Devices for measuring SKNA are need to be re-constructed, which takes considerable time.

Skin sympathetic nerve activity (SKNA) has recently been discovered from the electrocardiogram obtained from healthy volunteers. The raw physiologic electric signal from electrodes placed on the skin was reprocessed through filtering and integration using software to produce the SKNA signal. However, no study has yet provided knowledge on the effect of anesthetics on SKNA during general anesthesia.

The most commonly used anesthetic techniques during general anesthesia are the total intravenous anesthesia (TIVA) and anesthesia using inhalants such as sevoflurane or desflurane. For TIVA, the combination of propofol and remifentanil has been used and remifentanil is known for increasing vagal tone and inhibiting sympathetic nervous system as other opioids do. Sevoflurane is presumed to have no effect on parasympathetic or sympathetic tone. On the other hand, desflurane induces tachycardia and is noted for activating sympathetic activity. Previous studies on sympathetic nervous activity according to different anesthetics did not directly measure sympathetic tone but have relied on indirect measures such as blood pressure, heart rate, and heart rate variability.

In order to evaluate skin sympathetic nerve activity according to different anesthetics, we will be recruiting patients undergoing transurethral procedures, where the sympathetic tone is expected to be activated during anesthesia and surgery. The transurethral procedures consist of transurethral resection of bladder (TURB) and transurethral resection of prostate (TURP). During transurethral surgery, about 300mL of fluid is used to fill the bladder to secure surgical view and for irrigation. Bladder expansion causes sympathetic nerve activation and vasoconstriction, which will also increase SKNA signals. The purpose of this study is to measure skin sympathetic nerve activity according to different anesthetics during intraoperative events that stimulate sympathetic tone.

Inclusion Criteria:

• Scheduled to undergo elective transurethral procedures under general anesthesia

Exclusion Criteria:

• Diagnosed with autonomic dysfunction
• Current use of beta blockers
• Cardiac arrhythmia
• Absolute indication for either TIVA or inhalants, absolute contraindication for either TIVA or inhalants (adverse effects on either propofol or remifentanil, risk of malignant hyperthermia)