- lean (BMI, <30; n = 10)
- obese (30–39.9; n = 10)
- extremely obese (>40; n = 9).
All patients were given a 2-g dose of IV cefazolin 30 to 60 minutes before surgery.
During delivery, the team took two specimens of adipose tissue: one immediately after the skin incision and one later, after fascia was closed. They also obtained a specimen of myometrial tissue after delivery and a blood specimen after surgery was completed.
The concentration of cefazolin was then measured in adipose and myometrial tissue and in serum.
Findings. The researchers demonstrated that the mean concentration of cefazolin in the initial specimen of adipose tissue was significantly higher in lean patients than in obese and extremely obese patients. All 10 women who had a BMI less than 30 had a serum cefazolin concentration greater than 4 μg/g—the theoretical break-point for defining resistance to cefazolin. The initial adipose tissue specimen from two of the 10 obese patients and three of the nine extremely obese patients showed cefazolin concentrations less than 4 μg/g.
Of particular interest, two women—both of whom had a BMI greater than 40—developed a wound infection that required antibiotic therapy. Their initial and subsequent adipose tissue concentrations of cefazolin were less than the 4 μg/g break-point for resistance.
The concentration of cefazolin in the patients’ myometrial and serum specimens demonstrated a pattern similar to what the researchers observed in adipose tissue, but these results were not statistically significant across BMI groups. In fact, the cefazolin concentration in all groups’ myometrial and serum specimens exceeded the minimum inhibitory concentration for most potential pathogens in the setting of cesarean delivery.
Commentary
Clearly, prophylactic antibiotics are indicated for all women who are having a cesarean delivery. Antibiotics have their greatest impact when administered before the surgical incision is made; to exert their full protective effect against endometritis and wound infection, however, antibiotics should reach a recognized therapeutic concentration—not only in serum and myometrium but in the subcutaneous tissue.
The customary dosage of cefazolin for cesarean delivery prophylaxis has been 1 g. This study demonstrated that, although a 2-g dose of cefazolin reached a therapeutic concentration in myometrial tissue and serum, it did not consistently do so in the adipose tissue of obese and extremely obese patients.
WHAT THIS EVIDENCE MEANS FOR PRACTICE
Pending further investigation, I strongly recommend that all women who have a BMI greater than 30 receive a 2-g dose of cefazolin 30 to 60 minutes before cesarean delivery. Future research is needed to determine whether an even higher dosage is necessary to achieve a therapeutic concentration in the subcutaneous tissue of morbidly obese patients.
New therapies promise a better outcome in hepatitis C
Jacobson IM, McHutchison JG, Dusheiko G, et al; ADVANCE Study Team. Telaprevir for previously untreated hepatitis C virus infection. N Engl J Med. 2011;364(25):2405–2416.
The authors conducted an international Phase-3, randomized, double-blind, placebo-controlled trial of two different treatment modalities for chronic hepatitis C virus (HCV) infection. The authors assigned 1,088 patients who had HCV genotype-1 infection and who had not received prior therapy to one of three treatment groups:
- telaprevir (Incivek, Vertex Pharmaceuticals), an HCV genotype-1 protease inhibitor, combined with peginterferon alfa-2a (Pegasys, Genetech) plus ribavirin (Copegus, Genetech; Rebetol, Merck; etc.) for 12 weeks; patients then were given peginterferon alfa-2a plus ribavirin only for 12 additional weeks if HCV RNA was undetectable at weeks 4 and 12 or peginterferon alfa-2a plus ribavirin only for 36 weeks if HCV RNA was detectable at either time point (Group 1)
- telaprevir with peginterferon alfa-2a plus ribavirin for 8 weeks, then placebo with peginterferon alfa-2a plus ribavirin for 4 weeks, followed by 12 to 36 weeks of peginterferon alfa-2a plus ribavirin using the HCV RNA criteria applied to Group 1 (Group 2)
- placebo with peginterferon alfa-2a plus ribavirin for 12 weeks, followed by 36 weeks of peginterferon alfa-2a plus ribavirin (Group 3).
The primary endpoint of the trial was the percentage of patients who had undetectable plasma HCV RNA at 24 weeks after the last planned dose of the study drugs. The investigators considered that this endpoint represented a sustained virologic response.
Findings. Seventy-five percent of patients in Group 1 and 69% of those in Group 2 had a sustained virologic response. By comparison, only 44% of patients in Group 3 had a sustained response. The differences in outcome between Group 1 and Group 3, and between Group 2 and Group 3, were highly significant (P<.001). Virologic failure was more common among patients who had HCV genotype-1a infection than among those who had HCV genotype-1b infection.