Cardiopulmonary bypass-associated pulmonary injury is a common complication after infant cardiac surgery and may contribute to impaired oxygenation, prolonged mechanical ventilation, and longer intensive care stay. Lidocaine has anti-inflammatory and membrane-stabilizing properties and may attenuate perioperative lung injury. This investigator-initiated, randomized, placebo-controlled, double-blind trial will evaluate whether perioperative intravenous lidocaine reduces postoperative pulmonary injury in infants undergoing corrective non-palliative congenital cardiac surgery with cardiopulmonary bypass.

Infants undergoing cardiac surgery with cardiopulmonary bypass are at risk of postoperative pulmonary injury due to systemic inflammatory activation, ischemia-reperfusion injury, and disruption of the alveolar-capillary barrier. Intravenous lidocaine has been reported to exert anti-inflammatory, anti-arrhythmic, and potential organ-protective effects. However, evidence in infants undergoing cardiac surgery remains limited.

This randomized, double-blind, placebo-controlled superiority trial will enroll infants aged 0 to 12 months scheduled for corrective, non-palliative congenital cardiac surgery with cardiopulmonary bypass at a tertiary pediatric center. Participants will be randomized in a 1:1 ratio to receive either perioperative intravenous lidocaine or volume-matched normal saline placebo. The trial will assess postoperative pulmonary injury severity over the first 72 hours after surgery, together with respiratory, laboratory, echocardiographic, and safety outcomes until postoperative day 7 or at discharge.

Inclusion Criteria:

1. Infants aged 0 to 12 months.
2. Congenital heart disease requiring corrective, non-palliative cardiac surgery with cardiopulmonary bypass.
3. American Society of Anesthesiologists (ASA) physical status I to III.
4. Written informed consent provided by parent(s) or legal guardian(s).

Exclusion Criteria:

1. Multiple malformations, chromosomal abnormalities, or immunodeficiency.
2. Known or suspected allergy to lidocaine.
3. Concomitant continuous infusion of another local anesthetic.
4. Conditions associated with increased risk of lidocaine accumulation or toxicity, including severe conduction block or severe bradycardia.
5. ASA physical status IV or higher.
6. Severe malnutrition expected to substantially impair postoperative recovery.
7. Severe hepatic or renal dysfunction.
8. Significant pre-existing pulmonary disease or markedly impaired preoperative pulmonary function.
9. Central nervous system disorders that may increase susceptibility to lidocaine neurotoxicity, including epilepsy or prior central nervous system infection.
10. Use of medications that may interact with lidocaine or constitute an exclusion, including class I or class III antiarrhythmic agents, cimetidine, or antiviral drugs, as determined by the clinical team.
11. Current or recent participation in another interventional clinical trial in its active intervention phase.

Participants, parents/guardians, treating clinicians, investigators, and outcome assessors/statisticians will remain blinded to treatment allocation. Study medication will be prepared by designated anesthesia staff not involved in outcome assessment.