Analgesia and antiemetics Flashcards
What’s important to assess in a patient presenting with post-op pain?
It is important to assess the site of pain to be sure that it is incisional wound pain
What other causes of pain (other from wound pain) may be present in a post-operative patient?
- Musculoskeletal pain
- Bladder distension
- Intra-peritoneal bleeding
What to measure if a patient is not in pain at rest?
To assess pain on movement
How to assess post-op pain?
First-line treatment for severe pain
opioids
What’s the greatest concern in terms of opioid side effect after IV administration?
After intravenous (IV) administration is respiratory depression
An opioid antagonist (naloxone) and the facility to provide ventilatory support (bag-valve-mask) should be available where IV bolus doses of opioids are administered
What opioid and at what dose is the most commonly used for a severe pain post-op?
Morphine
- adult patient (who has not received a recent dose of an opioid) → typically require an IV bolus dose of 0.1–0.2 mg/kg
- elderly patients require significantly lower doses
What’s Morphine’s onset of action?
- Morphine has a slow onset of action → due to its low lipid solubility
- peak effect occurs 10-15 min after IV administration
- It should therefore be titrated by administering small doses (e.g. 2 mg) at set intervals (e.g. 5 min)
What should be monitored after administration of Morphine?
Observations of respiratory rate should continue for at least 15 min after the last dose (check hospital protocol)
What’s the onset of action of Fentanyl?
Fentanyl is highly lipid-soluble, and has a rapid onset of action
What’s the dose of Fentanyl that we should administer to the patient?
A bolus dose of 20-25 µ g (micrograms) IV may be administered to an adult, and repeated to a total of 100 µ g.
*It has a short duration of action, so its offset should be anticipated, and a longer-acting agent such as morphine administered, before its effect wears off
What’s meant by a ‘morphine sparing’ effect?
Drugs which if administered contemporaneously with opioids, they improve the quality of analgesia and decrease opioid requirements
Examples of drugs with ‘morphine sparing’ effect
- NSAIDs
- COX-2 inhibitors
- paracetamol
*if administered contemporaneously with opioids, they improve the quality of analgesia and decrease opioid requirements
What’s the most commonly used NSAID for post-op pain and what’s its administration route and dose?
Diclofenac
- IV dose of 75 mg
- subsequent doses may be administered orally or rectally
Side effects of NSAIDs
- bleeding
- renal impairment
- peptic ulceration
*The risk of adverse effects on renal function are increased by hypovolaemia, hypotension, pre-existing renal impairment, ACE inhibitors and nephrotoxic drugs such as aminoglycosides
What factors increase the risk of renal impairment while being on NSAIDs?
The risk of adverse effects on renal function are increased by:
- hypovolaemia
- hypotension
- pre-existing renal impairment
- ACE inhibitors
- nephrotoxic drugs (e.g. aminoglycosides)
What drugs (and doeses) is a suitable adjunct to opioid analgesia in an adult? (2)
- Parecoxib 40 mg IV →COX -2 inhibitor
- Paracetamol 1 g infused IV over 20 minutes
*A reduced dose of Paracetamol should be used in patients with liver disease
What’s the most common way of post-op analgesia provision following a major surgery?
Regional technique e.g. epidural catether
How to check the position of an epidural catheter?
The position of the epidural catheter should be checked → to ensure it has not been removed accidentally
In order to do so, the patient must be moved to either lateral or sitting position. This may in turn require the administration of systemic analgesia
The mark on the catheter at the skin, and depth to or length of catheter in the epidural space, should be recorded on the anaesthetic chart or epidural prescription chart.
Via examination of the epidural entry site, it should then be possible to determine whether the catheter is still in place
What must be determined when topping up epidural analgesia?
Initially, it needs to be determined whether there is:
- An effective epidural block, but the block height is inadequate
- There is inadequate block density
- No demonstrable block
This can be done by checking sensation to cold, with ice or cold spray. Sterilizing solution containing alcohol, which is volatile and takes its latent heat of vaporization from the skin, can be used
What to check and how before administrating a top-up of epidural analgesia?
- to check if a patient is normovolemic⇒ administration of a top-up local anaesthetic can cause hypotension
- BP should not be relied upon, as this may be increased by catecholamines produced in response to pain
- Capillary refill time (CRT), core-peripheral temperature gradient and urine output assist us in assessing whether a patient is normovolaemic
What are suitable drugs to administer via topping-up epidural anaesthesia?
- Bupivacaine 0.25 % or levobupivacaine 2.5 mg/ml
- Ropivacaine 5 mg/ml
- Fentanyl 100 μg may be added
A suitable dose of the above local anaesthetics is 5 ml, repeated once if necessary
What’s the location (on the catheter) where a top-up of epidural anaelgesia should be administered?
Administration set should be disconnected between the pump and the bacterial filter, not between the filter and the patient
