The association between vital signs and clinical outcomes in emergency department patients of different age categories

Abstract

Background: Appropriate interpretation of vital signs is essential for risk stratification in the emergency department (ED) but may change with advancing age. In several guidelines, risk scores such as the Systemic Inflammatory Response Syndrome (SIRS) and Quick Sequential Organ Failure Assessment (qSOFA) scores, commonly used in emergency medicine practice (as well as critical care) specify a single cut-off or threshold for each of the commonly measured vital signs. Although a single cut-off may be convenient, it is unknown whether a single cut-off for vital signs truly exists and if the association between vital signs and in-hospital mortality differs per age-category.

Aims: To assess the association between initial vital signs and case-mix adjusted in-hospital mortality in different age categories.

Methods: Observational multicentre cohort study using the Netherlands Emergency Department Evaluation Database (NEED) in which consecutive ED patients ≥18 years were included between 1 January 2017 and 12 January 2020. The association between vital signs and case-mix adjusted mortality were assessed in three age categories (18-65; 66-80; >80 years) using multivariable logistic regression. Vital signs were each divided into five to six categories, for example, systolic blood pressure (SBP) categories (≤80, 81-100, 101-120, 121-140, >140 mm Hg).

Results: We included 101 416 patients of whom 2374 (2.3%) died. Adjusted ORs for mortality increased gradually with decreasing SBP and decreasing peripheral oxygen saturation (SpO₂). Diastolic blood pressure (DBP), mean arterial pressure (MAP) and heart rate (HR) had quasi-U-shaped associations with mortality. Mortality did not increase for temperatures anywhere in the range between 35.5°C and 42.0°C, with a single cut-off around 35.5°C below which mortality increased. Single cut-offs were also found for MAP <70 mm Hg and respiratory rate >22/min. For all vital signs, older patients had larger increases in absolute mortality compared with younger patients.

Conclusion: For SBP, DBP, SpO₂ and HR, no single cut-off existed. The impact of changing vital sign categories on prognosis was larger in older patients. Our results have implications for the interpretation of vital signs in existing risk stratification tools and acute care guidelines.

Keywords: emergency department; geriatrics; risk management; triage.

Figure 1

Patient inclusion and flow through the study. Observational multicentre cohort study using the NEED. Three different age categories were included in which vital signs were measured. ED, emergency department; NEED, Netherlands Emergency Department Evaluation Database.

Figure 2

AORs for SBP, DBP, MAP and SpO₂ for in-hospital mortality (left side) and predicted in-hospital mortality (right side) as a function of vital signs in different age categories. Note that the black line is the pooled data of all three age categories together. The following potential confounders were entered in the model for in-hospital mortality through backward stepwise regression: age, gender, triage level, top 10 chief complaints, hospital, treating specialty, disposition, SpO₂ (except for association of SpO₂), temperature (except for association of temperature), Glasgow Coma Scale, lab tests, number of consultations in the emergency department and performed radiological test. AORs, adjusted odds ratios; DBP, diastolic blood pressure; MAP, mean arterial pressure; SBP, systolic blood pressure; SpO₂, peripheral oxygen saturation.

Figure 3

AORs for RR, HR and temperature for in-hospital mortality (left side) and predicted in-hospital mortality (right side) as a function of vital signs in different age categories. Note that the black line is the pooled data of all three age categories together. The following potential confounders were entered in the model for in-hospital mortality through backward stepwise regression: age, gender, triage level, top 10 chief complaints, hospital, treating specialty, disposition, SpO₂, temperature, Glasgow coma scale, lab tests, number of consultations in the emergency department and performed radiological test. AORs, adjusted odds ratios; HR, heart rate; RR, respiratory rate.