A method of recording electronic anaesthetic monitor data for research

Several recent ‘big data’ observational studies have found a correlation between intra-operative hypotension and poor outcome 1-3. However, although the 5th Edition of the AAGBI: Recommendations for standards of monitoring during anaesthesia and recovery 4 recommended the use of automated electronic anaesthetic record systems, they do not mandate them (yet), on the grounds of cost 5. We have previously argued that the AAGBI should insist on automated electronic data capture in the next iteration of the guidelines to stimulate manufacturers’ interest, and encourage hospitals’ investment in such systems for medicolegal and research purposes 6. At the AAGBI Annual Conference in Birmingham, September 2016, SW asked Draeger and GE Healthcare whether they made small, inexpensive hardware devices that recorded anaesthesia monitor data and converted it for spreadsheet/research analysis. Neither produced devices commercially (although they were used for equipment diagnostics and theatre network connectivity 7), so we identified our own strategy for recording and storing data, which we would like to share with research colleagues. The following, easily available hardware is required: a laptop computer, connected to a Keyspan (Tripp Lite, Newbury, UK) RS-232/DB9 (male) USB high-speed (230 kbps) PC/Mac serial adapter, connected to a StarTech (Northampton, UK) DB9 RS232 serial null modem adapter (female/female), connected to an ATEN (ATEN Technology, Irvine, CA, USA) UC232A USB to serial converter (male/USB), connected to USB port 4 of the anaesthetic monitor (Fig. 3), the total cost of which is ~£50 (US$62, €58). The Keyspan adapter needs to be configured via https://www.tripplite.com/support/USA19HS; any recognised serial to USB adapter should work provided the appropriate drivers are installed on the host computer. The total one-off cost of these adapters is around ~£50 (US$62, €58). Two free software programs permit data capture onto Apple (Cupertino, CA, USA) MacBook Air or Pro devices – Monitor2 (James Derrick, 2014, iTunes, free) and Vital Signs Capture (VSCapture, www.sourceforge.net). The former provides a polished graphical interface and permits the recording of drugs, interventions and production of a customisable chart as well as allowing the record to be saved in an encrypted format. The latter program provides a more basic command line interface and needs to be compiled either using the ‘Mono’ framework (www.mono-project.com) or Xamarin Studio (www.xamarin.com). It allows direct capture of the data to a comma separated value (.csv) file at a frequency chosen by the user. Both programs allow the captured data to be easily imported into an Excel (Microsoft, Redmond, WA, USA) spreadsheet for onward analysis, saved as a password-protected, encrypted file. Monitor2 requires the user to conform the serial port connected to the laptop. The default settings of 19200 baud, 8 data bits, 1 stop bit and Even parity are correct for GE Healthcare (Little Chalfont, UK) AS3 based anaesthetic monitors. Recording frequency can be set in the preferences as low as 0.5 s (maximum 120 s, default 5 s). VSCapture uses the same hardware setup and prompts the user to select the port in use. It then allows the user to select the logging interval (≥ 5s) before generating a log file. From a research perspective, automated recording of haemodynamic data reduces measurement bias 8, provides much greater information than intermittently recorded data or pre-induction vs. intra-operative nadir values 1-3, and should enable further insight into which aspects of hypotension (absolute/relative values, rate of change, duration, or combinations of these) are most correlated with ‘ischaemic’ end-organ outcomes (delirium, acute coronary syndrome, acute kidney injury) in research studies.