Perioperative analgesia

Question 1

Define pain

Answer 1

What the patient says it is

An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.

Question 2

What are the features of acute pain?

Answer 2

Recent onset
Probable limited duration
Identifiable cause

Question 3

What are the features of chronic pain?

Answer 3

Persists beyond the time of healing of an injury
>3 months
May not have an identifiable cause

Question 4

List the types of pain detected by nociceptors

Answer 4

Mechanical
Thermal
Chemical
-Endogenous
-Exogenous

Question 5

Define nociception

Answer 5

Transmission of painful stimulus, without consciousness

Question 6

What are nociceptors?

Answer 6

Specialised sensory receptors with high activation threshold. Used to detect harmful levels of stimulus.

Question 7

Differentiate between A-delta and C sensory fibres

Answer 7

A-delta: myelinated large nerves detecting sharp pain, activated by mechanical and thermal modalities

C: unmyelinated small nerves detecting dull aching pain, activated by all 3 modalities

Question 8

Describe the Gate control theory of pain

Answer 8

Inhibitory output from the substantia gelatinosa is regulated by noxious and non-noxious signals.

Non-noxious: increases inhibitory output ➔ less pain

Noxious: decreases inhibitory output ➔ more pain

Question 9

Name 4 noxious signals that open the gate of pain

Answer 9

Injury
Stress
Depression
Anxiety
Focusing on pain

Question 10

Name 3 non-noxious signals that close the gate of pain

Answer 10

Medication
Relaxation
Distraction
Positivity

Question 11

Outline the WHO pain ladder

Answer 11

Non-Opioid drug (single or combination)
Weak opioids drug added
Strong opioids

Question 12

Name 2 non-opioid drugs

Answer 12

Paracetamol
NSAIDs
COX2 inhibitors

Question 13

Name 2 opioids

Answer 13

Tramadol

Codeine

Question 14

Name 3 strong opioids

Answer 14

Morphine
Diamorphine
Oxycodone
Alfentanil
Fentanyl
Pethidine

Question 15

What are the benefits of paracetamol?

Answer 15

Simple pain relief
Antipyretic
Oral and IV

Question 16

Name 2 cautions of paracetamol

Answer 16

Liver failure

Patients weighing <50kg

Question 17

Name 2 NSAIDs

Answer 17

Ibuprofen
Diclofenac
Aspirin

Question 18

What are the benefits of NSAIDS?

Answer 18

Pain relief
Anti-inflammatory
Antipyretic

Question 19

Name 2 cautions of NSAIDs

Answer 19

Renal failure
Bleeding
Fluid retention
Bronchospasm
GI disturbance
Acute MI

Question 20

What are the benefits of codeine

Answer 20

Also available as mixture with paracetamol - co-codamol

Variable metabolism

Question 21

Name 2 side effects of codeine

Answer 21

Respiratory depression

Constipation

Question 22

What are the benefits of tramadol

Answer 22

Powerful analgesic

Oral or IV

Question 23

Name 1 caution of Tramadol

Answer 23

Caution in elderly ➔ confusion or agitation

Question 24

Name 2 side effects of Tramadol

Answer 24

Constipation

Addiction

Question 25

Name 3 adjunct pain medications

Answer 25

Clonidine
Ketamine
Local anaesthetic infusion
Gabapentin

Question 26

What are the benefits of patient controlled analgesia?

Answer 26

Patient controlled morphine syringe

Allows patients to control they analgesia, and reduces the variation in plasma levels. It has high satisfaction scores independent of actual pain control.

Question 27

How does pain affect post-op complications?

Answer 27

CVS: high HR, high BP, increased myocardial O2 demand
Resp: decreased VC, FRC, and TV, basal atelectasis, chest infections
GI: PONV, ileus
Urinary retention
VTE (DVT and PE)