Analgaesia and antiemetics Flashcards
What is the initial dose of morphine a young patient
0.1 - 0.2 mg/kg
What is the initial dose of morphine in the elderly
halve the initial dose and titrate (pain score)
When is the peak effect of a dose of morphine and how does this compare to fentanyl
Morphine - low lipid solubility
Peak effect: 10 - 15 minutes after IV administration
How is morphine dosing titrated?
Titrated to a pain score with 1 - 2 mg every minutes
Respiratory monitoring should be continued up to 15 minutes (peak effect)
How should fentanyl be administered for analgaesia
25 ug bolus doses repeated to a total of 100 ug and titrated to a pain score
What is the time to peak effect for fentanyl
2 - 3 minutes
What is the dose of IV diclofenac?
75 mg IV (max 150mg/24 hr)
What is the dose of IV Parecoxib?
40 mg IV (max 80 mg/24hr) less bleeding and PUD compared to NSAIDS - similar affects on renal function
What are some of the side-effects of NSAIDs?
Bleeding, renal impairment and peptic ulceration are some of the side- effects of NSAIDs.
How is IV paracetamol administered?
1 g IV over 20 minutes (max 4g/24hr)
Chronic liver disease: < 2- 3g/day (depending on co-morbidities e.g. malnutrition)
Acute liver disease: Contraindicated
How can it be established that the position of the epidural catheter is correct?
The epidural catheter depth is recorded after insertion. The markings on the catheter ever 1 cm with a double marking at 10 cm and a triple marking at 15 cm allow for the current and initial depth of the catheter to be known. This should be checked prior to administration of further regional anaesthesia.
What length of epidural catheter should be in the epidural space and why?
The distal 2 cm of the catheter to the tip are perforated with holes. This entire length should sit within the epidural space.
What should be done if movement to check if the epidural is still in place is too painful
Administer an epidural top up and observe the effect
What are the possible outcomes of the assessment of epidural effect?
- Effective block with adequate height
- Effective block with inadequate height
- Inadequate block density
- No demonstrable block
How is the epidural assessment performed
Cold spray dermatomes
What should be done if there is demonstrable block but it does not cover the extent of the surgical wound
Administer a bolus top up via the epidural infusion device
What should be done if the catheter is correctly positioned but there is inadequate density of sensory block or no demonstrable block
A more concentrated local anaesthetic solution is required
What should be done prior to top up of epidural
Check patients volume status ? BP ? HR ? CRT ? Urine output ? Mental State ? Core temperature
If normovolaemic -> administer epidural top-up
What drugs are suitable for epidural top up
Bupivacaine 0.25 %
OR Ropivacaine 0.5 %
5 ml of either of the above can be administered with 100 ug of fentanyl
This can be repeated once after 10 minutes if necessary
After an epidural top up how long should NIBP monitoring continue
for 20 minutes at 5 minute intervals - Rx hypotension with vasopressors
How long after the epidural top up can it be deemed successful/unsuccessful and what should be done if unsuccessful?
If after 30 minutes the epidural has failed –> systemic analgaesia should be administered
What should be considered prior to the removal of an epidural catheter
The epidural catheter may be removed provided that low molecular weight heparin (LMWH) has not been administered within the preceding 10 h.
Name and classify 6 common causes of PONV
Non-pharmacological
- Hypotension
- Hypoxia
- Dehydration
Pharmacological
- Volatile agents
- Opioids
- N2O
Name the four classes of antiemetics
H1 - Histamine 1 antagonists
D2 - Dopamine 2 antagonists
5HT3 - Serotonin 3 antagonists
Dexamethasone
Give examples and doses of an H1 receptor antagonist
Diphenhydramine (Benadryl) 10 - 50mg IV 4 - 6 hourly
Cyclizine (Valoid) 50 IV mg 8 hourly
Give examples and doses of an D2 receptor antagonist
Prochlorperazine 12.5 mg IM
Metoclopramide 10mg - weak D2 antagonist and minimal effect for PONV
Give an example and dose of an 5HT3 receptor antagonist
Ondansetron 4 - 8mg IV (better as rescue antiemetic)
What is the dose of dexamethasone for PONV
4 - 8 mg IV (Better as prophylactic antiemetic)
What is multi-modal treatment of PONV
When treating PONV, check whether prophylactic antiemetics have been administered. If so, use a drug from a different group, with a different mode of action, starting with a rapidly-acting drug that can be given IV.
A 35 year old patient has undergone a hysteroscopy. She is not in pain, her observations are all normal, but she is vomiting in recovery.
Which of the following would be appropriate antiemetic therapy?
Select one or more options from the answers below.
Possible answers: A. Cyclizine 50 mg IV B. Metoclopramide 10 mg IV C. Prochlorperazine 12.5 mg IV D. Ondansetron 4 mg IV E. Dexamethasone 8 mg IV
A. True. Cyclizine is an appropriate treatment, but is not the first choice, as it lacks the efficacy of 5HT3 antagonists, and has a less favourable side-effect profile.
B. False. Metoclopramide is not effective in the treatment of PONV.
C. False. Prochlorperazine should be administered IM, not IV: because of the slow onset of action it is not an ideal rescue agent.
D. True. The 5HT3 antagonists are the first choice, owing to their combination of efficacy and good side-effect profile.
E. False. Dexamethasone is an effective antiemetic, but is not an ideal rescue agent, owing to its slow onset of action.
