AC150

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Question

AC150 [Mar06] Q142, [Jul 06] Q19

The following versions probably represent the same MCQ recalled differently:

Which of the following would be most prophylactic against post-op nausea & vomitting?
 
A. Metoclopramide on induction 
B. Ondansetron 4mg after induction 
C. Dexamethasone 8mg shortly before the case finishes 
D. Dexamethasone 8mg on induction followed by Droperidol 0.3mg shortly before the case finishes 
You will be anaesthetising a woman for a lap-cholecystectomy who has a history of severe PONV.
You are planning to use a volatile anaesthetic agent. Which ONE of the following actions will
have the MOST effect on reducing her risk of PONV:
 
A. Omit nitrous oxide 
B. Give ondansetron 4mg shortly before the end of the case 
C. ?

AC150 ANZCA Version [Mar06] Q142, [Jul 06] Q19

A female patient with a history of severe postoperative nause and vomiting presents for abdominal 
surgery. If a volatile agent is used for maintenance of anaesthesia the most effective treatment
to reduce her risk of postoperative nausea and vomiting would be

A. avoidance of nitrous oxide
B. prophylactic dexamethasone (4 mg)
C. prophylactic droperidol (1.25 mg)
D. propylactic ondansetron (4 mg)
E. a combination of prophylactic dexamethasone and droperidol

Worked answer

AC150 ANZCA Version [Mar06] Q142, [Jul 06] Q19

A female patient with a history of severe postoperative nause and vomiting presents for abdominal surgery. If a volatile agent is used for maintenance of anaesthesia the most effective treatment to reduce her risk of postoperative nausea and vomiting would be

  • A. avoidance of nitrous oxide
  • B. prophylactic dexamethasone (4 mg)
  • C. prophylactic droperidol (1.25 mg)
  • D. propylactic ondansetron (4 mg)
  • E. a combination of prophylactic dexamethasone and droperidol - true: Droperidol is as effective as ondansetron, and if combined with dexamethosone would give even greater PONV prophylaxis

Comments

For the 1st version: surely D

For the 2nd version: B better than A but what about the other options?

For the 3rd version: definitely E --Drstitch 15:40, 10 May 2007 (EST)

see comments in AC143 re timing - give dex at beginning; ondansetron, droperidol at end of anaes.
From same ref - "Use of nitrogen instead of nitrous oxide reduced the incidence of PONV by 12%. The omission of nitrous oxide lowers the risk of PONV by a statistically significant but not clinically relevant amount."
and some comments re multimodal: "Administration of anti-emetic prophylaxis to patients with a low baseline risk for PONV is not justified, whereas high-risk patients should be treated with an anti-emetic combination (multimodal approach)...Based on the results from the IMPACT study, each tested anti-emetic agent (dexamethason, droperidol, ondansetron) and the use of total intravenous anaesthesia reduced the relative risk of nausea and vomiting to a similar extent, i.e. by 26%....The resulting relative risk of nausea and vomiting associated with a combination of interventions can thus be directly calculated as the product of the individual relative risks. As a consequence, the absolute risk reduction provided by a second or third intervention is less than that provided by the initial intervention (irrespective of which combination is chosen). A 70% reduction in the relative risk of postoperative nausea and vomiting is thus the best that can be expected, even when total intravenous anaesthesia is used in combination with three anti-emetics.
"PONV: A problem of inhalational anaesthesia?" Christian C. Apfel Best Practice & Research Clinical Anaesthesiology Vol. 19, No. 3, pp. 485–500, 2005Loum 00:11, 9 Jan 2008 (EST)

Answer is E. NEJM (June 2004) 350; 24 2441-2451. "A factoral trial of six interventions for the prevention of PONV". Figure 2 shows combinations of antiemetics, including dexamethasone and droperidol, superior to any single agent. The reason "female" is specified in the question is that droperidol was not shown to be effective in reducing PONV in men.--Gasbag 04:07, 11 May 2008 (EDT)

References

note: Cochrane PONV published 2006. see table 1,2 on pager 239!!

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