British journal of anaesthesia
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Although between 85% and 90% of patients with advanced cancer can have their pain well controlled with the use of analgesic drugs and adjuvants, there are some patients who will benefit from an interventional procedure. This includes a variety of nerve blocks and also some neurosurgical procedures. ⋯ Most patients about to undergo these procedures are already taking high doses of opiods and obtaining valid consent may pose problems. The use of peripheral nerve blocks, epidural and intrathecal infusions, and plexus blocks is discussed.
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The spinal cord is the first relay site in the transmission of nociceptive information from the periphery to the brain. Sensory signals are transmitted from the periphery by primary afferent fibres into the dorsal horn of the spinal cord, where these afferents synapse with intrinsic spinal dorsal horn neurones. Spinal projection neurones then convey this information to higher centres in the brain, where non-noxious and noxious signals can be perceived. ⋯ After nerve injury or conditions of inflammation, shifts can occur in these excitatory and inhibitory mechanisms which modulate spinal excitability, often resulting in the heightened response of dorsal neurones to incoming afferent signals, and increased output to the brain, a phenomenon known as central sensitization. In this review, we consider the ways in which spinal cord activity may be altered in chronic pain states. In addition, we discuss the spinal mechanisms which are targeted by current analgesics used in the management of chronic pain.