Better monitoring route may be through stomach
Tonometry provides early warning
For some patients, a smoother road to recovery may run through their stomachs. That's where changes in carbon dioxide levels in fluids can provide an early warning signal that the patient is about to take a turn for the worse, providing extra time to make vital treatment adjustments.
The device that does this is a Tonocap monitor, a balloon-tipped tube that is placed in the stomach through the nose or mouth. At 10-minute intervals, the monitor alerts nurses to increases in carbon dioxide levels, which if persistent, could lead to multiple organ system failure (MOSF), one of the leading causes of ICU deaths.
The early warning allows physicians to administer fluids, blood, oxygen or medication to avoid shock or sepsis. In short, the early warnings help detect, prevent, and reverse complications that may lead to MOSF. Avoiding MOSF can preserve more than 40% of an ICU's financial resources and help patients go home earlier, researchers report.
The monitor is not in widespread use, but its acceptance is growing. After eight years of clinical trials and approximately 800 reported clinical studies on the use of tonometric technology, the Tonocap monitor received U.S. marketing approval from the Food and Drug Administration in April 1997.
More than 400 have been sold, says the manufacturer, Datex-Engstrom Inc. of Tewkesbury, MA. Among the hospitals that currently use the Tonocap monitor are Duke University Medical Center in Durham, NC; Hermann Hospital in Houston; and Jackson Memorial Hospital in Miami.
Recently discovered phenomenon
The principle on which this monitoring system is based - tonometry - is a relatively recent phenomenon. Tonometry itself is a term used to describe the process of measuring gases in a hollow organ, such as the stomach. Conventional monitoring evaluates vital signs of the body as a whole. This approach has limitations because patients could already be in serious trouble during the time it takes to discover what the problem is.
On the other hand, regional monitoring requires examination of an organ, such as the stomach, where oxygen is used. This method produces earlier warnings of potentially avoidable complications.
With conventional monitoring, it could take hours or days for physicians to realize patients were unstable, says Richard Treat, MD, director of surgical critical care at Fairview Hospital in Cleveland. "Nurses would have to take blood tests every six hours at $135 a pop, and we'd have to wait two hours for results. A lot can happen while you're waiting for results. Now we can get real time analysis for faster intervention."
The process also is more staff friendly, says Gary Collin, MD, associate director of trauma at Carilion Roanoke (VA) Community Hospital. "Before the machines, the process of obtaining the sample to be analyzed was very labor-intensive for nurses. Now it's a matter of plug it in and flip a switch. It's a better indicator of mortality than anything that's been done before."
In a study presented at the Society of Critical Care Medicine convention in February in San Antonio, Joseph Civetta, MD, and fellow researchers determined that using the gastric catheters to help guide therapy resulted in $11,103 savings per ICU patient. Civetta is professor and head of the department of surgery at the University of Connecticut Health Center in Hartford and past president of the society.
Moreover, "there was significant shift to earlier ICU discharge," Civetta says. His study showed a reduction in ICU days from two weeks down to one to two days.
Investigators also compared ICU stays of patients using the catheters in 1993 and 1995. By monitoring carbon dioxide levels and using a prophylactic treatment of medication and vitamins, severity of illness scores from the Acute Physiology Age Chronic Health Evaluation system (APACHE II) were lowered by 39%.
What patients will benefit?
One physician who has used the tonometry monitoring even before the Tonocap was approved says it is effective for patients recovering from the most severe car accidents, gun shot wounds, pancreatitis, and from major surgery. "Eventually we may find more types of patients that could benefit from it," says Rao R. Ivatury, MD, professor of surgery at New York Medical College in Valhalla.
He tested the device on 57 patients with multiple trauma admitted to Lincoln Hospital in the Bronx in the early 1990s and found that the unexpected abnormal readings alerted physicians more quickly to major complications such as bacterial infections, complications of surgery, or a breakdown of sutures in the intestines.
"What we found is that it can deliver better results within the first 24 hours after injury. For most patients, the survival is much better, and organ failure rate is much lower," Ivatury says.
Other clinical studies found that the device also helps patients at risk of developing hypovolemia, septic shock, cardiogenic shock, severe acute respiratory failure, and severe acute pancreatitis, says the manufacturer.
It also can be used both during and after surgery, and for applications such as weaning patients off ventilators, acute respiratory distress syndrome, burns, and acute circulatory failure.
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