Australasian Anaesthesia 2011 - Australian and New Zealand ...

28 Australasian Anaesthesia 2011Neuraxial Block and Septicaemia 29These figures highlight an interesting discrepancy between pure lumbar punctures and spinal anaesthesia.It has been postulated that the lower incidence of meningitis with spinal anaesthesia compared to lumbar puncturesmay be due to the fact that people undergoing spinal anaesthesia are generally not infected (whereas thoseundergoing LP generally have a source of infection) and also the bacteriostatic properties of local anaesthetics. 2Another issue is that post spinal meningitis is probably under-diagnosed. As mentioned, the most common symptom(an isolated headache) may be confused with a post-dural puncture headache.Abscess FormationLike meningitis, the incidence of epidural abscess is low. 10 Most appear as individual case reports or in retrospectivereviews. Based on current data, it appears that most epidural abscesses are due to infections of skin, soft tissue,spine or haematogenous spread rather than due to catheter placement. The retrospective review of Baker et alreported epidural abscess to account for 2-12 cases per 100 000 admissions to tertiary hospitals. 11 The mostcommonly identified organisms were S. aureus (57%), streptococci (18%) and Gram negative bacilli (13%). Out ofthe 39 cases reported, only 1 was attributed to epidural catheter placement. Similarly, Ericsson et al reported 10cases of epidural abscess occurring at one teaching hospital over 10year period. 12 Of the 10 cases, only 1 wasattributed to epidural catheter placement. The remainder were due to repeated lumbar puncture in patients withmeningitis (2 cases), a paravertebral injection (1 case) and spontaneous (6 cases).When reviewing the literature limited to neuraxial blockade, there is equal paucity of data. The incidence appearsto be dependent on a variety of factors including population sampled (eg obstetric versus surgical), duration thatcatheter was in situ and whether the patient was immuno-compromised. The incidence quoted ranges from 1:1930(Wang et al) 13 to 1:100000 (Aromaa et al). 14 Analysis of the patients who developed epidural abscess has led toidentifying various risk factors that may increase its likelihood. These include poor aseptic technique, immunocompromisedpatients (including diabetics, patients on steroids, alcoholism, cancer), multiple attempts at insertion,type of surgery (urology and gynaecology more common due to risk of bacteraemia) and traumatic insertion. 15Although a theoretical risk, the reports of blood patch causing infectious complications appear to be limited tosuperficial abscess (Collis et al). 16 Pre-existing sepsis is regarded as a risk factor despite there being very littleevidence to support this.As mentioned, despite the lack of data, pre-existing sepsis is regarded as a relative contraindication to neuraxialblockade. In fact the current best evidence is that pre-existing sepsis does not increase the likelihood of infectiouscomplications. Two studies that showed this involved women with chorioamnionitis.Bader et al investigated the use of regional anaesthesia in patients with chorioamnionitis. 17 Out of 10047 women,319 were identified as having chorioamnionitis based on the presence of 2 or more of the following: pyrexia(>38˚ Celsius) on 2 or more occasions, maternal leukocytosis (white cell count > 20 000/µL), tachycardia (pulse>120/min), foul smelling amniotic fluid and uterine tenderness. Of the 319 women identified, 100 had blood culturestaken, of which 8 were consistent with a bacteraemia. 293 of the 319 women had some form of neuraxial blockade– 43 of these women had peri-procedural antibiotics. None of the 319 women, including those with a documentedbacteraemia, developed infectious complications.Goodman et al also reported similar results. 18 They retrospectively reviewed the records of 531 paturients whohad some form of neuraxial blockade and were then later identified as having chorioamnionitis. Of the 531 women,146 had blood cultures taken. Thirteen of these were positive. Antibiotics were given prior to the block in123 patients whilst one-third of patients had no antibiotics during the entire peripartum period. Like reported byBader and colleagues, there were no infectious complications identified in any of the patients.Another paper that supports this conclusion is a retrospective audit conducted at a single centre over a ten-yearperiod. 19 Forty-six epidurals were inserted in children who had a pneumonic empyema that required thoracotomy/decortication. Of the 46 patients, 23 exhibited signs of sepsis (temperature >38˚ C and white cell count > 14 000);21 had a leukocytosis but no pyrexia; 2 had a normal white cell count and were afebrile. These patients werefollowed up for three years post discharge. None of the patients developed any infectious complications, even atlong term follow up. Whilst it may be argued that with 46 patients, it would be difficult to detect even one epiduralabscess (given its low incidence), the results are nevertheless compelling.A retrospective review by Steffen et al highlighted the fact that bacterial colonisation does not translate intoinfectious complications. 20 Steffen et al performed a retrospective study of 502 epidurals inserted for abdominal,thoracic or trauma surgery. A standardised aseptic technique and post insertion dressing was employed. Therewas a daily monitoring of the puncture site. The catheter tips were removed in a sterile fashion and cultured. Theaverage catheterisation duration was 5 days. What was surprising was that despite an aseptic technique anddressing, there was a unexpectedly high bacterial colonisation rate (5.8%). The predominant bacterium culturedwas S. epidermidis (76%). The patients were all followed up for 6 months post insertion. No patient developedinfectious complications despite the apparently high colonisation rate.Recently, the results of a UK survey regarding epidural analgesia in patients with sepsis undergoing laparotomywere published. 22 This was a nation wide survey to 304 anaesthetic departments within the United Kingdom. Thesurvey consisted of questions as to whether a policy existed for the use of epidural analgesia in sepsis and questionsrelated to two vignettes. The response rate was 67% (211 departments). Only five hospitals (2%) had a policyregarding the use of epidurals in the face of sepsis. This perhaps highlights the fact that many people still holdconventional teachings to be true and thus do not require a policy. One hundred and fifty two (82%) of the 185respondents who routinely use an epidural for a laparotomy reported that they would do so in a patient with asuspected small bowel perforation but no signs of a systemic inflammatory response syndrome (SIRS). In patientswith clearly defined SIRS, forty-nine respondents (27%) said that they would use epidural analgesia. The mainreason cited for not using an epidural was fear of epidural abscess (116 respondents) followed by fear of haemodynamicinstability (102 respondents) and contraindication to potential use of activated protein C in management of sepsis(23 respondents). Although no consensus was made, it did highlight the changing opinion regarding the use ofepidurals in the face of sepsis amongst anaesthetists in the United Kingdom.RECOMMENDATIONSThe notion that neuraxial instrumentation is contraindicated during sepsis is controversial. The perceived increasedrisk of infective complications is based on case series and older studies (of limited relevance). Whilst there is atheoretical increase in risk, this is not seen when large retrospective studies are reviewed. The incidence of infectivecomplications remains low. Certainly, a high bacterial colonisation rate does not translate to a high infectiouscomplication rate. This then suggests that other factors also play a role in determining the likelihood of developinginfectious complications, such as diabetes, steroid therapy, alcoholism and cancer. The evidence that neuraxialinfection in the face of sepsis is limited, but may indicate that there is not an increased risk. As such the followingrecommendations may be made:1. Infectious complications as a result of neuraxial blockade are rare but potentially serious.2. The rate of infection must be minimised by adhering to strict aseptic technique (i.e. gown/gloves/mask/hat/drapes/alcohol based antiseptic). 223. The use of aseptic technique does not eliminate the risk of infectious complications.4. Rather than viewing sepsis as an absolute contraindication to neuraxial blockade (traditional view), it shouldbe viewed as a relative contraindication.5. Each case should be reviewed on its merits. A risk-benefit analysis needs to be performed. If there is acompelling reason to perform neuraxial blockade in the face of sepsis, it should be carried out usingperiprocedural antibiotics.6. The patient will need to be monitored closely postoperatively for signs of infection.