DP58: FEMORAL NERVE CATHETERS: NOT ALL RASHES ARE INFECTIONS
Sneha Raola, MD; Alisha Shah, MD; Paola Silva, MD; Erika Taco-Vasquez, MD
University of Florida
Introduction/Background: Continuous femoral nerve catheters (FNC) provide effective postoperative analgesia particularly in orthopedic surgery. However, erythema and pruritus following catheter placement may represent either catheter-related infection or allergic contact dermatitis to adhesives or antiseptic materials. Misdiagnosis may result in unnecessary antibiotic exposure or, conversely, delayed treatment of a developing infection. We present two cases of rash following FNC placement with differing etiologies to highlight distinguishing clinical features and guide management.
Methods: We conducted a retrospective review of two patients who developed rashes after FNC placement for postoperative analgesia. In both cases, StimuCath catheters were placed under sterile conditions (mask, gown, gloves) without immediate complications. Clinical presentation, timing of symptom onset, laboratory findings, distribution of rash, management, and outcomes were analyzed to identify factors differentiating infectious complications from allergic reactions.
Results: Case 1 involved a 75-year-old male (BMI 20 kg/m²) with a history of metastatic urothelial carcinoma with bone metastases, prior MRSA-related sepsis, chronic tobacco use, and an acute femoral DVT. He received a FNC placement one day prior to an open reduction and internal fixation of the right proximal femur along with postoperative prophylactic antibiotics. For the first five days of the catheter placement, no infectious concerns were noted. However, on day 6, the patient developed pruritus and erythema in the right groin, C-Reactive Protein (CRP) was 160, but blood cultures were negative. Oral antibiotics were initiated for presumed cellulitis. By day 8, a localized abscess developed requiring bedside incision and drainage, confirming infectious etiology.
Case 2 involved a 14-year-old female (BMI 24 kg/m²) with no significant past medical history who received a FNC for post-operative pain control after an outpatient left knee arthroscopy with manipulation. On postoperative day 3, she developed a pruritic, erythematous urticarial rash localized to the distribution of Mastisol. No other abnormalities were found. The rash resolved by postoperative day 7 without progression or intervention, likely pointing towards allergic contact dermatitis (ACD).
Discussion: These cases illustrate key differences between catheter-related infection and allergic contact dermatitis. Patient risk factors for post-operative peripheral nerve catheter infections include: obesity, immunocompromised/malnourished state, absence of perioperative antibiotics, male sex, tobacco use, higher ASA class, ICU stay and colonization with nasal MRSA preoperatively. Catheter related risk factors for post-operative peripheral nerve catheter infections include: catheter duration of >48 hours, location of block in groin/neck/axilla, non-tunneled catheters, and a Tuohy needle being used. Infection risk increases exponentially by day 4 of catheter placement.
ACD is a delayed type IV hypersensitivity reaction that occurs after prior sensitization to an allergen, presenting with erythema, edema, and pruritus localized to the area of contact. In this case, the eruption was confined to the adhesive application site, and without other signs/symptoms of infection, pointed to Mastisol as the likely cause. The overall incidence of Mastisol-induced ACD remains unclear due to limited published data.
Careful assessment of patient risk factors, timing, laboratory findings, and rash distribution is critical to determine the underlying cause. It can help prevent unnecessary antibiotic use while still ensuring prompt treatment for true infections.