How do anesthetics prevent people from feeling pain during surgery?

Anesthetics prevent the sensation of pain during surgery by suppressing responses to sensory stimulation through two primary mechanisms, depending on whether they are local or general agents.1

Local Anesthetics

Local anesthetics provide targeted relief by temporarily blocking the conduction of nerve impulses along peripheral sensory nerves. When administered, these drugs penetrate the fatty membrane of nerve fibers and block ion channels from the inside. By preventing the influx of sodium ions, they stop the electrical currents necessary to transmit pain signals from the site of trauma to the spinal cord and brain. Because thinner fibers—such as those conveying dull, aching pain—are the most susceptible, these agents can effectively eliminate pain while often leaving motor function intact.21

General Anesthetics

General anesthesia involves a loss of consciousness and acts primarily on the central nervous system. While the exact mechanisms are not fully understood, these agents are known to block the transmission of signals across synapses in the brain. They may function by inhibiting excitatory neuronal transmission or by stimulating inhibitory pathways, effectively preventing the brain from processing or registering pain during surgical procedures.13