Critical care

Controlling blood sugar of ICU patients by automatic insulin delivery

30 October 2006

The control of blood glucose levels is one of the most important factors for patients in intensive care units (ICU). Thousands die or suffer prolonged illness every year, simply because intensive care units are unable to monitor their patients' glucose levels during recovery. One EU project CLINICIP is developing an intelligent, automated glucose monitoring and control system to solve the problem.

Drawing a drug into a syringeThe reason for the large number of deaths is the fact that glucose affects blood toxicology, so careful management is essential to keep patients in the best possible health. Many ICUs cannot easily control the glucose levels in each patient's blood.

Healthcare staff rely on a technique called 'tight glucose control', also known as 'intensive insulin therapy', which uses insulin to control the glycaemic state of recovering surgical patients. The same method is also used to help patients at medical intensive care units to recover faster.

"Studies show that when patient's glucose levels are managed carefully, the mortality is reduced and the morbidity is reduced too," says Martin Ellmerer, scientific director of the CLINICIP project. "This is not just about diabetic patients, though it is important for them too. Glucose management is important, we know for sure, for medical and surgical intensive care patients. It's also important in paediatric intensive care cases. Intensive insulin therapy helps many different kinds of patient to survive or achieve a better recovery."

It is five years since medical science realised how vital glucose control is to ICU outcomes, but there is still no complete solution to glucose management, because it is a very, very difficult problem.

"Taking glucose levels manually is time-consuming, and even when you have accurate, regular data, the impact of glucose levels varies from patient to patient, as does the dose of insulin required. It's a very complex problem, one that seems to be even more complex in critical illnesses than in diabetes management," said Ellmerer.

Automated insulin delivery

The EU-funded project CLINICIP, the Closed Loop Insulin Infusion for Critically Ill Patients hopes to develop an intelligent, automated glucose monitoring and control system for ICUs. It's called 'closed-loop' because monitoring glucose levels and administering insulin would be completed by one self-contained system.

A closed-loop system needs inputs, analysis and outputs. The CLINICIP partners are developing a system that links glucose measurement to a control unit that assesses a patient's needs, and then releases insulin into a saline drip automatically.

They have already developed an algorithm to analyse how much insulin is needed, based on carbohydrate intake and current glucose levels. The team believe they have solved the problem, but it will require long-term validation to get the correct fine-tuning. That algorithm is in trials, and the partners hope to have initial results early next year.

"We are now testing the algorithm, which could be commercialised as a diagnostic support tool," says Ellmerer.

Internal or external glucose sensors?

Illustration of sensor on human bodyThe project is also currently studying sensor systems, both intra-vascular and extra-vascular — that is, within and outside the veins. If successful, automated sensor systems could greatly improve the survival chances of intensive care patients. They could also increase efficiency in clinical practice. That, however, is a long-term goal.

On the glucose sensor system, Ellmerer notes that, "Ideally we would like to use a sensor outside of the blood vessels. It's less invasive, and evidence suggests that it can provide a very accurate indication of real glucose levels in the blood."

But first the team must establish that the external sensor is accurate and reliable. The intravascular system is both accurate and reliable, but it is more invasive and time consuming, and not really appropriate for some types of patient such as cardiac arrest victims and infants.

The body interface obstacle

The major obstacle currently facing the project is the body interface, or how the sensor in the body links to the rest of the closed-loop system. Ellmerer says that the team would be interested in hearing from any industrial partners involved in this area.

Even if the body interface problem is solved soon, he believes the full closed-loop system will not be developed within the lifetime of the project, which ends in January 2008. The work will continue however. "There are bilateral agreements between many of the partners to continue the work that we've started here after the life of the project," said Ellmerer.

In the meantime, CLINICIP's algorithm has provoked intense interest among medical scientists, and there have been calls to make the algorithm available to all ICUs.

"But it's just not possible yet. We haven't established definitively that it is sufficiently accurate, reliable and safe," warns Ellmerer. "That assessment is under way now."

Source: IST Results.

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