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Computer takes guesswork out of anesthetizing

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February 21, 2010

The IT system automatically regulates anesthetic (Photo: Albino Méndez et al.)

The IT system automatically regulates anesthetic (Photo: Albino Méndez et al.)

Anesthetists cannot take their responsibilities lightly. Too little anesthetic and a patient may feel the whole procedure, too much and a patient might shuffle off this mortal coil. Researchers in the Canary Islands have taken the guesswork out of this thorny dilemma and developed a computer-controlled system that measures a patient's hypnotic state and applies the appropriate dose of anesthetic.

Between 1990 and 2002 in the USA, 5691 medical malpractice payments relating to anesthesia complications were made for on average $100,000. Variable factors such as age, weight, physical health and oddly enough, naturally red hair, introduce a large margin for error and when added to human error this can be potentially fatal.

Researchers from the Canary Islands together with a team of anesthetists from the University Hospital of the Canary Islands have developed an IT tool which automatically controls anesthesia during surgical operations. The new system records the patient's encephalogram (EEG) and bispectral index (BIS) which measures hypnotic state and the patient's level of consciousness.

The BIS value (a parameter without units) fluctuates between 100 and 0, 100 being the maximum state of alertness and 0 showing a lack of cortical electrical activity, the deepest state of unconsciousness. The IT application is based on adaptive Proportional Integral Derivative (PID) algorithms, a control-loop feedback mechanism which is linked to a pump that can automatically inject the right dose according to the measured and desired values to maintain the patient in the desired hypnotic state throughout the operation.

The study, which has been published in Computer Methods in Biomechanics and Biomedical Engineering, showed the results of simulations using various models, and also tests on 15 volunteer patients aged between 30 and 60 at the University Hospital of the Canary Islands. The common anesthetic Propofol was used in trials but could be substituted for others such as Isoflurane.

"The first results obtained, both in surgery and in the simulations, show that the system operates very satisfactorily, and has surgical applications with well-founded expectations of success", says Albino Méndez, lead author of the study and a researcher in the Anesthesia Control Group at the University of La Laguna (ULL).

The scientists hope that use of the IT system will improve anesthetic-dosing performance and aid patient recovery times as well as reducing operation cost. Additionally there is scope for the IT system to regulate other physiological variables such as blood glucose levels, temperature or blood pressure and they are looking to incorporate analgesia and muscle relaxation variables into the system in order to provide anesthetists with a comprehensive tool.

This system could be hugely beneficial to doctors and patients as it adapts the dose of the drug administered according to the individual characteristics (and hair color!) of each patient thereby taking the guesswork out and so reducing the margin for error that sometimes leads to tragedy.

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