Key Concepts
Introduction
Early warning score (EWS) systems are standardized track-and-trigger tools designed to detect early physiological deterioration before overt clinical crisis. The National Early Warning Score 2 (NEWS2) assigns weighted points based on six physiological parameters: respiratory rate (highest weighted parameter), oxygen saturation (with separate scales for patients with and without hypercapnic respiratory failure), use of supplemental oxygen, systolic blood pressure, heart rate, level of consciousness (using the AVPU scale: Alert, Voice-responsive, Pain-responsive, Unresponsive), and temperature. The scoring reflects the physiological compensatory mechanisms that occur during clinical deterioration: the sympathetic nervous system response produces tachycardia and hypertension initially, followed by hypotension as compensation fails; respiratory compensation manifests as tachypnea; tissue hypoxia causes decreasing oxygen saturation; and cerebral hypoperfusion produces altered consciousness. The aggregate score triggers a graded clinical response: low scores (0-4) require routine monitoring, medium scores (5-6 or any single parameter scoring 3) require urgent nursing assessment and consideration of escalation, and high scores (โฅ7) require emergency assessment by a critical care team. The nurse plays a central role in accurate parameter measurement, score calculation, appropriate escalation, and communication using SBAR...