Perioperative analgesia Flashcards
Define pain
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.
What are the features of acute pain?
Recent onset
Probable limited duration
Identifiable cause
What are the features of chronic pain?
Persists beyond the time of healing of an injury
>3 months
May not have an identifiable cause
List the types of pain detected by nociceptors
Mechanical Thermal Chemical -Endogenous -Exogenous
Define nociception
Transmission of painful stimulus, without consciousness
What are nociceptors?
Specialised sensory receptors with high activation threshold. Used to detect harmful levels of stimulus.
Differentiate between A-delta and C sensory fibres
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
Describe the Gate control theory of pain
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
Name 4 noxious signals that open the gate of pain
Injury Stress Depression Anxiety Focusing on pain
Name 3 non-noxious signals that close the gate of pain
Medication
Relaxation
Distraction
Positivity
Outline the WHO pain ladder
Non-Opioid drug (single or combination)
Weak opioids drug added
Strong opioids
Name 2 non-opioid drugs
Paracetamol
NSAIDs
COX2 inhibitors
Name 2 opioids
Tramadol
Codeine
Name 3 strong opioids
Morphine Diamorphine Oxycodone Alfentanil Fentanyl Pethidine
What are the benefits of paracetamol?
Simple pain relief
Antipyretic
Oral and IV
Name 2 cautions of paracetamol
Liver failure
Patients weighing <50kg
Name 2 NSAIDs
Ibuprofen
Diclofenac
Aspirin
What are the benefits of NSAIDS?
Pain relief
Anti-inflammatory
Antipyretic
Name 2 cautions of NSAIDs
Renal failure Bleeding Fluid retention Bronchospasm GI disturbance Acute MI
What are the benefits of codeine
Also available as mixture with paracetamol - co-codamol
Variable metabolism
Name 2 side effects of codeine
Respiratory depression
Constipation
What are the benefits of tramadol
Powerful analgesic
Oral or IV
Name 1 caution of Tramadol
Caution in elderly ➔ confusion or agitation
Name 2 side effects of Tramadol
Constipation
Addiction
Name 3 adjunct pain medications
Clonidine
Ketamine
Local anaesthetic infusion
Gabapentin
What are the benefits of patient controlled analgesia?
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.
How does pain affect post-op complications?
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)
