropriate neuromuscular monitoring and individualized ventilation strategies, these can enhance both laparoscopic surgical conditions and surgeon satisfaction ( 2.3) Knowledge Gaps

No previous studies have examined:

• Interaction between ventilator synchrony and NMB requirements.
• Impact of asynchrony on surgeon satisfaction metrics.
• Relaxant-sparing effects of optimized ventilation 3- Hypothesis
• Ventilator synchrony (PCV-VG+SIMV) reduces muscle relaxant consumption and improves surgeon satisfaction by minimizing the perception of inadequate paralysis. 4- Objectives
• Primary Objective.

1. Compare total intraoperative rocuronium consumption (mg/kg) between PCV-VG and PCV-VG + SIMV
2. To determine the frequency of additional muscle relaxant requests

• Secondary Objectives.

1. Surgical Conditions Assessement via Leiden-Surgical Rating Scale (Martini et al., 2014) (10)

• 1 = Extremely poor conditions
• 2 = Poor conditions
• 3 = Acceptable conditions
• 4 = Good conditions
• 5 = Optimal conditions 2. Residual Paralysis: TOF ratio <0.9 at PACU admission (Naguib et al., 2017) (11) 3. Ventilatory Mechanics: Peak pressure, dynamic compliance, PaO₂/FiO₂ 4. Recovery Metrics: Extubation time, PACU discharge readiness (Aldrete ≥9) (12) 5- Intraoperative complications or Challenges (gallbladder, bowel or vascular injuries, need for high insufflation pressure. Difficulty in gallbladder extraction or the need for extra trocar ports 5. Hemodynamics: MAP, HR, vasopressor requirements. 5- Methodology 5.1 Study Design
• Prospective randomized, double-blind, two parallel-groups controlled trial
• Setting: Operating rooms in King Fahad university Hospital
• Duration: Two years 5.2 Population Inclusion Criteria
• Adults aged 18-60 years undergoing elective laparoscopic cholecystectomy.
• ASA (American Society of Anesthesiologists) physical status I-II
• BMI 18-35 kg/m² Exclusion Criteria
• Severe COPD or restrictive lung disease
• Neuromuscular disorders
• Emergency surgery
• Morbid obesity 5.3 Randomization Patients will be randomly assigned to either the synchronized or non-synchronized ventilation group using a computer-generated sequence.

5.4 Blinding: There will be three group: group one (the anesthesiologist who will perform anesthesia and respond to the surgical requests, group two (the anesthesiologist who will design the specific anesthetic plan, and ventilator sitting and the third group (the anesthesiologist who will collect the research data) both group one and three as well as the surgeon are blind to the study design and group assignment. The group two anesthesiologist will leave the room and will not attend the surgery.

5.5 Intervention Groups

1. Non-Synchronized Group (Control): Ventilation managed using PCV-VG mode of ventilation.
2. Synchronized Group: Ventilation managed using PCV-VG plus SIMV (a mixed mode that supports patient-ventilator synchrony).

5.6 Ventilator Settings • Both groups will follow institutional protocols for initial ventilator settings, adjusted for tidal volume (6-8 mL/kg), accustomed respiratory rate, to maintain intraoperative normocapnia (EtpCO2 = 35-45 mmHg), PEEP = 5 cm H₂O, FiO2 =30-40%

5.7 Anesthesia Protocol

• Induction: Standardized use of propofol (2-2.5 mg/kg), and fentanyl (2mcg/kg) and an initial dose of rocuronium (0.6mg/kg).
• Maintenance: Balanced anesthesia with inhalational agents Sevoflurane (1.0 MAC)) and fentanyl infusion (1-2 mcg /kg/hr).
• Rocuronium top-up doses (0.1 mg/kg) to maintain the recommended level of relaxation for laparoscopic surgery (TOF = 1-2 twitches) [3,9], or upon surgeon request. 6-Data Collection Protocol

1. Primary Outcome:

• Total intraoperative muscle relaxant consumption (mg).
• Number of surgeon request for rocuronium top-up (0.1 mg/kg) due to:

1. Sustained diaphragmatic jerking (>5 sec) 2. Loss of surgical field exposure 3. Abdominal wall contraction 2. Secondary Outcomes:

• TOF ratio; Base line, postintubation, every 15 mins., at the time of each muscle relaxant request, at the conclusion of surgery \& before extubation.
• Asynchrony Index (AI): (%) = (Ineffective efforts + Double-triggering) / Total breaths × 100' (continues)
• Peak airway pressure /15 min
• Compliance /15 min
• Delivered tidal volume/15 min
• Surgeon satisfaction scores (Likert scale: 1-5). (13)
• Incidence of residual neuromuscular blockade (recurarization) in the PACU
• Vital signs /15 min (HR. NIBP, RR, and EtpCO2)
• Possible intraoperative complications or Challenges (gallbladder, bowel or vascular injuries, need for high insufflation pressure. Difficulty in gallbladder extraction or the need for extra trocar ports) 3. Patient demographics and surgical Data o Age, Sex, BMI, ASA status, and duration of surgery 7- Statistical Plan Sample Size Calculation If we assume the difference between the mean total dose of rocuronium between the control group and intervention group 35 mg., and a pooled standard deviation of 33 mg the study would require a sample size of 38 patients (19 patients for each group), to achieve a power of 90% and a level of significance of 5%. However, we will recruit 60 patients (30 in each group) in this study to compensate for any possible exclusion as well as to strengthen our ± statistical analysis.

Primary Outcome: Comparison of muscle relaxant consumption between groups using an independent t-test or Mann-Whitney U test (if non-normal distribution).

• TOF Ratios: Analyzed using ANOVA for repeated measures.
• Surgeon Satisfaction: Non-parametric tests (e.g., Wilcoxon rank-sum) for Likert scores.
• Categorical data: Categorical data: Chi-square/Fisher's exact
• Multivariate Analysis: for vital signs 8. Ethical Considerations
• Approval: Institutional Review Board (IRB)
• Consent: Written informed consent (Declaration of Helsinki)
• Data Safety: Anonymized storage.

1. Expected Outcomes \& Impact

• Anticipated Findings:
• 20-25% reduction in rocuronium with PCV-VG+SIMV
• Equivalent surgical conditions (Leiden scale ≥4/5)
• Lower residual paralysis (TOF <0.9 in 10% vs. 25%)
• Clinical Implications:
• Reduced NMB drugs \& related complications
• Cost savings from lower drug use
• Protocol for optimized ventilation in laparoscopy 9. Limitations
• Single-center design
• Surgeon subjectivity in Leiden scoring
• Generalizability to morbid obesity (BMI >35 excluded)