Understanding of Disease
- First reported soon after introduction of shunts: After the introduction of the first CSF shunt mechanisms for the treatment of hydrocephalus, published reports of infectious complications began to appear, with most pertaining to persistent bacteremia, endocarditis, and nephritis associated with ventriculoatrial shunting procedures (27, 39, 52, 112, 121). Subsequently, as other drainage cavities were used (i.e., pleural and peritoneal), different clinical patterns of infection presentation were recognized (112).
- Appreciation of varied presentation: As experience was gained, surgeons began to appreciate that most patients present with little evidence of general symptoms of infection (fever, tachycardia, irritability) (17, 19, 112). Rather, most show some degree of shunt malfunction or wound breakdown. However, some patients may develop serious life-threatening complications such as brain abscess, empyema, ventriculitis, bowel perforation, and septic shock (58, 64, 117, 136, 149, 171).
- Staphylococcus sp. predominant: As most reported series implicated Staphylococcus sp. as the infecting organism, it became evident that the vast majority of devices were contaminated at the time of insertion with normal skin flora or shortly thereafter by wound breakdown (21).
- Rate of infection related to amount of tissue manipulated: The greater the area of subcutaneous shunt components, the greater the risk of their infection. This risk is related to the number and size of incisions, their subcutaneous profile, and the increased length of operative time. The most practical route to divert fluid from the CNS into another cavity is attained by creating a subcutaneous tunnel with a cylindrical catheter connecting these spaces. Although trauma to soft tissues is minimized by experience and the use of blunt shunt passers, there is always some damage to the underlying tissues, which can contribute to infection.
- Poor penetration of antibiotics into the CNS: Prophylactic or therapeutic systemic antibiotic therapy is known to have extremely low threshold levels in CSF due to the blood-brain barrier.
- Advantage of tunneling EVD: The management of EVD using ventricular catheters that are tunneled under the scalp and externalized several centimeters from the insertion bur hole showed lesser infection rates (43, 128, 169).
- Development of shunt implant protocols: Our current understanding of infection mechanisms has led to streamlined protocols for patient selection, operating room environment, surgical techniques, and device selection that have contributed to a lower incidence of shunt infections (48, 49, 51, 91).
- Development of shunt infection protocols: With the development of new treatment strategies, it became evident that to achieve re-sterilization of CSF to allow proper shunt function, all implanted material had to be retired. The management of the associated hydrocephalus was then achieved with EVD (109, 133, 159). Initial attempts at management that sought to preserve the shunt device by simply treating with intravenous antibiotic therapy had a success rate of only 24% and an unacceptable mortality rate of 24% (84). Next, delivery of antibiotics into the shunt reservoir coupled with IV therapy was tried and achieved a success rate of approximately 40%. Current management in most centers includes shunt removal and concurrent placement of an EVD system during the initial IV antibiotic treatment followed by shunt replacement (159). This management protocol has a success rate of more than 90%.
- Introduction of valved shunt – 1952: The history of CSF shunt infection goes together with the introduction of shunting devices for the treatment of hydrocephalus. By the late 1940s Matson had introduced the concept of CSF fluid diversion from the lumbar subarachnoid space using a ureter. In addition to possibly losing a kidney and developing frequent electrolyte imbalances, infection usually complicated the recovery of these patients (80, 104). This dilemma was the same as that faced when the thoracic duct, fallopian tube, salivary glands, gallbladder, and ileum were used as recipient sites (98). In 1952 Nulsen and Spitz, working with an engineer and father of a child with hydrocephalus, reported the successful use of a spring and ball valve shunt (113). As an offshoot of this research, silicone was introduced into the medical industry with lesser rates of rejection of implanted devices (42, 71, 80, 82, 172). Pudenz introduced his one-way slit valve later that year (123).
- OR environment control: Control of temperature and laminar flow, dedicating specific rooms for shunt surgery into which no infected patients are taken, keeping the personnel traffic into and out of the operating room at a minimum, scheduling elective shunt insertions in low-weight infants as first cases of the day, and not removing the shunt components from their sterile packaging until immediately before insertion have become common practice in an effort to lessen the rates of shunt infection (48, 49, 51, 57, 99, 122).
- Surgical site preparation: Preoperative skin preparation with chlorhexidine soaps (122), skin isolation drapes, and adhesive skin coverings (which may be impregnated with iodine), prophylactic antibiotics at the induction of anesthesia (91, 125, 159), antibiotic irrigation solutions (bacitracin), and, lately, the introduction of antibiotic-impregnated catheters have impacted the rate of shunt infection (46, 77). Removal of scalp hair with clippers instead of shaving also has aided reduction in infection rates (167).
- Postoperative care: Postoperative wound care includes avoidance of unnecessary pressure on the wound and underlying shunt components, as skin erosion can occur in very-low-weight patients. Recent evidence indicates that postoperative wound dressings offer no additional benefit for prevention of infection when compared to simple antibiotic ointment over the wounds (166).
- Better antibiotics: With the introduction and development of modern era antibiotics, adequate penetration levels across the blood-brain barrier have been achieved, facilitating treatment of ventriculoperitoneal shunt infection (2, 9, 15, 17, 18, 33, 34, 40, 48, 66, 77, 78, 82). However, with their use antibiotic-resistant microorganisms have emerged (e.g., methicillin-resistant Staphylococcus aureus) (10, 54, 147).
- Treatments matching infection characteristics: As experience broadened, protocols using intraventricular antibiotics to manage recurrent and persistent shunt infections have been offered (72, 85). These protocols seek to bypass the poor penetration of systemic antibiotics through the blood-brain barrier (145).
- Antimicrobial shunt material: Experimentation with shunt materials has included the coating of shunt hardware with BioGlide® in an attempt to prevent microorganism adhesion, and impregnation of catheters with rifampin and silver in the hope of lessening the rate of infection (77, 82, 143). Problems were associated with some of these efforts, such as the increased risk for disconnection of the BioGlide® catheter, which ultimately led to its recall by the manufacturer (45).
- Location of skin incisions: Experience has shown that the proximal and distal incisions should be fashioned in such a way as not to overlie shunt hardware, and there should be at least a centimeter left between the incision and the shunt (97).
- Special considerations for neonates: Length of time since birth should be considered, as skin colonization usually occurs within the first 8 hours of life, and Staphylococcus sp. can be found in cultures from the forehead in almost 60% of normal newborns. A patient who has been previously admitted to a NICU and has multiple indwelling lines may be more prone to develop neonatal sepsis and shunt contamination from occult bacteremia. The author usually performs a ventricular tap in this group of patients and, depending on CSF characteristics, will await final culture results before committing to place a shunt. Patients who develop hydrocephalus from infectious complications such as bacterial meningitis should also be considered a high-risk group (44) in whom culture results should always be checked prior to shunt implantation.
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