Introduction: Close monitoring of arterial blood pressure (BP) is a central part of cardiovascular surveillance of patients at risk for hypotension. Therefore, patients undergoing diagnostic and therapeutic procedures with the use of sedating agents are monitored by discontinuous non-invasive BP measurement (NIBP). Continuous non-invasive BP monitoring based on vascular unloading technique (CNAP®, CN Systems, Graz) may improve patient safety in those settings. We investigated if this new technique improved monitoring of patients undergoing interventional endoscopy.

Methods: 40 patients undergoing interventional endoscopy between April and December 2007 were prospectively studied with CNAP® in addition to standard monitoring (NIBP, ECG and oxygen saturation). All monitoring values were extracted from the surveillance network at one-second intervals, and clinical parameters were documented. The variance of CNAP® values were calculated for every interval between two NIBP measurements.

Results: 2660 minutes of monitoring were recorded (mean 60.1±34.4 min/patient). All patients were analgosedated with midazolam and pethidine, and 24/40 had propofol infusion (mean 90.9±70.3 mg). The mean arterial pressure for CNAP® was 102.4±21.2 mmHg and 106.8±24.8 mmHg for NIBP. Based on the first NIBP value in an interval between two NIBP measurements, BP values determined by CNAP® showed a maximum increase of 30.8±21.7% and a maximum decrease of 22.4±28.3% (mean of all intervals).

Discussion: Conventional intermittent blood pressure monitoring of patients receiving sedating agents failed to detect fast changes in BP. The new technique CNAP® improved the detection of rapid BP changes, and may contribute to a better patient safety for those undergoing interventional procedures.