Common procedures in anaesthetics Flashcards
What is pain?
An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage.
What are the two categories of pain?
*Acute pain - new onset of pain
*Chronic pain - pain present for 3 months or more
What are the two aspects to the experience of pain?
- Sensory - the sensory signal transmitted from the pain receptor (“It is a sharp sensation, likely a needle”)
- Affective - the unpleasant emotional reaction to the pain (“It is excruciating, I can’t bear it”)
Which nerve fibres transmit pain?
- C fibres (unmyelinated and small diameter) - transmit signals slowly and produce dull and diffuse pain sensations.
- A-delta fibres (myelinated and large diameter) - transmit signals fast and produce sharp and localised pain sensations.
What are the main sensory inputs that generate a pain signal?
- Mechanical (e.g. pressure)
- Heat
- Chemical (e.g. prostaglandins)
What are the three steps to the analgesic ladder?
Step 1. Non-opioid medications like paracetamol and NSAIDS.
Step 2. Weak opioids such as codeine and tramadol.
Step 3. Strong opioids such as morphine, oxycodone, fentanyl and buprenorphine.
Examples of adjuvants (used alongside the analgesic ladder, or separately to manage neuropathic pain)
- Amitriptylline - tricyclic antidepressant
- Duloxetine - SNRI antidepressant
- Gabapentin - anticonvulsant
- Pregabalin - anticonvulsant
- Capsaicin cream (topical)
Side effects of analgesic meds (NSAIDS)
- Gastritis with dyspepsia (indigestion)
- Stomach ulcers
- Asthma exacerbation
- HTN
- Renal impairment
- Coronary artery disease, HF and strokes (rare)
NSAIDS contraindications
- Asthma
- Renal impaiment
- Heart disease
- Uncontrolled HTN
- Stomach ulcers
Opioids side effects
- Constipation
- Pruritus
- Nausea
- Altered mental state (sedation, cognitive impairment or confusion)
- Respiratory depression
Naloxone is used to reverse opioids effects in life-threatening overdose.
How are opioids used in palliative care?
Using opioids to control pain in palliative patients is a specific scenario where the doses are titrated and optimised over time. This involves using a combination of:
- Background opioids (e.g., 12-hourly modified-release oral morphine)
- Rescue doses for breakthrough pain (e.g., immediate-release oral morphine solution)
Rescue dose is usually 1/6 of background dose.
Why is adequate analgesia in the post-op period so important?
Helps encourage the patient to:
- Mobilise
- Ventilate their lungs fully (reducing the risk of chest infx and atelectasis)
- Have an adequate oral intake
What is PCA?
Patient controlled anaesthesia
Patient-controlled analgesia (PCA) involves an intravenous infusion of a strong opiate (e.g., morphine, oxycodone or fentanyl) attached to a patient-controlled pump. A PCA involves the patient pressing a button as pain develops to administer a bolus of opiate medication. The button will stop responding for a set time after administering a bolus to prevent over-use.
What are the two categories of chronic pain?
- Chronic primary pain - no underlying condition can adequately explain the pain
- Chronic secondary pain - an underlying condition can explain the pain.
How do we assess neuropathic pain?
DN4 questionnaire.
Score of 4 or more out of 10 indicates neuropathic pain.
