OBGMANAGEMENT A SUPPLEMENT TO OBG MANAGEMENT, FEBRUARY 2004 VACUUM-ASSISTED DELIVERY Improving patient outcomes and protecting yourself against litigation VACUUM-ASSISTED DELIVERY Practical techniques to improve patient outcomes I by Aldo Vacca, MD b/Gyns in general prefer vacuum-assisted delivery (VAD) over forceps-assisted delivery, although increased usage has also Obeen associated with more frequent reports of adverse out- comes.1,2 Attention to the details of technique can help prevent prob- lems and ensure the best patient outcomes. This supplement to THE FLEXION POINT: OBG MANAGEMENT serves as a A CRITICAL LANDMARK FOR VAD companion to Preserving the The fetal head is in complete flexion when the mentovertical diameter Option of Vacuum Extraction, points in the direction of descent (Figure 1). During deliveries in which an article appearing in the February 2004 issue. the fetal head is normally molded, the mentovertical diameter emerges on the sagittal suture approximately 3 cm anterior to the posterior fontanelle.4 This flexion point is a critical landmark for VAD; when the center of the extraction cup has been placed over the flexion point and axis traction is applied, conditions are optimal for delivery (Figure 2). Contents 1 VACUUM-ASSISTED DELIVERY Aldo Vacca, MD, Editor Disclosures Practical techniques to improve Associate Professor of Dr Vacca serves on the speaker’s Obstetrics and Gynecology bureau for Clinical Innovations, patient outcomes The University of Queensland Inc. Drs Billings and Vines I by Aldo Vacca, MD Brisbane, Australia have no commercial relationships to disclose. R. Gail Billings, PhD THE PHYSICS OF VACUUM EXTRACTION 7 Senior Research Scientist This supplement is supported Medical Physics Proper use of compression and traction by a grant from Clinical Salt Lake City, Utah for better patient outcomes Innovations, Inc. I by R. Gail Billings, PhD Victor L. Vines, MD (www.clinicalinnovations.com) Clinical Associate Professor of Obstetrics and Gynecology Copyright © 2004 Dowden Health 8 ESTABLISHING A PROTOCOL University of Texas Media The first step for reducing potential Southwestern Medical School for litigation Dallas, Texas I by Victor L. Vines, MD SUPPLEMENT TO OBG MANAGEMENT FEBRUARY 2004 S1 VACUUM-ASSISTED DELIVERY FIGURE 1 FIGURE 2 Fetal head and direction of descent Optimum placement for delivery 3 cm 3 cm F = flexion point F = flexion point During normal delivery conditions, the mentovertical The center of the extraction cup has been placed diameter emerges on the sagittal suture approximately over the flexion point, and axis traction is applied. 3 cm in front of the posterior fontanelle. Regardless of the head’s position, the clinician proximal interphalangeal joint is 5 to 6 cm, must be able to find the flexion point and cor- calculate the distance from the flexion point rectly position the cup. to the posterior fourchette of the perineum. This information is used to determine how far the center of the cup must be inserted. To facil- When the center of the cup is itate insertion, the suction tubes of some extrac- placed over the flexion point, tor cups have distance markers to indicate how conditions are optimal for delivery far the cup has been inserted (Figure 4). Cup selection and position Guidelines for patient selection and deter- Anterior devices. The pull devices attached to soft mination of VAD risk are described in the (silicone or plastic) and rigid (plastic or metal) Sidebar (p S4) and in Tables 1 and 2. anterior extractor cups are semirigid, limiting maneuverability within the birth canal and pre- Locating the flexion point senting a handicap whenever the flexion point is A practical approach to locating the flexion point not readily accessible.5 Anterior cups are best is as follows:5 used for deliveries in which the station is low or I Use the middle finger to identify the posteri- outlet and the fetal position is occipitoanterior or fontanelle, then move the finger forward (OA), rotated less than 45˚ (Table 3). along the sagittal suture approximately 3 cm Posterior devices. Maneuverability of rigid posteri- to the flexion point (Figure 3). or cups is not restricted; the suction tube on I With the finger on the flexion point and pal- these devices is in the same plane as the cup mar surface in a superior direction, note body. Posterior cups can be used for deliveries in where the back of the finger makes contact the occipitoposterior (OP) and occipital trans- with the fourchette. verse (OT) positions and for deliveries in I Keeping in mind that in an adult, the dis- the oblique OA position when the fetal scalp is tance from the tip of the middle finger to the not visible. S2 FEBRUARY 2004 SUPPLEMENT TO OBG MANAGEMENT SUPPLEMENT OBGMANAGEMENT FIGURE 3 FIGURE 4 Locating the flexion point Inserting the cup 6 cm 5 – 6 cm Distance markers on the suction Locating the flexion point and calculating the tube of the OmniCup indicate how distance from the posterior fourchette using the far the center of the cup has been examining finger. inserted. FIGURE 5 Confirming cup position Method of traction The extractor cup is correctly positioned over the flexion point when palpation indicates that the anterior fontanelle is at least 3 cm from the edge of the cup, and the sagittal suture is under the cup midline. Nonvisual digital confirmation of correct positioning is made possible because all com- monly used cups have maximum diameters of 6 to 7 cm and the fetal sagittal suture is 9 to 10 cm long.5 Therefore, in cups with a 6-cm diameter and with 9 cm as the distance between anterior One hand provides traction and posterior fontanelles in the normal infant, the and direction while the other distance from the anterior fontanelle to the cup monitors descent and prevents edge is approximately 3 cm. cup detachment. A correctly positioned cup is called a flexing median application (Figures 2 and 4). Other applications promote extension and asynclitism of the fetal head and either increase or fail to decrease the diameters of the presenting part. In PERFORMING THE PROCEDURE a deflexing application, the cup has been placed Inducing a vacuum closer to the anterior fontanelle; in a paramedian When correct positioning of the extractor cup has application, the extraction cup has been placed been confirmed, a vacuum of 500 to 600 mm Hg more than 1 cm to either side of the midline. is induced in 1 step.6 When the station is low or SUPPLEMENT TO OBG MANAGEMENT FEBRUARY 2004 S3 VACUUM-ASSISTED DELIVERY Appropriate patient selection: TABLE 1 Critical to success Predicting risk associated with VAD ndications for VAD vary with each case. Station Low-risk VAD Iof the fetal head is commonly used to predict Fetal caput visible and station low or outlet degree of risk (low versus high) in operative • Arrest of descent in second stage of labor vaginal delivery.3 Similarly, the risk associated with • Nonreassuring fetal status VAD can be predicted based on whether the scalp • Maternal exhaustion but satisfactory uterine is visible at the introitus (Table 1). Other variables contractions and some expulsive effort that may influence VAD outcome are listed in • Selective shortening of second stage Table 2; the presence of 3 or more of these • Delivery of “floating” head at cesarean section indicates a high-risk VAD. VAD should also be avoided in cases with: High-risk VAD* • Cephalopelvic disproportion; brow, face, or Fetal caput not visible and station low or mid breech presentation; gestation <34 weeks; or • Arrest of descent in second stage of labor high fetal head station (above ischial spines). • Nonreassuring fetal status • Inconclusive fetal position where scalp is not • Maternal exhaustion, epidural analgesia, and visible at introitus. diminished expulsive effort • Delivery of severely compromised fetus as • OA >45˚, OP/OT fetal positions a rescue procedure. Such an infant may be depressed at birth, and the VAD operator may * Contraindicated except for “qualified grade” operators be blamed. (see Physician Training, page 6) • Maternal exhaustion—do not increase VAD = vacuum-assisted delivery, OA = occipitoanterior, traction force to compensate for reduced OP = occipitoposterior, OT = occipital transverse expulsive power. • Excessive fetal head molding; traction force increases the risk of intracranial injury in unison. One hand provides traction and direc- in such cases. tion while the other monitors progress and pre- • Incomplete cervical dilation. Beware of the anterior lip of the cervix; do not attempt VAD vents cup detachment (Figure 5). The crossbar of before the cervix is completely dilated. the pull device should be held in the fingertips to limit traction force. outlet, a finger should be swept around the Traction should be maintained smoothly for periphery of the cup to ensure that no maternal the duration of the contraction and for as long as tissue has been trapped between the cup and the mother is pushing. As soon as the contraction scalp. Other safety tips for performing successful passes or the mother stops pushing, traction VAD are listed in Table 4. should cease. It should not be continued to pre- vent retraction of the head, because the lowest Establishing traction station reached at the end of 1 contraction is Gentle traction with the cup extractor is begun as regained quickly at the beginning of the next. soon as a contraction starts and the mother push- Some sign of progress should be evident es. Between contractions, the vacuum may be with each pull: descent of the presenting part, either maintained or decreased, depending on flexion of the head or correction of asynclitism, operator preference.3 There is no evidence that and autorotation from OP and OT positions. If maintaining the vacuum is harmful or that no progress is observed after 2 pulls, stop traction decreasing it is beneficial.7 and complete delivery by cesarean section if the Traction is meant to be an adjunct to the scalp is not visible at the outlet.