Infective Endocarditis

N C Joshi
Infective Endocarditis Prophylaxis And Prevention
Successful prevention of infective endocarditis depends upon several factors including close medical supervision and follow up, avoidance of risk factors, proper dental hygiene and prophylactic use of antibiotics during surgical procedures especially dental extraction and operative procedures of oropharynx, gastrointestinal or genitourinary tract.

Dental and respiratory tract procedures
Parenteral - oral combined : Aqueous Crystalline Penicillin G (30,000 U/kg up to 1 million units) mixed with procaine penicillin (600,000, U) IM, 30 - 60 min before procedure; followed by Penicillin V orally ( 500 mg over, 250 mg under 60 lb) every 6h for 8 doses.
Penicillin V (2g), 30 - 60 min before procedure; followed by oral schedule as above.
For patients allergic to penicillin: Erythromycin (20 mg/kg, up to 1 g), 1 ½ h before procedure followed by half this dose every 6 h for 8 doses.
or genitourinary procedures
Aqueous crystalline penicillin G (30,000 U/kg, up to 2 million units) IM 


IV 30 - 60 min before procedure: 


Ampicillin (50 mg/kg, up to 1g), IM 30 min before procedure.


Streptomycin (20 mg/kg, up to 1 g ),

Followed by 2 additional doses every 12 h

The successful treatment of IE has 2 major goals:
- To eradicate microorganisms.
- To correct or at least limit the cardiac and the extracardiac complications caused by infection.

Choice of the proper antibiotic is necessary because the organisms are located within the vegetations. The antibiotic chosen should bactericidal and has to be given for a prolonged period of time (6-8weeks). The mode of administration should be intravenous whenever possible. The dose given should be modified ideally on the basis of results of the serum bactericidal levels. Optimal therapy depends on isolating the infective organism and determining its drug susceptibility. In the toxic patients, therapy should be initiated immediately while in less toxic patients, treatment may be delayed till blood culture results are known.

Since streptococcus viridans continues to be the most common cause of endocarditis, penicillin remains antibiotic of choice to initiate therapy.

Penicillin alone is sufficient when the organism are sensitive to serum levels of penicillin of 0.1 mcg/ml or less. If organisms require more than 0.1mcg/ml penicillin as it occurs in 10% of the patients, larger doses of penicillin are used or an aminoglycoside is added. The synergism between penicillin and aminoglycoside has been demonstrated. When penicillin is contraindicated cephalosporin or Vancomycin is indicated.

Treatment for enterococci requires use of Ampicillin or penicillin and aminoglycoside.

For, methicillin sensitive staphylococcal aureus - Nafcillin or Cefazolin with aminoglycoside and for methicillin resistant staphylococci- Vancomycin and aminoglycoside or Vancomycin and Rifampicin with aminoglycoside gives better results.

Amphotericin B is the drug of choice in endocarditis due to candida and therapy should continue for 6 weeks.

If treatment is initiated before blood cultures are obtained or in culture negative endocarditis a combination of penicillin and aminoglycoside can be used. If there will be no improvement within 72 hours, Vancomycin should replace penicillin. In postoperative endocarditis, therapy should be initiated using vancomycin.

If blood cultures continue to be negative for 2 weeks after the onset of therapy, the patient has to be reevaluated. If there is clinical improvement therapy should be continued and if there is no improvement, attempts at identifying fastidious organisms and fungi should be made and proper therapy instituted.

Despite of aggressive medical therapy of infective endocarditis and its complications, some patients may prove refractory to treatment. In these patients, surgical intervention may prove not only necessary but life saving.

Suggested regimen
S. viridans Sensitive to penicillin
Penicillin G 200,000 U/ kg /day in 4- 6 doses IV (maximum 20 million units) for 4-6 weeks.
S. viridans Resistant to penicillin
Penicillin G as above plus Streptomycin 30-50 mg/kg/day in 2doses, IM for 2 weeks
S. aureus coag+
Sensitive to penicillin
Penicillin as for S. viridans given for 6 -8 weeks
S. aureus coag+  Resistant to penicillin
Methicillin 200 mg/kg/ day in 4 -6 doses IV for 6-8 weeksplus gentamicin 4 -6 mg/kg/day in 2-3 doses IV for 2 weeks.
S. aureus coag+  Resistant to methicillin
Vancomycin 50 mg/kg/day in 4 doses, IV for 6- 8 weeks
Enterococci (S. fecalis)
Ampicillin 200 mg/kg/day in 6 doses, IV for 6 weeks plusgentamicin 4-6 mg/kg/day in 2-3 doses IV for 2-4 weeks.
Pseudomonas aeruginosa
Carbenicillin 400 - 600 mg/kg/day in 4-6 doses (max 20 - 30 g) IV plus gentamicin 4-6 mg/kg/day in 2-3 doses, IVor tobramycin 3-5 mg/kg/day in 3 doses IV.
Serratia marcescens
Gentamicin 4- 6 mg/kg/day in 2-3 doses IV pluscarbenicillin 400 - 600 mg/kg/day or amikacin 15 mg/kg/day in 2 doses (max 1.5 g)
Candida or aspergillus
Amphotericin B - test dose : 0.25 mg/kg IV over 4- 6 hours gradually increasing up to 1mg/kg (max 50mg) per day. Mix with 5% dextrose in water in a concentration of 0.1 mg/ml plus 5 - fluorocytosine 150 mg/kg/day PO in 4 

Survival of patients with infective endocarditis depends upon causative organism and associated complications. Mortality rate is 7-10% with streptococcus viridans and 25% with staphylococcus aureus. It is more in infants and in patients without co- existing heart disease and fungal IE. Most deaths are due to complications of embolic episodes and refractory heart failures. Few patients die due to sepsis.

Infective Endocarditis Infective Endocarditis 01/02/2002
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