Analgaesia and antiemetics

Question 1

What is the initial dose of morphine a young patient

Answer 1

0.1 - 0.2 mg/kg

Question 2

What is the initial dose of morphine in the elderly

Answer 2

halve the initial dose and titrate (pain score)

Question 3

When is the peak effect of a dose of morphine and how does this compare to fentanyl

Answer 3

Morphine - low lipid solubility

Peak effect: 10 - 15 minutes after IV administration

Question 4

How is morphine dosing titrated?

Answer 4

Titrated to a pain score with 1 - 2 mg every minutes

Respiratory monitoring should be continued up to 15 minutes (peak effect)

Question 5

How should fentanyl be administered for analgaesia

Answer 5

25 ug bolus doses repeated to a total of 100 ug and titrated to a pain score

Question 6

What is the time to peak effect for fentanyl

Answer 6

2 - 3 minutes

Question 7

What is the dose of IV diclofenac?

Answer 7

75 mg IV (max 150mg/24 hr)

Question 8

What is the dose of IV Parecoxib?

Answer 8

40 mg IV (max 80 mg/24hr) less bleeding and PUD compared to NSAIDS - similar affects on renal function

Question 9

What are some of the side-effects of NSAIDs?

Answer 9

Bleeding, renal impairment and peptic ulceration are some of the side- effects of NSAIDs.

Question 10

How is IV paracetamol administered?

Answer 10

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

Question 11

How can it be established that the position of the epidural catheter is correct?

Answer 11

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.

Question 12

What length of epidural catheter should be in the epidural space and why?

Answer 12

The distal 2 cm of the catheter to the tip are perforated with holes. This entire length should sit within the epidural space.

Question 13

What should be done if movement to check if the epidural is still in place is too painful

Answer 13

Administer an epidural top up and observe the effect

Question 14

What are the possible outcomes of the assessment of epidural effect?

Answer 14

1. Effective block with adequate height
2. Effective block with inadequate height
3. Inadequate block density
4. No demonstrable block

Question 15

How is the epidural assessment performed

Answer 15

Cold spray dermatomes

Question 16

What should be done if there is demonstrable block but it does not cover the extent of the surgical wound

Answer 16

Administer a bolus top up via the epidural infusion device

Question 17

What should be done if the catheter is correctly positioned but there is inadequate density of sensory block or no demonstrable block

Answer 17

A more concentrated local anaesthetic solution is required

Question 18

What should be done prior to top up of epidural

Answer 18

Check patients volume status
? BP
? HR
? CRT
? Urine output
? Mental State
? Core temperature

If normovolaemic -> administer epidural top-up

Question 19

What drugs are suitable for epidural top up

Answer 19

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

Question 20

After an epidural top up how long should NIBP monitoring continue

Answer 20

for 20 minutes at 5 minute intervals - Rx hypotension with vasopressors

Question 21

How long after the epidural top up can it be deemed successful/unsuccessful and what should be done if unsuccessful?

Answer 21

If after 30 minutes the epidural has failed –> systemic analgaesia should be administered

Question 22

What should be considered prior to the removal of an epidural catheter

Answer 22

The epidural catheter may be removed provided that low molecular weight heparin (LMWH) has not been administered within the preceding 10 h.

Question 23

Name and classify 6 common causes of PONV

Answer 23

Non-pharmacological

1. Hypotension
2. Hypoxia
3. Dehydration

Pharmacological

1. Volatile agents
2. Opioids
3. N2O

Question 24

Name the four classes of antiemetics

Answer 24

H1 - Histamine 1 antagonists
D2 - Dopamine 2 antagonists
5HT3 - Serotonin 3 antagonists
Dexamethasone

Question 25

Give examples and doses of an H1 receptor antagonist

Answer 25

Diphenhydramine (Benadryl) 10 - 50mg IV 4 - 6 hourly

Cyclizine (Valoid) 50 IV mg 8 hourly

Question 26

Give examples and doses of an D2 receptor antagonist

Answer 26

Prochlorperazine 12.5 mg IM

Metoclopramide 10mg - weak D2 antagonist and minimal effect for PONV

Question 27

Give an example and dose of an 5HT3 receptor antagonist

Answer 27

Ondansetron 4 - 8mg IV (better as rescue antiemetic)

Question 28

What is the dose of dexamethasone for PONV

Answer 28

4 - 8 mg IV (Better as prophylactic antiemetic)

Question 29

What is multi-modal treatment of PONV

Answer 29

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.

Question 30

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

Answer 30

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.