Can Blood Gas Enhance Early Warning Systems by streamlining ICU Transfer Decisions: A Qualitative Systematic Review

ImportanceDelay in transfer to Intensive Care Unit (ICU) is associated with known adverse clinical and economic outcomes. There are several early warning systems (EWS) that help identify patients that could benefit from earlier ICU transfer but are fraught with challenges when used to measure delays. An objective time stamped blood test metric, such as a blood gas analysis (BGA), could be a valuable adjunct in identifying patients and measuring delays in who require intrahospital transfer to the ICU. BackgroundDelays in transferring critically ill patients to the ICU are linked to increased mortality, organ failure, prolonged recovery, and higher hospital costs. While EWS systems like MEWS, NEWS2, and eCART aim to detect deterioration using vital signs and medical data, they often rely on intermittent and/or subjective inputs. Despite advances, including AI-driven models, most systems still lack accuracy to detect and quantify transfer delays, an important operational metric. ObjectiveThis review explores the clinical and operational impact of ICU transfer delays and evaluates the potential role of BGA as an objective, time-stamped adjunct biomarker for early identification of high-risk patients. We also assess whether BGA could be integrated into EWS tools to enhance predictive accuracy. MethodsWe conducted a systematic literature review of studies published between 1994 and 2024 using PubMed, EMBASE, Cochrane, and NIH databases. Inclusion criteria focused on studies that examined ICU transfer delays, BGA parameters (e.g., lactate, pH, base excess), and clinical outcomes in adult or pediatric patients. Studies were excluded if they had small sample sizes (n < 50), lacked outcome data, or were not published in English. ResultsThe review found that delays in ICU transfer are consistently linked to worse clinical outcomes and higher healthcare costs. While EWS tools have improved early recognition of patient deterioration, they still lack objective, time-stamped markers to measure delays. Approximately one-third of the included studies specifically examined BGA parameters in relation to ICU transfer or outcomes. Elevated lactate levels and abnormal pH values correlated with increased ICU admission, adverse prognosis and mortality risk. Despite this, BGA is not currently integrated into most clinical decision-making tools used for ICU triage. ConclusionBGA represents a promising, underutilized tool that could fill a critical gap in current ICU triage systems. As a time-stamped, objective measure of physiological instability, BGA could enhance the accuracy, timeliness and measurability of ICU transfer decisions--especially when combined with electronic medical records and modern EWS platforms. Future research should focus on evaluating BGA as a predictive input within next-generation EWS tools, with the goal of reducing ICU transfer delays, improving patient outcomes, and optimizing hospital resource use.