Interventional pain procedures and surgeries, while considered minimally invasive, can have serious, life-threatening infectious complications. The risk of infection varies considerably based on the type of procedure and patient risk factors. Therefore it is essential that all practicing interventional pain medicine physicians have a thorough understanding of potential infectious risks, signs, and symptoms, methods to minimize infections, how to identify infections, and management of infections for each type of interventional procedure performed. This chapter summarizes the available literature, national recommendations, and expert opinions on the prevention, recognition, and management of procedural and surgical complications with a goal to improve physician awareness and patient care in the fields of interventional pain medicine and neuromodulation.
Keywordscomplication, infection, interventional, neuromodulation, pain
Infections related to interventional pain procedures and implantable devices vary considerably based on the target location, responsible pathogens, anatomical structures involved, collateral damage, and severity. Surgical site infections (SSIs) have been shown to significantly increase mortality, prolong hospital length of stay, and reduce health-related quality of life. In addition, SSIs cost the US health care system an estimated $3.5–$10 billion annually. The total cost of a single spinal cord stimulator (SCS) infection has been estimated to range from $28,500 to $54,500 in the United States.
Recently there has been a global emphasis by national and international agencies and societies to create and promote recommended best practices to reduce SSI rates. Despite these efforts, SSI rates have not significantly declined. SCS infection rates are higher than those of other implantable devices, including cardiac pacemakers and total joint replacements. A recent international survey of 506 physicians who perform SCS implants was conducted to examine compliance rates for the Centers for Disease Control and Prevention (CDC), National Institute for Health and Care Excellence (NICE), and Surgical Care Improvement Project (SCIP) infection control practice recommendations. Only four of the 15 questions had compliance rates ≥80%, thus further highlighting the need for physician education in the field. Both current infection rates for implantable pain devices and survey responses suggest a need for improved education for interventional pain physicians on infection control practices.
This chapter will summarize the current literature and recommendations for commonly performed interventional pain procedures, with a distinction made between implantable device surgery including SCS and intrathecal drug delivery systems (IDDS) and nonimplantable device procedures including epidural steroid injections, facet blocks, neuraxial and peripheral nerve blocks, joint injections, sympathetic blocks, radiofrequency, discography, and vertebral augmentation ( Tables 86.1 and 86.2 ). For implantable pain therapies, more detailed recommendations for the entire perioperative process (preoperative, intraoperative, and postoperative) will be provided.
|Trigger point injections||Interlaminar epidural steroid injections (C, T, L, S)||Intradiscal procedures (C, T, L)||Intrathecal catheter and pump implants/revisions|
|Peripheral nerve blocks||Transforaminal epidural steroid injections (C, T, L, S)||Peripheral nerve stimulation trials||Peripheral nerve stimulation trials/implants|
|Facet joint and medial branch nerve block injections and radiofrequency ablation||Spinal cord stimulation trials||Spinal cord stimulation implants/revisions|
|Musculoskeletal and joint injections||Indwelling catheters (epidural, intrathecal)|
|Sacroiliac joint injections and sacral lateral branch blocks||Vertebral augmentation (vertebroplasty and kyphoplasty)|
|Paravertebral blocks (C, T, L) |
Sympathetic blocks (stellate, thoracic, splanchnic, celiac, lumbar, hypogastric)
|Single-shot intrathecal drug trials|
|Intrathecal pump refills|
|Risk Reduction Techniques #||A||B||C||Implantable Therapies|
|Identification and optimization of patient risk factors||X||X||X||X|
|Staphylococcus aureus screening and decolonization for carriers||Implantable trials a||X|
|Preprocedural intravenous antibiotics||X||X|
|Hand-washing with soap and water or an alcohol-based hand rub||X||X||X||X|
|2–5-minute surgical hand scrub||X||X|
|Do not wear hand or arm jewelry||X||X||X|
|Sterile surgical gown||X||X|
|Surgical cap and mask||X||X||X|
|Patient skin antisepsis with chlorhexidine||X||X||X||X|
|Full-length body drape||X||X|
|Use of styletted needle||X||X||X|
|Sterile C-arm cover||X||X|
|Sterile ultrasound probe cover and gel||X||X||X||X|
|Wound irrigation with sterile saline||X|
Definition of Surgical Site Infection
SSI has been defined by the CDC. Identification of an SSI is based on physical exam findings of localized pain/tenderness, swelling, erythema, heat, or purulent drainage, as well as cultures and radiologic findings ( Fig. 86.1 ). Superficial SSIs involve the skin and subcutaneous tissues, while deep SSIs involve the fascia and muscle layers. Superficial and deep SSIs occurring in the absence of an implantable device are defined as occurring within 30 days after the operation. When a device is implanted, a deep SSI is defined as occurring within 1 year post implant.
Pathogens Associated With Surgical Site Infections
Organisms causing SSIs can be categorized as coming from an endogenous or exogenous source. The most common pathogens in descending order are Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus, Escherichia coli, and Pseudomonas aeruginosa. The most common source of infection is from the patient’s own flora. It has been shown that pathogenic S. aureus isolated from an infected wound matches cultures from the patient’s nares 80%–85% of the time.
Scope of Interventional Pain Procedures and Risk of Infection
Interventional pain procedures and surgeries vary considerably based on the pain syndrome being treated, practitioner technique, and surgical theater environment. The invasiveness of procedures varies, and thus different infection control practices must be considered. Recommendations for the prevention of SSIs have been published by the CDC, NICE, and SCIP ( Table 86.3 ).
|86.3.1 Preoperative Recommendations|
|Recommendations||CDC Evidence Rankings||SCIP Process of Care Performance Measures||NICE Guidelines||Authors’ Additional Recommendations|
|Identify and treat all remote infections||IA|
|Identify patient risk factors||✓|
|Optimize glucose control||IB|
|Discontinue tobacco use||IB|
|Require patients to shower or bathe with an antiseptic agent prior to surgery||IB|
|Preoperative screening and decolonization for SA carriers||✓|
|Do not routinely use nasal decontamination for SA||✓|
|Appropriate selection of intravenous antibiotic prophylaxis based on hospital pathogens and type of surgery/procedure||IA||✓||✓|
|Weight-based antibiotic dosing||✓|
|Appropriate prophylactic antibiotic received within one hour prior to surgical incision (two hours for vancomycin)||IA||✓||✓|
|Appropriate agent selection for skin antisepsis (povidone-iodine or chlorhexidine)||IB||✓|
|Vancomycin should not routinely be used||IB|
|Preoperative surgical scrub for at least 2–5 min using an appropriate antiseptic. Scrub the hands and forearms up to the elbows||IB||✓|
|Keep nails short and do not wear artificial nails||IB||✓|
|Sterile gown and gloves||IB|
|Do not wear hand or arm jewelry||II||✓|
|Do not use hair removal routinely||IA||✓|
|If hair is removed, use electric clippers immediately before surgery||IA||✓||✓|
|Evaluate for skin lesions or areas of local infection||✓|
|Apply preoperative antiseptic skin preparation in concentric circles moving toward the periphery||II|
|Wide prep and drape||✓|
|86.3.2 Intraoperative Recommendations|
|Recommendations||CDC Evidence Ranking||SCIP Process Care Performance Measures||NICE Guidelines||Authors’ Additional Recommendations|
|Wear a surgical mask in the OR if sterile instruments are exposed||IB|
|Wear a cap or hood to fully cover hair in the OR||IB|
|Wear two pairs of sterile gloves when there is a high risk of glove perforation and the consequences of contamination are high||✓||✓|
|Use sterile surgical gowns that are effective barriers when wet||IB||✓|
|If an incise drape is used, use an iodophor-impregnated drape||✓|
|Laminar flow and HEPA filters in OR||IB|
|Limit OR traffic||II||✓|
|Keep OR doors closed during procedure||IB|
|Adhere to principles of asepsis when placing spinal or epidural catheters||IA|
|Limit tissue trauma, maintain hemostasis, eradicate dead space, and avoid the electrocautery at tissue surface||IB||✓|
|Vigorous wound irrigation with bulb syringe||✓|
|Limit surgical time||✓|
|86.3.3 Postoperative Recommendations|
|Recommendations||CDC Evidence Ranking||SCIP Process of Care Performance Measures||NICE Guidelines||Authors’ Additional Recommendations|
|Prophylactic antimicrobial discontinued within 24 h of surgery||✓|
|Occlusive dressing for a minimum of 24–48 h||IB||✓|
|Do not routinely use topical antimicrobial agents for surgical wounds that are healing by primary intention||✓|
|Continued comorbidity optimization||✓|
|Close postoperative wound surveillance||✓|
|When SSI is suspected, prescribe an antibiotic that covers the likely causative organisms. Consider local resistance patterns and the results of microbiological tests in choosing an antibiotic.||✓|
|Consult an infectious disease specialist if any sign or warning signals of infection are present||✓|
|Wash hands before and after dressing changes||IB|
|Use sterile technique for dressing changes||II||✓|
|Educate patient and family on proper incision care, symptoms of SSI, and importance of reporting symptoms||II||✓|
Despite an emphasis to reduce SSIs, the rate of infections has remained relatively stable over the past two decades. In the United States, approximately 500,000 SSIs occur annually, accounting for 17% of all nosocomial infections. The relative risk of central nervous system infection following paraspinal injections has been estimated to be about 1/1000 (0.1%). The risk of developing an epidural abscess from an indwelling catheter for postoperative analgesia has been reported to be 1 in 1930 catheters (0.05%). Infection rates associated with single-shot peripheral nerve blocks are also low. A retrospective study examining 7476 patients who received an ultrasound-guided single injection peripheral nerve blockade using a low level disinfection technique in combination with a sterile transparent film transducer barrier reported no indications of block-related infections. Although the overall rate of bacterial colonization with peripheral nerve block catheters is high, the risk of reported infection is low. There have only been a few reports of infectious complications related to facet injections; thus the true incidence is unknown. Incidence of disc infection with discography has been estimated to be 0.15% per patient and 0.08% per disc injected. Published systematic reviews on SCS and IDDS report infection rates ranging from 3.4% to 10% and 2.4% to 4.6%, respectively.
Preoperative Risk Reduction
Patient Risk Factors
Physicians should identify patient-related risk factors prior to performing a procedure, and efforts should be made to correct any modifiable risk factors ( Table 86.4 ). Postmarket surveillance data on SCS and IDDS implants revealed 38% and 70% of patients with SCS and IDDS infections, respectively, had a medical comorbidity that increased their risk of infections. Smoking has been associated with an increased risk of SCS infections, likely secondary to the development of microvascular disease, leading to tissue ischemia and poor wound healing. Although the biological effects of cancer and chemotherapeutic drugs can weaken host immunity, a retrospective study demonstrated that implantable pain therapies can still be utilized in cancer patients without significantly increasing the risk of SSI when appropriate infection control measures are taken.
Preoperatively, a thorough history and physical exam should be performed to identify patient risk factors. Many measures can be taken to reduce the risk of SSIs, such as glucose optimization, tobacco cessation (for at least 4 weeks), optimization of viral load in HIV patients, minimizing/avoiding perioperative steroids, and treatment of remote infections (e.g., urinary tract). Nonmodifiable risk factors need to be documented, and a discussion with the patient regarding the associated increased risk of infection should occur prior to the pain intervention.
Staphylococcus Aureus Carriers
Staphylococcus aureus is the leading cause of SSIs, accounting for approximately 20% of all SSIs, 30% of implantable cardioverter-defibrillator (ICD) implants, and 60% of all prosthetic joint infections. Greater than 80% of nosocomial S. aureus infections are endogenous, and the number of cases of methicillin-resistant S. aureus (MRSA) SSIs is increasing. S. aureus nasal colonization rates have been reported from 20% to 80%, depending on the population studied.
Methicillin-sensitive S. aureus (MSSA) and MRSA carriers have been shown to have a significantly higher risk for developing an SSI (two to nine times higher). Therefore identification of carriers followed by decolonization protocols is critical in reducing SSI rates and has been recommended as an infection control measure. Decolonization of S. aureus carriers has also been shown to be a cost-effective treatment.
Decolonization protocols have described the application of mupirocin 2% nasal ointment applied twice daily, combined with chlorhexidine gluconate soap total-body washes daily for a duration of 5 days immediately preceding surgery. Utilization of decolonization protocols in individuals that are colonized reduces the rate of postoperative infections by greater than 50%. No data exist to support the use of routine decolonization protocols in patients who do not test positive for S. aureus colonization.
Preoperative antibiotic prophylaxis has been shown to significantly reduce the risk of SSIs, and the incidence of wound infection by approximately 50%, regardless of the type of surgery. Antibiotic prophylaxis ( Table 86.5 ) is recommended for implantable pain therapies (i.e., trials and implant stages). Proper antibiotic selection, route of administration, dosing, and timing are critical, as suboptimal implementation has been found to increase the risk of infection twofold to sixfold. Cephalosporins are recommended as first-line agents. If a patient has a β-lactam allergy, clindamycin or vancomycin are alternative antibiotics. In individuals colonized with MRSA or at high risk for MRSA (e.g., institutions that have a high rate of MRSA infections), vancomycin is recommended.
|Antibiotic||Standard Intravenous Dosing||Timing Prior to Incision||Redosing Interval||Indications|
|Cefazolin||1 g ≤ 80 kg |
2 g > 80 kg
3 g > 160 kg
|Within 30–60 min||3–4 h (CrCl > 50 mL/min) |
8 h (CrCl 20–50 mL/min)
16 h (CrCl < 20 mL/min)
|Clindamycin||600 mg ≤ 80 kg |
900 mg > 80 kg
1200 mg > 160 kg
|Within 30–60 min||6 h (CrCl > 50 mL/min) |
6 h (CrCl 20–50 mL/min)
6 h (CrCl < 20 mL/min)
|(1) β-lactam allergy|
|Vancomycin||1 g ≤ 80 kg |
2 g > 80 kg
3 g > 160 kg
|Within 120 min||8 h (CrCl > 50 mL/min) |
16 h (CrCl 20–50 mL/min)
None (CrCl < 20 mL/min)
|(1) β-lactam allergy |
(2) Known MRSA colonization
In order for antibiotic prophylaxis to be effective, minimum inhibitory concentrations (MIC) must be reached prior to surgical incision and maintained throughout the duration of the surgery. Preoperative antibiotics should be administered intravenously (IV) prior to incision time (30–60 minutes prior to incision or 120 minutes of incision for vancomycin). Cefmetazole 2 g IV administered immediately prior, 15 minutes prior, and 60 minutes prior to incision all showed MIC90 in blood and tissue samples throughout surgical procedures, lasting on average 2.1–2.4 hours. In order to reach MIC, weight-based dosing is needed. Weight-based dosing (2 g of cefazolin in morbidly obese patients) prior to gastroplasty was shown to decrease SSI rates to 5.6%, compared with 16.5% when 1 g of cefazolin was administered.
The kidneys excrete the majority of antibiotics used for surgical prophylaxis. The exception is clindamycin, which is primarily excreted via the biliary system. Therefore creatinine clearance must be taken into account prior to antibiotic dosing. Redosing is needed when the duration of surgery is longer than two half-lives of the administered antibiotic (see Table 86.5 ).
The continuation of antibiotics in the postoperative period is not recommended beyond 24 hours for clean surgical wounds. Prolonged antibiotic use in the postoperative period does not improve outcomes and may result in poorer outcomes. Specifically, the continuation of antibiotics in the postoperative period has been associated with delayed normalization of body temperature and elevation of the C-reactive protein (CRP) level. The SCIP guidelines recommend the discontinuation of antibiotics within 24 hours of surgery.
There are no recommendations or evidence for the use of antibiotic prophylaxis in the majority of routine interventional pain procedures (i.e., epidural steroid injections, facet blocks); however, for those that are considered higher risk for infection (i.e., indwelling catheters, and device trials/implants), antibiotic prophylaxis is recommended. For discography and other intradiscal procedures, controversy exists on the need for IV and/or intradiscal antibiotic administration. Intravenous antibiotics do not reliably achieve adequate intradiscal concentrations. Therefore intradiscal antibiotics have been recommended. However, ex vivo studies examining the effects of high antibiotic concentrations on cultured human intervertebral disc annular cells demonstrated deleterious effects on cell survival, cell proliferation, and metabolic rates. Bogduk et al. demonstrated with pooled data that the prevalence of discitis when antibiotic medications are not used is 0.24% (95% confidence intervals: 0.11%–0.37%), which is higher than the reported overall incidence of 0.15% per patient.
Appropriate surgical scrubbing of the hands and forearms is a CDC Category IB and NICE recommendation. Commercially available antiseptic solutions in the United States contain alcohol, chlorhexidine, and/or povidone-iodine. There is evidence that chlorhexidine-based scrubs reduce the number of colony-forming units compared with povidone-iodine scrubs; however, the data supporting its clinical relevance are lacking. The duration of the surgical scrub appears to be the most important factor to ensure adequate hand hygiene and limit bacterial counts. Surgical hand-washing lasting between 2 and 5 minutes results in statistically fewer CFUs when compared with hand-washing techniques of lesser duration.
The removal of hand and wrist jewelry prior to surgical scrub is a CDC Category II and NICE recommendation, as well as an American Society of Regional Anesthesia and Pain Medicine (ASRA) recommendation when performing regional anesthesia. The presence of hand jewelry increases bacterial counts on the hands of health care workers, even after hand-washing.
The method of hand hygiene required to minimize the risk of infections associated with interventional pain procedures has not been clearly established. Hebl recommended thorough hand-washing with an alcohol-based antiseptic prior to performing regional anesthetic techniques, but did not recommend a specific method or duration. For implantable devices and indwelling catheters, a full surgical scrub is recommended.
Appropriate Hair Removal
The CDC Category IA and NICE do not recommend routine removal of hair to reduce the risk of SSI, and if hair is removed clippers are the method of choice. Timing and method of hair removal appear to be the most important factors to consider. A meta-analysis looking at hair removal techniques concluded that there is no difference in SSI rates when comparing no hair removal to hair removal with chemical or clipper methods; however, shaving methods do increase the risk of SSIs. Both clipping and shaving hair 24 hours or more before an operation significantly increases the risk of SSI. There are no data to evaluate the efficacy of hair removal strategies prior to interventional pain procedures.