Feature | June 22, 2006| Mike Arani

Continuous Blood-Glucose Monitoring: Unplugging the Possibilities for Critical Care Patients

Joining continuous wireless glucose monitoring systems with the central monitoring system in the CCU could have powerful impact on morbidity and mortality rates.

Minimed's Guardian RT REAL-Time wireless blood-glucose monitoring system.

Sugar, the sweet touch of every taste, could make some lives quite sour. Recent studies have shown a direct correlation between blood sugar level and survival rate of critically ill patients.
A study published in the December issue of Mayo clinic proceedings on blood-sugar levels in 1,826 intensive care unit patients showed that hyperglycemia (high blood-sugar levels) increased the patient's chance of death. The findings have important implications for the management of blood sugar in critically ill patients — even a modest degree of hyperglycemia was associated with a substantial increase in deaths in patients with a wide range of medical and surgical diagnoses, according to James Krinsley, M.D., director of Critical Care at the Stamford Hospital in Stamford, CT, and author of the study.
Hyperglycemia is a common condition in critically ill adults. Standard clinical practice has been to tolerate a moderate degree of hyperglycemia in these patients, but Dr. Krinsley believes that while hyperglycemia can be a marker of severity of illness, it may also worsen outcomes of the illness. He suggests that tight glycemic control results in improved vascular function and lower risk of infection. For example, patients undergoing hormone therapy of any sort could have severe blood-glucose level fluctuations that require continuous monitoring.
These studies suggest the immediate need for a new approach to hospital blood-glucose management; the implementation of continuous glycemic control is clearly an urgent necessity for all critical care patients, not only diabetics. The available conventional testing methods, though accurate, are not administered nearly as frequently as needed, and the technology is not the most up-to-date.
In a hospital, it would be impossible to perform a strip test every hour over several days, and even this would fall short of the mark — most studies show that even hourly testing is not frequent enough. Some hospitals use LifeScan's SureStepFlexx for continuous blood- glucose monitoring. This system, though accurate and user-friendly, is not a truly continuous monitoring device. The fact that it requires a blood sample and a strip makes it fairly conventional.
The need for a real-time monitoring system that could collect, interrupt and display the blood-glucose level at any instant without the need for blood samples is clearly present. An electrode-like connection, perhaps wireless, between the patient and the central monitoring system seems achievable considering the available technology.
In the Marketplace
Continuous monitoring of diabetics' blood sweetness has been a hot topic in the patient monitoring industry in the past few years, and some significant progress has been made. Medtronic’s MiniMed division and DexCOM both have introduced wireless continuous blood-glucose monitoring systems that can record and store blood-glucose levels — wirelessly — and alert clinicians of any dangerous fluctuations.
MiniMed's Guardian RT system, recently approved by the FDA for patients over the age of 18 with Type 1 and Type 2 diabetes, is a doctor-prescribed, patient-owned continuous glucose monitoring system that displays an updated “REAL-time” glucose value every five minutes and alerts patients when glucose levels become too high or too low, helping them take action before a problem occurs. The technology gives patients access to real-time glucose readings and alarms around the clock. Using the Solutions Software for Guardian RT, up to 21 days of the glucose fluctuation graph can be downloaded to show the effect of meals, exercise, insulin and medication on glucose levels. (Source: www.minimed.com)
FDA-cleared this March, the DexCOM STS Continuous Glucose Monitoring system is a patient-insertable, short-term sensor that wirelessly transmits blood-glucose readings to the DexCom STS Receiver. The DexCom STS Sensor includes a wire-like sensor that is inserted via the DexCom STS Applicator by the user or clinician just under the skin, where it is held in place by an adhesive to the skin. The user wears the DexCom STS Sensor for up to three days before it is replaced. After three days, the patient removes the sensor from the skin and discards it. A new sensor can then be used with the reusable STS Transmitter and STS Receiver. (Source: www.dexcom.com)
In both the Minimed and DexCom systems a disposable sensor is inserted under the skin via an insertion device (the insertion is virtually painless). The sensor is then connected to a transmitter that is secured on the skin. The data collected by the sensor is transmitted to a monitor wirelessly via radio frequency wave. The sensor does not have to be replaced for 72 hours.
Potential CCU Application
Although these systems can be used in hospitals on critically ill patients individually, the available wireless communication infrastructure available in hospitals could easily enable their integration into the central monitoring systems.
In order to synchronize these systems with a hospital central monitoring network, an algorithm must first be adapted to receive, interrupt and display the data on a central monitoring display unit. After that, the DexCom or MiniMed monitors can be connected to the central monitoring network, via a USB port, for instance.
If the CCU unit is equipped with a Wireless Telemetry Monitoring System (WTMS), then wireless communication is possible directly between the WTMS and the transmitter on the patient's body. In both cases, an amplifying interface can be placed near the patient to ensure reliable connectivity.
Currently, the Minimed and DexCom systems are intended for individual diabetic patient applications. However, with a few modifications in the data transfer interface and monitoring software, these systems can be easily implemented in critical care units and completely eliminate the labor and pain that goes into conventional strip glucose testing.
The most valuable aspect would be the continuous monitoring capability that is vital for better patient care.

Mike Arani, MS, biomedical engineering, is a research analyst with the Frost & Sullivan North American Healthcare Practice. He focuses on monitoring and analyzing emerging trends, technologies and market behavior in the patient monitoring industry.