Of the first 2000 incidents reported to the Australian Incident Monitoring Study, 1256 occurred in relation to general anaesthesia and 81 of the latter were first detected by blood pressure (BP) monitoring. A further 25 incidents not associated with general anaesthesia were first detected by blood pressure monitoring, giving a total of 106. In the monitor detection of incidents in relation to general anaesthesia, BP monitoring ranked fourth after oximetry, capnography and low pressure alarms. On the other hand, 38 incidents in which the problem was primarily one of significant change in BP were first detected by means other than the BP monitor (20 clinically, 12 by pulse oximetry and 6 by ECG). Early detection rates of hypotension were 60% for invasive methods, 40% for automated non-invasive (NIBP) devices and 30% for manual sphygmomanometry. There were 21 reports of BP monitor “failure”; the 11 of these which occurred with NIBPs involved unexplained false “low” or “high” readings and failure to detect profound hypotension, and led to considerable morbidity and at least one death. The 10 cases of invasive monitoring failure were predominantly due to mains power loss, hardware breakage or operator error. In a theoretical analysis of the 1256 GA incidents, it was considered that on its own, BP monitoring would have detected 919 (73%), but in the vast majority, by the time this detection has occurred, potential organ damage could not be excluded. It is recommended that BP be measured at regular intervals dictated by clinical requirements (usually at least every five minutes). BP monitoring should be supplemented by other modalities in accordance with the College of Anaesthetists guidelines and when immediate and reliable detection of change in BP is critical, invasive monitoring should be used.
Noninvasive cardiac output and blood pressure monitoring cannot replace an invasive monitoring system in critically ill patients