Change in guidelines

The epidural has been recognized for many years as the most effective analgesia method for obstetrical labor. Several different administration protocols have been evaluated over the years with the aim of reducing side effects.

Epidurals have been incriminated in the increase of instrumented births. It is indeed possible that the motor block induced by the epidural reduces the pelvic tonus and the ability of the mother to push during the second stage of the labor. Furthermore, this motor block might lead to a ill rotation of the foetal head within the pelvis, which could lead to instrumentation (suction cups, forceps).

In the investigator's institution, an ongoing study also provided interim that showed that the use of a low concentration of local anesthetics (as opposed to a higher concentration) tends to decrease the instrumentation and cesarean sections rate in the institution's population.However, the optimal administration mode of the local anesthetic in the epidural remains unknown.

In the last few years, there has been a growing interest for a new method of administration of the solution within the epidural, by programmed intermittent bolus. This method allows a better distribution of the local anesthetics in the epidural space, compared to a continuous perfusion.

This study therefore focuses on the relationship between the use of epidural with programmed intermittent boluses and the rate of instrumented deliveries and cesarean sections.

The exact mode of administration of boluses is also subject to discussion in the literature. One can question whether it is preferable to administer smaller boluses more frequently or larger less frequent boluses. A few studies have investigated this issue and recommend to administer larger and more spaced bolus (10 mL to 60 minutes).This better matches the sought after physiology (ie a wider distribution in the epidural space) and provides equivalent analgesia to smaller, more frequent boluses.

The epidural has been recognized for many years as the most effective analgesia method for obstetrical labor. Several different administration protocols have been evaluated over the years with the aim of reducing side effects.

Epidurals have been incriminated in the increase of instrumented births. It is indeed possible that the motor block induced by the epidural reduces the pelvic tonus and the ability of the mother to push during the second stage of the labor. Furthermore, this motor block might lead to a ill rotation of the foetal head within the pelvis, which could lead to instrumentation (suction cups, forceps).

In 2001, the COMET study showed that the use of low anesthetics concentrations decreases the motor bloc and allows to increase the rate of vaginal deliveries and decrease the rate of instrumented births.

In the investigator's institution, an ongoing study also provided interim that showed that the use of a low concentration of local anesthetics (as opposed to a higher concentration) tends to decrease the instrumentation and cesarean sections rate in the institution's population.

However, the optimal administration mode of the local anesthetic in the epidural remains unknown.

In the last few years, there has been a growing interest for a new method of administration of the solution within the epidural, by programmed intermittent bolus. This method allows a better distribution of the local anesthetics in the epidural space, compared to a continuous perfusion.

Several studies have been performed and show that this mode of administration allows to decrease the local anesthetics injected dosis and gives a better maternal satisfaction. A meta-analysis performed in 2013 also shows a tendency towards the decrease of instrumented deliveries with this method. Sadly, no studies up to this date have the needed power to prove this point with certainty.

This study therefore focuses on the relationship between the use of epidural with programmed intermittent boluses and the rate of instrumented deliveries and cesarean sections.

The exact mode of administration of boluses is also subject to discussion in the literature. One can question whether it is preferable to administer smaller boluses more frequently or larger less frequent boluses. A few studies have investigated this issue and recommend to administer larger and more spaced bolus (10 mL to 60 minutes).This better matches the sought after physiology (ie a wider distribution in the epidural space) and provides equivalent analgesia to smaller, more frequent boluses.

Inclusion Criteria:

• Women over 18 years of age
• Primiparous
• Pregnancy over 36 weeks of gestational age and <42 weeks of gestational age
• Written informed consent
• Cervical dilatation between 3 and 6 cm at recruitment
• Single pregnancy
• Foetus in cephalic position

Exclusion Criteria:

• Participation refusal or epidural contra-indication
• Multiparous
• Allergy to the products used
• Twin pregnancy
• Height <1m55 and/or narrow pelvis, as shown by imagery
• Language barrier
• Patients with a BMI superior or equal to 35 (computed with the weight at the beginning of the pregnancy)
• Cervical dilatation at recruitment <3 or >6 cm
• ASA score (American Society of Anesthesiologists) 3 or 4
• Foetus in transverse or seat position