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Patient monitor and ventilation workstation alarming patterns during cardiac surgery


For improvement of patient safety, monitors and ventilator workstations are equipped with alarms. However, alarms are only suggestive if they indicate critical variations in the patient's condition. Great numbers of false alarms can lead to a crying wolf phenomenon with consecutive ignored critical situations. The objective of this study was to characterize the patterns of alarming of a currently available patient vital sign monitor (Kappa XLT; Draeger) and an anesthetic workstation (Zeus; Draeger) during cardiac surgery.


A prospective, observational study including 25 consecutive elective cardiac surgery patients. In all patients a predefined alarm setting was used. During 25 surgical procedures, all incoming patient data and alarms from the monitor and the anesthetic workstation were digitally recorded. Additionally, the anesthesiological workplace was filmed from two different views to assess reaction to the alarms. All events of alarming were retrospectively annotated. Alarms were categorized: valid/not valid, relevant/not relevant and medical reaction yes/no. Alarms were annotated as relevant if measurement was technically correct and showed a threshold violation. Alarms were relevant if there was a need for medical reaction.


During 124 hours of recording, 9,460 alarms in 48 categories were registered. A total of 3,054 (32%) alarms were of technical origin or static alarms and were not considered. The remaining 6,406 alarms were further analyzed. In total, 1,954 alarms were not valid and not relevant. A total of 4,452 alarms were valid (69%), 1,742 of these were clinically relevant and induced a reaction of the physician, 1,773 were relevant without a reaction of the physician. About 65% of the considered alarms were threshold violations (48% blood pressure). Nine hundred and thirty-seven alarms were valid but not relevant.


Approximately 80% of the total 9,460 alarms had no therapeutic consequences. Thirty-one per cent of the considered alarms were annotated as not valid. Sixty-nine per cent of the considered alarms were valid alarms, separated into 39% relevant alarms, 21% nonrelevant alarms and 40% relevant alarms without reaction of the physician. The majority of the static alarms occurred during the use of the extracorporeal circulation. Implementation of procedure-specific settings and optimization in artefact or technical alarm detection could improve patient surveillance and safety.

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Schmid, F., Goepfert, M., Diedrichs, S. et al. Patient monitor and ventilation workstation alarming patterns during cardiac surgery. Crit Care 13 (Suppl 1), P468 (2009).

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