Wound Infection

Mrs. H.W. has a wound infection. She’s a 35 year old woman who had a primary cesarean section 10 days ago. She was seen in the emergency room because of a gradual onset of lower abdominal pain, fever and redness around the wound.

Her temperature was 100.8.  A modest elevation in temperature is common but not universal with wound infections. She had a small elevation of her white blood cell count to 13,500.

The most striking finding was the redness and induration of her transverse abdominal wound. The redness of the skin extended about 4 cm above and below the incision, worse on the right side, but still present on the left side as well. The redness was warm to the touch and thickened or indurated.  To help in following the spread or resolution of the redness, I used a permanent marker to draw an outline around the margins of the redness. If the redness later crosses the line, then I know we’re losing the infection battle. If it recedes from the line, I know we’re winning.

The line where the cut edges of the skin came together looked like it was healing well, except for a 1 cm segment on the right side, and that area was slightly separated, with small amount of purulent drainage, staining the bandage which the patient had put in place.

Before probing the wound, I checked the rest of her, making sure her lungs were clear, and her abdomen soft and not tender. This is important because if her abdomen were generally sore and tense, then I’d like an imaging study like an abdominal CT scan to assess the intra-abdominal extent of the problem. I’d also rather explore the wound in the operating room to more quickly deal with the issue of abdominal wound dehiscence, should it be found.

In her case, her abdomen was normal, other than tenderness in the immediate area of the incision, so I felt comfortable exploring the wound in the emergency room. I started by gently cleansing the area of the wound with antiseptic. Then I used a cotton-tipped applicator to push through the oozing area of the wound into the subcutaneous space. As soon as the applicator reached that space, about 20 cc of purulent liquid came out around the applicator. This confirmed a subcutaneous wound infection.

I removed the cotton-tipped applicator and replaced it with culturette applicator, to obtain a specimen for a wound culture. Of necessity, this culture was aerobic, but once the wound opening was large enough, I could insert a tuberculin syringe into the wound to aspirate some purulence that I could send capped and sent for an anaerobic culture.

Having obtained my cultures, I again explored the wound with a sterile cotton-tipped applicator, using it as a probe to determine the extent of the abscess cavity. As I expected based on the skin appearance, the abscess cavity extended nearly the entire length of the wound, both left and right.

I used my gloved finger to “unzip” the skin incision, separating the skin edges bluntly. I could also have used an instrument to accomplish this, but the important thing with a wound infection is to open the entire length of the infected area. If you try to open only a small area to allow for drainage, you won’t be able to clean out the infected debris located deep within the wound, and will probably prolong her recovery rather than speed her recovery.

In this case, I didn’t use any anesthesia for the wound opening. This is a matter of judgment. When the incision was first made, both the ascending and descending superficial skin nerves were cut, causing the immediate area of the incision to be somewhat numb. Many patients will tolerate wound manipulation with only this pre-existing pain relief. Others will require more substantial pain relief (IV narcotics) and occasionally a major anesthetic will be needed, depending on the circumstances of the individual case. Local, injectable anesthetic is usually not done since you would be traumatizing the deep skin tissues in the presence of frank infection and possibly spreading that infection.

Once I opened the wound, I first made certain that the strong fascial layer was still intact. If there were any fascial separation, I would have stopped and moved to the operating room with a major anesthetic to cleanse the wound and repair the abdominal dehiscence. In her case, the fascia was intact, as I had suspected. I flushed the would with large amounts of irrigation fluid. I used normal saline, although lactated ringers could also be used. Reports of good results with clean tap water have also been published. I think the most important thing is not the specific electrolyte solution or its sterility, but the mechanical cleansing and dilution of the  infected debris

While irrigating the wound, I used gauze pads to mechanically cleanse the subcutaneous tissues. Here, a light touch is necessary because while it is important to debride or remove all necrotic or infected tissue, it is also important to avoid unnecessarily traumatizing the tissues. Some physicians in this situation would use some hydrogen peroxide as an irrigant, to bubble out the debris. Unfortunately, while hydrogen peroxide is a reasonably effective mechanical debrider, it is also quite toxic to cells, and most of us have abandoned its use in all but the most problematic wounds.

Once cleansed of debris and thoroughly irrigated with several liters of fluid, I placed some damp Kerlix in the wound. I placed it loosely, but made sure that it came into contact with all of the subcutaneous space, layering it gently into the wound. Then I covered the wound loosely with a dry ABD pad, taped around the margins to the skin. Here, the idea is that the damp loose gauze will gradually dry out as the moisture is wicked up into the dry covering gauze and then evaporates. As the damp gauze dries, the gauze fibers adhere to the wound. At the next dressing change, which we perform three times a day, we removed the gauze, pulling out any additional loose tissue or cellular debris. This “wet to dry” dressing change is very useful for cleaning up infected wounds.  For this to work the best, the outermost pad must be taped only around the margins, to allow the wound moisture to evaporate. If taped completely across the outer bandage, the tape does not breath and will trap the moisture rather than allowing it to escape.

The most important aspect of dealing with this wound abscess was the draining of the purulence, along with mechanical debridement of the infected tissue and subsequent wound care. With localized infections, this alone, without antibiotics, will usually be effective.

But with evidence of systemic symptoms or any evidence of local spread of infection, antibiotics may be useful and sometimes essential for a prompt recovery. In this patient, with red, indurated skin edges and a fever, I started some antibiotics to cover the presumed pathogens, among them staph aureus, staph epidermidis, e. coli, and Proteus mirabilis. I selected a first generation cephalosporin, pending the patient’s clinical response and wound culture results.

I re-evaluate the wound each day, checking for evidence of healthy granulation tissue throughout the wound. Once the wound is cleaned up and has only healthy granulation tissue, then we have two options: Secondary closure, or closure by secondary intention. With secondary closure, we stop packing the wound and instead either tape the skin edges together or place a few loose sutures to bring the skin edges together. So long as the wound is completely clean and granulating, this secondary closure should quickly heal, minimizing the duration of recovery and reducing the risk of reinfection

Alternatively, we can continue to loosely pack the wound with gauze, but leaving the packing in place for two or three days at a time, to minimize the disruption of the wound whenever the gauze is removed. Eventually, this wound will completely granulate itself closed, from the bottom up, and eventually from one side to the other side. This approach requires considerably more time to completely close (months), but reduces the risk of another deep abscess forming.

Techniques to avoid wound infection include gentle handling of tissues, minimizing crushing, clamping, electro-cautery and foreign materials such as sutures or ligatures. Irrigation and prophylactic antibiotics can also be useful. In selected patients, wound drainage, active or passive can be helpful in preventing the buildup of serous fluids that not only separate the healing tissues, but can act as a culture medium for any bacterial contamination. Some predisposing factors cannot be easily changed, such as obesity, diabetes, chronic illness, or impairment of the immune system. In some patients, despite your best efforts, a wound infection may still occur.

So Mrs. H.W. has responded nicely to these measures. You can see that the redness is completely gone and the induration has resolved. Through good wound care, her incision now is filled with healthy granulation tissue. The edges were taped together yesterday, and she’s going home today. We’ll take another look at the wound in the office in a few days.

Her wound culture grew out Proteus Mirabilis and Staph Epidermidis. The Staph was sensitive to the cephalosporin we gave her, but the Proteus was not. Interestingly, in the few days it took to get the culture results back, the patient recovered and had no ongoing clinical evidence of infection. So we stopped her antibiotics and will await her full recovery. In her case, the cultures were not helpful clinically since she recovered despite the presence of an antibiotic-resistant organism. But in another case, had she not gotten better after a couple days of aggressive wound management, then the culture results could have guided our antibiotic choice.

Last Modified Jul 21, 2016 @ 12:52 pm

Last Modified Jul 21, 2016 @ 12:52 pm

A Training Simulation in Introductory Obstetrics & Gynecology