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What you need to know about
T-Stat® NP Cranial Monitoring

What is T-Stat?

T-Stat is an FDA approved Tissue Oximeter.

T-Stat measures the amount of available oxygen in the blood AFTER a tissue has extracted as much as it can absorb. It is a noninvasive measure of perfusion that does not require invasive catheters or blood sampling.

Because T-Stat measures blood in the tissues, it is different than a Pulse Oximeter, which measures blood in the arteries, as shown here (Figure 1):

Figure 1. Tissue Oximeters Detect and Monitor Low or Unstable Perfusion

What is the benefit of T-Stat?

At multiple centers, in vascular surgery and in ICU care, the use of tissue oximeters has been shown to lower the risk and incidence of multi-organ failure and death due from low or impaired delivery of oxygen to tissues and organs.

T-Stat is now available with a probe that monitors within the internal carotid distribution. The probe is placed nasally, as shown below:

Differences between somatic and cranial oxygenation can be seen, with somatic oxygenation falling early and deeply, in most cases, prior to a drop in cranial saturation

What should I normally see?

For healthy patients, T-Stat normally reads 63-75% (neonates read slightly lower) (figure 2, at right).

T-Stat normals are very DIFFERENT than pulse oximeter normals. This is because the tissues of healthy patients normally remove enough oxygen from arterial blood to drop T-Stat levels to 25% to 35% below the pulse oximeter.

What is abnormal, and what do these readings mean?

There are 2 important ways to think about abnormal T-Stat readings at the bedside.

First, consider the T-Stat reading . T-Stat readings below 55% are rarely normal, and indicate an increased risk of inadequate oxygen delivery (figure 3, at right)

T-Stat values below 40% in adults, and below 35% in children, have been shown to lead to metabolic acidosis via lactic acid production.

If left untreated, T-Stat values below 30% may rapidly lead to tissue death.

Second, consider the gap between T-Stat and the Pulse Oximeter . The gap between tissue and pulse oximeter readings grows with impaired oxygen delivery.

A difference of 38% or more between T-Stat and Pulse Oximeter suggests an impaired delivery of oxygen to tissue.

Low T-Stat readings and widened Pulse-Tissue gaps may be caused by:

_•    Decreased systemic blood flow (hypovolemia, shock, heart dysfunction)
_•    Vascular lesions and inadequate revascularization
_•    Anemia
_•    Increased metabolism (fever, stress, sepsis)
_•    Changes in drips, medications, or ventilator settings that worsen perfusion

How long does it take to place a T-Stat sensor?

A T-Stat endoscopic measurement is made in seconds. Placing the T-Stat sensor during endoscopy or surgery may require 1-3 minutes. Follow placement instructions, available online or in T-Stat packaging.

What care does a T-Stat sensor require?

If a T-Stat sensor is reading well, the monitor will display a green dot and "Monitoring" at the bottom of the screen. If T-Stat is NOT getting a good signal, the monitor will show a yellow or red dot with a warning message. Correcting the displayed problem often restores readings.

The illuminated sensor tip should never press against tissue. Pressure on the tissue by the sensor tip may disrupt local tissue blood flow and cause the saturation to fall.

T-Stat is sensitive to free blood under the probe, which oxygenates in room air and elevates the T-Stat reading. Probe removal and cleaning with an alcohol swab may be required.

What if I have more questions?

Read the T-Stat brochure or instructions, available online at www.spectros.com. If you have additional questions, you may call us at 1-877-TSTAT-303, or email your question to info@spectros.com.

(Cranial About rev 2007.11.22)