Gas Gangrene of Extremity

Question 1

True/False: Most cases of gas gangrene are caused by clostridial species.

Answer 1

False - multiple, nonclostridial infections, including staph and strep, make up more than half the cases

Question 2

What is the most common cause of gas accumulation within a wound?

Answer 2

Direct injection at the time of injury

Question 3

What is the mortality of gas gangrene?

Answer 3

15-70%

Question 4

What is the key to treatment of gas gangrene?

Answer 4

1. Rapid diagnosis, 2. Early broad spectrum antibiosis, 3. Supportive Care, 4. Early debridement

Question 5

Along with colonization and release of exotoxins, what more is needed for clostridial species to cause gas gangrene?

Answer 5

Low oxygen tension in tissues, secondary to either tissue injury or chronic low blood flow, as found in diabetes or surgical devascularization

Question 6

What exotoxin is the most lethal?

Answer 6

alpha toxin (phospholipase C), which causes profound shock via direct cardiotoxicity, hemolysis, increased capillary permeability, and leukocyte dysfunction

Question 7

What malignancy has been associated with gas gangrene?

Answer 7

Metastatic Colorectal Carcinoma

Question 8

Why does C. perfringens thrive in low oxygen states?

Answer 8

It is a facultative anaerobe - growth and exotoxin activity arrests at 100% oxygen.

Question 9

What injuries predispose to gas gangrene?

Answer 9

Crush, MVAs, open fractures, wounds involving large muscle mass, high velocity missiles, and iatrogenic

Question 10

What are the cutaneous findings of gas gangrene?

Answer 10

Pain out of proportion to exam, crepitus, edema, skin bronzing/necrosis, and hemorrhagic bullae

Question 11

What diagnostic tests are necessary to evaluate a wound for gas gangrene?

Answer 11

None - it is a clinical diagnosis

Question 12

What are the first treatment steps in dealing with gas gangrene?

Answer 12

Aggressive medical therapy - resuscitation, broad spectrum antibiotics, possible transfusion (with evidence of exotemic hemolysis or coagulopathy)

Question 13

What first line antibiosis is recommended in clostridial gas gangrene?

Answer 13

High dose Penicillin G

Question 14

What first line antibiosis is recommended in non-clostridial gas gangrene?

Answer 14

Triple therapy - Penicillin, Tobramycin, and Clindamycin (for example)

Question 15

True/False: Antibiotics and incision/drainage may be sufficient in treating gas gangrene.

Answer 15

False - surgical debridement is the only effective management

Question 16

Along with close hemodynamic monitoring, what is a necessary part of post operative care in gas gangrene?

Answer 16

Wound hygiene - wet to dry dressing changes or VAC acceptable; plastic surgery consult may advised

Question 17

What potential benefits are there to negative pressure wound therapy?

Answer 17

1. Removal of excess fluids, 2. Increased local blood flow, 3. Decreased bacterial counts

Question 18

What are the reported benefits of hyperbaric oxygen therapy in dealing with gas gangrene?

Answer 18

Possible decreased mortality and decreased duration of antibiotic therapy (controversial - shown only in dogs)

Question 19

What is the proposed beneficial mechanism of action of hyperbaric oxygen in gas gangrene?

Answer 19

Inhibition of alpha toxin, inhibition of bacterial replication, and improved tissue oxygenation

Question 20

What conditions predispose to nonclostridial gangrene?

Answer 20

Diabetes, chronic vascular compromise, radiation, cholecystitis, and following appendectomy

Question 21

What are the most common isolates from nonclostridial gangrene wounds?

Answer 21

beta hemolytic strep, S. aureus, Streptococcus, Bacteroides, Peptostreptococcus, and aerobic coliform bacteria. Candida and Mucormycosis have been cultured in diabetics.

Question 22

What waterborne bacteria cause gas gangrene?

Answer 22

Aeromonas hydrophilia (gram negative rod from leech bites) and Vibrio vulnificus (gram negative from marine environment); both traditionally cause gastroenteritis, but may cause gas gangrene if they enter the skin