TetraGraph is a newly developed EMG-based, quantitative, battery-powered neuromuscular monitoring system intended for daily clinical use. The primary aim of this clinical investigation is to examine the applicability (ease of use, equipment need, etc.), repeatability (precision or internal consistency) and performance (signal quality, accuracy of outcome, voltage of stimulation output before and during a stimulus) of the Tetragraph device in patients undergoing elective surgeries requiring neuromuscular blockade.

The TetraGraph will be tested in 50 consenting patients undergiong elective surgeries requiring neuromuscular blockade. The left of right hand of the patients will be randomly studied. After the induction of anesthesia but before the administration of muscle relaxant train-of-four (TOF) stimulation will be started with 30 mA current intensity, 0.2 msec pulse duration at 20 sec intervals. The stimulation will be left to run until extubation. The TetraGraph device will be set not to show measurement results on the screen but save them on the SD card for later analysis. This way TetraGraph will not influence clinical decisions and patient care. During the operations we will record the number of muscle twitches in return to stimulation, the time and dose of muscle relaxant and opioid administration, the time of use of electrocautery and the skin temperature.

Inclusion Criteria:

1. Age 18 years or older.
2. American Society of Anesthesiology (ASA) physical status I-III criteria (Table I).
3. Subject has provided written informed consent.

Exclusion Criteria:

1. Presence of an underlying neuromuscular disease.
2. Presence of renal or hepatic disease.
3. Subject has open skin sores in the locations needed for electrode application (forearms).
4. Patient is taking anti-seizure medication
5. Patient is taking oral anti-cholinesterase (e.g., therapy for myasthenia gravis)
6. Magnesium sulfate administration is required

Patients undergoing elective surgeries requiring muscle relaxation