Elsevier

Journal of Critical Care

Volume 29, Issue 5, October 2014, Pages 775-779
Journal of Critical Care

Outcomes
Low tissue oxygen saturation at emergency center triage is predictive of intensive care unit admission,☆☆,

https://doi.org/10.1016/j.jcrc.2014.05.006Get rights and content

Abstract

Purpose

Timely recognition of critical patients by emergency center triage is an ongoing challenge. Peripheral tissue oxygen saturation (Sto2) measurement has been used to monitor shock patients’ responses to resuscitation. Interest has developed in evaluating Sto2 as a triage tool, but limited studies have addressed critically ill patients.

Material and methods

This is a single-center, retrospective study of 158 emergent cancer patients with hypotension and/or modified systemic inflammatory response syndrome who underwent Sto2 spot measurement at triage.

Results

Of the 57 patients with Sto2 less than 70%, 17 went to the intensive care unit (ICU), whereas only 14 of the 101 patients with Sto2 of 70% to 89% (P = .01) went to the ICU. There was no significant difference in non-ICU hospital admission or mortality between the 2 groups. The odds ratio of ICU admission for patients with Sto2 less than 70% relative to those with Sto2 of 70% to 89% was 2.64 (95% confidence interval, 1.18-5.87) and 2.87 (95% confidence interval, 1.23-6.66) when adjusted for mean arterial pressure, pulse, and temperature.

Conclusions

In this patient population, an Sto2 less than 70% significantly increased the risk of ICU admission. Tissue oxygen saturation at triage identifies critical patients who may not be recognized by vital signs alone. Tissue oxygen saturation measurement could help providers make earlier decisions regarding hospital resource allocation.

Introduction

Critically ill patients, particularly those with signs of hemodynamic instability, need prompt diagnosis and treatment. Patients with these signs have impaired tissue perfusion and oxygenation, which is usually detected in clinical practice by macrocirculatory parameters or global hemodynamic measurements such as blood pressure and arterial blood oxygen saturation [1]. In such patients, microcirculatory changes precede macrocirculatory changes secondary to the diversion of blood to more vital organs such as the heart and brain. Detecting these microcirculatory changes could lead to earlier diagnosis and improved clinical outcomes [1]. Researchers have shown that optimizing global hemodynamic parameters does not always resolve microcirculatory derangements; therefore, correcting macrocirculatory parameters may not ensure adequate delivery of oxygen to the tissues [2]. Near-infrared spectroscopy has been introduced as a noninvasive tool to monitor microcirculation and tissue oxygen saturation (Sto2). This technique is based on the different absorption properties of oxygenated and deoxygenated hemoglobin level in small blood vessels (ie, arterioles, venules, and capillaries) to measure peripheral tissue oxygenation [3].

Tissue oxygen saturation, measured by near-infrared spectroscopy, has been used in various clinical settings. Initially, its main clinical role was in monitoring the resuscitation of trauma patients [4], [5]. More recent work has focused on using Sto2 to monitor the response of intensive care unit (ICU) patients with septic shock to resuscitation and treatment. In this patient group, low Sto2 after resuscitation has been found to indicate poor prognosis [6], [7], [8]. Vorwerk and Coats [6] looked at septic patients presenting to the emergency center (EC) to determine if Sto2 was associated with mortality. They showed that, upon presentation to the EC, patients with sepsis have an abnormally low Sto2, and after resuscitation, those who failed to normalize their Sto2 had a higher mortality [6]. Thus far, the primary utilization of Sto2 has been with the continuous Sto2 monitor, which was designed to record measurements continuously throughout ICU admission. Many studies have also used the vascular occlusion test in conjunction with the continuous Sto2 monitor to test for microcirculatory dysfunction [8], [9]. For instance, Shapiro et al [9] showed that, in a group of sepsis patients presenting to the EC, the initial Sto2 was lower in patients with septic shock, and the recovery slope had the strongest correlation with organ dysfunction and mortality. The recent development of a point-of-care Sto2-measuring device (InSpectra Sto2 Spot Check, model 300; Hutchinson Technology, Hutchinson, MN) that does not require a costly probe per each patient use has allowed for the expansion of potential applications of this technology. This device uses a reusable probe, which must be replaced after use in 300 to 400 patients. Since the release of the point-of-care device, interest has developed in evaluating Sto2 as a triage tool in the EC. The abstract presented by Miner et al [10] looked at the use of Sto2 in patients presenting to an EC triage and its correlation with a triage acuity score and hospital admission. That result showed no difference between Sto2 measurements and the nurse-assigned triage score in the ability to predict subsequent treatment or the need for intravenous fluids or medications. In their work, patients who were critically ill were not addressed because they were excluded from the analysis [10].

One of the biggest challenges in a busy EC is ensuring that patients who are critically ill are recognized quickly. Toward that end, our aim was to ascertain the usefulness of Sto2 in triage as an independent predictor of prognosis or measure of acuity and to determine whether the use of Sto2 as part of a triage routine had an additional benefit over that conferred by measuring vital signs. Our study focused on cancer patients at high risk for sepsis and sought to determine whether using Sto2 at triage would help us predict hospitalization, ICU admission, and 10-day mortality.

Section snippets

Study design

We conducted a single-center, retrospective cohort study of the predictive value of Sto2 using data from patients admitted to the EC of a comprehensive cancer center between 3/15/2012, and 11/30/2012. The EC services approximately 22 000 visits per year. Fifty-one percent of the patients who present to the EC are admitted. Our EC uses a 3-tier triage system that classifies patient’s acuity as emergent, urgent, and nonurgent. Patients were included in the study if upon presentation to the EC

Results

A review of the electronic medical records identified 167 medical patients with cancer or a history of cancer, who had undergone an Sto2 spot check and who were then screened for inclusion into the study. Six patients with Sto2 at least 90% and 3 patients younger than 18 years were excluded, leaving a total of 158 cancer patients in our study population. Of these, 57 patients had an Sto2 less than 70%, and 101 patients had an Sto2 of 70% to 89%. The study patients’ baseline clinical and

Discussion

Our objective was to determine whether Sto2 levels measured at triage by a point-of-care Sto2-measuring device in patients with suspected sepsis based on modified SIRS criteria could be used as a predictor of hospitalization, ICU admission, and death and could thus identify critically ill patients earlier. We found that, in a select group of high-acuity patients, an initial low Sto2 (< 70%) resulted in a higher frequency of ICU admissions. Based on the low area under the curve, it would be

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    No research support to disclose. No conflict of interest.

    ☆☆

    Guarantor: Kelly Merriman.

    Author contributions: Hadil Bazerbashi, Kelly Merriman, Katy M. Toale, Patrick Chaftari, Maria Teresa Cruz Carreras, Sai-Ching J. Yeung, and Terry W. Rice all made substantial contributions to the study’s conception and design or acquisition of data or analysis and interpretation of data; drafted the submitted article or revised it critically for important content; and provided final approval of the version to be published.

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