The goal of this observational study is to measure the cognitive load (mental effort) of anesthesia nurses during real surgical procedures at Hospital Clínic de Barcelona, Spain. The main questions it aims to answer are:

• Does cognitive load vary across the three phases of anesthetic care (induction, maintenance, and emergence/recovery)?
• Is cognitive load higher during general anesthesia than during spinal anesthesia with sedation?
• How do surgical specialty and patient complexity relate to cognitive load?
• How does monitor alarm perception relate to cognitive load during surgery?

Participants (anesthesia nurses) will complete the NASA Task Load Index (NASA-TLX) questionnaire - a validated 6-item tool measuring mental effort - three times per surgical case: after induction or spinal block, during maintenance, and after patient awakening or sedation reversal. They will also answer 4 brief questions about alarm management at the end of each case. No changes are made to clinical care. Participation adds approximately 11 minutes per surgical case.

Anesthesia nurses manage up to 72 tasks per hour during surgical procedures, including vital sign monitoring, drug administration, airway management, alarm response, and surgical team coordination. Despite this high workload, the cognitive load of anesthesia nurses has received little scientific attention. Most studies focus on simulation rather than real clinical settings.

This prospective observational study uses the Raw NASA Task Load Index (NASA-TLX) to quantify subjective cognitive load in anesthesia nurses across three phases of anesthetic care (T1: post-induction/spinal block; T2: maintenance; T3: extubation/wake up), comparing general anesthesia (endotracheal intubation or laryngeal mask) versus spinal anesthesia with sedation. Additionally, an exploratory module examines nurses' perception and management of monitor alarms and its association with cognitive load.

This is the first European study to measure cognitive load in anesthesia nurses using a validated instrument in a real surgical setting.

Inclusion Criteria:

• Registered nurse anesthetist actively working at Hospital Clínic de Barcelona.
• Minimum 3 months in the current anesthesia nursing position.
• Voluntary participation with signed informed consent.
• Scheduled surgery (including deferred urgent surgery) or solid organ transplantation.
• General anesthesia (endotracheal intubation or laryngeal mask airway) or spinal anesthesia with sedation.
• Minimum duration of 30 minutes.

Exclusion Criteria:

• Refusal to participate or withdrawal of informed consent.
• Spinal anesthesia without sedation.
• Exclusive regional anesthesia without sedation.
• Sedation alone without regional technique.
• Duration less than 30 minutes.
• Cases involving an unexpected intraoperative emergency requiring urgent additional personnel.
• Cases started under spinal anesthesia converted to general anesthesia for any clinical or technical reason.

Registered nurse anesthetists actively working at Hospital Clínic de Barcelona, a university tertiary care hospital, assigned to the following operating rooms: main surgical block, ambulatory surgery unit (CMA), interventional radiology suite (RIO), DIVAS intraoperative radiotherapy unit, and transplant operating room.

Individual participant data (IPD) to be shared includes the anonymized case-level dataset containing: NASA-TLX subscale scores (T1, T2, T3), surgical case characteristics (anesthetic technique, surgical specialty, ASA, duration), and exploratory alarm management variables (VAS, P1, P2, P3). Participant-level data (experience, training) will be included in anonymized form. No directly identifiable information will be shared.

IPD and supporting documents will be available starting 6 months after publication of the primary results article (estimated 2027-2028) and will remain available for 5 years.

IPD will be available upon reasonable request to the principal investigator (vcaro@clinic.cat). Requestors must provide: (1) a brief description of the proposed use, (2) institutional affiliation, and (3) agreement to data use conditions. Data will be shared as anonymized datasets in CSV format. No individual participant can be identified from the shared data.