Pain Management Flashcards
Define Pain
An unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage
What are the two broad distinctions of pain?
Acute
Chronic
What are the four distinctions of chronic pain?
Nociceptive
Neuropathic
Visceral
Mixed
What are the two distinctions of neuropathic pain?
Central
Peripheral
Give examples of acute pain
Trauma
Post-op flare
Give examples of nociceptive pain
Osteoarthritis
Rheumatoid arthritis
Give examples of central neuropathic pain
Post-stroke MS Spinal cord injury Migraine HIV related neuropathic pain
Give examples of peripheral neuropathic pain
Post-hepatic neuralgia
Diabetic neuropathy
Give examples of visceral pain
Internal organ pain
Pancreatitis
IBS
Give examples of mixed pain
Lower back pain
Cancer
Fibromyalgia
What are the goals of pain management?
Minimise stress response/neuroendocrine effects
Minimise adverse effects on wider systems
Patient comfort and satisfaction
What are the three stages of the WHO pain ladder?
Step 1 - simple analgesics (aspirin/paracetamol)
Step 2 - opioids (mod pain) + simple analgesics
Step 3 - opioids (sev pain) + simple analgesics
How does Paracetamol work?
MoA uncertain
What are the two main actions of Paracetamol?
Analgesia
Antipyretic
What formulations is Paracetamol available in?
Tablets (+ soluble) Capsules Suspension Suppository Infusion
What are the major problems with Paracetamol?
Side effects uncommon
Overdose common - liver damage (14 tabs)
What is the treatment for Paracetamol overdose?
Acetylcysteine
How do NSAIDs work?
Inhibit COX - prevent formation of prostaglandins/thromboxanes
What are the three main actions of NSAIDs?
Analgesia
Antipyretic
Anti-inflammatory
What formulations are NSAIDs available in?
Tablets (+ soluble) Capsules Suspension Suppository Creams Gel Patch Infusion
What are the major GI adverse effects of NSAIDs?
GIT erosion & ulceration
What are the major renal adverse effects of NSAIDs?
Reduce renal blood flow - acute failure
Na/K/H2O retention
What are the major respiratory adverse effects of NSAIDs?
Bronchospasm
What are the major haematological adverse effects of NSAIDs?
Reduce platelet aggregation
- Aspirin irreversible
- NSAIDs reversible
How should NSAIDs generally be used?
Lowest effective dose
Shortest period of time possible
Co-prescription of a PPI
What are the clinically common weak opioids?
Codeine
Dihydrocodeine
Dextropropoxyphene
Tramadol (po)
What are the clinically common strong opioids?
Morphine Diamorphine Oxycodone Buprenorphine Fentanyl
When are weak opioids most effective?
When used in combination with paracetamol
What CYP450 protein is responsible for the metabolism of Codeine-Morphine?
CYP450 2D6
What populations are unable to metabolise Codeine-Morphine?
10% caucasian
90% chinese
When are strong opioids used?
Acute pain
Persistent non-cancer pain
Palliative care
What is the ceiling effect?
The point at which increasing dose does not increase analgesia
What type of painkiller does not have a ceiling effect?
Strong opioids
What routes of administration are available for strong opioids?
Oral Rectal Transdermal Sublingual Topical Intramuscular Subcutaneous Intravenous Epidural Intrathecal
What are the major adverse effects of opioids?
Nausea & Vomiting Constipation Sedation Respiratory depression Hypotension Urinary retention
What are the three steps taken when initiating morphine treatment?
Pain assessment
Determine opioid requirement
Convert daily dose to MR formulation
What is breakthrough pain?
Transient exacerbation/recurrence of pain in a mainly stable patient
When does breakthrough pain commonly occur?
End of dose failure
Incident pain
Spontaneous, unpredictable pain
How do you control breakthrough pain?
Add 10% total daily regular dose prn
Describe the treatment structure with i.m. opioids
4 hourly
Several doses to achieve adequate levels
Variable absorption
Painful
What is the preferred drug for Patient Controlled Analgesia?
Morphine i.v.
What drugs can be prescribed for PCA if the patient has an allergy to Morphine?
Tramadol
Oxycodone
Fentanyl
What are the advantages of PCA?
Rapid analgesia Ready prepared Patient satisfaction No dose delay No peaks/troughs
What are the disadvantages of PCA?
Expensive
i.v.
Training
Monitoring
Describe epidural opioids
Alternative to PCA
Mixture of local anaesthetic and opioid
What are the major adverse effects of epidural opioids?
Hypotension
Infection
‘wrong route’
What is the most common epidural opioid preperation?
Fentanyl w/ (levo)bupivicaine
Describe syringe drivers
Continuous subcutaneous infections
When are syringe drivers indicated?
Unable to take medicines by mouth
Bowel obstruction
What is the most common opioid used in syringe drivers, and why?
Diamorphine
Excellent aqueous solubility
What parameters should be monitored when treating with opioid?
Pulse BP Resp rate Ox saturation Pain intensity Sedation score Opioid usage/side effects
How does Tramadol work?
u agonist
Inhibits NA uptake/5-HT
What is the side effect profile of Tramadol?
Less opioid side effects
Nausea/hallucinations
How is Tramadol absorbed?
70% absorbed po
Peak 2 hrs
How does Naloxone work?
Opioid antagonist –> reverses effects of opioids
How should Naloxone treatment be structured?
Repeated doses given i.v. (short half life)
Gradual titration
-May induce pain
What is the typical cause of neuropathic pain?
Damage/lesion somewhere between a peripheral nerve and the brain
What are the symptoms of neuropathic pain?
Burning Electric shock Pins/needles Scalding Shooting Stabbing
What are the signs of neuropathic pain?
Continous pain
Evoked pain
-Hyperalgesia
-Allodynia
What are the pharmacological treatments for neuropathic pain?
TCAs Anticonvulsants Opioids Local anaesthetics Capsaicin
How do TCAs work?
Inhibit NA/serotonin reuptake
What limits the use of TCAs?
Widespread adverse effects
What are the two most clinically common anticonvulsants?
Gabapentin
Pregabalin
How do anticonvulsants work?
Prevent voltage dependent Ca channel activation in dorsal horn neurones
