18.9 Persistent Post Surgical Pain

Question 1

a) Define persistent postoperative pain. (Also known as chronic or persistent post-surgical pain) (3 marks)

Answer 1

> > Pain developing after surgical
procedure

> > Lasting greater than two months.

> > Other causes excluded,
including preoperative cause.

IASP Def

Question 2

b) Which surgical procedures are most commonly associated with persistent postoperative pain? (5 marks)

Answer 2

> > Inguinal hernia repair.

> > Coronary artery bypass grafting (CABG).

> > Thoracotomy.

> > Femoral popliteal bypass.

> > Hip and knee arthroplasty.

> > Amputation.*

> > Mastectomy.

> > Vasectomy*.

> > Caesarean section.

Question 3

c) What are the risk factors for development of persistent postoperative pain? (8 marks)

Answer 3

Preoperative:
» Genetic susceptibility.
» Preoperative pain.
» Psychological factors: anxiety, fear of surgery, tendency to catastrophise.
» Poor social support.
» Age: increasing age reduces risk.
» Possibly female gender.

Intraoperative:
» Procedure that involves significant nerve and tissue damage.
» Specific procedures, see part (b).

Postoperative:
» Poor pain control postoperatively, days of poor control being worse than
single episode of severe pain.
» Radiotherapy.
» Neurotoxic chemotherapy.

Question 4

d) What pathophysiological changes occur at spinal cord level during the transition from acute to
persistent postoperative pain? (4 marks)

Answer 4

1&raquo_space; Repeated peripheral nerve stimulation
or nerve damage causes
increased sodium channel expression, *

2 = resulting in reduced threshold
for, or spontaneous,
firing of peripheral nerves.

3 This results in increased glutamate
release from these first-order
neurones at the dorsal horn.

4 Glutamate receptor density of postsynaptic membranes on second-order
neurones increases.

Transmission occurs in previously
inactive second order neurones,

neurones that do not normally
transmit pain information,

and transmission may persist
beyond duration of initial input,
‘central sensitisation.’

> > Microglia, activated by nerve damage,
release substances that further
sensitise and excite neurones.