The incidence of unintended dural puncture (UDP) during attempted epidural insertion among the obstetric population has been found to be approximately 1.5%.1 This complication may be associated with a high rate of postdural puncture headache (PDPH),2 prolonged hospitalization,3and possibly even chronic headache.2 Less-frequent complications may include posterior reversible encephalopathy syndrome,4–6 pneumocephalus,7and subdural hematoma.8
The risk factors for UDP are unclear. Recent studies reported several risk factors, including the anesthesiologist’s experience and time of day.9,10 Another study in a training institution found an increased incidence of UDP in parturients undergoing epidural placement during the beginning of month, which coincided with the start of the month-long obstetric anesthesia resident rotation.11
Most of the published data only address anesthesiology factors predisposing to UDP, rather than identifying obstetric factors that may increase the risk for UDP. Additionally, data regarding the association between UDP and pregnancy outcomes are scarce.
Therefore, we primarily aimed to identify which demographic and obstetric factors are associated with risk for UDP in parturients. We hypothesized that specific obstetric characteristics such as high parity or advanced cervical dilation at the time of initiation of epidural analgesia are associated with risk for UDP. Second, we aimed to evaluate the labor and delivery outcomes (ie, mode of delivery) in cases of witnessed UDP.
We conducted a retrospective study of all UDPs during attempted vaginal delivery between the years 2004 and 2013, at a single tertiary, university-affiliated medical center with approximately 10,000 annual deliveries. Labor and delivery outcome of women with UDPs was compared with that of women who received uncomplicated epidural analgesia. For each case in the study group (UDP), 2 previous and 2 consecutive deliveries of women who received epidural analgesia performed by the same anesthesiologist (control group) were matched. This study was approved by the Institutional Review Board of Rabin Medical Center – Beilinson Campus.
In our hospital, anesthesiologists begin working in the delivery suite only after they have completed at least 2 years of residency and have previously performed 300 to 500 spinal anesthetic procedures for cesarean delivery and a large number of supervised epidurals on non-obstetric patients.
According to departmental protocol, after each epidural catheter insertion, the anesthesiologist records in a separate log book details of the block, including patient name, time of day, name of anesthesiologist, and whether UDP with the epidural needle occurred. This is a mandatory part of anesthesia documentation. UDPs were defined as the appearance of cerebrospinal fluid through the epidural needle, cerebrospinal fluid aspiration through the epidural catheter or positive epidural test dose (development of a motor block within 3–5 minutes after administration of 2.5 mL of 2% lidocaine or 8 mL of 0.1% bupivacaine). Every UDP was matched with the 2 previous and 2 consecutive epidurals performed by the same anesthesiologist per the log book. To minimize the possibility of under-reporting UDP, data were cross-referenced with the midwife charting system.
Patient data were obtained from our departmental electronic and print records. Recorded patient characteristics included maternal age, gravidity, parity, and body mass index (BMI) as well as obstetric factors at the time of epidural insertion: amniotic membrane status (intact or ruptured), induction of labor, oxytocin administration, latent or active phases of labor, and degree of cervical dilation in centimeters. Latent phase was defined as under 4 cm cervical dilation and active phase of dilation was defined as equal to or greater than 4 cm cervical dilation measured by either a midwife or obstetrician 1 hour or less before the epidural analgesia was performed. Epidural data including needle and catheter depth and pain measured by verbal numeric scale (VNS) (0–100, 0 – no pain, 100 – worst pain imaginable) 30 minutes after epidural insertion also were recorded. Finally, the interval from epidural insertion until delivery (neuraxial-to-delivery interval), mode of delivery, dural puncture, PDPH, performance of epidural blood patch, and length of hospital stay were identified.
Our departmental protocol of management in cases of UDP was to insert a spinal catheter and institute continuous spinal analgesia with 2–4 mL/h of a solution containing bupivacaine 0.08% and fentanyl 2 μg/cc. If the VNS was greater than 70/100 at 30 minutes or any time afterwards, a top up dose of 2 mL of the same solution was given. The spinal catheter was left in situ for 24 hours. In cases of failure to thread, the epidural was resited in a different interspace. Our epidural analgesia protocol was an initial bolus of 15 mL of 0.1% bupivacaine and fentanyl 100 μg given as 2 separate doses followed by patient-controlled epidural analgesia (bupivacaine 0.08% and fentanyl 2 μg/cc, basal rate 8–12 mL/h, patient-administered bolus 5 mL, lockout interval 15 minutes).
After delivery, women were assessed by an anesthesiologist twice daily. PDPH was defined according to the International Headache Society’s International Classification as a postural headache occurring after a dural puncture that is worsened by assuming an upright position and improved by moving to a supine position.12 In cases of PDPH, women were given oral acetaminophen 1 g/day, caffeine 300 mg/day, ibuprofen 1200 mg/day, and dipyrone 3 g/day. If the VNS was greater than 70/100 after 24 hours, or if there was no improvement in symptoms after initiation of conservative treatment, an epidural blood patch was offered. The blood patch procedure was performed by a senior anesthesiologist. If the patient complained of headache recurrence after the blood patch, a neurologist was consulted and either a brain computed tomography or magnetic resonance imaging was performed. If imaging was normal and pain persisted, a repeat blood patch was performed. Prolonged hospitalization was defined as hospitalization duration of more than 48 hours and 96 hours after vaginal and cesarean deliveries, respectively.
Univariate analysis was used to investigate the relationships between each of the risk factors and the occurrence of UDP. The Shapiro-Wilk test was used to test for normality. Student t test and Mann-Whitney U test were used to compare continuous variables with and without normal distribution between the groups, respectively. The χ2 and Fisher exact tests were used for categorical variables. Differences were considered significant when P value was less than .05. Variables that were found to be different between the groups (P < .05) in the bivariate analysis as well as variables that were hypothesized to potentially affect the likelihood of UDP based on clinical grounds were entered to the multivariable logistic regression model. Binary logistic regression analysis was used to evaluate the effects of the following factors on the UDP occurrence: maternal age, pregestational BMI, parity, amniotic membrane status (intact or ruptured), labor induction, oxytocin augmentation, and degree of cervical dilation at procedure. Estimated odds ratios were used to quantify the effects. We further evaluated the possible factors affecting PDPH. Multicollinearity diagnostic tests were performed with the variance inflation factor (Supplemental Digital Content l, http://links.lww.com/AA/B468). The Hosmer-Lemeshow test was performed to test for goodness of fit in the logistic regression. Data analysis was performed with the SPSS v21.0 package (IBM Corp, Armonk, NY).
During the study period, 46,668 epidurals were performed: 177 (0.4%) were recognized as UDPs. Baseline demographic and obstetric characteristics of the study population are listed in Table 1. There was no significant difference in maternal general characteristics between the 2 groups, including maternal age, gravidity, parity, maternal comorbidities, induction of labor and gestational age at delivery. Parturients with UDP had a significantly greater degree of median cervical dilation at the time of epidural insertion and significantly many of them were in active phase of labor. This group also had a significantly greater rate of intact amniotic membranes than the control group.
Table 2 outlines the data regarding the epidural catheter insertion. There was no difference in dural puncture incidence with choice of lumbar interspace or medium (air versus saline) used for loss-of-resistance. The UDP group had a greater average needle depth insertion than the control group.
Obstetric outcomes are reported in Table 3. Women with the UDP and subsequent continuous spinal analgesia had lower VNS pain scores than women in the control group 30 minutes after insertion. Neither labor duration nor mode of delivery differed between the groups. Women who had UDP had a longer mean length of hospital stay. There were no infectious complications because of spinal catheterization.
Data regarding the management and complications after UDP are listed in Table 4. Ten epidural catheters were resited in the epidural space at a different interspinous space because of technical complications. One hundred seven women (60.5%) developed PDPH; 38 (35.5%) received an epidural blood patch. One of these women had persistent pain after receiving blood patch and received a repeat blood patch. In multivariable logistic regression analysis, after we controlled for possible factors affecting UDP (maternal age, BMI, parity, degree of cervical dilation at time of initiation of analgesia, premature rupture of membranes, induction of labor, oxytocin administration), premature rupture of membranes was associated negatively with the rate of UDP (adjusted odds ratio [aOR] 0.55; 95% confidence interval [95% CI] 0.32–0.93, P = .02), whereas the degree of cervical dilation in centimeters at the time of epidural insertion was associated positively with the risk of UDP (aOR 1.23; 95% CI 1.04–1.42, P = .01) (Table 5); however, in a model with only cervical dilation at the time of epidural insertion and premature rupture of membranes, cervical dilation remained associated with UDP (P < .001), but premature rupture of membranes did not (P = .073) (Table 6).
In multivariable logistic regression analysis, after we controlled for possible factors affecting PDPH (maternal age, BMI, parity, cervical dilation before anesthesia, VNS pain values postanesthesia, loss of resistance technique, needle depth and catheter depth, and mode of delivery), multiparity was associated with PDPH after UDP (aOR 20; 95% CI 3–100, P = .004). In multivariable logistic regression analysis, after controlling for possible factors affecting prolonged hospitalization (maternal age, parity, induction of labor, gestational week at delivery and mode of delivery), UDP was associated with significantly increased odds of prolonged hospitalization (aOR 2.82; 95% CI 1.85–4.28, P < .001).
In this study, we aimed to identify obstetric risk factors for UDP and to report obstetric variables associated with this complication in a retrospective case control study design. Our main result is that after we controlled for obstetric and anesthetic factors, the degree of cervical dilation in centimeters before epidural analgesia was significantly and independently associated with the risk of UDP.
We found a low UDP rate, compared with previous studies that described a rate of 0.5–1.5%.1 One possible explanation is anesthesiologist experience. Previous studies included procedures performed by residents in their first year of residency, whereas in our study only residents who performed a large number of epidurals on non-obstetric patients and who completed at least 2 years of residency were allowed to begin supervised work in the delivery ward. In addition, because of the large parturient population and limited anesthesiologist workforce, anesthesiology residents perform, at a minimal, four 24-hour shifts in the delivery ward every month, with approximately 15–20 epidurals per shift. Therefore, residents are highly experienced in performing epidurals. Additionally, in 2 studies published in 2001, there was a dural puncture rate of less than 1%13,14 Similarly, in a retrospective study conducted in Northwestern University during the years 2004–2013, the UDP rate was 0.53%, only slightly greater than our reported incidence.15
We found that the group of parturients with UDP had greater degree of cervical dilation at the time of epidural insertion. The greater degree of cervical dilation was demonstrated among parturients with and without premature rupture of membranes (P = .0011, P = .0098, respectively, Mann Whitney U). This finding is reasonable as greater degree of cervical dilation is associated with more frequent and painful contractions, making patient co-operation with the procedure more difficult. In addition, at greater degree of cervical dilation, there may be pressure by the spouse or midwife to perform epidural analgesia before the parturient delivers.16 In contrast, Hollister et al17 found no evidence of an association between degree of cervical dilation and the risk for UDP (P = .41); however, it is possible that the study was underpowered for this analysis.
Other variables such as BMI or loss of resistance to air versus saline were not found to influence the rate of dural puncture. This finding differs from a 1993 study by Hood et al18 in which a greater rate of UDP was found in morbidly obese parturients. Of note, a newer study found no difference in UDP rates between obese and normal-weight women.19 Our study corroborates a Cochrane review, which found that there was no difference in UDP rates using loss of resistance to air or saline.20
Previous articles addressing the risk for PDPH after dural puncture have shown a decreased PDPH incidence after unintentional dural puncture in parturients with an increased BMI, even after controlling for pushing during labor.15,21 Our study found that only multiparity was a risk factor to develop PDPH after UDP. We are unsure of the reason for this, although women with small children at home may need to be more active and need to spend more time in the upright position.
The rate of PDPH after UDP was 60.5%, which is similar to the rate previously reported.22 Recent articles, however, showed lower rates of PDPH when continuous spinal analgesia was performed after UDP when compared with our rate.23 Our study did not corroborate this low rate, although it must be noted that 10 of our 177 parturients did have their epidural replaced as opposed to having continuous spinal analgesia.
The weakness of this study includes its retrospective design and the relatively low rate of recognized UDP. Possible confounding factors for UDP such as needle bevel direction and patient cooperation were not recorded.24 An additional limitation of this study is the fact that parturients in our hospital are relatively lean; results may be different in areas where obesity is more prevalent.
In conclusion, women with a greater degree of cervical dilation in centimeters at the time of initiation of epidural labor analgesia are at greater risk for UDP. Unintentional dural puncture does not seem to be associated with adverse obstetric outcomes except for prolonged length of hospital stay. There was a high rate of PDPH after UDP.
Name: Sharon Orbach-Zinger, MD.
Contribution: This author helped design the study, conduct the study, analyze the data, and write the manuscript.
Conflicts of Interest: Sharon Orbach-Zinger declares no conflicts of interest.
Name: Eran Ashwal, MD.
Contribution: This author helped conduct the study, analyze the data, and write the manuscript.
Conflicts of Interest: Eran Ashwal declares no conflicts of interest.
Name: Lilach Hazan, MD.
Contribution: This author helped conduct the study.
Conflicts of Interest: Lilach Hazan declares no conflicts of interest.
Name: Danielle Bracco, BA.
Contribution: This author helped conduct the study and write the manuscript.
Conflicts of Interest: Danielle Bracco declares no conflicts of interest.
Name: Alex Ioscovich, MD.
Contribution: This author helped design the study and write the manuscript.
Conflicts of Interest: Alex Ioscovich declares no conflicts of interest.
Name: Liran Hiersch, MD.
Contribution: This author helped design the study and conduct the study.
Conflicts of Interest: Liran Hiersch declares no conflicts of interest.
Name: Andrey Khinchuck, MD.
Contribution: This author helped design the study and conduct the study.
Conflicts of Interest: Andrey Khinchuck declares no conflicts of interest.
Name:Amir Aviram, MD.
Contribution: This author helped conduct the study and write the manuscript.
Conflicts of Interest: Amir Aviram declares no conflicts of interest.
Name: Leonid A. Eidelman, MD.
Contribution: This author helped design the study, analyze the data, and write the manuscript.
Conflicts of Interest: Leonid Eidelman declares no conflicts of interest.
This manuscript was handled by: Cynthia A. Wong, MD.
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