1 Houston, USA 2 London, UK
EditorThe report of unexplained fitting in three parturients suffering post-dural puncture blockade (PDPH) by Drs Oliver and White1 failed to mention the relationship between seizures and pneumocephalus secondary to the injection of air to detect loss of resistance (LOR). Omission, too, by the authors to describe which medium was used to test for LOR was especially significant to us, as we recently presented an incident to our morbidity and mortality meeting of a convulsion in a 29-yr-old parturient who, after an uneventful epidural for labour using air for LOR, developed PDPH. A blood patch was performed 10 days later, again using air for LOR. Regrettably, a dural tap complicated the blood patch, which otherwise was successful until the following day when the patient failed to observe strict bed rest orders, got out of bed and the headache recurred. The severity of the headache resulted in her remaining hospitalized, and being treated with fluids, bedrest, analgesics and i.v. caffeine. However, the headache continued, the patient became emotionally labile and 2 days after the blood patch, she suffered a generalized convulsion. A neurological examination revealed no deficit, but a magnetic resonance imaging (MRI) scan revealed pneumocephalus and features suggestive of postpartum microvascular angiopathy. The patient was transferred to the hospitals stroke unit, received continued conservative treatment, improved and was discharged 10 days thereafter.
These events drew the attention of the obstetric anaesthestists at our hospital to the question of which medium is best used to test for LOR. A literature search revealed no reports, other than anecdote, supporting the contention that LOR is more easily determined using air.2 3 Furthermore, the claim by proponents of the air technique that air more easily allows detection of cerebrospinal fluid (CSF) leaking from the epidural needle after inadvertent dural puncture is challenged by reports advocating either the use of a dipstick for testing emitting fluid for pH and protein, or assessing its warmth by allowing the fluid to drip onto the dorsum of the anaesthestistss hand or arm.4 However, of much greater importance than reports that use of normal saline for detection of LOR is associated with a better endpoint,5 6 better quality of analgesia,7 and lesser incidence of dural puncture, bloody tap or patchy block,8 9 are reports linking use of air with iatrogenic morbidities.10 These include pneumocephalus (causing headache,11 nausea, vomiting, seizures, and/or hemiparesis12), spinal cord and nerve root compression (causing transient back pain,13 radicular pain,14 motor weakness, paraesthesia or paraplegia1517), delayed recovery,18 patchy block,19 s.c.2022 or retroperitoneal23 24 emphysema, and venous air embolism.2528
The occurrence of a seizure and pneumocephalus in our patient, albeit accompanied by a post-partum microvascular angiopathy, allied to the numerous reports of adverse outcomes associated with the use of air for LOR, has resulted in the first author altering his technique from air to normal saline after 29 years of clinical practice, and adoption of normal saline by the Department of Anesthesiology at our hospital as the recommended medium of choice when testing for loss of resistance.
A. A. van den Berg
L. Nguyen
M. von-Maszewski
H. Hoefer
Houston, USA
EditorWe would like to thank van den Berg and colleagues for their interest in our case reports. We acknowledge that pneumocephalus secondary to using a loss of resistance to air technique can be a cause of seizures. However, a loss of resistance to saline technique was used in all three of our cases. Indeed in 1998 a UK survey of obstetric anaesthetists showed 52.7% used a loss of resistance to saline technique and 57.2% taught this technique.2
We note that i.v. caffeine was used to treat this patients PDPH and she subsequently suffered a generalized convulsion. I.V. caffeine is known to cause seizures,29 and thus would need to be considered as a differential cause of this patients convulsion.
C. D. Oliver
S. A. White
London, UK
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