The effect of the location of tetanic stimulus on photoplethysmography signals will be studies in patients under general anesthesia.
A 5 second 100 Hz 70 mA tetanic stimulus will be applied to three different locations in a random order in patients who are under general anesthesia. Tetanic stimuli are used routinely during general anesthesia to assess effectiveness of neuromuscular blockade. These tetanic stimuli are noxious stimuli that elicit a stress response which can be quantified using photoplethysmography. This study investigates if the magnitude of the tetanus induced stress response is dependent on the location of the tetanic stimulus as measured by photoplythysmography.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
DIAGNOSTIC
Masking
NONE
Enrollment
12
5 second 100 Hz 70 mA tetanic stimulus will be applied to three different locations in a random order
University of California San Francisco
San Francisco, California, United States
Photoplethysmography (PPG)
Change in the PPG signal in response to tetanic stimulus. A tetanic stimulus will cause vasoconstriction which can be recorded as a decrease in PPG AC/DC. The outcome measure is the maximum decrease in AC/DC from baseline. Maximum decrease happens typically in 30-60 seconds after the stimulus. Thus, data was collected immediately before (baseline) and for 2 min after the stimulus. After the stimulus AC/DC values return to baseline in a few minutes. Baseline AC/DC measures a relative state of blood vessel tone. In anesthetized patients the AC/DC values can range from close to 0 to above 10. The higher the value, the more vasodilated the subject is.
Time frame: 1-2 minutes
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