OPIODS Flashcards
What is hyperalgesia?
It is an increased sensitivity to pain
What is life threatening about opioids?
They can cause respiratory depression
What is acute pain?
- Pain that is of recent onset and is less than 6 weeks.
- Usually resolves with healing
What is chronic pain?
- Pain that is is present for more than 3 months
- outlasts the potential for healing
How does depolarisation happen in the dorsal horn of the spinal cord?
Th nerve free endings(nociceptors) being stimulated cause depolarisation and then an impulse is generated
What type of pain do delta fibres transmit?
-sharp, well-localised pain followed by a dull and persistent pain via the C-fibres
What inflammatory markers are released?
- potassium
- serotonin
- hitamine
- substance P
- cytokines
- prostaglandins
- nitric oxide
What favourable effects of opioids do we want?
- analgesia
- euphoria, tranquility
- synergism
- cardiovascular effects
- respiratory depression
What is the function of opiods on the vagal nuclei?
It causes decreased heart rate and vasodilation(eg. if the surgeon opens up the patient and starts messing in there, the patient won’t have tachycardia and increased heart rate
What can you do to reverse respiratory depression caused by opiods?
- provide oxygen
- mechanical ventilation
- naloxone to reverse however very short acting(around 0 minutes)
What are the things we can do to prevent respiratory depression?
- Decrease the dose of analgesia
- monitor the patients closely
- provide mechanical ventilation
- provide multimodal analgesia
Which drugs are lipophillic and hydrophillic?
- morphine-hydrophilic
2. fentanyl-lipophilic
Why do we need to give an infusion after a bolus of fentanyl?
-fentanyl is short acting and so we need to infuse it over time to ensure the patient does not feel pain during
What is morphine terminated by?
elimination
What is fentanyl terminated by?
redistribution
What drugs are categorised as the first step/simple analgesics?
- paracetamol
- NSAIDS
- Codeine
What drugs are categorised as the second step/moderate analgesics?
- Tramadol
2. Higher dose of codeine
What drugs are categorised as severe pain analgesics?
- morphine
2. fentanyl
What are the most NB factors regarding paracetamol?
- acts centrally and peripherally via the COX-3 enzyme
- no anti-inflammatory effects
- anti-pyretic
- possible hepatic necrosis and failure(give N-acetylcysteine to protect from liver damage
What is the onset of action and duration of action for paracetamol?
- onset: 30 minutes
2. duration: 2-5 hours
What is perfalgan?
-It is a IV form of paracetamol that has an onset of duration of 5-10 minutes
Where do NSAIDS work?
- COX-1 and COX-2
What are the effects of NSAIDS on thromboxane production?
1.
What are the effects of NSAIDS on thromboxane production?
- reduced platelet aggregation and risks of bleeding
What are the side effects of NSAIDS?
- gastric irritation
- bronchospasm
- renal dysfunction
- platelet dysfunction
- hepatotoxicity
- myocardial dysfunction
What is the dosage of Ibuprofen?
200-400 mg orally 8 hourly
What is the dosage of codeine?
30-60 mg orally 4-6 hourly
-available as a syrup or tablet
What is the additional mechanism of tramadol?
-it inhibits noradrenaline and serotonin(5-HT) at the presynaptic nerve endings
What are the side effects of pethidine?
- originally intended as an anti-cholinergic
- can produce dry mouth, tachycardia, convulsions, hyperpyrexia, coma,
What is the dosage of morphine that adults and children can get IV and IM?
- 0,1-0,2 mg.kg 4-6 hourly
oral dose is double the parenteral
How much do we titrate morphine intra-operatively?
1-5mg IV
How much more is fentanyl more lipid soluble than morphine?
600 times
What is the onset of action and duration of action of fentanyl?
- onset: 3-4 minutes
2. duration: 30-40 minutes
How does fentanyl help with LMA/ETT insertion?
It relaxes the laryngeal reflexes
What is the difference between fentanyl ,alfentanil and sufentanil?
sufentanil and alfentanil are short acting when given as boluses
-alfentanil is particularly good at inhibiting the effect of increased BP and HR
Remifentanil?
-ultra-short acting opiate as a result of rapid metabolism by non specific plasma and tissue esterases
What is naloxone?
- acts on all the pain receptors
- can cause pulmonary oedema, arrythmias, hypertension
What does NSAIDS work on?
Cox 2+3
What does paracetamol work on?
COX 1+2
What are the intra-op signs of pain?
- Hypertension because of sympathetic stimulation
- FRC decreases
- FEV1 decreases
- Hyperglycaemia
