• Jean M. Pottinger, RN, MA
• Stacy A. Coffin, MD Loreen A. Herwaldt, MD

       INTRODUCTION

Infectious complications related to regional anesthesia are rare. Since the only information is available in case reports and retrospective surveys, it is likely that these complications are underreported. The objective of this chapter is to summarize information from the literature on infections associated with regional anesthesia, as well as to discuss the mechanism and to suggest strategies to prevent these complications.

       PATHOGENESIS OF INFECTIONS ASSOCIATED WITH CENTRAL NEURAXIAL BLOCKADE

Microorganisms from exogenous or endogenous sources may gain access to the subarachnoid, epidural, or tissue space surrounding peripheral nerves in several ways. Microorganisms from the patient’s or anesthesia practitioner’s flora can be inoculated directly when a catheter or needle is inserted into those spaces. Several reports in the literature suggest that infections are on occasion caused by the anesthesia practitioner’s flora.^1–3 For example, Trautmann and colleagues reported a case of meningitis caused by a Staphylococcus aureus strain that was identical by pulsed-field gel electrophoresis to the S. aureus isolate from the anesthesiologist’s nose.² Microorganisms can also enter the epidural space by hematogenous spread from other body sites, such as infected skin,^2,4 or by migrating along the catheter tract.^5,6 Several case reports suggested that infection was caused by spread of bacteria from infected sites through the bloodstream to the epidural space.^7–9 Others maintain that infections at distal sites are not contraindications to epidural anesthesia. For example, Newman concluded that distal infections did not increase the risk of epidural infection because traumatic injuries are often infected and no epidural catheter-related infections were identified among over 3000 patients who had epidural neural blockades for postoperative or posttraumatic analgesia.¹⁰ The anesthetic agents injected into the patient’s subarachnoid or epidural space are another possible source of infection. Infections from contaminated multidose vials are likely to be rare because most anesthetic drugs are weak bases dissolved in acidic solutions that inhibit growth of bacteria and fungi^11–13; besides most multidose local anesthetic solutions contain a bacteriostatic agent. Nevertheless, the case report by North and Brophy suggests that contaminated multidose vials still can be a source of infection. These authors reported an infection in which S. aureus isolates with matching phage types were recovered from an abscess and a multidose lidocaine vial.¹

Clinical Pearls

        To assess whether contamination of the anesthetic agent or the equipment (needles, syringes, tubing) is related to subsequent infections, investigators have cultured these items after they have been used with patients or during simulations. In four studies, 0–29% of used catheters were contaminated,^14–17 and James and coworkers found that 5 of 101 syringes used to inject anesthetic agents were contaminated.¹⁴ Ross and coworkers drew up 0.25% bupivacaine into control syringes and into syringes used to induce continuous lumbar epidural neural blockade (test syringe) in 18 obstetric patients.¹⁸ After each dose from the test syringe, the investigators cultured the contents of both the test and control syringes. Six of 18 test syringes were contaminated with bacteria, compared with only 1 of 18 control syringes. Raedler and associates cultured 114 spinal and 20 epidural needles after use for single lumbar injections.¹⁹ Twenty-four cultures (17.9%) grew microorganisms: 15.7% coagulasenegative staphylococci, 1.5% yeasts, 0.8% each enterococci, pneumococci, and micrococci. These authors concluded that it is easy to contaminate the needle and that anesthesiologists need to improve their hygienic measures. Despite finding contaminated equipment or anesthetic solutions, these investigators did not identify any infected patients,14–18 and thus, none of the authors were able to correlate contamination with infection.

       INFECTIONS ASSOCIATED WITH EPIDURAL BLOCKADE

There are numerous case reports in the literature of infections occurring after epidural neuraxial blockade, attesting to the fact that such complications can be severe (Table 72–1).^{1,7,9,19–55} Thirty-five of 48 patients in these case reports acquired epidural or intraspinal abscesses. Three patients had injections only, 1 patient had injections and several catheters, and 47 patients had catheters. Among the 38 patients who had catheters and for whom the duration of catheterization was specified, the median duration of catheterization was 3 days (range 50 min to 6 weeks). The median time to onset of the first signs or symptoms of infection was 4 days (range 1–4.8 months) after catheter placement. S. aureus caused 27 of 42 infections from which bacterial pathogens were isolated. P. aeruginosa caused five infections and Streptococcus spp. caused five. Three patients died and 27 nearly or fully recovered.

        It should be kept in mind that the number of reported cases does not allow us to assess the true frequency of infections after epidural neural blockade. However, several investigators have done studies to assess this risk. When reviewing 350 reports in the literature, Dawkins found no reports of infection after thoracic or lumbar epidural block, but he identified 8 (0.2%) reports of infection after 3767 sacral epidural blocks used for operative procedures and for obstetrics 1969.⁵⁶ More recently, Dawson reviewed the literature and found rates of deep infection ranging from 0 to 0.7% and rates of superficial infection ranging from 1.8 to 12%.⁵⁷

        Scott and Hibbard surveyed all obstetrics units in the United Kingdom and identified 1 epidural abscess in approximately 506,000 epidural neural blocks.⁵⁸ In contrast, Palot and colleagues identified 3 cases of meningitis in 300,000 patients who had undergone epidural blocks.⁵⁹ Three smaller series of obstetric epidural neural blockades (some 12,000 patients) did not identify any infections.^60–62 Similarly, in a recent study by the French SOS group on complications of regional anesthesia Auroy and coworkers did not identify any infections in 29,732 epidural neural blocks given for obstetrical procedures.⁶³ Together, the results of these five studies suggest that 4–5 serious infectious complications (ie, epidural abscesses or meningitis) occur per 1 million obstetric epidural neural blocks.

        A number of studies have assessed infections associated with epidural neural blockades done for operative procedures or for short-term pain relief. However, these studies report fewer patients than the studies of epidural neural blockade for obstetric procedures. We summarized findings from nine studies in Table 72–2.^{47,51,63–69} Brooks and associates found 4 infections among 4832 (0.08%) patients undergoing epidural neuraxial blockade for surgical procedures or for labor and delivery.⁷⁰ All four infections occurred in healthy young women who underwent cesarean sections; two infections were superficial (0.04%), and two involved the epidural space (0.04%). In contrast, Holt and colleagues reported 53 (1.8%) local infections and 11 (0.4%) central nervous system infections related to approximately 3000 epidural catheters.^71,72 The median duration of catheterization was 8 days for patients with local infections and 15 days for those with generalized symptoms (p = 0.01). Catheters removed from patients with clinical symptoms were more heavily colonized than those removed from asymptomatic patients. However, 59 of 78 catheters with positive cultures were removed because patients were symptomatic, suggesting that this observation may have been affected by ascertainment bias.

^a Although discrepancies exist in the two reports, these articles may report the same patient.

^b Patient was given epidural anesthetic agents and epidural steroids.

^cPatient had more than one epidural catheter.

NS = not specified, PVD = peripheral vascular disease, ESR = erythrocyte sedimentation rate, WBC —white blood cell count.

Adapted, with permission, from Hospital Epidemiology and Infection Control, 3rd ed. C. G. Mayhall (ed): Lippincott Williams & Wilkins, 2004.

Clinical Pearls

Given that the number of infections identified in any study has been low, the results reported by investigators who calculated the upper boundaries of the infection risk associated with epidural neural blockade are particularly important because they provide a better estimate of the true risk than do studies that report only the number of infections and the number of procedures. For example, Strafford and coworkers did not identify skin infections or epidural abscesses among 1458 pediatric patients who had epidural analgesia to control perioperative pain.⁷³ These investigators calculated the incidence of clinical infection to be 0 with a 95% confidence interval from 0% to 0.03%, or 3 infections per 10,000 procedures. Auroy and colleagues, as noted previously, did not identify any infections among 29,732 procedures done for deliveries.⁶³ They calculated 95% confidence intervals of 0/10,000 to 1/10,000 procedures. Darchy and associates evaluated 75 patients, 9 (12%; incidence density rate of 2.7/100 catheter days) of whom acquired local infections. None of the patients acquired deep infections.⁶⁵ Based on these data, Darchy and associates estimated the upper risk of spinal space infections to be 4.8% for catheters that remained in place for 4 days. Of note, these estimates are considerably higher than those of Strafford and coworkers⁷³ and higher even than the rates found by Du Pen and associates among patients with epidural catheters for long-term pain control⁷⁴ (see next paragraph).

Data from Hospital Epidemiology and Infection Control, 3rd ed. C. G. Mayhall (ed): Lippincott Williams & Wilkins, 2004.

        In general, epidural catheters inserted for long-term pain control become infected more frequently than those used for short periods of time. Du Pen and associates identified 30 superficial (9.3/10,000 catheter-days), 8 deep catheter track (2.5/10,000 catheter-days), and 15 epidural space (4.6/10,000 catheter-days) infections among 350 patients who had long-term epidural catheters.⁷⁴ Similarly, Zenz and colleagues identified two cases of meningitis among 139 patients (1.4%, or 2.1/10,000 catheter-days) treated for pain due to malignancy.⁷⁵ Coombs reported that 10 of 92 (10.9%) cancer patients acquired local infections, and 2 (2.2%) acquired meningitis.⁷⁶ Malignancy and reduced immunocompetence might be additional risk factors in the long-term catheter population.

       INFECTIONS ASSOCIATED WITH SUBARACHNOID BLOCKADE

Case reports in the literature indicate that serious infections can occur as complications of subarachnoid neural blockade (Table 72–3)^{2,3,5,6,77–91} Of the 26 infections reported in these case reports, 8 were meningitis, 4 were epidural abscesses, 2 were soft tissue abscesses, and 2 were infections of a disk or of a disk space. The median time to onset of signs or symptoms of infection was 1 day (range 1 h to 2 months) for all infections and 18 h (range 1 h to 10 days for meningitis). Streptococcal species caused 11 of the 23 infections from which bacterial pathogens were identified, and S. aureus caused 2 infections and Pseudomonas spp. caused 4. Twenty-one patients recovered fully. Compared with infections after epidural neural blockade, infections associated with subarachnoid neural blockade were more likely to be caused by streptococci, and patients were more likely to recover fully. Table 72–4 reviews data from nine studies or reviews, which, if taken together, suggest that the rate of infection is approximately 3.7 per 100,000 subarachnoid neural blockades.^63,91–98

       INFECTIONS ASSOCIATED WITH COMBINED EPIDURAL & SUBARACHNOID BLOCKADE

At present there are few reports in the literature about infectious complications of using combined epidural and subarachnoid neural blockade (CSE). We identified eight case reports of infections (nine infections) after combined procedures^51,99–105 (Table 72–5). The median time to onset of signs or symptoms or infection was 21 h (range 8 h to 9 days) for all infections and 18 h (range 8 h to 3 days) for meningitis. Signs or symptoms of epidural abscesses were first noted 19 days after the procedures. Streptococcal species caused three of six cases of meningitis and S. aureus caused all three epidural abscesses. Eight of nine patients recovered fully. We identified only one study that assessed rates of infection associated with combined procedures. Cascio and Heath identified 1 case of meningitis after about 700 (≈0.1%) combined epidural and subarachnoid neural blockades.⁹⁹

Adapted, with permission, from Hospital Epidemiology and Infection Control, 3rd ed. C. G. Mayhall (ed): Lippincott Williams & Wilkins, 2004.

Adapted, with permission, from Hospital Epidemiology and Infection Control, 3rd ed. C. G. Mayhall (ed): Lippincott Williams & Wilkins, 2004.

       INFECTIONS ASSOCIATED WITH PERIPHERAL NERVE BLOCKS

Continuous regional anesthetic techniques utilizing peripheral nerve blocks have become more popular in recent years for postoperative pain management especially for orthopedic procedures.^106,107 Only a few studies have addressed infectious complications related to these procedures. The study by Auroy and coworkers of French anesthesiologists did not identify any infections after 43,946 peripheral blocks.⁶³ Bergman and colleagues identified 1 patient among 368 patients (405 axillary catheters) who had a local S. aureus skin infection in the axilla after 48 h of axillary analgesia.¹⁰⁸ The patient recovered fully with antibiotic treatment. Meier and colleagues reported 8 superficial skin infections among 91 patients who had continuous interscalene catheters for an average of 5 days.¹⁰⁹ Nseir describes a case of fatal streptococcal necrotizing fasciitis following axillary brachial plexus block.¹¹⁰ Adam reported a psoas abscess complicating femoral nerve block catheter.¹¹¹

        Cuvillion and coworkers obtained cultures of 208 femoral catheters when they were removed after 48 h.¹¹² Fifty- four percent of the catheters were colonized with potentially pathogenic bacteria (71% Staphylococcus epidermidis, 10% Enterococcusspp., and 4% Klebsiella spp.). These investigators also reported three episodes of transient bacteremia, but they did not identify any abscesses or episodes of clinical sepsis.¹¹⁰ None of the groups provided information about the aseptic techniques used for catheter insertion.

        Other reports include cases of osteomyelitis following digital blocks¹¹³ and hematoma block for fracture repair,¹¹⁴ as well as orbital cellulites from sub-Tenon’s anesthesia.^115,116

        All these reports emphasize the importance of maintaining strict asepsis when performing continuing peripheral nerve blocks.

       PREVENTION OF INFECTIONS ASSOCIATED WITH REGIONAL ANESTHESIA

To date there is no consensus regarding infection control measures that are necessary when administering central neuraxial blockades. Most anesthesiologists agree that they should prepare the patient’s skin with an antimicrobial agent, wash their hands with an antimicrobial soap, and wear sterile gloves. However, anesthesiologists disagree about the necessity of other precautions.^117–123 For example, several surveys indicate that only 50–66% of anesthesia staff wear masks when performing epidural and subarachnoid neural blockades.^124–126

        The review of studies on infections associated with epidural anesthesia indicates that there is no consensus regarding patient risk factors for infectious complications of epidural neural blockade.¹⁰⁷ Few studies have been designed to assess risk factors for infection associated with epidural or subarachnoid neural blockades, possibly in part because these infections are rare. In fact, we identified only one case- control study that was done to evaluate risk factors for infections associated with epidural neural blockade.¹²⁷ Dawson and colleagues evaluated epidural neural blockades done for postoperative pain relief and found that procedures done between April and August had a sixfold higher risk than those done during other months (95% Cl 1.28–28.12, p = 0.009). The risk of infection was lower if a bag rather than a syringe was used to administer the anesthetic agent (odds ratio 0.17, 95% Cl 0.02–1.34, p = 0.05). Of the two risk factors identified by this study, only the latter, use of syringes, could be addressed by practice changes.

Related posts:

Regional Anesthesia in the Patient with Preexisting Neurologic Disease. The History of Local Anesthesia. Stimulating Catheters. Ultrasound-Assisted Nerve Blocks in Adults. Cutaneous Blocks for the Upper Extremity. Cervical Plexus Block.