Case Study
A fit and well primiparous woman who was in established labor at 39 weeks requested an epidural for labor analgesia. During insertion, it was noted that free-flowing clear liquid was seen from the hub of the Tuohy needle. Initially, the anesthesiologist reinserted the stylet to stop the flow of CSF and then prepared to insert an intrathecal catheter (ITC). Two milliliters of low-dose epidural mix (0.1% bupivacaine with 2 µg/ml fentanyl) was injected down the ITC and flushed with 2 ml 0.9% saline. After the procedure, the anesthesiologist explained that an accidental dural puncture (ADP) had occurred and the implications that this may have. The woman was closely monitored with regard to her cardiovascular status and the height of the block. The ITC was clearly labeled as an intrathecal catheter rather than epidural catheter, and the midwife and obstetric team caring for the patient were informed. The attending anesthesiologist reviewed the patient regularly and provided further doses as required via the catheter. The parturient subsequently delivered vaginally without any further intervention, and the ITC was removed.
On day one after delivery, the woman described a fronto-occipital throbbing headache when sitting up and standing. She had some relief of symptoms when lying flat. Based on the history and an entirely normal neurologic examination, a post–dural puncture headache (PDPH) was diagnosed. She was advised to keep hydrated, prescribed regular analgesia, and kept under observation. Her symptoms persisted, and on day two post-ADP, she had a successful epidural blood patch. The patient was discharged later that day and followed up for 1 week via telephone by the anesthesiologist.
Key Points
After recognition of an ADP, there are two immediate options: ITC insertion via the Tuohy needle or removal of the needle and another epidural sited.
Regardless of the subsequent management option chosen, the complication of an ADP should be explained along with the likelihood of experiencing a PDPH.
The patient was treated with an epidural blood patch, which provided complete relief of her symptoms. She was followed up regularly and given information about potential complications.
Discussion
A dural puncture refers to the puncture of both the dura and the underlying arachnoid mater. It may occur with the Tuohy needle or more rarely with the epidural catheter perforating the arachnoid mater after an initial tear by the Tuohy needle. The incidence of dural puncture during epidural insertion varies in the literature and is quoted as between 0.19 and 3.6 percent.1 A meta-analysis of the obstetric literature described a PDPH rate of up to 52 percent after an ADP from pooled data of all needle types.2 PDPH rates may differ depending on the needle used. A study comparing 18-gauge Sprotte with 17-gauge Tuohy needles showed a lower incidence of PDPH with the 18-gauge needles (55 versus 100 percent) after recognized ADP despite no difference in ADP rate.3 Untreated ADP, with a persistent CSF leak, can have serious consequences such as cranial nerve palsy, subdural hematoma, seizures, and chronic headache. Senior anesthesiologists with experience of ADP should be involved in the management of these patients.
Risk Factors
Several risk factors for ADP have been identified in the literature. One proposed factor for increasing the risk of PDPH is the direction of the bevel of the needle in relation to the dural fibers. It is thought that if the bevel is inserted perpendicular to the dural fibers, as opposed to longitudinal, higher rates of PDPH occur. Studies have compared these two insertion techniques. In one study, a group of patients had epidurals inserted with the bevel perpendicular to the dural fibers, and in the second group, the bevel was inserted parallel to the dural fibers and then rotated once in the epidural space.4 There was a lower incidence of PDPH after ADP in the second group (5/21 versus 14/20). However, a similar study showed no difference in the rates of PDPH,5 and there are concerns that the rotation of the epidural needle in itself may cause ADP. Other factors considered as risks for ADP are relative inexperience of the anesthesiologist, movement of the laboring patient, and repeated epidural attempts. Using a loss-of-resistance technique to air to locate the epidural space has been discontinued by some anesthesiologists because of concerns that it is associated with a higher rate of ADP. However, a meta-analysis of prospective randomized trials showed no difference in ADP or PDPH when using loss of resistance to air compared with saline.6
Signs of an ADP
It is often obvious that an ADP has occurred when free-flowing CSF streams from the Tuohy needle. This is as opposed to only a few drops of saline, which may be seen when using the loss of resistance to saline technique. If there is doubt over which fluid is coming from the Tuohy needle, the characteristics shown in Table 11.1 can be used to distinguish CSF from saline. If an epidural catheter is inserted either purposefully or unintentionally after an ADP, CSF will be continuously aspirated from the catheter.
Table 11.1 Comparison of Simple Tests to Differentiate CSF from Saline
| CSF | Saline | |
|---|---|---|
| Temperature | Warm | Cool |
| Glucose | Present | Absent |
| Protein | Present | Absent |
| pH | <7.5 | >7.5 |
ADP may go unrecognized until either the epidural catheter is used or the parturient describes a PDPH following the procedure. Individual studies quote the incidence of unrecognized ADP at between 16 and 36 percent of all dural punctures, which equates to 0.13–0.29 percent of all epidurals performed.7, 8 A UK survey of obstetric units reported a 10.5 percent national incidence of unrecognized dural punctures.9 An epidural catheter cannot perforate the dura but can perforate the arachnoid mater.10 Therefore, if no CSF is seen flowing through the Tuohy needle initially but on use of the epidural catheter a dense motor block occurs, it may indicate that the Tuohy needle was initially placed in the subdural position.
Other mechanisms for unrecognized dural puncture have been described. The Tuohy needle may tent the dura and cause a small tear. This will not allow CSF to flow back through the needle and results in the correct placement of an epidural catheter. During the second stage of labor, the increased pressure in the epidural space may lead to an extension of the original tear into the arachnoid mater and later produce a headache.11 Another hypothesis describes the lumen of the Tuohy needle becoming occluded by either the ligamentum flavum or a blood clot, preventing the backflow of CSF12 despite the dura being punctured. However, this would be more likely if loss of resistance to air technique is used rather than saline.
Initial Management of ADP
Immediate options after recognition of an ADP during Tuohy needle insertion are to reinsert the stylet into the Tuohy needle, remove the whole thing, and then attempt a second epidural insertion or insert an ITC through the ADP site. Neither of these options has robust evidence to favor one over the other. Despite some literature describing safe and effective analgesia with an ITC, some anesthesiologists would reattempt epidural insertion.
Second Epidural Attempt
The stylet should be reinserted into the Tuohy needle prior to removal. This will stop further CSF leakage and reduce the incidence of tissue being caught in the needle tip on withdrawal. An epidural can then be sited one space cephalad to the previous attempt. Caution should be exercised with local anesthetic dosing because some of the epidural mixture may move through the dural tear into the intrathecal space. Given this risk, all top-ups should be administered by the anesthesiologist in an incremental manner. The patient should be closely monitored, anticipating a high block or cardiovascular compromise. The midwife and obstetric team must also be aware of an ADP and risk of catheter migration.
Intrathecal Catheter
Three to four centimeters of an epidural catheter can be inserted into the intrathecal space and used to provide labor analgesia. A dose of 2 ml of a low-dose epidural mixture such as 0.1% bupivacaine with 2 µg/ml fentanyl can be given via the ITC to provide analgesia, with all top-ups being cautiously given by an anesthesiologist. After each dose, the catheter should be flushed with 2 ml of saline to compensate for the dead space in the epidural catheter and filter. A continuous infusion of a low-dose epidural mixture running at 2–3 ml/h has also been described. Intrathecal lidocaine is not advocated after studies have shown that it is associated with neurotoxicity, the risk of which may be increased with prolonged and repeated administration.13 All intrathecal catheters should be labeled clearly, and the midwife and obstetrician looking after the patient should be informed that the woman has an intrathecal catheter in situ.
After a difficult epidural attempt that leads to an ADP, an anesthesiologist may prefer to use the ITC to provide analgesia rather than a second attempt at an epidural.
As stated earlier, a dural puncture may not be recognized until the epidural catheter is inserted, where, on aspiration, a continuous flow of CSF is noted. In this case, the epidural catheter could be left in situ and managed as an intrathecal catheter.
Along with nerve injury, there are concerns regarding infection with intrathecal catheters and the efficacy of analgesia they provide. However, a retrospective review of 761 patients who had had intrathecal catheters over an 11-year period showed that no patients developed serious infective or neurologic complications (e.g., meningitis, spinal or epidural abscess, hematoma, arachnoiditis, or cauda equine).14 When used for labor analgesia, the failure rate for intentional ITC placement was 2.8 percent (3/108), and for ITC placed after ADP it was 6.1 percent (40/653). Notably, there was a high failure rate when ITC was used to provide surgical anesthesia for cesarean delivery (37.2 percent). Despite this, ITCs are used to provide anesthesia at cesarean section, and doses of hyperbaric bupivacaine 2.5–7.5 mg and an opiate (fentanyl 10–25 µg, morphine 25–100 µg, or sufentanil 2.5–10 µg) have been suggested.15
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