Utilizing NPWTi-d to Achieve Source Control of Complex Polymicrobial Necrotizing Aeromonas hydrophila Infection Following a Traumatic Amputation: A Case Report

The management of aquatic injuries is inherently challenging due to a number of difficult-to-anticipate sequelae. Propeller injuries significantly complicate management, owing to significant contamination, delayed ischemia, and exposure to unusual water-associated organisms.¹

The purpose of this case study was to present a circumstance where source control was achieved in a patient that suffered from a polymicrobial necrotizing Aeromonas hydrophila infection following a traumatic aquatic amputation via negative pressure wound therapy with instillation and dwell time (NPWTi-d) in a time period where debridement was unable to be performed.

A 26-year-old female was airlifted to the author’s facility in Shreveport, Louisiana, after a boating injury sustained in a lake with brackish water. The patient was swimming to the stern (rear) of the boat when the propeller was engaged, causing her right lower extremity to be sucked into the propeller blade and subsequently collide with the cavitation plate, resulting not only in multiple deep parallel lacerations but also open fracture of the femur. A makeshift tourniquet was applied directly after initial injury and was replaced by a combat application tourniquet shortly thereafter per emergency medical staff. She was diverted from the nearest trauma center due to inclement weather, resulting in a longer-than-anticipated transport. During transport, she received 13 units of packed red blood cells and 8 units of fresh frozen plasma.

Admission day 0

Upon arrival, the patient was noted to have significant avulsion injuries as well as a Gustilo IIIB fracture.² She was rush-rolled to surgery for a transfemoral amputation due to the extent of injury (Figure 1).

Admission day 1

The patient returned to the operating room (OR) for surgical debridement of devitalized tissue, further washout with normal saline, and application of traditional continuous negative pressure wound therapy at -125 mm Hg (NPWT; V.A.C.ULTA; 3M + KCI). At that time, the resultant soft tissue defect measured about 90.0 cm x 45.0 cm, tracking superiorly from above the anterior superior iliac spine down to the end of the amputation stump.

Admission day 3

Early serial washouts were performed due to delayed-onset necrosis and presumption of gross contamination of wound (Figure 2).

Admission day 4

Right hip and labial edema and fluctuance were noted. Lab work revealed a procalcitonin (PCT) level of 18.76 and lactic acid of 3.7. The patient also began to have tachypnea, tachycardia, and hypotension, which prompted an emergent return to the OR. Postop, the patient remained hypotensive on maximum doses of levophed, vasopressin, and bicarb.

Admission day 5

The critical care team was consulted and diagnosed the patient as having a rare phenotype of septic shock called macrophage activation syndrome, and she was started on therapeutic plasma exchange (TPE) and continuous renal replacement therapy (CRRT).³

Admission days 6 and 8

Serial surgical debridements (once on admission day 6 and twice on admission day 8) were initiated due to the aggressive myonecrosis⁴ and further tissue devitalization (Figure 3). During each trip to the OR, the residual femur had to be revised, shortening the residual limb. Clinicians were concerned that, continuing the current course, the patient was poised for a hip disarticulation, which could decrease her options regarding mobility considerably. Wound cultures came back positive for A hydrophila, Streptococcus pyogenes, and Proteus mirabilis.

Admission day 9

Control of the infectious source was not achieved at this time, as evidenced by rising white blood count (WBC), ferritin, and PCT levels, as well as continued encroaching necrosis within the wound. During this trip to the OR, upon induction of anesthesia, the patient coded twice and returned to the intensive care unit (ICU) in critical condition (ICU stay: 26 days). Due to hemodynamic instability and the inability to tolerate anesthesia at that time, the decision was made to attempt source control utilizing NPWTi-d (V.A.C. VERAFLO Therapy; 3M + KCI). The initial settings were instillation of 100 mL of 0.125% Dakin’s solution, dwell time of 5 minutes, and interval 2 hours of NPWT at -125 mm Hg.⁵ At this time, the wound measured 51.0 cm x 38 cm x 4 cm with 6.0 cm undermining along the superior border (Figure 4). Exposed support structures were protected by application of a nonadherent dressing (ADAPTIC Non-Adhering Dressing; 3M + KCI) before foam placement. In regions of grossly necrotic tissue, the V.A.C. VERAFLO CLEANSE CHOICE Dressing (3M + KCI) was utilized to soften, solubilize, and ultimately facilitate in the removal of slough and fibrinous tissues.

Admission day 11

Lab values normalized rapidly with downtrending of WBC, ferritin, and PCT. The improvement in the patient’s status allowed weaning of inotropes, cessation of TPE and CRRT, and extubation.

Admission day 13

During bedside dressing changes of NPWTi-d, a substantial decrease in necrotic tissue, an increase in vascularity, and significant granulation were noted (Figure 5).

Admission day 17

The patient returned to the OR for a washout (normal saline) and an attempted femoral nerve block. At this point in time, no further necrosis was evident. Substantial granulation tissue and rapid fibrocartilage callus formation were noted (Figure 6). In the OR, the residual neurovascular bundle was protected by incorporating it within a residual portion of vastus medialis musculature. The NPWTi-d settings were switched to instillation of 80 mL of normal saline with a dwell time of 5 minutes and a 2-hour interval of NPWTi-d at -125 mm Hg. The dressing was changed at admission day 21 with no alteration in therapy.

Admission day 25

The patient was returned to the OR for washout and NPWTi-d replacement. At this time, the wound measured approximately 25.0 cm x 30.0 cm and demonstrated a significant amount of coverage over the femur fragment (Figure 7). Dressing changes were performed every 3 days until admission day 43.

Admission day 43

The patient was taken to the OR for tangential excision and split-thickness skin graft. Continuous traditional NPWT set at -125 mm Hg was applied over the skin graft site. Dressing changes were performed every 3 days until admission day 51.

Admission day 51

The split-thickness skin graft showed 100% take with no residual regions of tissue loss noted (Figure 8).

At 167 days after the initial injury, the patient had her first prosthetic fitting and also took her first steps on the prosthetic leg (Figure 9).

The current standard of care for myonecrotic infection is rapid, definitive, surgical debridement with timely return to the OR for washouts.⁶ However, in cases such as this one, the patient’s status may not allow for the requisite frequent OR visits in order to manage such an aggressive presentation. A hydrophila typically causes mild to moderate infection but can lead to more severe forms of necrotizing infection, especially in those with comorbid conditions and poor immune function, due to its production of aerolysin, a pore-forming cytotoxin.⁷ A recent study by Fernández-Bravo et al⁸ shows that A hydrophila necrotizing infections can be potentiated by other microbes such as S pyogenes and P mirabilis, which further complicates the care of polymicrobial infected wounds.⁸ In a study evaluating methods of decontamination of cadaveric tissues, sodium hypochlorite was noted to be the most effective, especially in contaminated musculoskeletal tissues.⁹ Although this may seem unrelated, it is not absurd to believe that the same principles could be adapted in order to decontaminate a patient’s grossly soiled wound. Targeted antibiotic instillation is becoming a more prevalent treatment option but has been shown to be ineffective in deep, myonecrotic Aeromonas infections.¹⁰ Taking these findings into consideration, instillation with a bactericidal solution is suggested.

The therapies utilized in this case series not only allowed the author to get ahead of an aggressive infection but also spared tissue. Without these modalities, the situation indicated that the patient was progressing toward a hip disarticulation, which would have significantly impacted the patient’s future mobility.

Negative pressure with instillation and dwell time allowed for instillation of targeted topical therapy. When used in conjunction with intravenous antibiotics and surgical debridement, NPWTi-d can be a crucial tool in obtaining source control and providing patients with improved quality of life further along the continuum of care.

Author: Richard Hill, RN, CWCN

Affiliation: Wound Ostomy Nurse, Natchitoches Regional Medical Center, 501 Keyser Avenue, Natchitoches, LA 71457

Correspondence: Richard Hill, RN, CWCN, Wound Ostomy Nurse, Natchitoches Regional Medical Center, 501 Keyser Avenue, Natchitoches, LA 71457; Hill.richardb@gmail.com

Disclosure: Mr. Hill serves as a paid consultant and is a member of the 3M + KCI Speaker’s Bureau.