Funding inadequate

Continuous femoral nerve block (CFNB) techniques continue to be increasingly used in the management of postoperative pain after total knee arthroplasty. Although the risk of full blown infection with CFNB has been poorly defined, the rate of catheter colonization after antisepsis with povidone-iodine has been demonstrated to be high (Cuivillion et al. showed the rate of colonization to be 57% after 48 hours). Recently, several anecdotal case reports have demonstrated severe infectious complications including psoas abscess and necrotizing fasciitis associated with continuous nerve block techniques. As the use of CFNB techniques increase in popularity, infectious complications will undoubtedly become more common.

The American Society of Regional Anesthesia and Pain Medicine recommends the routine use of antiseptic solutions with an alcohol base for skin disinfection before peripheral regional techniques due to their penetration of the stratum corneum and their rapid and prolonged effect. Chlorhexidine(chloraprep) has been proven to be better than povidone iodine solution for skin preparation before epidural catheter and intravascular device insertion (Kinirons et al., Ostrander et al., Mimoz et al.,). The goal of this prospective trial therefore is to determine if an alcoholic solution of 0.5% chlorhexidine is more effective than an aqueous solution of 10% povidone-iodine in reducing catheter colonization and reducing skin flora associated with short term ( 48 hours) postoperative continuous femoral nerve catheter placement. The investigators will also compare the ability of chloraprep and betadine disinfection at the time of catheter placement to prevent bacterial contamination of the continuous femoral catheter.

After antisepsis four different cultures will be analyzed:

1. The femoral nerve catheter will be removed after 48 hours and a culture of the distal tip of the femoral nerve catheter will be performed between the 2 arms.
2. immediately before skin antisepsis, a culture of the the skin will be performed to identify baseline skin flora.
3. immediately after antisepsis with both betadine and chlorhexidine, a culture of the skin will be performed to assess antiseptic efficacy.
4. just prior to removal of the femoral nerve catheter, a culture of the skin/catheter interface will be performed between the 2 arms.

Inclusion Criteria:

• ASA 1-3,
• Undergoing primary total knee arthroplasty.

Exclusion Criteria:

• Hypersensitivity/allergy to antiseptics,
• Recent opioid/alcohol abuse,
• Presence of contraindications to regional anesthesia,
• Coagulation disorder,
• Diabetic/femoral neuropathy,
• Prior surgery to inguinal area,
• Patient refusal.