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Update


UPDATE: INFECTIOUS DISEASE

The focus here is twofold: dealing with H1N1 influenza in vulnerable populations and taking up strategies to prevent postoperative infection in women undergoing cesarean delivery

June 2010 · Vol. 22, No. 06

IN THIS ARTICLE

Six recent articles stand out in the field of infectious disease:

  • an assessment of outcomes of seriously ill patients who were hospitalized early in the course of the H1N1 influenza epidemic. The authors highlight major differences in the epidemiology of this infection, compared with regular seasonal flu
  • an examination of outcomes of pregnant women who developed H1N1 influenza
  • an exploration of the use of blunt needles during cesarean delivery to prevent glove perforation
  • an evaluation of the utility of prophylactic antibiotics in ostensibly low-risk women undergoing scheduled cesarean delivery
  • a look at the timing of antibiotic prophylaxis for cesarean delivery
  • a comparison of skin preparation techniques in the prevention of surgical-site infection.

The focus on cesarean delivery in most of these studies seems particularly appropriate, now that this operation has become the most frequently performed major surgical procedure in US hospitals.

H1N1 virus hits hardest during pregnancy and chronic illness

Jain S, Kamimoto L, Bramley AM, et al, for 2009 Pandemic Influenza A (H1N1) Virus Hospitalizations Investigation Team. Hospitalized patients with 2009 H1N1 influenza in the United States, April-June 2009. N Engl J Med. 2009;361(20):1935–1944.

This retrospective survey of patients hospitalized for at least 24 hours for treatment of influenza-like illness included 272 patients who were given a diagnosis of H1N1 influenza, based on real-time, reverse-transcriptase, polymerase chain reaction assay. Sixty-seven (25%) of these patients were admitted to an ICU, and 19 (7%) died. All of the patients who died had been treated in an ICU, and two thirds had an underlying medical condition. Three of the deaths involved pregnant women. None of the patients who died received antiviral therapy within 48 hours of the onset of symptoms. Those who died were also less likely to have been vaccinated against seasonal influenza in 2008–2009.

Details of the trial

The 272 patients included in this study sample represented 25% of the total number of patients hospitalized in the United States for treatment of influenza between April and mid-June 2009. They exhibited the following characteristics:

  • median age: 21 years
  • race and ethnicity: 30% were Hispanic, and 27% were non-Hispanic white
  • most common symptoms: fever and cough, although diarrhea or vomiting was reported in 39% of patients
  • underlying medical illness: present in 73% (198 patients), including 60% of children and 83% of adults. At least two underlying medical conditions were present in 32% of patients. Asthma was the most common comorbid condition
  • pregnancy: 18 patients were pregnant. Four of the pregnant patients also had asthma, and two had diabetes
  • obesity: 29% of adults were obese. Morbid obesity was present in 26%. More than 75% of obese and morbidly obese patients had at least one underlying medical illness
  • bloodwork at admission: 20% of patients were leukopenic; 37% were anemic; and 14% were thrombocytopenic
  • chest film: 40% of patients who underwent chest radiography had findings consistent with pneumonia. Findings included bilateral infiltrates in 66 patients, a unilobar infiltrate in 26, and multilobar infiltrates in two
  • antiviral therapy: 75% ultimately received antiviral drugs, with a median time from onset of illness to initiation of therapy of 3 days (range, 0–29 days). Only 39% received antiviral therapy within 48 hours of the onset of symptoms
  • antibiotic therapy: 79% of patients received antibiotics for presumed superimposed bacterial infection. The most commonly used antibiotics were ceftriaxone, azithromycin, vancomycin, and levofloxacin.

Study offers 4 useful lessons

The study by Jain and colleagues offers clinically applicable lessons:

  • it reinforces the point that children and young adults, including pregnant women, are at increased risk of serious morbidity and mortality
  • it demonstrates that most seriously affected patients have at least one underlying medical condition, such as asthma
  • it highlights the importance of pregnancy and morbid obesity as major conditions that contribute to serious complications from influenza. The 7% prevalence of pregnant patients is significantly higher than the 1% prevalence that would typically be expected with seasonal influenza. Similarly, the 26% prevalence of morbid obesity greatly exceeds the estimated 5% prevalence in the adult US population
  • it confirms the importance of treating patients early in the course of their illness with antiviral drugs such as oseltamivir. Notably, none of the patients who died received treatment within 48 hours of the onset of illness, when the drugs are most likely to be effective.

How to treat H1N1 influenza

The vast majority of strains of the 2009 H1N1 virus are susceptible to oseltamivir and zanamivir, but essentially all strains are resistant to amantadine and rimantadine.1 Therefore, all individuals who are hospitalized should be treated with one of two regimens:

  • oseltamivir, 75 mg orally, twice daily for at least 5 days
  • zanamivir, 10 mg by inhalation, twice daily for at least 5 days.

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.

WHAT THIS EVIDENCE MEANS FOR PRACTICE

If there is a clinical suspicion of influenza in a pregnant or postpartum patient, treat her immediately with one of the antiviral regimens outlined on page 38—regardless of the outcome of the rapid test for influenza.

Blunt needles reduce needle sticks during cesarean delivery

Sullivan S, Williamson B, Wilson LK, Korde JE, Soper D. Blunt needles for reduction of needlestick injuries during cesarean delivery. Obstet Gynecol. 2009;114 (2 Pt 1):211–216.

Using glove perforation as a proxy for needlestick injuries, Sullivan and colleagues compared blunt needles with sharp needles during cesarean delivery. Ninety-seven women had all anatomic layers reapproximated using blunt needles, and 97 had them reapproximated using sharp needles. The overall glove perforation rate was 12.3%. For sharp needles, the perforation rate was 17.5%, and for blunt needles it was 7.2% (relative risk [RR], 0.66; 95% CI, 0.49–0.89). The key protective effect of the blunt needles was confined to the assistant surgeon (RR, 0.54; 95% CI, 0.41–0.71). The RR for glove perforation involving the primary surgeon was 0.8 (95% CI, 0.53–1.2).

Details of the trial

Glove type, number of gloves, needle size, and type and gauge of suture material were left to the discretion of the surgeon. Glove perforations were identified by filling the gloves with 1,000 mL of water and applying pressure to the palm and each finger. The secondary endpoint of the study was physician satisfaction with the needle. Primary and assistant surgeons reported comparable levels of dissatisfaction with blunt needles, compared with sharp needles (P < .001). However, 92% of primary surgeons and 93% of assistant surgeons rated the blunt needles as at least “acceptable” for use.

Needle stick has led to hepatitis B transmission

Earlier studies reported a rate of glove perforation of 20% to 26% during open abdominal procedures. In an investigation at our center, we noted glove perforation in 13% of cesarean deliveries.5 In this and another investigation, the frequency of perforation did not vary with the level of training of the surgeon or time of day of the procedure.5,6 The most common sites of perforation were the thumb, index finger, and middle finger of the non-dominant hand. The most common mechanism of injury was handling the needle with the operator’s gloved hand rather than with an instrument.

Double-gloving significantly reduces the risk of injury to the inner glove and, subsequently, to the surgeon’s skin. (Note: Double-gloving does not decrease tactile sensation or increase the risk of mishap.6)

Continued...
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