Question

James is a 45 year old man who is brought into the clinic after cutting his right hand with a knife while installing carpet. He has cleaned his hand and wrapped the cut in a bandage which has stopped the bleeding. His physical examination reveals a clean 2 inch laceration (cut) in his right palm which is well-approximated (the edges of the wound align). His vital signs are stable, and he has agreed to surgical repair of his laceration. He states that his pain is a 6/10, and describes it as being a sharp pain, directly in the area of the laceration.

• What type of pain is James experiencing? Be specific about the type and subtype, and explain your rationale.
• In 3-6 sentences, explain the transmission of James’ pain. Include the transduction, transmission, modulation, and perception of the pain.
• Laceration repair involves the use of a needle to draw the suturing material through the healthy tissue. What type of analgesia do you expect to be used to control James’ pain while repairing his laceration? Explain why that type of analgesia would be used, as well as the specific mechanisms by which it will control James’ pain.

Answer 1

In this case the individual is experiencing Nociceptive type of pain.( superficial somatic pain)

Nociceptive pain is caused by stimulation of the sensory nerve fibers, which are present in the skin. Nociceptive pain can be classified according to the site of origin and they are divided into Visceral, which is pain associated with visceral structures like heart, intestines, etc, Deep somatic pain, which refers to pain in tendons, muscles, ligaments or deep blood vessels, etc and lastly Superficial somatic pain, this type of pain activated by nociceptors inthe skin, which include minor wounds or first degree burns.

When an injury occurs the nociceptors on your skin or tissue gets activated, there are two types of fibers, A fibers which cause pain immediately and C fibers which cause pain aftert he stimulus has happened. Membranes of these fibers contain voltage gated ion channels so when an injury happens there is an influx of sodium ions, which causes depolarization in the cell leading to generation of an action potential, these signals are conducted to the dorsal horn of the spinal cord, the action potential causes the presynaptic terminal to release variety of pro-nociceptive substances like substance P into the synaptic cleft, this activates postsynaptic synaptors, which results in influx of ions that depolarizes second order neurons, when a second order neuron is depolarized, it generates an action potential that is releayed through spinothalamic tract to the brain stem and than to thalamus and finaly to the cerebral cortex, where pain is perceived.

During laceration repair, a form of an injected numbing medication is used, for example lidocaine ( local anasthesia) these type of medication works by stopping the sodium ions from passing through the voltage-gated channels. So the signals for pain are stopped even before the signals are formed.