Appropriate technique is important when the vacuum extraction (VE) is used. [18, 19, 20, 21] The safety and success of vacuum-conducted extraction operations depend on the following:

The accuracy of the initial cup application (ie, cup center over flexion or pivot-point)

Case choice

The traction technique, including degree of effort (number of tractions), vector of traction, method of applied force

The fetal cranial position (including deflection) and fetal station at the time of application

The cup design

The fetopelvic relationship

If the prerequisites for VE operation are met, informed consent is obtained. Thereafter, the position, station, and attitude of the fetal head are verified by pelvic examination and an instrument is chosen. To correctly insert and position the cup, a specific protocol is followed. [18, 19]

Correct application

Once what is believed to be a proper cup application is established, sufficient vacuum (100-150 mm Hg) to fix the cup to the fetal head is applied. A check of the cup should then again be done to ensure no maternal tissue is present before higher pressure that is required for traction is employed.

The labia are separated and the cup is compressed to allow insertion into the vagina. In order to effectively assist a vaginal delivery, placement of the vacuum should be at the correct flexion point. This is done so that the flexion point is an imaginary spot over that midline of the sagittal suture, approximately 6 cm from the anterior fontanelle and 3 cm from the posterior fontanelle (see figure). The center of the cup is placed at the pivot point, making the edge of the cup ~3 cm from the anterior fontanelle and just at the edge of the posterior fontanelle.

Cranial flexion or pivot point. View Media Gallery

Access to the posterior fontanel is usually partially blocked once the extractor cup is correctly placed, rendering this familiar landmark unusable. The further the cup center is displaced from the cranial pivot or flexion point, the greater the failure rate. Traction with an oblique application results in progressive cranial deflexion or twisting (see the image below).

Incorrect sites for cup placement. View Media Gallery

This actually increases the work of the extraction by presenting an ever larger cranial diameter to the birth canal. [19]

Traction

Once the surgeon has verified cup placement, full vacuum is applied (450-600 mm Hg) and traction follows, paralleling the uterine contractions. The direction of pull on the traction handle changes as the fetal head transverses the pelvic curve (see the images below).

Traction efforts are timed to coincide with uterine contractions. Once the contraction begins, the vacuum pump is actuated until the appropriate degree of vacuum pressure is reached. Traction by the surgeon follows, with the force applied to the extractor handle gradually increased to the desired level, paralleling the rise in uterine force generated by the contraction.

As force is applied maternal expulsive efforts continue. As each contraction wanes, the tension on the extractor handle is relaxed. Attempting traction without the assistance of maternal bearing down efforts and/or a uterine contraction is less effective. These techniques simply predispose to failure and risk a fetal scalp injury from a pop-off.

In the relaxation phase between contractions, the vacuum can either be maintained or reduced to less than 200 mm Hg. Both techniques are acceptable. Continuous vacuum throughout the procedure and intermittent vacuum with the vacuum released between contractions, have been studied in a randomized trial. [22] No differences between groups are noted with regard to the speed of delivery, rates of instrument failure, or maternal or fetal outcomes. Thus, the use of either technique is at the discretion of the surgeon. The authors favor vacuum reduction.

A 2012 Cochrane review examined the safety and efficacy of rapid versus stepwise negative pressure application for vacuum extraction. The authors found that rapid negative pressure application reduces the duration of vacuum extraction without affecting maternal or neonatal outcomes. [23]

During traction, the surgeon should place the nondominant hand within the vagina, with the thumb on the extractor cup and one or more fingers on the fetal scalp. So positioned, the accoucheur follows the descent of the presenting part and can judge the appropriate and changing angle for traction while gauging the relative position of the cup edge to the scalp. This helps to detect cup separation. The vector of traction is in the curve of the pelvis. The initial angle for traction depends on the station but is usually downward, then progressively extending upward as the head emerges. Once the head has been extracted, the vacuum pressure is relieved, the cup removed and the usual techniques to complete the delivery are followed.

Jerking motions and oblique pulls are best avoided as they risk cup displacement. Any attempt at rotation of the device may lead to detachment or fetal scalp injury. Under traction, the fetal head usually rotates automatically as descent occurs.

An episiotomy is not recommended as a routine measure during a VE operation unless the soft tissue impedes the descent of the presenting part. Episiotomy has been shown to increase the incidence of third and fourth degree lacerations.

Ideally, descent of the presenting part should begin with the initial traction effort, assuming proper coordination with the maternal bearing down efforts and the uterine contractions. If the operator is uncertain that descent has occurred, a maximum of 2 additional tractions may be attempted. [24] The failure to clearly achieve fetal station after properly timed traction in the correct vector of force mandates prompt reassessment of the procedure both in terms of technique and desirability. Recurrent tensioning of the scalp without descent of the presenting part (negative traction) predisposes to cup pop-offs and is believed to increase the risk for scalp injury.

Limits to effort

The maximum duration of a vacuum extraction is unknown. A maximum of 2-3 pop offs, three sets of pulls and/or a total application time of 15-20 minutes have all been recommended, though some argue for lower time limits. [25]

When the number of pop-offs or the acceptable number of total tractions efforts are considered, the literature is inconsistent. In terms of traction number, studies performed with forceps and rigid-cup extractors have consistent findings. In approximately 85% of births, seemingly independent of whether the delivery is via forceps or the VE, the delivery occurs with 4 or fewer tractions. [26, 27, 28]

Although several studies have demonstrated a relationship between duration of cup application and development of cephalohematoma, the major morbidity of these lesions was largely cosmetic.

Table 2. Number of Tractions Required in Vacuum Extraction and Forceps Deliveries* (Open Table in a new window)

Number of Traction Efforts Successful Malmström Vacuum Extractor Deliveries (n=433) Successful Forceps Deliveries† (n=555) 1-2 296 (68.4%) 213 (38.4%) 3-4 108 (24.9%) 270 (48.6%) ≥5 29 (6.7%) 72 (12.9%) * Breech, cesarean delivery, and transverse lies, are excluded. [28] † Type unspecified

The upper number of acceptable pop-offs is similarly not established. Clinical experience indicates that more than 2 pop-offs is sufficient, especially if progress has been minimal and the cup application and traction technique were proper. However, the correct number is not established.

Sequential instrument use

Recent studies by Gardella [29] and Towner [30] involving large numbers of cases report that sequential operations (vacuum extraction/forceps) are associated with an increased risk for fetal intracranial hemorrhage (ICH), exceeding the risk when either forceps or VE are used alone. Similar data concerning an enhanced risk from combined procedures comes from review of the 1998 Food and Drug Administration (FDA) advisory paper on VE, [31] as well as other sources. However, this has not been the finding in all series. [32] Additional discussion of intracranial injuries and instrumental delivery occurs in Choice of Instrument.

Injuries from multiple instrument use are most likely when a degree of unrecognized fetopelvic disproportion is present and, despite difficulty, the clinician cannot refrain from pursuing a vaginal operative delivery. When one type of instrument is applied and fails, no absolute prohibition exists to trying a different device. However, limiting effort and case choice are critical.

In some cases, changing the delivery instruments can constitute good management. These include those in which technical problems, such as a malfunctioning hand pump, a misapplied vacuum cup, or traction in the incorrect vector of force, are believed to be the cause of failure. The least desirable cases are those in which traction without progress or multiple pop-offs occur following a correct application of the vacuum extractor and appropriate traction.

For most obstetric surgeons, the failure of a properly applied delivery instrument should be followed by a prompt cesarean delivery.

Prophylactic antibiotics

Traditionally, antibiotics have not been administered for the sole indication of an instrumental delivery either with the VE or forceps. No compelling data suggest that prophylactic treatment is appropriate. [33] Antibiotics should be administered to women during labor/parturition following the usual obstetric indications and not specifically for an instrumental delivery.

Documentation

Vacuum extraction is potentially associated with delayed complications in neonates that might later be associated rightly or wrongly to the events of parturition. Especially in reference to all obstetric manipulations, full reporting in the medical record is prudent.

Preoperative note includes the following:

Intentions of the surgeon/limits of effort intended

Clinical setting

Discussion of consent process

Complemented by a detailed post procedure note

Surgical operation documentation is as follows:

Parallel the documentation practices for other surgical procedure; either dictate the procedure or use a computer template

For dictations, follow the institutional requirements for documentation (eg, preoperative/postoperative diagnoses, procedure, surgeons)

Contents of surgical note are as follows:

The indications for the operation/clinical setting that prompted intervention

Document that a consent process preceded the operation

Discuss maternal/fetal evaluations prior to the application of the instrument (eg, examination, Leopold, ultrasound)

Include standard prerequisites for vaginal delivery procedure present (eg, full dilation, engagement, bladder empty)

Record the station, position, and orientation of the fetal head

Report number of tractions and pop-offs (if any)

Total time of cup application

Report any complications (eg, maternal or fetal injuries) and their repair

Notifications that the pediatrician knows a VE has occurred

Report any other technical aspects of the procedure

Medical record is as follows: