Train-of-four

The train-of-four (TOF) is a clinical test used to assess how well muscle relaxants are working during anesthesia. A device delivers four small electrical stimuli to a nerve, usually in the arm, and measures the muscle's response. If the muscles respond equally, the relaxation is minimal. If responses weaken or disappear, it indicates increasing muscle relaxation. The TOF helps anesthesiologists determine the right amount of muscle relaxant to use, ensuring patient safety and effective paralysis during surgery while avoiding excessive relaxation or residual effects afterward.