Recognition of deterioration: track-and-trigger and early-warning scores

The recognition of deterioration is the single most improvable step in the chain of survival for the acutely ill patient. In-hospital cardiac arrest is rarely a sudden, unpredictable event: it is usually preceded by measurable physiological deterioration over hours, much of it documented in the observation chart before the arrest. The premise of track-and-trigger systems is that this deterioration is detectable, that it follows recognisable patterns, and that a standardised, graded response to it prevents avoidable arrests and admissions to critical care. For the emergency physician the same principle governs the front door: the patient who arrives abnormal, or who trends abnormal while waiting, is the patient about to deteriorate, and a structured early-warning assessment converts that signal into an action. ^[1]

The antecedents of arrest

Studies of in-hospital cardiac arrest consistently show antecedent physiological abnormality in the hours before the event. Systematic review identified 36 papers describing 25 distinct track-and-trigger systems, with none meeting all quality standards; in 15 qualifying datasets sensitivity and positive predictive value were low (median 43.3 and 36.7), and available data were insufficient to identify the best system.^[1] The observations most commonly deranged before arrest are the respiratory rate, heart rate, blood pressure, conscious level and the temperature — exactly the parameters aggregated in the modern early-warning scores. Critically, the abnormality is often present and recorded but not acted upon, which frames deterioration as a failure of the response system rather than of detection alone.

The intervention was tested prospectively in 1695 acute medical admissions with a Modified Early Warning score trigger of more than 4 for urgent medical and outreach review: there was no change in mortality at any score band and rates of cardiopulmonary arrest and intensive-care or high-dependency admission were similar to the preceding year, with the authors concluding benefit is hard to demonstrate without further standardising the response to abnormal values.^[2] On reproducibility, a prospective ward study (114 patients inter-rater, 45 intra-rater, four raters) found only fair to moderate agreement on most parameters and fair agreement on aggregate scores, with better agreement on triggers and better reliability in simpler systems.^[3]

References13ShowHide

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