Agreement between non-invasive and invasive arterial blood pressure measurements in anaesthetised dogs, with emphasis on the hypotensive range: a systematic review and meta-analysis of method-comparison studies

Invasive intra-arterial blood pressure is the clinical reference standard in anaesthetised dogs, but non-invasive methods (Doppler, conventional oscillometry, high-definition oscillometry) are used routinely, with measurement error that varies by device and by pressure level. This protocol describes a systematic review and meta-analysis of method-comparison studies quantifying the agreement (population limits of agreement, Tipton & Shuster framework) between non-invasive and invasive blood pressure measurements in anaesthetised dogs, with emphasis on the hypotensive range. Review question: In dogs under general anaesthesia, what is the agreement between non-invasive blood pressure measurement methods and invasive blood pressure, with emphasis on population limits of agreement within the hypotensive range? PECOS: - Population: dogs under general anaesthesia - Index method: Doppler, conventional oscillometry, high-definition oscillometry (HDO) - Comparator: invasive intra-arterial blood pressure - Outcomes: bias, precision, limits of agreement, proportional bias - Study design: method-comparison studies with paired measurements This review does not aim to define a universal non-invasive threshold for hypotension. Instead, pooled population limits of agreement will be used to quantify the expected uncertainty associated with non-invasive blood pressure measurements within the hypotensive range in anaesthetised dogs, to support clinical interpretation of measured values rather than replace invasive monitoring or establish universal treatment thresholds. The complete protocol, database-specific search strategies, statistical analysis plan, review-specific risk-of-bias instrument, and data-extraction form are provided as separate version-controlled attachments.