Clinical Review

UPDATE: INFECTIOUS DISEASE

OBG Manag. 2010 June;22(6):36-46

References

1. Antiviral drugs for influenza. The Medical Letter. 2009;51(1325):89-92.

2. Wenzel RP, Edmond MB. Preparing for 2009 H1N1 influenza. N Engl J Med. 2009;361(20):1991-1993.

3. Perez-Padilla R, Rosa-Zambori D, deLeon SP, et al. Pneumonia and respiratory failure from swine-origin influenza A (H1N1) in Mexico. N Engl J Med. 2009;361(7):680-689.

4. H1N1 vaccine for prevention of pandemic influenza. The Medical Letter. 2009;51(1322):77-78.

5. Chapman S, Duff P. Frequency of glove perforations and subsequent blood contact in association with selected obstetric surgical procedures. Am J Obstet Gynecol. 1993;168(5):1354-1357.

6. Lancaster C, Duff P. Single versus double-gloving for obstetric and gynecologic procedures. Am J Obstet Gynecol. 2007;196(5):e36-e37.

7. Smaill F, Hofmeyr GJ. Antibiotic prophylaxis for cesarean section. Cochrane Database of Systematic Reviews. 2002;(3):CD000933.-doi:10/1002/14651858.

8. Prophylactic antibiotics in labor and delivery. ACOG Practice Bulletin No. 47. American College of Obstetricians and Gynecologists. Obstet Gynecol. 2003;102(4):875-882.

9. Sullivan SA, Smith T, Chang F, Hulsey T, Vandorsten JP, Soper D. Administration of cefazolin prior to skin incision is superior to cefazolin at cord clamping in preventing postcesarean infectious morbidity: a randomized controlled trial. Am J Obstet Gynecol. 2007;196(5):455.e1-e5.

10. Costantine MM, Rahman M, Ghulmiyah L, et al. Timing of perioperative antibiotics for cesarean delivery: a metaanalysis. Am J Obstet Gynecol. 2008;199(3):301.e1-e6.

11. Tita ATN, Hauth JC, Grimes A, Owen J, Stamm AM, Andrews WW. Decreasing incidence of postcesarean endometritis with extended-spectrum antibiotic prophylaxis. Obstet Gynecol. 2008;111(1):51-56.

12. Tita AT, Owen J, Stamm AM, Grimes A, Hauth JC, Andrews WW. Impact of extended-spectrum antibiotic prophylaxis on incidence of postcesarean surgical wound infection. Am J Obstet Gynecol. 2008;199(3):303.e1-e3.

13. Burke JF. The effective period of preventive antibiotic action in experimental incisions and dermal lesions. Surgery. 1961;50:161-168.

14. Gordon HR, Phelps D, Blanchard K. Prophylactic cesarean section antibiotics: maternal and neonatal morbidity before and after cord clamping. Obstet Gynecol. 1979;53(2):151-156.

15. Cunningham FG, Leveno KJ, DePalma RT, Roark M, Rosenfeld CR. Perioperative antimicrobials for cesarean delivery: before or after cord clamping? Obstet Gynecol. 1983;62(2):151-154.

16. Kaimal AJ, Zlatnik MG, Chang YW, et al. Effect of a change in policy regarding the timing of prophylactic antibiotics on the rate of postcesarean delivery surgical-site infections. Am J Obstet Gynecol. 2008;199(3):310.e1-e5.

17. Tita AT, Rouse DJ, Blackwell S, Saade GR, Spong CY, Andrews WW. Emerging concepts in antibiotic prophylaxis for cesarean delivery: a systemic review. Obstet Gynecol. 2009;113(3):675-682.

18. Chaiyakunapruk N, Veerstra DI, Lipsky BA, Saint S. Chlorhexidine compared with povidone-iodine solution for vascular catheter-site care: a meta-analysis. Ann Intern Med. 2002;136(11):792-801.

19. Culligan PJ, Kubik K, Murphy M, Blackwell L, Snyder J. A randomized trial that compared povidone iodine and chlorhexidine as antiseptics for vaginal hysterectomy. Am J Obstet Gynecol. 2005;192(2):422-425.

These same regimens should be used for outpatients who are at high risk of complications.

Ideally, antiviral treatment should be administered within 48 hours of the onset of symptoms, but do not withhold treatment even if more than 48 hours have elapsed since the onset of illness.^2,3

Both oseltamivir and zanamivir are also effective for prevention of infection in susceptible patients who have been exposed to H1N1 influenza. The appropriate dosage of oseltamivir for prophylaxis is 75 mg orally once daily for 10 days. The corresponding dosage of zanamivir is 10 mg by inhalation once daily for 10 days.¹

The most effective method of prophylaxis, of course, is vaccination with the new H1N1 vaccine.⁴ There are two forms of the vaccine—a live virus nasal vaccine and an inactivated vaccine for intramuscular administration. Pregnant women should receive only the inactivated vaccine.

The key reservoirs of all influenza A viruses are migrating waterfowl, pigs, and humans. The current H1N1 strain of virus contains eight unique RNA segments that are a mixture of components from avian, pig, and human influenza viruses.² The pandemic resulting from this virus is unusual because the continent of origin was North America (Mexico) rather than Asia, the season of origin was spring rather than fall, and the patients at greatest risk of dying have been children and young adults rather than infants and the elderly.³

WHAT THIS EVIDENCE MEANS FOR PRACTICE

Women who are pregnant or planning to become pregnant should be vaccinated against H1N1 influenza. Use the inactivated virus if a woman is already pregnant.

After exposure to H1N1 influenza, unvaccinated pregnant women and other patients at high risk of developing the virus should be given oseltamivir or zanamivir prophylactically, using the dosage and route of administration described above for prophylaxis.

Pregnant women and other high-risk patients who exhibit symptoms of H1N1 influenza should be given oseltamivir or zanamivir, using the dosage and route of administration described above for treatment, ideally within 48 hours of the onset of symptoms.

For pregnant and postpartum patients, base treatment of H1N1 flu on symptoms, not rapid tests

Louie JK, Acosta M, Jamieson DJ, et al. Severe 2009 H1N1 influenza in pregnant and postpartum women in California. N Engl J Med. 2010;362(1):27–35.

Louie and coworkers describe the outcome of a statewide surveillance program by the California Department of Public Health. They reviewed the medical records of 94 pregnant women, eight women who were within the first 2 weeks postpartum, and 137 nonpregnant women of reproductive age who were hospitalized with confirmed 2009 H1N1 influenza between April 23 and August 11, 2009.

Eighteen pregnant women and four postpartum patients (22%) required intensive care, and 16 (73%) of these women had to be ventilated mechanically. Of the 18 pregnant women who required treatment in the ICU, 12 delivered in the hospital, and four underwent emergent cesarean delivery in the ICU.

Eight (8%) of the 102 pregnant and postpartum patients died. None of these eight women received antiviral therapy within 48 hours of the onset of symptoms. In fact, for pregnant and postpartum patients, a delay in administration of antiviral therapy beyond 48 hours after the onset of symptoms produced a 4.3 relative risk of death (95% confidence interval [CI], 1.4–13.7), compared with patients who were treated early in the course of their infection.

Details of the trial

The women in this trial had the following characteristics:

gestational age: five (5%) of the 94 pregnant women were in the first trimester, 35 (37%) were in the second trimester, and 54 (57%) were in the third trimester
underlying conditions were present in 34% of the pregnant and postpartum women and 60% of nonpregnant women. These conditions placed them at increased risk of complications from influenza. The most common underlying condition was asthma
antiviral therapy was administered to approximately 80% of both pregnant and nonpregnant women. However, only 50% of pregnant women and 34% of nonpregnant women received treatment within 48 hours of the onset of symptoms
antibiotic therapy was given to 45% of pregnant women and 58% of nonpregnant women for presumed secondary bacterial infection
false-negative test results: 153 women underwent rapid tests for influenza, 38% of which were falsely negative.

Treat pregnant patients expediently

This article is an excellent complement to the study by Jain and colleagues described on page 37. It strikingly illustrates the heightened risk of morbidity and mortality that pregnant women face when they develop H1N1 influenza. Louie and coworkers documented an influenza-specific mortality ratio (maternal deaths for every 100,000 live births) of 4.3. They also provide clear evidence of the perils of relying on rapid diagnostic tests and withholding antiviral treatment if the rapid test is negative. In their series, 38% of rapid tests were falsely negative. In pregnant women, when antiviral therapy was delayed more than 48 hours, the relative risk of death was 4.3, compared with patients who were treated within 48 hours of the onset of symptoms.