Download Introduction to the use of Prophylactic Antibiotics

Kofinas Perinatal
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Providing Care to the Unborn ®
Alexander D. Kofinas, MD
Director, Kofinas Perinatal
Associate Professor, Clinical Obstetrics and Gynecology
Cornell University, College of Medicine
Introduction to the use of Prophylactic Antibiotics in Obstetrics
The frequency of infection varies from 35 - 40% in most studies reviewed.
Endomyometritis the most frequent postoperative complication results in prolonged
hospitalization and increased cost. Risk factors for puerperal infection are traditionally
considered to be Cesarean Section, Prolonged Rupture of Membranes with its increased number
of pelvic examinations, low socioeconomic status or indigent population and other risk factors
i.e. virulent organisms in the vaginal flora or the presence of a large inoculum.
For the past 20 years, interest in the perioperative and prophylactic use of antibiotics for
cesarean section has been stimulated by a number of events, including the high rate of
postoperative infections, the recent increase in the rate of cesarean section, and the success of
infection prophylaxis in vaginal hysterectomy. In over 30 well-designed controlled studies,
perioperative antibiotics have been noted to significantly decrease post-cesarean section
infectious morbidity. These regimens have resulted in a reduction of infection rates by more than
50 per cent owing mainly to decreases in uterine and wound infections. Several studies have
compared one antibiotic to another for prophylaxis and found no significant differences.
Regimens for prophylaxis begun after cord clamping are as effective as those begun
preoperatively and may avoid otherwise unneeded septic work-ups of the neonate. For several
antibiotics, single-dose prophylaxis has been found to be just as effective as three doses. Still, 10
to 20% of patients receiving prophylactic antibiotics have febrile disease, primarily of uterine
origin. Furthermore, the administration of perioperative antibiotics in cesarean section may be
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Providing Care to the Unborn ®
complicated by other clinical considerations; among these are significant alterations in the flora
of patients receiving prophylactic antibiotics and developing pelvic infection. Documentation of
a shift in the flora toward organisms such as enterococci, Bacteroides, Enterobacter, and
Pseudomonas raise the concern about the emergence of resistant bacteria with the widespread use
of antibiotics.
Antibiotic prophylaxis in cesarean section should be limited to patients at high risk for
infectious disease. Only a short perioperative course of antibiotics should be administered,
commencing after cord is clamped and one additional dose 6 hours later if the length of surgery
or complexity of the procedure warrants an additional dose.
Prophylactic antibiotics appear to act in two principal ways. By destroying some bacteria
and slowing the growth of others, they directly decrease the size of the bacterial inoculum at the
surgical site. Prophylactic antibiotics also alter the characteristics of the serosanguineous fluid
that collects in the pelvic cavity after operation, rendering it less suitable to support the growth of
microorganisms. Other possible mechanisms of action include interference with the production
of bacterial proteases and interference with attachment of bacteria to mucosal surfaces. In
addition, antibiotics may, in a way that is not completely understood, enhance the host's
phagocytic capacity.
Three clinical criteria should be fulfilled to justify perioperative use of
prophylactic antibiotics.
 The surgical procedure, by necessity, must be performed through a contaminated operative
field. In obstetrics, the operation is inevitably associated with considerable bacterial
contamination of the endometrial and peritoneal cavity
 There must be a high incidence of postoperative infection, that is exceeding 15 - 20%. As
noted above if some form of prophylaxis is not administered, the incidence of post-cesarean
section endomyometritis is unacceptably high in most patient populations, averaging 35 40%.
 The primary disease process would involve a risk of infection which may result in a more
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Providing Care to the Unborn ®
serious sequelae, (e.g. as is seen in patients who have an endomyometritis resulting in septic
shock, pelvic abscess, and septic pelvic vein thrombophlebitis).
The Department of Obstetrics and Gynecology recommends the use of prophylactic perioperative
antibiotics in the following conditions and in any other circumstance that the physician in charge
considers it appropriate:
1. in all women who have a prolonged labor with rupture of membranes
2. in all women who undergo multiple examinations prior to delivery
3. in women with short duration of labor, and intact membranes and women undergoing
elective cesarean section but are considered at risk for post operative infection ( e.g. patients
of a lower socioeconomic status, presence of anemia and/or a compromised immune status,
diabetics etc.).
The following regimens are considered acceptable to be used in cases where prophylaxis
is deemed necessary.
1. Ampicillin 2 gm IV x 1 dose
2. Cefazolin 2 gm IV x 1 dose
3. Cefotetan 2 gm IV x 1 dose
It is not the intention of this guideline to alter those practices of administration of
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Providing Care to the Unborn ®
prophylactic agents in obstetrics. This should bring to the forefront the thought of
utilizing various agents in a single dose which has been found to be just as effective as
multi-dose prophylaxis. If any questions arise regarding the use of prophylactic agents
this should be addressed by the attending physician or Perinatologist on-call.
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