Cuvillon, Philippe MD; Ripart, Jacques MD, PhD; Lalourcey, Laurent MD, MSc; Veyrat, Eric MD; L’Hermite, Joel MD; Boisson, Christophe MD, MSc; Thouabtia, Ezzedine MD; Jacques Eledjam, Jean MD
Major hip, femoral, or knee surgical procedures are often associated with severe postoperative pain, especially within the first two postoperative days. Continuous femoral nerve block provides better pain control than IV patient-controlled analgesia with morphine (1). It induces fewer side effects than epidural analgesia (nausea, vomiting, pruritus, arterial hypotension, and urinary retention) (2). Therefore, it is considered a suitable choice for postoperative analgesia after such surgery.
Because the catheter is inserted near the femoral nerve and vascular structures, the safety of this technique could be questioned. Moreover, femoral venous access has a frequent rate of bacterial colonization (from 13% to 34%) (3,4). Therefore, the safety of continuous femoral nerve block could be questioned with regard to infectious complications.
The purpose of the present study was to determine prospectively the incidence of catheter bacterial colonization and/or infection in postoperative adult patients having femoral nerve catheters inserted for analgesia. In addition, side effects and complications (including vascular and nerve injury) were noted from the insertion to the removal of the catheter and 6 wk later.
After approval from our IRB and oral informed consent, patients scheduled for hip, femoral, or knee surgery were prospectively included. Noninclusion criteria were age <18 yr or >80 yr, blood clotting impairment, allergy to local anesthetics, history of recent local or generalized infection, neurological deficits, inability to use visual analog pain scores (VAS), and refusal.
The procedure for catheter insertion was standardized. Continuous femoral nerve catheters were placed before surgery and performed after the “three in one” or “Iliofascial” technique with a nerve stimulator (5,6). In the preanesthesia room, the patient was monitored (Sao2, electrocardiogram, noninvasive pressure, venous access). The skin was prepared with 1% polyvidone iodine and draped with sterile operative drapes. After local skin anesthesia (2 mL 1% lidocaïne), the femoral nerve was localized using a nerve stimulation technique. The needle (Contiplex; B Braun, Melsungen, Germany) connected to a nerve stimulator (Stimulator; B Braun) was inserted through the skin. Its position was accepted when an output <0.5 mA elicited a quadriceps motor response (dancing patella). The metal needle was removed and the catheter was introduced through the cannula and pushed 10–15 cm into the psoas compartment (7). When the catheter insertion was difficult, 20 mL saline solution (0.9%) was injected through the cannula to ease the catheter placement. The catheter was secured with adhesive strips and a transparent adhesive dressing (Opsite®; Smith and Nephew Medical Ltd., Hull, England). After tests for vascular placement (aspiration, injection of 3 mL 2% lidocaine with 1:200,000 epinephrine), analgesia was induced with 30 mL of an equal parts mixture of 0.5% bupivacaine and 2% lidocaine with 1:200,000 epinephrine. To verify the correct position of the catheter, the cutaneous sensation in the area of the femoral nerve was assessed using a cold test. Spinal or general anesthesia was induced and surgery performed. After surgery, the catheter was connected to a pump (Abbott Pain Manager®, Abbott Laboratories, North Chicago, IL) and continuous infusion (10 mL/h) of local anesthetic was continued for 48 h (0.125% bupivacaine for the first 102 patients and 0.2% ropivacaine for the next 109).
Additional postoperative analgesia was standardized IV paracetamol (2 g/6 h) and ketoprofen (100 mg/12 h). When VAS >3.5, additional subcutaneous morphine was given (0.1 mg · kg−1 · 4 h−1). Postoperatively, the patient was checked every 4 h by a field nurse. Data collected included VAS (0 = no pain, 10 = worst pain), heart rate, arterial blood pressure, respiratory frequency, presence of nausea or pruritus, and neurological disorder. The insertion site was checked once a day by a nurse for local signs of infection or blood through the catheter. All surgical patients received IV antibiotics for 48 h perioperatively (cefamandole 750 mg/6 h, according to the French Society of Anesthesia consensus conference).
After 48 h, catheters were carefully removed, and 3 cm of the distal portion was cut and cultured within 2 h using a semiquantitative procedure (8). Fifteen colony-forming units were considered to represent colonization of the catheter. When the culture was positive, muscle psoas echography was performed to look for abscess. Catheters were immediately removed and cultured in cases of the following suspected complications: fever (>38.5°C), shivering, white blood cell count >10000/mm3, local cellulitis or pus, suspected signs of neurological or cardiac local anesthetic toxicity, and if blood was noted in the catheter (possible IV catheter migration). When neurological or cardiac local anesthetic toxicity was suspected, the blood concentration of local anesthetic was determined. The time to insert the catheter was defined as the time elapsed from the beginning of aseptic procedure to the time of dressing on the site of catheter insertion.
Noninfectious complications were divided into initial complications, 48-h complications, and 6-wk complications and noted by members of the pain service. Initial complications were failure of nerve location, difficult or impossible catheter insertion, inadvertent vascular puncture, impossible initial bolus injection (including kinked catheter), and major leak of local anesthetic solution at the insertion site. Complications after 48 h were kinked catheter, partial or total inadvertent removal of catheter, vascular backflow through the catheter (aspiration test performed once a day), lack of sensory block (cold test in the area of femoral nerve at 24 and 48 h), and pain at the insertion site. Complications after 6 wk were nerve injury (paresthesia, motor or sensory femoral deficit).
The following infectious complications were noted: positive catheter cultures, cellulitis or edema at the insertion site, positive blood culture, positive echography of psoas (abscess). The primary end points were the rate of colonization or infectious complications and VAS score. The secondary end points were adverse effects.
Data were expressed as mean ± sd (parametric data) and median (5°–95°) (nonparametric data), as appropriate. The results were assessed statistically with multiple logistic regression to demonstrate associations between catheter tip colonization and clinical variables (demographic data, ASA physical status, type and duration of surgery, time to insert the catheter). For all analyses, P < 0.05 was used to determine significance.
From June 1, 1997 to December 31, 1998, 214 patients were included. Three femoral nerve blocks failed (nerve not localized) (1.4%). Thus 211 catheters were placed and studied. The patient characteristics and the type of surgery are listed in Table 1.
VAS scores are listed in Table 2. Supplemental analgesia was infrequent. The median additional morphine consumption was 0 (0–43) mg for 0 to 24 h and 0 (0–24) mg for 24 to 48 h.
Initial complications are reported in Table 3. The catheter insertion was difficult in 20 patients. After injection of 20 mL 0.9% saline solution through the cannula, insertion of the catheter was always performed. In three case, the initial bolus injection was impossible because of a kinked catheter and injection was possible after the catheter was pulled back 5 cm. Three (3/211) sensory blocks failed. Complications after 48 h are listed in Table 4.
Bacterial analysis was performed for 208 patients, because three catheters were accidentally removed before 48 h and were not cultured. Positive cultures were seen in 120 catheters (57%). Staphylococcus was the most frequent organism. Other organisms are reported in Table 5. Echography of the insertion site and the psoas muscle were performed when catheters were positive; no abscesses were identified. Three transitory signs of systemic sepsis were noted (bacteriemia, shivering, and temperature over 39°C). Symptoms spontaneously disappeared after catheter removal. No correlation was observed between catheter colonization and weight, age, ASA physical status, duration and type of surgery, emergency surgery, or approach to the femoral nerve catheter insertion (“three in one” or “Iliofascial”) (P > 0.05). After 6 wk, no septic complications were noted by the surgeon or the anesthesiologist at the surgical procedure site or at the catheter insertion skin site.
One patient had neurological changes (confusion and trembling) without cardiovascular symptoms after 24 h infusion. The anesthetic solution infusion was immediately stopped. Neurological findings resolved spontaneously after 3 h. The patient’s symptoms were not the result of excessive local anesthetic blood concentration (blood concentration of bupivacaine was 2.1 μg/mL). After 6 wk, one femoral paresthesia (0.4%) without motor deficit was noted. This nerve damage partially recovered after 1 yr.
In the present study, continuous femoral nerve catheters were inserted in 211 patients, lasting 48 h for 208 patients. Postoperative analgesia was excellent. VAS median score was 1 (0–7) at the 4th hour and did not increase throughout the block. This is consistent with other studies (1,2). Initial complication rates (Table 2) are similar to those reported previously (1,6,9). Singelyn et al. (1) reported fewer difficult catheter insertions (0%). Rates of kinked catheter (1.4% in this study) occurred in 0% for Singelyn et al. (1). The rate of inadvertent removal of catheters (1.4%) is acceptable when compared with that reported in the literature (0% to 20%) (1,5,7).
Severe complications were rare in this study. No major vascular injury was noted, but at six weeks one patient complained of femoral sensory nerve dysfunction (paresthesia). At one year, the femoral paresthesia partially disappeared (electromyographic and echography studies eliminated surgical section or hematoma). This case demonstrates that there is a risk of nerve injury with a femoral catheter, but this study (with a limited number of patients) did not evaluate the prevalence of this risk.
In this study, femoral nerve catheter colonization was common (57%). This rate is frequent but not surprising. Similar studies with epidural or caudal catheters demonstrated common colonization rates. McNeely et al. (10) found 20% caudal catheter colonization and Kost-Byerly et al. (11) revealed 35% epidural catheter colonization in children. As compared with adult or pediatric epidural catheter colonization reported in the literature, the present study showed an increased incidence of femoral nerve catheter colonization (10,11). The site of femoral nerve catheter insertion may have influenced our results compared with the epidural insertion site. The site of femoral nerve catheter insertion is just lateral to the femoral venous access site. This site has an increased risk of contamination with fecal or urinary organisms with rates of catheter colonization from 13% to 34%(3,4). These percentages for femoral venous access are similar or often more than other sites (jugular or subclavian) (4). Moreover, in a similar study (12) with a limited number of patients, we demonstrated that a popliteal insertion site had a very small bacterial colonization (7.5%).
Prophylactic antibiotics, local anesthetic solution (bacteriostatic effect), and antimicrobial filters (0.2-μm) decrease the risk of infection and alter the flora of the skin (10,13). Moreover, transparent occlusive dressing, and iodine solution and type of aseptic procedure may influence the bacterial proliferation of our results (14). The role of those different factors for femoral nerve catheter colonization must be confirmed by a large randomized study.
Staphylococcus epidermidis was the most common organism isolated, as was seen in epidural catheter studies (11). This organism has been generally regarded as a pathogen of little clinical significance. In this study, none of the 120 colonized catheters had long-term infectious complications. Three patients presented with increased temperatures and bacteriemia at the 24 and 48 h. Culture of the femoral catheter and hemoculture were positive for the same organism (Staphylococcus epidermidis). Bacteriemia and fever disappeared when those three catheters were removed without any antibiotic therapy. Those three cases confirmed the importance of closely monitoring the patients to detect infection immediately.
No abscess was seen using echography when the catheter culture was positive. This procedure need not be routinely performed when catheter colonizations are positive, but when shivering, fever, or pain occur at the insertion site, echography is easy to perform and might determine whether computed tomography scan or magnetic resonance imaging scan are indicated.
We conclude that continuous femoral nerve block for postoperative analgesia is effective, but induces a frequent rate of catheter colonization. Serious complications are rare. We do not recommend systematic bacterial analysis of the catheter, but infections complications require immediate catheter removal, catheter culture, and consideration of psoas muscle echography or other imaging.
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