Rapid sequence induction (RSI) is a standard anesthesia technique used in patients at risk of aspiration. Although tracheal intubation following RSI is a frequent and painful procedure, no study has yet evaluated nociception using the Analgesia Nociception Index (ANI) during this procedure.

This monocentric prospective observational study aims to describe the impact of RSI on pain measured by ANI, and to explore early complications (desaturation, hypotension, regurgitation) and factors associated with pain and complications. 150 patients undergoing RSI in the visceral surgery operating room at CHPG Monaco will be analyzed.

Background: RSI is a standard technique in anesthesia, primarily used to minimize the risk of aspiration. European guidelines leave the choice of hypnotic and neuromuscular blocking agent to the practitioner; the role of analgesics is not addressed. RSI induces sympathetic reactions linked to intense painful stimulation. Several monitors enable nociception assessment during general anesthesia, including in paralyzed patients (ANI, NOL, SPI). To date, no study has explored pain using the Analgesia Nociception Index during RSI.

Hypothesis: Rapid sequence induction induces sympathetic reactions associated with intense painful stimulation, which can be quantified using ANI.

Primary objective: To describe the impact on pain monitored by ANI of rapid sequence induction in anesthesia.

Secondary objectives: (1) Describe early complications (desaturation, hypotension, regurgitation); (2) Explore factors associated with pain; (3) Explore factors associated with complications.

Methods: Prospective monocentric observational cohort study, in routine care, with no additional examinations beyond standard management. Patients are monitored according to Société Française d'Anesthésie et de Réanimation (SFAR) guidelines, with additional non-invasive cutaneous electrodes placed on the right pectoral area for ANI monitoring. Induction begins after preoxygenation of at least 3 minutes. Induction drugs are at the discretion of the anesthesiologist. A timer is started at injection of the first induction drug (T0). Hemodynamic and ANI parameters are recorded during the first 5 minutes.

Data collected: date of intervention, age, sex, ASA score, Mallampati score, Cormack classification, preoperative analgesics (paracetamol within 4h, nefopam, tramadol, morphine, ketoprofen), induction drugs (hypnotic: propofol/etomidate/ketamine; opioid: remifentanil/alfentanil/sufentanil; neuromuscular blocker: succinylcholine/rocuronium), heart rate and systolic/diastolic blood pressure (T preO2, T1min, T3min, T5min), ANI and SpO2 (T preO2, minimum value <5min), intubation device (McGrath / Airtraq / direct laryngoscopy), time between neuromuscular blocker injection and cuff inflation, presence of postoperative sore throat at 24h.

Statistical analysis: descriptive analysis of patient characteristics; mixed models for evaluation of variables over the 5 minutes post-RSI; multivariate models to identify associated risk factors. Two-sided p-values <0.05 will be considered statistically significant. Analyses performed with R software.

Follow-up duration: 24 hours per patient. Total inclusion period: 24 months.

Inclusion Criteria:

• Age >= 18 years
• Patient requiring tracheal intubation after rapid sequence induction in the visceral surgery operating room
• Pain monitoring by Analgesia Nociception Index (ANI) as part of general anesthesia

Exclusion Criteria:

• Patient with atrial fibrillation at the time of intubation following rapid sequence induction
• Patient on long-term beta-blocker therapy

Patient requiring tracheal intubation after rapid sequence induction

Data are fully anonymized and collected in a routine care context; individual participant data will not be shared