I thank Drs. Edsall, Dr. Lambert, and Drs. Moen, Dahlgren, and Irestedt for their interest on this controversial topic, and for their insightful comments and questions. Their remarks clearly show the hurdles to overcome in developing evidence-based guidelines for strict aseptic technique during neuraxial instrumentation in anesthesia practice.
Dr. Edsall raises a question that is often debated and quite controversial: Is the loss of resistance to saline superior to that to air? Although many complications, including pneumocephalus, nerve root compression, subcutaneous emphysema, venous air embolism, incomplete analgesia, and paresthesias, have been attributed to the loss of resistance to air,1there is no mention in the anesthesia literature regarding air as a source of contamination in the epidural space. I would argue that there is a significantly higher chance of contamination from the large volume of air over the tray than the small amount injected with the syringe. The only way to prevent the epidural tray from being exposed to air is to do the procedure in a vacuum. Furthermore, epidural abscess has only been demonstrated to occur as a result of skin bacteria passing through a needle track, contaminated syringes, or local anesthetics, or hematogenous spread from another source.2
Dr. Edsall correctly points out that there are many reports of spotty or incomplete blocks when using air instead of saline.3,4Beilin et al. 4demonstrated that more parturients in the air group had incomplete analgesia and higher visual analog pain scores requiring additional local anesthetic when compared with those in the saline group. A survey in the United Kingdom demonstrated that use of loss of resistance to saline has progressively increased among obstetric anesthesiologists from just over 50% in 1998 to 74% in 2003.5Interestingly, another United Kingdom survey demonstrated that although almost 60% of respondents first learned to identify the epidural space with loss of resistance to air, nearly a quarter have changed to loss of resistance to saline.6I must admit that I, trained using intermittent loss of resistance to air, have been reluctant to change to saline for fear of having increased complications. However, given the abundance of data supporting the use of the loss of resistance to saline and the lack of complications when switching from one technique to the other,6I am strongly considering a change in my practice.
Dr. Lambert seems to have misinterpreted my comments and, furthermore, feels that a 1:10,000 risk of post–dural puncture meningitis is acceptable. As noted in my editorial7and the comments of Drs. Moen, Dahlgren, and Irestedt, Baer's statistics suggest that many cases of post–dural puncture meningitis are unreported and unrecognized, suggesting that the actual US rate is higher than reported.8In addition, as discussed by Dr. Moen in his letter and eloquently stated by Dr. Reynolds,9risk varies with both clinical practice and patient population. Causes of complications are multifactorial and include the performance of neuraxial techniques by trainees who may not be able to maintain sterility as well as experienced anesthesiologists. These techniques in parturients may be higher risk for infective complications if a laboring patient has skin contamination with amniotic fluid, blood, or other body secretions. Finally, laboring rooms are less likely to provide aseptic conditions when compared with operating rooms.
Even if we assume that the US rate is 1:10,000, why is the provision of general anesthesia to American Society of Anesthesiologists physical status I or II patients nearly 100-fold safer than that of spinal anesthesia? A 1:10.000 risk is neither an ultrasafe system (1:1,000,000) nor a high-reliability organization (1:100,000) but rather a system that is in need of immediate improvement.10I am not necessarily advocating that sterile gowns be used. However, adoption of uniform sterile safety guidelines and continued study of the efficacy of these techniques is important. After all, many of the recently drafted American Society of Regional Anesthesia guidelines on aseptic techniques during neuraxial anesthesia11,12were extrapolated from the medical and surgical literature, and clearly state that a specific outcome cannot be guaranteed.
To clarify the sentence that Dr. Lambert and other readers may have found unclear: “we must institute uniform sterile safety practices that have been proven [hand washing], or seem by common logic to be prudent [facemasks], and continue to study techniques used in other arenas [gowns for central venous catheters] to determine their utility.” Evidence has implicated upper mouth commensals in cases of post–dural puncture meningitis. Experience informs us that practitioners talk and sometimes sneeze or cough during a procedure. Because infection control data suggest that the use of facemasks will diminish spread of infectious organisms from droplets, it would also seem prudent to wear a facemask when performing this procedure. I never implied that it is logical that gowns should be used for neuraxial instrumentation. In fact, to quote, “Although Baer states that all aspects of sterile technique are part of the ’standard-of-care defense,' there [are] no data that support the use of sterile gowns during the performance of neuraxial techniques.” I assume that Dr. Lambert wears a mask when doing neuraxial techniques. I am hopeful that he does agree that wearing a mask is a speedy and painless solution to a problem, post–dural puncture meningitis, whose morbidity and mortality dwarf the inconvenience of the mask.
The comments of Drs. Edsall, Moen, Dahlgren, and Irestedt regarding postoperative outcomes measures and root cause analysis deserve a closer look. The American Society of Anesthesiologists*clearly states that anesthesia care is a continuum and that it should be documented as such. The postanesthesia care is more than the stay in the postanesthesia care unit and should include a postanesthesia visit. Although other healthcare providers may inform us of major anesthetic-related complications, we will discover our own complications most quickly and thoroughly only by routine institution of postoperative visits. I completely agree with Drs. Moen, Dahlgren, and Irestedt's recommendation that all patients with evidence of post–dural puncture meningitis be evaluated for the contributing factors including aseptic standard. Educating our medical, surgical, and obstetric colleagues regarding potential complications related to anesthetic practice is a worthy endeavor.
There are two points that, although not related to any of these letters, I would like to raise. The first one has to do with a typographical error in my editorial related to the American Society of Anesthesiologists Task Force on Infection Control.†7I inadvertently wrote “maximal sterile barrier precautions during central venous catheter infection” rather than “central venous catheter insertion.” The second point has to do with the recently published guidelines for aseptic techniques during regional anesthesia.12I wrote that although a chlorhexidine solution has a faster and stronger bactericidal effect than povidone iodine, the consensus stopped short of recommending an alcohol-based chlorhexidine antiseptic solution for skin disinfection before neuraxial techniques (electronic personal communication, Joseph M. Neal, M.D., Staff Anesthesiologist, Virginia Mason Medical Center, Seattle, Washington, and Editor-in-Chief, Regional Anesthesia and Pain Medicine , April 2006). However, it seems that in the final revision of the guidelines, the decision was made to encourage the use of an alcohol-based chlorhexidine solution as the antiseptic of choice before regional techniques.12The expert panel felt strongly that although the US Food and Drug Administration has not approved chlorhexidine before lumbar puncture, it has a significant advantage over povidone iodine because of its onset, efficacy, and potency (verbal personal communication, James R. Hebl, M.D., Assistant Professor, Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota, November 2006). Upon contacting the Food and Drug Administration, the panel found that the lack of approval was not because of toxicity but because of lack of scientific data. Interestingly, povidone iodine is also not approved for lumbar puncture. Finally, it is important to mention that the guidelines conclude that there are insufficient data regarding the routine use of surgical gowns before performing a regional technique.12
Harvard Medical School, Brigham and Women's Hospital, Boston, Massachusetts. firstname.lastname@example.org