Objective: To evaluate the ability of pre-defined clinical criteria to identify patients who subsequently suffer cardiac arrest, unplanned intensive care unit admission or unexpected death; to determine the ability of modified criteria to identify these patients.
Design: Nested, matched case-control study.
Setting: Seven Australian public hospitals.
Patients and participants: Four hundred and fifty cases and 520 controls matched for age, sex, hospital, and hospital ward.
Measurements and results: Highest and lowest respiratory and heart rates, lowest systolic blood pressure, presence of threatened airway, seizures or decrease in Glasgow Coma Scale score of greater than two points and incidence of the three adverse events were measured. Combining a heart rate greater than 140, respiratory rate greater than 36, a systolic blood pressure less than 90 mmHg and a greater than two point reduction in the Glasgow Coma Scale identified adverse events with a sensitivity of 49.1% (44.4-53.8%), specificity of 93.7% (91.2-95.6%), and positive predictive value of 9.8% (8.7-11.1%). Adding threatened airway, seizures, low respiratory rate and low heart rate did not substantially improve sensitivity (50.4%; 45.7-55.2%). After modifying the cut-off values for respiratory rate, heart rate and systolic blood pressure, the best achievable positive predictive value remained below 16%.
Conclusions: In combination, the respiratory rate, heart rate, systolic blood pressure, and level of consciousness identify patients at risk of cardiac arrest, unplanned intensive care admission or unexpected death with high specificity; however the sensitivity and positive predictive value are relatively low, even after modification of the activation criteria cut-off values.