Intensive Care
Design
After the successful trial, funding was obtained to design and build six devices for automatically setting infusion pumps to the correct dose rate, removing the tedious hand calculations and streamlining the introduction of the new sedation management protocol. The design had to be robust, reliable, simple and suitable for use in an ICU.
First the specifications were broken down into manageable blocks, and a decision taken on whether each block would be performed by electronics, the microprocessor within the Infuse- Rite or the support PC. Each of the functional blocks was then designed and where possible tested independently.
In the early design stages a Failure Mode and Effects Analysis was performed. This specified possible faults (such as incorrect drug delivery), the effects of each fault (over- or under-sedation), and possible causes (such as a flat battery). The severity of each failure and the likelihood of each possible cause was scored to determine the significance of each cause. The most significant causes of failure were then mitigated with design changes (for example, introducing a low-battery alarm).
After numerous design iterations, further testing, and adjustments, the result is surprisingly simple looking: an ergonomically-designed rectangular plastic box with five control buttons and a small screen. Obviously considerable attention was paid to making the device as easy to use as possible. For example the buttons are labelled with both words and intuitive symbols (the universally known play, stop and fast forward (bolus) symbols common to VCRs). These buttons provide nurses with a simple way of giving patients a drug bolus, preparing them for a stressful procedure and other common tasks.
The device controls a Graseby 3500 syringe pump, covering its front panel and further simplifying the ICU equipment by making the pump’s 20 buttons redundant. The complex sedation algorithm is implemented within the Infuse-Rite, which communicates to the pump the appropriate infusion rate. Even the colour has been matched to the Graseby infusion pump to ensure the Infuse-Rite looks as if it belongs.
Ease of use
The Infuse-Rite is straightforward to use. Nurses plug it into a PC, and, using a specially written program, set up a patient’s details and the rate at which initial background infusion will be administered. The Infuse-Rite is then unplugged and attached to a Graseby pump, and the infusion begins. The sedation rate can be increased by pressing a single button, which delivers a preprogrammed bolus. The algorithm recalculates the infusion rate automatically, and it is passed directly from the Infuse-Rite to the pump without any nursing intervention. With the built-in decay towards zero infusion, and the automatic transfer of information to the pump, the Infuse-Rite has virtually eliminated the possibility of long-term over-sedation, and has markedly reduced opportunities for human error.
Christchurch Hospital now has ten Infuse-Rites, which have been successfully used on over 600 patients for periods ranging from a few hours to 32 days. ICU nurses agree they reduce risk, are simple to use and are proving reliable. Optimised sedation control has virtually eliminated the need for restraints. Previously, poorly sedated patients sometimes had to be strapped to their beds for their own safety. Similarly, nurses are reporting fewer assaults from agitated, under-sedated patients.
COP Outcome development and evaluation
Furthermore, the research team have been comparing treatment data from Christchurch Hospital ICU since the implementation of the Infuse-Rites with a benchmark unit elsewhere – with favourable results. Over a period of 17 months the average mechanical ventilation time per patient at the Christchurch ICU was 45.4 hours, compared with the benchmark unit’s 50.2 hours – a 9.5% reduction. Similarly the average amounts of midazolam and propofol (a top-up medication given when agitation is difficult to manage) per patient per hour were 1.6mg in Christchurch vs 3.0mg, and 11.9mg vs 47.7mg respectively. This means that Christchurch ICU patients were sedated for less time and at lower doses.
