Development of High Blood Sugar Levels in Critically Ill and ICU Patients

Critically ill and intensive care unit (ICU) patients may become resistant to insulin and have high blood sugar levels even without a previous history of diabetes. Intensive insulin therapy can help these patients, as shown in a 12-month study of 1548 critically ill surgical patients. In this study, maintaining glucose levels between 4.4 and 6.1 millimoles per liter reduced mortality by 42%, morbidity (the number of people with illnesses), the need for intensive care, and the risk of complications.

To maintain blood sugar levels under control, medical staff have to take blood samples to test the sugar levels frequently. However, this mode is often impossible due to the high workload and cost associated with caring for critically ill patients. Manual sampling can also introduce errors and delays when using laboratory services. These factors may lead to errors or delays in treatment.

Researchers are working on a way to develop a real-time glucose monitoring system that could mean never having to worry about managing their blood sugar levels again. For doctors treating critically ill patients, this system could provide valuable information to help them make treatment decisions.

The study aimed to develop a low-risk, reliable decision-supporting automated system for maintaining glycemic control of ICU patients. Setup times, success rate, flushing volume, pain, and user satisfaction were assessed in this study.

The Study Method on the Automated Blood Sampling for Glycemic Control of ICU Patients

The study used two special catheters inserted into the left arm to allow the patient to move freely throughout the study period of 30 hours. One catheter would get blood from veins manually as a reference, and the other would take blood samples through the automated blood sampling (ABS) machine.

In the ABS, the machine takes 4 milliliters (ml) of blood and collects it in a buffer loop for each sample. Then about 1.69 ml of this drawn blood was immediately branched off, and approximately 1 ml was pumped into the waste container before collecting samples in a vial for analysis. The remaining blood in the buffer loop (about 2.3 ml) was immediately reinfused into the subject. Following sampling, flushing fluid was pumped through the tubing to clean it.

Six healthy male volunteers were the study subjects. They received four meals at 5:00 pm (dinner), 9:00 pm (snack), 8:00 am (breakfast), and 12:00 pm (lunch) for their pre- and postprandial glucose concentration profiles. Blood samples were generally taken at hourly intervals. After each meal, however, the frequency of sampling (manual and automatic) was increased to four samples per hour for three hours. After that, two samples were taken at 30-minute intervals before the resumption of hourly monitoring. Seven blood samples were also taken throughout the study to determine activated partial thromboplastin times. The expected blood consumption was 187.7 ml per volunteer.

The study subjects attended the trial center at 11:00 am on Day 1, having fasted from at least midnight onward. A physician connected the sampling systems by inserting the catheters into the veins in the left forearm to allow free movement by the patient throughout the 30-hour study period.

The Results

The median Pearson coefficient of correlation between manually and automatically withdrawn blood samples was 0.976. The system error was -3.327 ± 5.546%. Through Clark error grid analysis, 420 data pairs were analyzed, showing that 98.6% of the data were in zone A and 1.4% were in zone B, signifying extreme reliability of ABS. Insulin titration error grid analysis revealed an acceptable treatment in all cases. Moreover, a 17.5-fold reduction in blood-withdrawal failures due to occluded catheters was achieved by the added implementation in the ABS of a “keep vein open” saline infusion.

The catheters were well tolerated.

The Conclusion

This study showed that the ABS system could maintain euglycemia with greater precision than manual sampling. The system was also easy to use with a high success rate, thus, providing significant time savings for medical staff. The machine represents a promising alternative to frequent manual blood sampling.

Reference

An Automated Discontinuous Venous Blood Sampling System for Ex Vivo Glucose Determination in Humans