Among the characteristics of an ideal technique for labor analgesia, we should be able to offer the following: rapid onset, predictable and good quality of analgesia, and adjustable depth and duration of the block.

Additionally, it must be easy to perform and with minimal or absent maternal and fetal side effects.

Among available techniques, we have epidural, combined spinal epidural (CSE) and dural puncture epidural (DPE).

We also have to consider mother’s expectations, clinical context and situation, cultural and social factors.

All these techniques are based on an epidural catheter. We´ll try to find out which of them is better and under which circumstances with a better profile for mother and fetus.

Management of patients’ expectations

The sources of information about labor analgesia, usually come from friends, internet, social media, and don’t give accurate information. Sometimes, this kind of sources provoque more confusion than real information to parturients.

When we offer one technique to parturients, it is vital to know: timing, spread of analgesia, quality of motor and sensory block and concerns on maternal or fetal side effects.

One of the most asked questions is related to prolongation of labor or increase in cesarean delivery (CD) rates: Evidence says ‘NO’, if we compare diluted solutions combined with opioids and we compare neuraxial techniques to other analgesic methods (parenteral opioids).^1-3

Epidural technique

It is usually performed using a loss of resistance technique (with air or saline), and with a 17-19G needle passing through it a 19-20 G catheter into the epidural space (usually multiorificial). This catheter is recommended to be placed 4-5 cm inside of the epidural space (if less than 4 cm, the incidence of failure is higher, and if more than 6 cm, the incidence of unilateral block is higher).^4-7

The incidence of failure of analgesia is variable, depending on the definitions and may be as high as 23%.^{8 9}

Sacral block sparing may be difficult when epidural technique is used, as large diameter and thick myeline sheaths of sacral fibers may be difficult to reach, knowing also that lumbar solutions trend to spread cephalad, instead of sacrally.^10-12 So, sacral spread is not optimal when epidural technique is used. This fact is not better when a lower lumbar interspace is selected.¹³

Combined spinal epidural technique

It is used an epidural needle to reach the epidural space, and once it is done, a long spinal needle (25-27G) is passed through the epidural needle to reach the subarachnoid space. The return of cerebrospinal fluid (CSF) is the objective proof of the correct spinal placement of the second needle. Once a small amount of medication (usually local anesthetics combined with opioids) is given via intrathecal, the spinal needle is removed, and an epidural catheter is inserted, to maintain analgesia epidurally as long as it is needed.

CSE technique provides a fast onset analgesia, faster than epidural,^{14 15} and with a more uniform spread of analgesia, what leads to a lower failure rate and higher maternal satisfaction.^{14 15}

The concerns of CSE are:

The use of an untested catheter. It looks that the incidence of failure is lower when CSE has been used as an initial technique.¹⁶

Augmented uterine tone The uterine reactivity after initiation CSE technique can result in uterine hypertonus, needing sometimes the administration of a tocolytic (i.e., nitroglycerine, terbutaline). It occurs less commonly with the DPE and epidural.¹⁷

Fetal bradycardia CSE, compared to epidural is associated with a higher incidence.^18-20 The mechanism associated to this bradycardia is not 100% clear, butprobably it is secondary to a sudden decrease in the plasmatic level of cathecolamines,^{21 22} If epinephrine decreases more rapidly (tocolytic) than norepinephrine, it results in a beta2 activity loss and consequently, uterine irritability, tachysystole and uterine hypertonus. If it is sustained in time, fetal bradycardia may appear.^{23 24} It is usually a transient event that is not related to an increase in CD rate, but may increase anxiety of patient and health providers.

Transient measures of intrauterine resuscitation (stop oxytocin, maternal hypotension treatment, oxygen, fluids and left uterine displacement) and occasionally the use of tocolytics.

Prevention is not possible, but high opioid doses have been associated more often to fetal bradycardia.^{25 26}

Pruritus appear more often after a CSE, compared to epidural. Its maximal effect is 15 minutes after intrathecal administration of opioids, and it is solved at 60 minutes.^{27 28} It can be reversed with mu opioid receptor antagonists.²⁹

Dural puncture epidural (DPE)

DPE is another neuraxial technique that improves block quality, compared to classic epidural, without the side effects of CSE (fetal bradycardia, uterus hypertonus, pruritus). This technique has been a matter of research mainly from Tsen L et al, and during the last few years, from other groups.³⁰

The DPE introduces the epidural needle and then the spinal through it until CSF is seen flowing. No medication is administered intrathecally. Once the spinal needle is removed, an epidural catheter is inserted and the epidural analgesia starts. It is supposed that the epidural drugs pass through the dural hole into the intrathecal space. This translocation of drugs has been demonstrated with contrast, in vitro and in cadavers.^31-33

The spinal needle for a DPE is recommended a 25-26G, as the 27G has not demonstrated any advantage compared to epidural.^{33 34}

25-26G use of DPE has shown a faster onset compared to epidural (66), with a better analgesia quality, specially in sacral spread terms (better S2 block coverage, lower PCEA use, and better bilateral symmetric distribution of analgesia).^{17 30 35 36}

The length of the spinal needle introduction, and the failure to obtain CSF, are matters of concern and must be solved from the technical point of view. If CSF is not obtained, the failure rate of the epidural catheter is much higher.³⁴

The published onset times of DPE are slightly faster than epidural, but not as fast as CSE,¹⁷ with a better sacral spread than epidural (S2 block was achieved in 100% of parturients under CSE and DPE and only 62%.¹⁷ DPE also needed fewer top up interventions.

DPE also presents some potential risks:

Meningitis following a dural puncture. It is rare, and more related to lack of sterility during the technique performance. Its incidence is not higher compared to epidural.^36-38

PDPH its incidence is around 1%, not higher than following CSE and epidural.³⁹ It looks that the incidence of PDPH is more related to the design of the needle (cutting bevels) than the caliber.³⁹

Final considerations and summary ⁴⁰

The election of a neuraxial analgesia technique for labor pain should be individualized, considering parturients’ thoughts and believes, culture, team factors and clinical features.

The associated risks to CSE (fetal bradycardia and uterus hypertonus), will be investigated in the future, and it will allow a better management of risks

Neuraxial ultrasound can be helpful when difficult placement is anticipated for any cause.

The incidence of equivocal identification of epidural space because of anatomical variants is 10%, increasing the risk of accidental dural puncture.

DPE is an option whenever it is done with a 25-26G spinal needle and CSF is seen in the spinal needle, to decrease the risk of failure.

The exploration of new techniques and methods to decrease the failure of epidural analgesia, will increase in the next future.

Risk benefit exact knowledge in DPE, will come in the next few years, as many more women will receive DPE techniques.

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