Analgesia in oral surgery Flashcards
Briefly overview the arachidonic acid pathway
Tissue injury results in damage to the phospholipid bilayer of cells
This leads to release of arachidonic acid which then gives rise to two pathways.
Leukotrienes are released
- bronchoconstricton
- asthma attacks
- smooth muscle constriction
Prostaglandins released
- causing pain and inflammation
Thromboxane released
- causing platelet aggregation
What does a prostaglandin do?
sensitise tissues to other forms of pain and inflammation
Such as leukotrienes
So decrease in prostaglandins moderates pain
When can aspirin be used for treatment? What are its properties?
effective at TMJ pain and dental pain
Superior anti-inflammatory to paracetamol
Ibuprofen more used now
Analgesic, antipyretic, anti-inflammatory
what is the mechanism of action for aspirin?
inhibits COX-1 and COX-2 mechanisms
- reduces platelet aggregation
- decrease prostaglandin release
How does aspirin decrease elevated temperature as an antipyretic?
prevents temperature raising effects of interleukin-1 and rises in brain prostaglandins
How does aspirin act as an anti inflammatory?
Prostaglandins are vasodilators hence affecting capillary permeability
Aspirin decreases prostaglandins hence lowering inflammation
What adverse effects are there of aspirin? Give an example for each
GIT sensitivity - mucosal lining, increased acid secretion and blood flow
Hypersensitivity - bronchospasms, asthma attack, rashes or other allergies
Overdose - tinnitus, metabolic acidosis (acid retention)
Aspirin burns - mucosal due to salicylic acid
What groups should be wary of taking aspirin? Why?
Those with GIT issues such as gastric ulcers or GORD
Asthmatics due to hypersensitivity reactions (ask if used NSAIDS before and had any issues?)
Bleeding abnormalities and anticoagulants
Pregnant/breast feeding - impair platelet function
Those on steroids or other NSAIDS - 25% will have peptic ulcer which aspirin can perforate
Renal/hepatic impairment - metabolised in liver and excreted in kidney, can cause nephrotoxicity
Children under 16
Elderly
What is Reye’s syndrome?
Rare disease causing swelling in the liver and the brain
- Profound swelling in the brain with 50% mortality rate
Symptoms include
- lethargy
- seizures
- coma
Mainly in children after viral infection, and those who have taken aspirin while having viral infection
When is aspirin completely contraindicated?
1- children under 16, or breast feeding
2 - previous or active peptic ulceration
3 - haemophilia
4 - hypersensitivity to aspirin or other nsaids
How would you prescribe aspirin for Odontogenic pain?
2 x 300mg tablets, 4 x daily preferably after food
Maximum dose is 4g / day
What can you prescribe if MH indicates to not use aspirin but an NSAID is needed?
Lansoprazole - 1 capsule per day for 5 days
Gastro-resistant omeprazole - 1 capsule per day for 5 days
Help vs prophylaxis of gastric issues when using nsaids
How would one prescribe ibuprofen?
1 tablet four times daily, preferably after food
Max dose 2.4g daily
When should one show caution for prescribing ibuprofen?
- peptic ulcers previous or active
- asthmatics or those with previous hypersensitivity reactions to NSAIDS
- the elderly
- pregnancy or lactation
- kidney, liver or cardiac impairment
- on nsaids
Indications of ibuprofen overdose?
Tinnitus
Nausea
Vomiting
When is ibuprofen completely contraindicated?
- previous history of GIT bleeding
- active GIT ulceration
- any previous perforation of GIT
What is the mode of action of paracetamol?
Paracetamol indirectly inhibits COX (cyclooxygenase) activity by blocking the positive feedback hyperoxides have on the metabolism of arachidonic acid
This occurs mainly in the pain pathways of CNS - in the thalamus
Why is paracetamol safer in those with GIT issues?
Little to no effect on peripheral prostaglandins
Hence little to no GIT irritation
What cases should one show caution when giving paracetamol?
Hepatic or renal impairment
Alcohol dependence
How would one prescribe paracetamol?
2 x 500mg tablets 4 times daily
Maximum dose is 4g daily
Emphasise never take more than this in 24 hours
What occurs during paracetamol overdose
Hepatocellular necrosis
Liver damage 3-4 days after ingestion leading to liver failure and death
How do opioid analgesics work?
Act in the spinal cord
- especially in dorsal horn pathways as a central regulator of pain
They are relatively ineffective for dental pain
What are some problems with opioid medications
Withdrawal symptoms due to tolerance
Tolerance - doses must be progressively increased
Smooth muscle issues - constipation or urine retention
Give some side effects of opioids
- xerostomia
- sweating
- headache
- bradycardia
- palpitations
