To the Editor:—
The largest single group of patients receiving central blockades worldwide is undoubtably parturients. Fortunately, serious complications are rare, as pointed out in two recent studies published in Anesthesiology.1,2
Ruppen et al. found six epidural hematomas and justly considered these numbers inadequate to produce a robust estimate of event rates. Because of their study design, several cases reported in the literature are excluded from the statistical calculation performed in the meta-analysis. For example, the Closed Claims project included three spinal hematomas in obstetric patients.3Many other excluded cases occurred in patients with impaired coagulation due to preeclampsia or large blood loss, conditions that might predispose even to a spontaneous spinal hematoma.4–6Nonetheless, despite frequent bloody taps and thrombocytopenia, spinal hematoma is rare in obstetric patients.7,8The compliant spinal canal in a young individual permits the introduction of volumes that may cause severe symptoms and permanent damage in an older person with a stenotic spinal canal.
However, a healthy parturient receiving epidural blockade for pain relief might overnight turn into a patient with severe coagulopathy. The calculated low risk then no longer applies to this patient. Such was the case with one patient in our study9: After delivery, the epidural catheter was removed before transferring the patient to the intensive care unit for treatment of the syndrome of hemolysis, elevated liver enzymes, and low platelets, and the subsequent spinal hematoma was diagnosed with delay. The perception of low incidence in the healthy parturient contributes to underestimation of risk when she becomes affected by coagulopathy.
Whereas patient characteristics seem to influence development and outcome after some severe complications, such as spinal hematoma and epidural abscess, no predisposing conditions are found for iatrogenic meningitis. Purulent meningitis will develop in any patient, however healthy, if bacteria are introduced into the spinal fluid, devoid of any immunologic defense. Dr. Baer's comprehensive review of post–dural puncture meningitis (PDPM) includes reports of three tragic and unnecessary deaths in previously healthy obstetric patients. These cases could reflect a higher incidence of PDPM due to lower hygienic standards in the obstetric setting, lower diagnostic preparedness, or higher motivation to report these cases. Finally, the parturient could be at higher risk of developing PDPM. The reason being that α-hemolytic streptococci are normally part of the flora in the genitourinary tract and fluids containing these bacteria obviously will cover the lower backs of many parturients. As a consequence, faulty skin disinfection before performing a central blockade in the parturient could be more hazardous than in the average surgical patient.
The author and the editorial comment both address the incidence of PDPM.10Important as this may seem, we would like to quote a recent editorial by Prof. Reynolds: “there can be no such thing as a ’true incidence' of an infective complication, …, as its occurrence will vary with the number of risk factors both in local clinical practice and among the patient population.”11
We agree with Dr. Baer that these three mortalities, the increasing antimicrobial resistance of viridans streptococci, and oropharyngeal presence of more invasive pathogens should be sufficient for every anesthetist to adopt truly aseptic technique whenever performing a central blockade.
Analyzing literally every aspect of PDPM, the author does, however, leave one question unanswered: Why do physicians have such an aversion to facemasks? The editorial comment proposes the remedy, advocating shift in culture, guided by responsible leadership and compelling guidelines. To this we can only totally agree. We would also like to add a further question: Shouldn't all cases of PDPM be subject to epidemiologic evaluation and thorough scrutiny of the hygienic standard in the departments where PDPM has occurred? The polymerase chain reaction is no longer exclusive and expensive, and clarifying the pathogenetic pathway in cases of PDPM certainly deserves our attention. After lumbar puncture, the failure of bacterial growth is not uncommon, neither in community-acquired meningitis nor in PDPM. In our series of 29 cases, culture was positive in 12 cases, and 11 of these were α-hemolytic streptococci (not 28 as quoted by Baer).9Immediate incubation of cerebrospinal fluid in medium for anaerobic blood culture might favor growth.
Dr. Baer makes the assumption that hundreds of cases with PDPM have gone unreported and unrecognized. This assumption is strengthened by the fact that viridans streptococci are low-grade pathogens that may cause subtle symptoms. In our study, only 14 of 29 patients presented classic symptoms of meningitis.9In several of the remaining cases, correct diagnosis of PDPM was reached only because of a high level of suspicion. Worldwide, many cases of PDPM have probably unintentionally been cured by antibiotic treatment intended for some other infection. In view of the numerous reports of PDPM published, it would seem awkward primarily to propose the diagnosis of aseptic meningitis before excluding an infectious origin when presented with a similar case.
One pitfall in the diagnosis of PDPM in the obstetric patient is the anticipation of severe headache after accidental dural puncture. When signs of meningeal irritation such as photophobia or vomiting are present, these might be accompanying symptoms of severe post–dural puncture headache, but the suspicion of PDPM should arise. The combination of headache and infection in a patient recently subject to central blockade should be a warning signal.
As with spinal hematoma and epidural abscess, the symptoms of PDPM often appear after discharge from hospital, and the care of the patient is the responsibility of a physician not necessarily familiar with anesthetic procedures. It is our duty as anesthetists to inform colleagues in other specialities regarding the signs and symptoms of these potentially extremely dangerous complications. An information leaflet distributed among general practitioners regarding post–dural puncture headache has been shown to improve their knowledge of this complication.12Similarly, information regarding the rarer, but potentially more serious complications might be of great value.
We should be grateful for the significant contribution offered by Dr. Baer.
*County Hospital, Kalmar, Sweden. email@example.com