An ideal electronic anesthesia recording system would be capable of not only recording physiological data but also injectable drug doses given, including those given incrementally from one syringe, without recourse to manual data entry. We compared 2 prototype devices which wirelessly recognized individual syringes and measured changes in their plunger positions via 2 different optical noncontact means, allowing calculation of incremental drug doses given.METHODS:
Both devices incorporated a radio-frequency identification reader, which wirelessly read a unique code from a radio-frequency identification tag within syringe drug labels. A custom-designed cradle oriented any inserted 1-mL to 20-mL syringe in a repeatable position. The “laser” device had a moving laser beam broken by the end of the syringe plunger. The infrared (IR) device measured time of travel of IR light from a sender to a syringe plunger and back to a receiver. Both devices could therefore determine the drug and volume administered since the previous occasion when any syringe had been used. For each syringe size of 1, 2, 5, 10, and 20 mL, 121 plunger-length measurements were made over their full range, with each machine against a reference method of water filling and weighing using a randomized de Bruijn sequence.RESULTS:
For every syringe size, the laser device showed greater accuracy and precision, lower bias, and narrower limits of agreement (95% confidence intervals = bias ± 1.96 SD) than the IR device when compared to the reference method. For all syringe sizes, the range of bias was −0.05 to 0.32 mL for the laser and −2.42 to 1.38 mL for the IR. Lin concordance correlation coefficient values for the IR versus reference methods ranged from 0.6259 to 0.9255, with the lowest coefficients seen in syringes with the shortest distance of plunger travel (2 and 5 mL), while in laser versus reference comparisons, these coefficients were similar (0.9641–0.9981) over all syringe lengths.CONCLUSIONS:
Both devices measured syringe volume changes, demonstrating potential for measuring incremental drug doses, recording these, and also the time of each measurement. The IR device had no moving parts, which would be advantageous in a clinical situation. However, the current embodiment was not deemed accurate enough for clinical use, potentially remediable through improvements in hardware and software design. The laser device showed high accuracy and precision over all syringe sizes and contained volumes, and was considered potentially accurate enough for clinical use with suitable development.