Intra-operative monitoring--many alarms with minor impact.

Alarms are key components of peri-operative monitoring devices, but a high false-alarm rate may lead to desensitisation and neglect. The objective of this study was to quantify the number of alarms and assess the value of these alarms during moderate-risk surgery. For this purpose, we analysed documentation of anaesthesia workstations during 38 surgical procedures. Alarms were classified on technical validity and clinical relevance. The median (IQR [range]) alarm density per procedure was 20.8 (14.5-34.2 [3.7-85.6]) alarms.h⁻¹ (1 alarm every 2.9 min) and increased during induction and emergence of anaesthesia, with up to one alarm per 0.99 min during these periods (p < 0.001). Sixty-four per cent of all alarms were clinically irrelevant, whereas 5% of all alarms required immediate intervention. The positive predictive value of an alarm during induction and emergence was 20% (95% CI 16-24%) and 11% (95% CI 8-14%), respectively. This study shows that peri-operative alarms are frequently irrelevant, with a low predictive value for an emerging event requiring clinical intervention.