Necrotizing soft tissue infections: Clinical sciences

Necrotizing soft tissue infections, or NSTIs, are rapidly progressing infections causing extensive destruction of soft tissues, including the epidermis, dermis, subcutaneous tissues, fascia, and muscle. Because the depth of the infection can vary, NSTIs can present as necrotizing forms of cellulitis, fasciitis, and myositis.

These infections can occur anywhere in the body and rapidly lead to limb loss, severe systemic toxicity, and even death if left untreated. Of the various types, necrotizing fasciitis is associated with the highest mortality rate because of how quickly it can spread within the body. While the vast majority of NSTIs can be diagnosed clinically, additional tools like a CT scan and LRINEC score can be used to differentiate between NSTI, possible NSTI, and non-necrotizing infections.

When a patient presents with chief concern suggesting NSTI, your first step is to perform an ABCDE assessment to determine whether the patient is stable or unstable. If the patient is unstable, you must stabilize the airway, breathing, and circulation first. This includes obtaining IV access, initiating IV fluid resuscitation, and continuously monitoring vital signs.

Once you have initiated your acute management, your next step is to perform a focused history and physical exam. History may include severe pain, fever, chills, and foul-smelling discharge. In addition, don’t forget to ask about risk factors for NSTI, such as recent trauma, recent surgery, injection drug use, immunosuppression, or diabetes mellitus. For patients with diabetes, also ask which medications they take, because some types are associated with Fournier’s gangrene, which is necrotizing fasciitis of the perineum.

On exam, you might see signs of systemic instability such as altered mental status, tachycardia, or hypotension, which can all be attributed to sepsis or septic shock. The exam will also reveal signs of local infection like erythema, edema, and indurated skin or soft tissue that is firm to touch. In addition, you might find necrotic tissue with foul-smelling discharge. Finally, crepitus is another important finding to look out for because it indicates the destruction of subcutaneous tissues by gas-forming organisms. Crepitus feels like tiny pops of air or crunch under the skin. If you find it on a physical exam, you should have a high suspicion for necrotizing fasciitis, which is the most aggressive form of NSTI and a surgical emergency.

However, even in the absence of crepitus, any combination of these clinical findings supports your diagnosis of necrotizing soft tissue infection with sepsis or septic shock.

Here’s a clinical pearl! Keep in mind that this is a clinical diagnosis, but sometimes the infection is too deep and the exam findings might be hidden, so additional diagnostic workup like imaging can be obtained but must not delay treatment.

Because NSTI with sepsis or septic shock is a life-threatening infection, you need to start treatment as soon as possible. First, if possible, obtain blood cultures before starting broad-spectrum IV antibiotics, but don’t delay giving the antibiotics if cultures can’t be immediately obtained. Then, consult the surgical team to evaluate for an emergent operative exploration, debridement, and wound cultures. This is the most important part of the treatment because the infection spreads rapidly along the fascial plane, so removing the infected and necrotic tissue is the only effective method of source control. Finally, continuously provide supportive management for sepsis or septic shock with IV fluid resuscitation and vasopressor support if needed.

Here’s a clinical pearl! Most of the time, necrotizing fasciitis is definitively diagnosed intraoperatively with direct visualization of the obliterated fascia. The patient might need aggressive debridement with multiple surgeries over the course of days to weeks to achieve adequate source control.

Now that we have discussed unstable patients, let's switch gears and talk about stable patients. Because the majority of NSTIs in stable patients are diagnosed clinically, your first step is to obtain a focused history and physical. You can also order labs like CBC, CMP, CRP, CK, and lactate.

On history, patients often report severe pain, redness, swelling, and warmth of the affected area. Additionally, they might report systemic symptoms like fever, chills, malaise, and myalgias. In some cases, the patient may notice a foul-smelling discharge from the wound. Again, don’t forget to ask about risk factors for NSTI, such as recent trauma or surgery, injection drug use, immunosuppression, diabetes mellitus, and which medications they take.