Define pain. (10% of marks) Describe the anatomical and immediate physiological components of the response to pain arising from the insertion of an arterial line. (90% of marks)
The pain pathways following arterial line insertion involve sensing the stimulus and transmitting the sensation to the central nervous system. It was expected candidates could provide some detail about the major features along this pathway including a description of sensors, nerve types, spinal cord input and decussation with subsequent projection to higher centres. Better answers provided additional details about modulation and descending pathways. The question also required a description of the physiology with some discussion of the mediators involved and explanation of how a stimulus or tissue may result in the perception of pain. Common omissions included insufficient detail of the pain pathway and limited or no discussion of the physiological components.