Effect of Neuromuscular Block Depth on Driving Pressure and Postoperative Respiratory Events in Abdominal Surgeries

Patients will be randomized into two groups:

Deep neuromuscular blockade group (TOF count 0, PTC 1-2) Moderate neuromuscular blockade group (TOF count 1-2) Driving pressure (Plateau pressure - PEEP) will be recorded intraoperatively. Postoperative critical respiratory events will be assessed within 30 minutes in the post anesthesia care unit (PACU).

• Rocuronium (Drug): Rocuronium will be administered intravenously as bolus and continuous infusion to achieve target neuromuscular blockade depth according to group allocation. Neuromuscular function will be monitored using quantitative TOF monitoring.

Primary outcomes

• Mean Intraoperative Driving Pressure [From immediately after intubation until the end of surgery (intraoperative period)]: Driving pressure will be calculated as plateau pressure minus positive end-expiratory pressure (PEEP) during volume-controlled ventilation. Measurements will be recorded at 30-minute intervals throughout surgery, and the mean value per patient will be calculated.

Secondary outcomes

• Incidende of Postoperative Critical Respiratory Events [From immediately after extubation and until 30 minutes after arrival to PACU]: Critical respiratory events (CRE) include hypoxemia (hemoglobin oxygen saturation < 90%), hypoventilation (respiratory rate < 8 breaths/min or arterial carbon dioxide tension > 50 mmHg) or upper-airway obstruction (stridor or laryngospasm) requiring an active and specific intervention (ventilation, tracheal intubation, opioid or muscle relaxant antagonism, insertion of oral/nasal airway or airway manipulation).

Sex: All, ages: 18 Years to any, accepts healthy volunteers

Inclusion Criteria:

* Elective abdominal surgery under general anesthesia that is expected to last longer than one hour
* ASA I-II-III
* Age ≥18 years
* Written informed consent

Exclusion Criteria:

* Refusal to participate in the study
* ASA ≥ IV
* Age <18
* Obesity (BMI>30) and cachexia (BMI <18)
* Laparoscopic surgery
* Emergency procedure
* Allergy to drugs used during induction and maintenance of general anesthesia
* Presence of psychiatric/neurologic/neuromuscular disease
* Risk of malignant hyperthermia or having any relative with history of malignant hyperthermia
* Use of medications that may affect neuromuscular function (anticonvulsants, aminoglycosides, magnesium salts, etc.)
* Pregnancy
* Presence of advanced chronic lung disease (asthma, COPD, etc.)
* Presence of advanced liver and renal disease (creatinine>1.6, liver function tests above twice the normal range)

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