Implementation of a novel postoperative monitoring system using automated Modified Early Warning Scores (MEWS) incorporating end-tidal capnography

• Published in: Journal of clinical monitoring and computing 2017-10, Vol.31 (5), p.1081-1092
• Main Authors: Blankush, Joseph M., Freeman, Robbie, McIlvaine, Joy, Tran, Trung, Nassani, Stephen, Leitman, I. Michael
• Format: Article
• Language: English
• Subjects: Alarm systems; Analgesia; Anesthesiology; Automation; Blood pressure; Capnography; Carbon dioxide; Cardiovascular disease; Coronary artery disease; Critical Care Medicine; Demographics; Devices; Diabetes mellitus; Early warning systems; False alarms; Health Sciences; Heart rate; Hypertension; Intensive; Mathematical analysis; Medicine; Medicine & Public Health; Messages; Original Research; Oxygen; Patients; Respiratory rate; Sleep; Sleep apnea; Statistical significance; Statistics for Life Sciences; Workloads
• ISSN: 1387-1307; 1573-2614
• DOI: 10.1007/s10877-016-9943-4

Modified Early Warning Scores (MEWS) provide real-time vital sign (VS) trending and reduce ICU admissions in post-operative patients. These early warning calculations classically incorporate oxygen saturation, heart rate, respiratory rate, systolic blood pressure, and temperature but have not previously included end-tidal CO2 (EtCO 2 ), more recently identified as an independent predictor of critical illness. These systems may be subject to failure when physiologic data is incorrectly measured, leading to false alarms and increased workload. This study investigates whether the implementation of automated devices that utilize ongoing vital signs monitoring and MEWS calculations, inclusive of a score for end-tidal CO 2 (EtCO 2 ), can be feasibly implemented on the general care hospital floor and effectively identify derangements in a post-operative patient’s condition while limiting the amount of false alarms that would serve to increase provider workload. From July to November 2014, post-operative patients meeting the inclusion criteria (BMI > 30 kg/m 2 , history of obstructive sleep apnea, or the use of patient-controlled analgesia (PCA) or epidural narcotics) were monitored using automated devices that record minute-by-minute VS included in classic MEWS calculations as well as EtCO 2 . Automated messages via pagers were sent to providers for instances when the device measured elevated MEWS, abnormal EtCO 2 , and oxygen desaturations below 85 %. Data, including alarm and message details from the first 133 patients, were recorded and analyzed. Overall, 3.3 alarms and pages sounded per hour of monitoring. Device-only alarms sounded 2.7 times per hour—21 % were technical alarms. The remaining device-only alarms for concerning VS sounded 2.0/h, 70 % for falsely recorded VS. Pages for abnormal EtCO 2 sounded 0.4/h (82 % false recordings) while pages for low blood oxygen saturation sounded 0.1/h (55 % false alarms). 143 times (0.1 pages/h) the devices calculated a MEWS warranting a page (rise in MEWS by 2 or 5 or greater)—62 % were false scores inclusive of falsely recorded VS. An abnormal EtCO 2 value resulted in or added to an elevated MEWS score in 29 % of notifications, but 50 % of these included a falsely abnormal EtCO 2 value. To date, no adverse events have occurred. There were no statistically significant demographic, post-operative condition, or pre-existing comorbidity differences between patients who had a majority of true alarms from those who had mo