Sugammadex for preventIoN oF pOst-operative pulmoNary complIcAtions (SINFONIA): protocol for an embedded mixed-methods process evaluation.

BACKGROUND

The Sugammadex for preventIoN oF pOst-operative pulmoNary complIcAtions (SINFONIA) trial is a multi-centre, pragmatic, randomised superiority trial comparing sugammadex with neostigmine to reverse neuromuscular block after major abdominal or thoracic surgery. Neuromuscular blocking agents are routinely administered during general anaesthesia to facilitate intubation, ventilation, and surgical access. Residual neuromuscular block remains common despite reversal and is associated with increased risk of post-operative pulmonary complications. Sugammadex reduces residual paralysis compared with neostigmine, but its effect on patient-centred outcomes remains uncertain, and clinical equipoise persists. As intervention delivery is embedded within complex intra-operative decision-making, variation in implementation may influence trial outcomes. An embedded process evaluation will characterise intervention delivery and identify contextual and organisational factors influencing implementation across sites. This protocol describes the rationale, aims, and methods of the SINFONIA process evaluation.

METHODS

This embedded mixed-methods process evaluation is informed by the PrOcess Evaluation of Trials In Critical care (POETIC) framework, examining Context, Fidelity, Dose, Reach, and Quality of Delivery. A logic model was developed, describing relationships between contextual factors, intervention delivery and trial outcomes. An explanatory sequential design will first analyse quantitative data describing intervention delivery, followed by qualitative data explaining observed variation. Data will be collected via electronic survey and semi-structured interviews, with findings integrated with the main trial results.

DISCUSSION: This embedded process evaluation will characterise SINFONIA intervention delivery across sites, explain how contextual factors shape implementation, and support interpretation of trial findings through integrated process evaluation evidence.

CLINICAL TRIAL REGISTRATION: ISRCTN.com ISRCTN15109717. Registered on 21 December 2022.