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Critically appraised topic

Critically appraised topic. FERNANDO B. SERRA III. June 23, 2010. The Case. 29-year old female , ASA 1, with diagnosis of pelvic endometriosis with bilateral endometriotic cyst, for laparoscopic oophorocystectomy During referral to consultant, premedications were discussed:

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Critically appraised topic

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  1. Critically appraised topic FERNANDO B. SERRA III June 23, 2010

  2. The Case • 29-year old female, ASA 1, with diagnosis of pelvic endometriosis with bilateral endometriotic cyst, for laparoscopic oophorocystectomy • During referral to consultant, premedications were discussed: • Nalbuphine 10mg and Promethazine 25mg IM 1hour PTOR – for sedation • Ranitidine 50mg or Omeprazole 20mg PO HS – to decrease gastric contents and increase gastric pH – to minimize risk of acid aspiration syndrome if ever patient vomits post-operatively

  3. The Case • Postoperative nausea and vomiting are among the most common and distressing symptoms after laparoscopic surgery. This poses risk for Acid Aspiration Syndrome. • Aspiration of acidic gastric contents during vomiting causes chemical pneumonitis characterized initially by diffuse bronchospasm, hypoxemia, and atelectasis. • Morbidity increases directly with volume of aspirate and inversely with the pH of the aspirate. • Aspirates above 0.4–1.0 ml/kg and with pH below 2.0–2.5 are most serious (Acid Aspiration Syndrome)

  4. The Question • Between ranitidine and omeprazole, which is a better premedication in reducing the risk for acid aspiration syndrome among patients for elective surgery? • Reduce Gastric Volume • Increase Gastric pH • Ranitidine – H2 receptor antagonists • Omeprazole – proton pump antagonist

  5. PIOM • Population - patients for electvive surgery • Intervention - ranitidine vs omeprazole • Outcome - reduced risk for acid aspiration syndrome • Methodology - randomized controlled trial

  6. The Search • Terms: • Ranitidine • Omeprazole • Acid Aspiration Syndrome • Elective surgery • Limits: • Randomized Controlled Trial • Free Full Text Article

  7. The Search • http://www.ncbi.nlm.nih.gov/pubmed/

  8. The Journal • A Comparison of Lansoprazole, Omeprazole, and Ranitidine for Reducing Preoperative Gastric Secretion in Adult Patients Undergoing Elective Surgery • Kahoru Nishina, MD, Katsuya Mikawa, MD, Nobuhiro Maekawa, MD, Yumiko Takao, MD, Makoto Shiga, MD, and HidefumiObara, MD

  9. The Journal • A prospective randomized double blinded study of 200 adult patients ASA 1 undergoing elective surgery. • Patients were divided into 8 groups (n=25 each) according to their premedication: Lansoprazole-lansoprazole (Group L-L), lansoprazole-placebo (Group L-P), placebo-lansoprazole (Group P-L), omeprazole-omeprazole (Group O-O), omeprazole-placebo (Group O-P), placebo-omeprazole, (Group P-O), placebo-ranitidine (Group P-R), or placebo-placebo (Group P-P) • Gastric fluid was aspirated via an orogastric tube after intubation, and the volume and pH of the aspirate were measured.

  10. Appraising Validity • Were the patients randomly assigned to treatment groups? • Yes. • Sample size of 200 ASA 1 patients for elective surgery were randomly assigned to one of eight groups as follows (n = 25 for each group): • L-L, L-P, P-L, O-O, O-P, P-O, P-R, and P-P. • where L, 0, R, and P indicate lansoprazole (30 mg per dose), omeprazole (80 mg per dose), ranitidine (150 mg), and placebo, respectively.

  11. Appraising Validity • Was allocation concealed? • No mention of concealment

  12. Appraising Validity • Were the groups similar at the start of the trial? • Yes. • The overall averages of age, weight, and height of the patients were 38 + 12 yr old, 60 + 10 kg, and 176 + 10 cm, respectively (mean 5 SD, P > 0.05 for all variables among eight groups).

  13. Appraising Validity • Were patients treated equally? • Yes. • All patients fasted overnight. Premedications were taken with 20mL of water • For each treatment regimen, the first medication was administered at 9:00 PM on the day preceding surgery and the second at 5:30 AM on the day of surgery. • No other premedicants were administered.

  14. Appraising Validity • Were patients treated equally? • Induction of anesthesia in all cases was started at 8:30 AM. with intravenous thiopental and maintained with sevoflurane and nitrous oxide in oxygen. • The lungs were ventilated, with care taken to avoid inflation of the stomach. • Tracheal intubation was facilitated by administration of vecuronium. • All inductions were uneventful and no patients had coughing, laryngospasm, or vomiting during induction.

  15. Appraising Validity • Were patients treated equally? • After tracheal intubation, a 16-Fr orogastric tube was inserted into the stomach and verified by auscultation over the epigastrium during introduction of 10 mL air.

  16. Appraising Validity • Were patients and caregivers/outcome assessors blinded to treatment assignment? • Yes • Randomized double blinded study • Patients were blinded to treatment received • Gastric fluid samples were obtained by gentle aspiration with a 50-mL syringe by an investigator who was unaware of the patient’s preanesthetic medication

  17. Appraising Validity • Were all patients who entered the study accounted for? Were patients analyzed in the groups to which they were originally randomized? • Yes • However, in 15 patients, volume aspirated was very small; the gastric fluid remained in the gastric tube and could not be aspirated into the syringe • These small quantities were recorded as a volume of 0 mL and excluded from pH measurement

  18. Results

  19. Appraising the Results • How large was the treatment effect? • Relative Risk (RR) = risk of the outcome in the treatment (ranitidine) group / risk of the outcome in the control group. • RR = 0/0.48 = 0 • Since the RR < 1, ranitidine 150mg PO 3 hours PTOR decreases the risk of acid aspiration syndrome

  20. Appraising the Results • How large was the treatment effect? • Absolute Risk Reduction (or Difference) (ARR) = risk of the outcome in the control group - risk of the outcome in the ranitidine group • ARR = 0.48 – 0 = 0.48 = 48% • The absolute benefit of ranitidine is a 48% reduction in rate of acid aspiration syndrome

  21. Appraising the Results • How large was the treatment effect? • Number Needed to Treat (NNT) = inverse of the ARR and is calculated as 1 / ARR. • NNT = 1/0.48 = 2.08 • We would need to treat 2 people in order to prevent 1 event

  22. Appraising the Results • How precise was the measurement of the treatment effect? • p < 0.05 = difference is statistically significant

  23. Conclusions • Between ranitidine and omeprazole, which is a better premedication in reducing the risk for acid aspiration syndrome among patients for elective surgery? • Single dose of oral ranitidine 150mg 3 hours PTOR is a better premedication for reducing the risk of acid aspiration syndrome

  24. Appraising Applicability • Is my patient similar to those in the study that the results can apply? • Yes

  25. Appraising Applicability • Will the results help me in caring for my patient? • Yes

  26. Appraising Applicability 3. Is the treatment feasible in my setting? • Yes

  27. Critically appraised topicThank you FERNANDO B. SERRA III June 23, 2010

  28. Appraising the Results • How large was the treatment effect? • Relative Risk Reduction (RRR) = 1 – RR • RRR = 1 – 0 = 1 • Ranitidine reduced the risk of acid aspiration syndrome by 100% relative to that occurring in the control group

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