General Information
Meningitis and epidural abscess are two serious infections associated with neuraxial techniques.
Incidence
The rarity of both these conditions makes it almost impossible to accurately estimate the incidence of each, with huge variation among studies and surveys. Issues with reporter bias, unknown denominators, changing practice over time, varying operator experience, and population risk factors all affect incidence. Generally, it has been found that fewer neuraxial infections occur in the obstetric population compared to the surgical population.
Meningitis: reported incidence ranges from 1 in 39,000 (from an analysis of 9 studies) to 1 in 235,000 spinal/CSE anesthetics.
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Epidural abscess: reported incidence ranges from 1 in 8,300 to 1 in 303,000 epidural anesthetics.
Most epidural abscesses occur in patients who have not received neuraxial analgesia/anesthesia. They occur spontaneously in the general population due to hematological spread of a remote focus of infection to the epidural space. Only 5.5% of epidural abscesses are thought to be related to epidural anesthesia, and these patients are often elderly and immunocompromised, developing an epidural abscess following prolonged epidural catheterization. This combination of events rarely occurs in the obstetric population.
1. Meningitis
Iatrogenic meningitis is also known as “postdural puncture meningitis” because of its close temporal association with dural puncture.
a. Symptoms
Symptoms usually appear anywhere from a few hours up to 8 days after spinal or CSE anesthesia. Cases secondary to Aspergillus may take up to a month to become symptomatic.
Headache and fever occur early, often with neck pain, vomiting, and other signs of meningism, such as nuchal rigidity and photophobia. These signs and symptoms have been mistaken for those associated with postdural puncture headache, a more common complication of neuraxial anesthesia. Drowsiness with decreased level of consciousness, seizures, and coma may follow.
c. Diagnosis
Lumbar puncture with CSF examination shows
i. CSF is frequently cloudy
ii. raised white cell count
iii. raised protein level
iv. low glucose compared with blood
In cases with suspected raised intracranial pressure or epidural abscess, an MRI or CT scan is safer.
Causative Organisms
i. Streptococcus viridans (alpha-hemolytic streptococci) – causes approximately 85% of cases, but can be difficult to grow in conventional culture medium.
ii. Aspergillus species (fungi) – responsible for several cases in India and Sri Lanka due to contaminated syringes.
Group B Streptococcus, Staphylococcus aureus, Pseudomonas aeruginosa have also been isolated
Community-acquired meningitis is caused by Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae.
Sources of Infection
S. viridans is commonly found in the upper airway/oropharynx and in the vagina.
Some case reports have found a direct link to bacteria cultured from the mouth of providers performing neuraxial anesthesia who did not wear a mask.
d. Risk Factors
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Dural puncture
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Bacteremia – organisms in blood can be transported into the CSF during spinal anesthesia
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Difficult placement of epidural increases the risk of undetected dural puncture allowing passage of organisms
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No mask worn by anesthesia provider during neuraxial procedure
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Labor – meningitis is reported less frequently in patients receiving spinal anesthesia for elective cesarean section
e. Treatment
The early administration of intravenous vancomycin (to cover beta-lactam–resistant organisms) and a third-generation cephalosporin is recommended. Culture and sensitivity results, once known, will guide further treatment. Unfortunately, S. viridans is becoming increasingly resistant to antibiotics.
f. Prognosis
Prognosis is usually good. However, mortality in the Aspergillus cases mentioned previously was 50-80%.
2. Epidural Abscess
This rare complication is a medical emergency that relies not only on early treatment, but more importantly, on early diagnosis to prevent permanent neurologic damage and even death.
a. Symptoms
Symptoms usually develop 4-10 days (median of 5 days) after removal of the epidural catheter, but may take several weeks, initially presenting with fever and severe back pain with associated localized tenderness. Signs of meningism may be part of the clinical picture.
Radicular pain can develop, progressing to motor weakness, sensory loss, reduced or absent reflexes, sphincter dysfunction, and finally paraplegia. Inflammation around the puncture site with serious fluid leakage may occur. As with meningitis, misinterpretation of early symptoms in obstetric patients, as well as late presentation of neurological deficits, may delay diagnosis.
b. Diagnosis
i. Suspicion of an epidural abscess necessitates an emergency MRI.
ii. Leukocytosis and a raised C-reactive protein may be present even in the absence of neurological signs and can aid diagnosis.
iii. Blood cultures should be sent for culture and sensitivity to identify the organism.
Lumbar puncture is contraindicated due to the risk of intrathecal spread of infection and spinal coning.
Causative Organisms
Similar organisms are found in spontaneous abscesses as those abscesses associated with epidurals. Most are bacterial, with Staphylococcus aureus being the most common. Pseudomonas, Streptococcus, and Staphylococcus epidermidis have also been isolated.
Sources of Infection
Primarily from the patient’s skin, with organisms migrating down the catheter or tissue track to the epidural space. Colonies of organisms occur in the hair follicles, where disinfectant may not reach.
Other sources include hematogenous spread from local soft tissue, and urinary and respiratory infections. Intravenous drug abusers are particularly at risk for hematogenous spread.
c. Risk Factors
i. Poor aseptic technique that fails to disinfect the patient’s skin adequately and allows contamination of epidural equipment.
ii. Difficult or traumatic epidural placement with multiple attempts creating more than one route for tracking of organisms and an increasing risk for poor aseptic technique.
iii. Prolonged catherization, especially in immunocompromised patients.
iv. Lying in a bed contaminated with amniotic fluid or urine.
v. Immunocompromised patients with diabetes or HIV, those on long-term steroids or immunosuppressive therapy following organ transplantation or treatment for malignancy.
d. Treatment
Decompression laminectomy within 8 hours of onset of symptoms is the first-line treatment and can prevent permanent neurologic damage, especially if neurologic signs are mild or absent at the time of surgery. In addition, antibiotic therapy should be continued for 2-4 weeks. While awaiting culture and sensitivity results from blood cultures or the abscess pus, antibiotics selected should be bactericidal to S. aureus, have a low side effect profile for prolonged use, and be able to penetrate bone to treat spondylodiscitis.
Conservative treatment with antibiotics alone has been used successfully in some cases, but neurologic deterioration has also occurred in nearly 20%, despite appropriate antibiotics. Discuss appropriate antibiotic selection with the hospital pharmacy and infectious disease consultants.
Dorsal abscesses, well-circumscribed by MRI scan, may be amenable to percutaneous drainage.
e. Prognosis
In just under 100 years, the mortality from epidural abscess has dropped dramatically, from almost 100% at the beginning of the 20th century to 15% by the mid-1990s. Complete recovery has been reported in 38-43% of patients, with severe neurologic deficit occurring in 15-27%. There is no significant difference in prognosis between patients who develop epidural abscesses following epidural anesthesia and those who had no neuraxial procedure.
Prevention of Neuraxial Infection
Prevention of a complication is always better than having to treat one. Due to the paucity of cases of both meningitis and epidural abscess, recommendations for prevention of neuraxial infection are often based more on information from case reports, common sense, and evidence from similar procedures in different populations and specialties than on evidence from research targeting this problem directly.
Remove rings, bracelets, and watches
The presence of these items impedes effective hand washing, with evidence showing higher bacterial counts after hand washing when these items are not removed.
No false fingernails
These have been shown to be associated with a higher likelihood of gram-negative bacteria on hands and fingertips even after hand washing. Nail length and nail polish have not been found to be risk factors but chipped nail polish may increase bacterial counts.
Wear a scrub hat and a fresh surgical mask for each patient.
Absence of a scrub hat has been associated with increased bacterial counts in the operating room. The wearing of surgical masks during neuraxial blocks has been controversial. While various trials have shown that wound infection is not increased by failing to wear one in the operating room, we know that bacteria from the oropharynx or nose of anesthesiologists not wearing masks while performing neuraxial procedures has been directly linked to cases of iatrogenic meningitis and epidural abscess. Masks are most effective during the first 15 minutes of being worn. They also protect us, the provider, against patient’s pathogens.
Should we wear a sterile gown?
There is no evidence that a sterile gown makes any difference to infection rates, but they may reduce contamination of the catheter when worn by inexperienced operators.
Wash hands and put on sterile gloves
Alcohol-containing antiseptic solutions have the most effective and longest-lasting bactericidal action when compared to non-alcohol containing antiseptics such as 4% chlorhexidine, povidone iodine, or non-antimicrobial soaps, which are poorly bactericidal. Sterile gloves are an important part of the aseptic set-up, but if hands are not washed appropriately, bacteria will multiply rapidly under the gloves and get onto the sterile field if a glove is punctured.
Use sterile drapes.
Applied securely to the patient’s back to prevent any skin organisms from contaminating the sterile field.
Clean the back with chlorhexidine in alcohol rather than iodine.
Chlorhexidine in alcohol has all the desirable features of a disinfectant. It rapidly kills nearly all gram-positive and negative bacteria (including methicillin-resistant S. aureus). After application to the skin, it penetrates the hair follicles, where colonies of bacteria can accumulate, is effective for several hours after application, is not inactivated by blood or other body fluids, and is non-irritant to the skin. It outperforms povidone iodine in all these areas. Two applications are recommended as being more effective than one.
There have been concerns about neurotoxicity associated with chlorhexidine. To minimize the risk, it is important to avoid the chlorhexidine coming into contact with any equipment or solutions that will be used for neuraxial block placement. Consider using chlorhexidine spray or specific swap applicators such as Chloraprep®, so there is no free-standing solution on the cart.
Avoid multiple-use bottles of cleaning solution.
Bottles of povidone iodine become contaminated with repeated use, although this does not appear to be a problem with chlorhexidine in alcohol multiuse bottles.
Avoid contaminating equipment, especially parts that will enter the patient.
Use of a bacterial filter connected to catheter hub.
There is no evidence that this reduces catheter contamination with short-term epidurals.
Fix epidural catheters in place with sterile, occlusive dressings.
There is conflicting evidence regarding effectiveness, as bacteria already present on the skin can still track down the catheter. Chlorhexidine-impregnated dressings which reduce skin colonization and absorb blood and other exudates (which may be a source of organisms) for several days are useful for prolonged catheterization. In obstetric patients, catheters are rarely in for an extended length of time, and a sterile dressing should be sufficient.
In patients with bacteremia, place neuraxial block more than 30 minutes after i.v. antibiotic administration.
This minimizes the risk of hematological spread of bacteria.
Avoid prolonged catheterization in immunocompromised patients.
This combination of two risk factors may be additive for adverse outcomes. Prophylactic antibiotics may be advisable if prolonged epidural analgesia is considered essential. Racemic local anesthetics, such as bupivacaine and lidocaine, have some bactericidal activity in concentrations used for epidural anesthesia and may offer some benefit.
What's the Evidence?
Reynolds, F. “Neurological infections after neuraxial anesthesia”. Anesthesiol Clin. vol. 26. 2008. pp. 23-52. (A review of the spectrum of infectious processes that can be seen after neuraxial anesthetics, and how to prevent or minimize them.)
Grewal, S, Hocking, G, Wildsmith, JAW. “Epidural abscesses”. Br J Anaesth. vol. 96. 2006. pp. 292-302. (A case series describing a rare complication.)
Hebl, JR. “The importance and implications of aseptic techniques during regional anesthesia”. Reg Anesth Pain Med. vol. 31. 2006. pp. 311-323. (The ASRA guildelines on aseptic technique that every anesthesiologist should know.)
“American Society of Anesthesiologists Practice Advisory for the Prevention, Diagnosis, and Management of Infectious Complications Associated with Neuraxial Techniques”. Anesthesiology. vol. 112. 2010. pp. 530-45. (This is an extension of the ASRA guidelines endorsed by ASA that has similar recommendations.)
Green, LK, Paech, MJ. “Obstetric epidural catheter-related infections at a major teaching hospital: a retrospective case series”. Int J Obstet Anesth. vol. 19. 2010. pp. 38-43. (A case series of infections related to epidural catheters in parturients showing a rate of 1:2371 for deep tissue infections.)
Darouiche, RO, Wall, MJ, Itani, KMF. “Chlorhexidine-alcohol versus povidone-iodine for surgical-site antisepsis”. N Engl J Med. vol. 362. 2010. pp. 18-26. (Chlorhexidine is superior for cleaning the skin prior to surgery; it is endorsed for skin preparation before neuraxial techniques by both ASRA and ASA.)
Bogod, D. “The sting in the tail: antiseptics and the neuraxis revisited”. Editorial. Anaesthesia. vol. 67. 2012. pp. 1305-1320. (Discussion reagrding the concerns about neurotoxicity associated with chlorhexidine used for cleaning the skin prior to neuraxial block placement.)
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