Antibiotics

Question 1

What is the antibiotic prophylaxis for scheduled c-sections?

Answer 1

2g Cefazolin
Consider 1g in pt <80kg
3g in pt >120kg (no clear benefit in reduction in SSI but based on MIC studies)
Within 60 minutes

Question 2

What does pre-csection vaginal prep benefit?

Answer 2

Decreased endometritis and postoperative fever, esp in patients who are ruptured or laboring. No decrease in surgical wound infections.

Question 3

What is the downside of prophylactic antibiotics for GBS in obstetrics?

Answer 3

Increases in E Coli sepsis primarily in preterm and low birth weight infants.
Increase in GBS resistance

Question 4

What is the single biggest risk factor for postpartum infection?

Answer 4

Cesarean delivery

Question 5

What are options for treatment of post-partum endometritis?

Answer 5

Unasyn 3g IV q6h
Gent IV q8  (dosing 80mg-150mg by weight) + clindamycin 99mg IV q8
Vancomyci q8h (febrile through gent/clinda)

Question 6

What is the treatment for intra-amnionitic infection (chorioamniotis) diagnosed before delivery?

Answer 6

1 dose of post-partum antibiotics (Unasyn or Gent/Clinda)

Question 7

What are the pharmacokinetics of antibiotics in pregnancy?

Answer 7

Decreased plasma concentration due to:

• increase in GFR > decreased half life
• Increased plasma volume > increased volume of distribution
• Hormone mediated increase in binding proteins
• Decreased gastric emptying

Question 8

What is the impact of prophylactic antibiotics before cesarean section?

Answer 8

Reduction in post-partum endometritis, nearly 60%. Even with term prelabor cesarean delivery.

Question 9

What is the benefit of adjunctive azithromycin prophylaxis in c-section?

Answer 9

Reduction in endometritis, wound infection, or other infections (50% reduction, NNT 17).
No RCT in elective cesarean delivery, therefore only used in non-elective cesarean

Question 10

What are indications to re-dose antibiotics during a c-section?

Answer 10

Surgical time >2 half-lives of the antibiotic (4hrs for cefazolin)
EBL >1500cc

Question 11

When are latency antibiotics indicated?

Answer 11

Pre-term pre-labor rupture of membranes less than 34w
When fetal lung maturity is not documented and delivery is not imminent
NOT preterm labor with intact membranes
NOT >34w (deliver!)

Question 12

What does ACOG recommend for latency antibiotic regimen?

Answer 12

2 days IV ampicillin/erythromycin
5 day course oral amoxicillin/ erythromycin
Can substitute azithromycin

Question 13

Should you use antibiotics for latency in preterm labor?

Answer 13

No! No benefit. Possible long-term harm (functional impairment in infancy, however no difference at 11 years)

Question 14

When should you consider antibiotic prophylaxis for endocarditis on L&D?

Answer 14

Patients who have:

• cyanotic cardiac disease (unrepaired cyanotic CHD, palliative shunt)
• prosthetic valves/device
• prior infective endocarditis
• cardiac transplant patients structurally abnormal valve with valve regurgitation

NOT mitral valve prolapse
“Consider” - based on highest risk. Primarily for undergoing dental procedures, but can consider on L&D

Question 15

What antibiotic prophylaxis is given for 3rd of 4th degree lacs?

Answer 15

Single dose of cefotetan or cefoxitin (or clindamycin if PCN allergic)

Protective against wound complications (70% wound infection reduction)

Question 16

Is antibiotic prophylaxis indicated for cerclage?

Answer 16

Practice bulletin says “insufficient evidence”
May be associated with increased latency time >28 days.
No indication for abdominal cerclage.

At DH:

• cefotetan 2g IV for ultrasound-indicated cerclage, exam-indicated or rescue cerclage
• plus bacitracin lavage for rescue/exam indicated cerclage

Question 17

Is antibiotic prophylaxis indicated for manual removal/D&C/Bakri?

Answer 17

No data. However studied increased risk of post-partum endometritis.

Commonly use cefotetan x1

Question 18

What is the microbiology of intra-amniotic infection?

Answer 18

Upward migration of vaginal flora.
Polymicrobial - Ureaplasma, Mycoplasma, Anaerobes, GNR, GBS.
Genital mycoplasma most commonly detected in culture

Question 19

What are risk factors for IAI?

Answer 19

Long length of labor
Length of rupture of membranes

Others: multiple SVE after ROM, nulliparity, mec stained fluid, STI, GBS, BV, internal monitoring

Question 20

Diagnostic criteria for chorioamnionitis

Answer 20

Fever (>39 or >38 sustained 30 minutes apart)
AND
FHR tachycardia
Maternal WBC >15
Purulent fluid from os

ACOG suggests isolated fever >39 without clear source can be managed as chorio

Confirmed diagnosis only by gram stain, culture, histopathology

Question 21

What is the antibiotic treatment for chorioamnionitis?

Answer 21

Unasyn (amp-sulbactam)
Amp/Gent
Cefoxitin / Cefotetan

Question 22

When do we screen for GBS?

Answer 22

universal GBS screening between 36 0/7 and 37 6/7 weeks of gestation.

Question 23

How long are GBS tests good for?

Answer 23

5 weeks

Question 24

When does a GBS positive patient not need prophylaxis?

Answer 24

Cesarean section that is pre-labor and pre-rupture of membranes

Question 25

When are antibiotics given in GBS unknown?

Answer 25

<37w gestational age
GBS positive in prior pregnancy
Maternal temp
Rupture > 18 hours

Question 26

What are indications for GBS prophylaxis?

Answer 26

+ GBS rectovaginal swab
GBS bacteriuria any time in pregnancy
h/o neonate with GBS sepsis

Question 27

How do we treat GBS bacteriuria?

Answer 27

If >105 CFU/mL - treat urinary infection and abx prophylaxis

If <105 CFU/mL - don’t treat urinary infx, do give abx prophylaxis

Question 28

What antibiotics are primarily used for GBS?

Answer 28

PCN G, 5mil IV then 2.5-3 million q4hr.

Ampicillin 2g IV then 1g q4h

Question 29

How do we do prophylaxis for GBS in PCN allergic patient?

Answer 29

Cefazolin 2g (if low risk reaction)
Clindamycin 900mg IV q8h
Vancomycin 20mg/kg q8h (if clinda-resistant)