Intrathecal catheterisation after accidental dural puncture: real‐world data, real‐world benefits and real‐world barriers

Consent for epidural analgesia during labour is routinely accepted practice, although may at times appear somewhat performative; a distressed parturient, enduring a lurid list of complications, tethered to barely processable numbers [1], whilst figuratively (often literally) screaming for analgesic relief. In the unfortunate event of accidental dural puncture, as cerebrospinal fluid flows down the epidural needle, the immediate sinking thoughts of the anaesthetist are, inevitably, guilt, follow-up of a supine patient in a darkened room and epidural blood patching. What remains precedent in that moment is the maternal request for pain relief and their consent for epidural analgesia. Can anaesthetists balance the immediate maternal analgesic priority with attenuation of an as-yet unexperienced complication, post-dural puncture headache? Is this ‘paternalistic’ readjustment of management necessarily at odds with the maternal priority and are there unspoken issues of consent? Binyamin et al., in a large retrospective real-world study [2], evaluated intrathecal catheter insertion and management following accidental dural puncture, on incidence of post-dural puncture headache and requirement for epidural blood patch. Amongst a cohort of over 90,000 parturients, there were 550 (0.59%) accidental dural punctures. Epidurals were re-sited in 331 (60.2%) and intrathecal catheters placed in 219 (39.8%). Intrathecal catheter insertion did not reduce the incidence of post-dural puncture headache but did reduce epidural blood patch (adjusted OR 0.82). Leaving the intrathecal catheter in situ for 24 h was not beneficial, but the injection of intrathecal saline (10 ml) reduced the incidence of both post-dural puncture headache (adjusted OR 0.85) and requirement for epidural blood patch (adjusted OR 0.75). This is an interesting and welcome addition to the often confusing landscape regarding immediate management of accidental dural puncture. In summary, should you cause an accidental dural puncture tomorrow, results suggest threading an intrathecal catheter for analgesia and removing it immediately following delivery, after first injecting 10 ml of saline, to reduce both incidence of post-dural puncture headache and requirement for epidural blood patch. Interpretation of the retrospective, observational data presented requires some caution given the inherent limitations and risk of bias in studies of this type. Several treatment decisions were at the individual anaesthetist's discretion: whether to insert an intrathecal catheter or re-site the epidural; duration of intrathecal catheter insertion; whether to inject saline; and whether to treat post-dural puncture headache patients with hydrocortisone and/or cosyntropin. Management of the intrathecal catheter during labour was protocolised. Data were collected on loss-of-resistance technique but are not reported. Conceivably air vs. saline, for example, could affect incidence and severity of headache following accidental dural puncture. The authors report criteria for how post-dural puncture headache was diagnosed and the decision to perform epidural blood patch, although it is not clear whether this was strictly protocolised or adhered to. In ‘atypical’ presentations, a neurologist ruled on post-dural puncture headache diagnosis. There is no data on atypical headache presentations between groups, nor whether neurologists used a consistent diagnostic approach. Results show the re-sited epidural group had significantly greater ‘need for multiple attempts’ (80.4% vs. 31.4%) but do not define ‘attempt’ or ‘multiple’. Importantly, amongst the re-site group, it is unclear whether ‘multiple attempts’ refers to only the primary procedure, only the re-site procedure, or both. Is it the re-site which predisposes to multiple attempts (and higher subsequent complication rate) or was the initial epidural procedure more difficult in the re-site group vs. the intrathecal catheter group? This has obvious implications for interpretation of subsequent outcomes, distinct from whether patients had an intrathecal catheter or not. Post-dural puncture headache rates were unaffected by siting an intrathecal catheter (without saline), but the epidural blood patch rate was lower (headaches appear less severe in the intrathecal catheter group), which could conceivably relate to fewer attempts, rather than management with an intrathecal catheter per se. However, as the authors discuss, addressing questions such as those studied by Binyamin et al. via a randomised controlled trial is not straightforward. Consent for randomisation (intrathecal catheter or re-site) would need to be undertaken before the event. Given an incidence of accidental dural puncture of 0.5–1%, this would mean recruiting at least 100 times as many women as were randomised. A trial sample size of around 4000 parturients would be required to show an effect of intrathecal catheter on post-dural puncture headache, and potentially orders of magnitude more, to clearly define the effect. Recruitment of 100–200 times this number of women makes this an unfeasible proposition. Further, the consent and randomisation burden may fall on junior staff, out of hours, increasing their cognitive load, possibly directing them towards a less familiar intervention, with additional risks and management implications. Blinding would also be difficult. A randomised controlled trial may not be realistic. The methodological approach by Binyamin et al. was to design a ‘real-world’ study. There is growing interest in the use of real-world data and compelling arguments for why it may be useful in the kind of clinical setting reported. The UK National Institute for Health and Care Excellence (NICE) recently published a real-world ‘living’ evidence framework [3]. It defines real-world data as “data relating to patient health or experience, or care delivery collected outside the context of a highly controlled clinical trial”. Real-world data are predominantly observational in nature and potential data sources are legion. Whilst treatment interventions have normally been studied using randomised controlled trials, real-world studies can produce valid evidence of treatment effects, although some discordance with randomised controlled trial evidence remains [4, 5]. Real-world data can be gathered more quickly and with less funding burden [6], helping to expedite patient access to new therapies. The inclusion of pregnant women in clinical trials is a neglected area, as demonstrated during the recent COVID-19 pandemic [7]. Randomised controlled trial data often excludes perceived ‘vulnerable’ groups, contributing to health inequalities. Real-world data may have a role in bridging this gap [8]. Pragmatic approaches towards difficulty-to-study areas, such as reported by Binyamin et al., are of interest and should be applauded. If we are to adopt routine use of intrathecal catheters following accidental dural puncture into clinical practice, we must be satisfied of three criteria; first, an intrathecal catheter has a tangible benefit in mitigating post-dural puncture headache/epidural blood patch; second, the parturient is not placed at an analgesic disadvantage; and third, that we do not, in an abundance of good intentions, merely mitigate one complication by exposing women to another. Reviewing available evidence suggests that intrathecal catheters can provide at least as good labour analgesia as re-sited epidurals [9-11]. Heesen et al. showed no difference in quality of analgesia between the two approaches. Relative risk for adequate analgesia for intrathecal catheter vs. re-sited epidural was 1.05 (95%CI 0.83–1.32) [12]. The analgesic failure rate of intrathecal catheters does not appear to be any greater than would be anticipated for an epidural catheter [10, 12]. Concerns about intrathecal catheters include inadvertent drug errors, high/total spinal, damage to the neuraxis and a conduit for infection. In a 12-year study of 761 intrathecal catheters, three incidences of high/total spinal and one of respiratory depression were recorded, but no serious neurological complications [11]. In their review, Orbach-Zinger et al. note no serious neurological sequelae reported in studies associated with intrathecal catheters, despite isolated case reports [9]. Re-siting an epidural following accidental dural puncture may itself be associated with higher risk of complications [13]. There is no clear conflict between the provision of effective labour analgesia and the attempt to mitigate post-dural puncture headache, by siting an intrathecal catheter following accidental dural puncture. Addressing the primary question of whether an intrathecal catheter can have a tangible benefit in mitigating post-dural puncture headache/epidural blood patch, the authors present compelling results which are corroborated by published literature. The finding that 10 ml of saline injected before removal of the intrathecal catheter reduced the incidence of both post-dural puncture headache and the need for epidural blood patch is striking. Other studies have used a similar approach. Charsley et al. found that 10 ml of saline injected intrathecally dramatically reduced or eliminated, respectively, post-dural puncture headache and requirement for epidural blood patch [14]. In a retrospective review of accidental dural punctures, Bolden et al. found that spinal catheters reduced requirement for epidural blood patch, with an additional protective benefit following saline injection [15]. Izquierdo et al. retrospectively compared patients with either intrathecal catheter plus injected saline (per unit protocol) or repeat epidural (data pre-dated intrathecal catheter protocol) and showed significant reduction in both post-dural puncture headache and epidural blood patch [10]. The purported mechanism of effect is cerebrospinal fluid (CSF) volume expansion, mitigating the leak causing post-dural puncture headache symptoms. But does this theory have physiological plausibility? Circulating CSF volume is approximately 150 ml and is replenished four times daily. Re-absorption and secretion are under homeostatic control [16]. If the injection of 10 ml of saline is indeed protective, it seems unlikely that it is due, solely, to a volume effect. At the point of injection, most patients will be asymptomatic, and may not develop post-dural puncture headache symptoms for 24–72 h, by which time the entire CSF volume may have turned over up to 10 times. Commonly postulated mechanisms for post-dural puncture headache include intracranial hypotension, sagging and traction of pain-sensitive structures and compensatory intracranial vasodilation. A further mechanism may be increased compliance of the lumbar sub-arachnoid space following dural puncture. This leads to exaggerated orthostatic caudal CSF movement, intracranial hypotension and the classic ‘positional’ headache [17, 18]. This theory offers some plausibility as to the mechanism of epidural blood patch, which reduces lumbar sub-arachnoid space compliance, preventing cranio-spinal CSF excursion on standing. Experimental evidence and new hypotheses may lead to a revised understanding of CSF dynamics and new therapies [19]. Further work to elucidate the protective mechanism of saline will help to optimise treatment regimes. In obstetric, medical and neurosurgical contexts, inconsistencies exist between patient presentations, MRI findings, CSF volume losses and CSF pressure drops, suggesting that headaches are not fully explained by a single mechanism or traditional teaching [17, 20, 21, personal communication with neurosurgeon]. The aetiology of post-dural puncture headache is likely to be multifactorial and remains incompletely understood. The contribution of factors and any synergism between them, may be inconsistent between patient presentations. This could account for the volume of conflicting studies showing positive and negative treatment effects for a range of therapeutic interventions. It is difficult to tailor therapies without a clear understanding of the pathophysiology; one-size may not fit all. However, epidural blood patch is clearly an effective treatment. A final consideration is towards consent for unanticipated placement of an intrathecal catheter; a distinct procedure to epidural placement, with unique risks, for which no prior consent has been granted. In their editorial, Ainsworth and Cook discuss the challenges of informed consent for anaesthetists [22], conceding that it may often fall short, under legally scrutiny, and noting increased consent claims against anaesthetists [23]. Chrimes and Marshall summarised this as “The illusion of informed consent” [24]. The complexities of consent when deciding on immediate action to manage an accidental dural puncture in a labouring woman are considerable. Shared decision-making has superseded paternalism in the consent process. The Montgomery ruling [25] further shifts the emphasis towards individual patients, rather than ‘perceived’ medical wisdom. Information should ideally be shared and discussed before patients arrive in hospital, which is often the case for labour analgesia information. Should epidural consent include discussion of accidental dural puncture management, as the most common serious complication? Or is this the thin end of the wedge; unnecessarily burdening parturients, and over-medicalising birth? If not previously discussed, is further consent required to site an intrathecal catheter, following accidental dural puncture? Intuitively, it would be, and yet this presents an almost impossible task, given the circumstances. There is a considerable body of evidence suggesting the efficacy of intrathecal catheters following accidental dural puncture in reducing post-dural puncture headache and requirement for epidural blood patch. This large study by Binyamin et al. [2] presents further compelling, supportive real-word data. The authors should be congratulated on their valuable addition. In implementing the proposed management strategy, units should agree a clear protocol-guided policy [10], forming their own critical conclusions on available evidence. This will reduce the cognitive and emotional burden on the anaesthetist at whose hands the accidental dural puncture occurs, and unburden junior staff, out of hours. This anticipatory approach is likely to be more efficacious and safer than ad-hoc individual decision making and inconsistent practice within units. Perhaps it is time to add consent for labour analgesia with an intrathecal catheter, in the event of accidental dural puncture, to our pre-procedural routine? Thanks to Mr C. Barrett, consultant neurosurgeon, Institute of Neurological Sciences, Queen Elizabeth University Hospital, Glasgow, for his insight and comments. Also, Dr R. Kearns, consultant anaesthetist, Glasgow Royal Infirmary and Dr M. Shaw, statistician, University of Glasgow/Department of Medical Physics, Glasgow Royal Infirmary, for advice on sample size calculation. No competing interests declared.