The Vacuum Extractor
The vacuum extractor is a suction device applied to the baby's head to allow the doctor to help deliver the baby by pulling and possibly repositioning the baby's head within the birth canal. The use of the vacuum extractor does not replace the need for pushing by the mother; rather, it is used to supplement the mother's efforts. After the vacuum has been appropriately positioned on the baby's head, the doctor applies traction in coordination with the contractions of the uterus and the mother's pushing. The success of the vacuum extractor depends largely upon correct application and the mother's ability to push effectively.
The vacuum extractor consists of three main parts: a cup that is designed to fit snugly against the top of the baby's head, a suction device that is capable of generating negative pressure, and plastic tubing that connects the cup to the suction device. The first cups used for vacuum extraction were metal. However, newer designs used materials such as plastic or silicone that are more pliable and more easily applied. In addition, they are less likely to injure the skin on the baby's head. When properly applied, the cup causes a slight elongation of the baby's head. The handle attached at the base of the cup allows the doctor to pull without injuring the scalp.
Several types of suction devices are currently in use. The most common is a hand-held pump that produces a negative pressure when the handle is squeezed. Electric devices are also available. Both types of suction devices are equipped with gauges that monitor the amount of pressure being generated. Release valves allow rapid disengagement of the pressure as needed.
Although the use of forceps dates back to the early nineteenth century, vacuum extraction is a relatively new procedure that was first described in the 1950s. Since that time, the popularity of the vacuum extractor has steadily increased. The development of safer and more effective equipment led to a 37% increase in the number of vacuum deliveries between 1985 and 1992. The number of forceps deliveries decreased by 22% during the same time period, perhaps indicating a shift in preference toward vacuum extraction over forceps-assisted delivery in indicated cases.
Performance of Vacuum-assisted Delivery
After the decision to perform a vacuum-assisted vaginal delivery has been made, the doctor assesses the size of the baby and the size of the patient's birth canal. The baby's weight can be estimated by examination of the patient's abdomen and the size and shape of the pelvis is assessed by vaginal exam. In addition, the position, station, and shape of the baby's head must also be determined.
Anesthesia is usually required to comfortably perform the delivery. Epidural anesthesia is preferred because it allows the most pain relief in the vagina and vaginal opening. During the course of labor, the pain relief of the epidural may begin to wear off and an additional dose of medication may be required prior to the vacuum procedure. When the delivery must be performed quickly (as in the case of fetal distress) or when the patient refuses an epidural, a local anesthetic may be injected into the perineum and vagina to numb the vaginal opening and lower portions of the birth canal. This type of anesthesia is often all that is required.
During the delivery, the mother must be lying on her back. The head of the bed may be elevated if this is more comfortable. The delivery bed is designed to allow the foot of the bed to be removed and leg holders to be used. This allows more room for placement of the vacuum cup and delivery of the baby. After the mother is properly positioned, a soap solution may be used to clean the vaginal opening and perineum. The bladder should be drained before the procedure to avoid injury to the bladder and to ensure that there is no obstruction of the birth canal. This can be accomplished by passing a small plastic catheter into the bladder to remove all of the urine. During the vacuum placement and delivery, it may be helpful if assistants help to raise the mother's legs by elevating her feet. This facilitates maximum opening of the pelvis.
The doctor will then fold the soft plastic cup of the vacuum in half and insert it into the vagina. After the cup is applied to the baby's head, the doctor checks to make sure no vaginal or cervical tissue has been trapped between the cup and the baby's head. During the next contraction, the mother continues pushing and pressure is applied using the hand pump or the electric suction machine. Approximately 0.6?0.8 kg/cm2 of pressure is generated over a period of 5 to 10 seconds. After adequate pressure has been produced, the physician gently pulls on the handle at the base of the cup. The traction should be intermittent and coordinated with the mother's pushing. Between contractions, the pressure in the vacuum is released and the cup is left in place. As the next contraction begins, the pressure is once again produced and traction is applied. If it detaches during a contraction, it is replaced. If the vacuum must be replaced more than three times, attempts at vaginal delivery may be abandoned. The delivery should occur after three to four pushes or within 20 minutes after the vacuum is first applied. In cases where there is no further descent of the baby's head despite adequate traction, attempts at vacuum delivery should be discontinued and delivery by cesarean section should occur. The use of forceps after a failed attempt at vacuum extraction has been associated with greater risks to the mother and baby.
In some cases, an episiotomy will be required once the baby's head reaches the vaginal opening. This can be performed easily just prior to the delivery. One advantage of the vacuum extractor is that it is less likely than forceps to cause significant vaginal tears or require an episiotomy. Once the baby's head has reached the vaginal opening, the pressure can be released and the vacuum cup removed from the baby's head. The remainder of the delivery should progress as in a normal vaginal delivery. Immediately following delivery of the head, the baby's nose and mouth are suctioned. If the umbilical cord is looped around the baby's neck, it will be gently lifted over the top of the baby's head. One final push should deliver the baby's shoulders and the rest of the baby will follow easily.
Following the delivery of the baby, the doctor delivers the placenta and a thorough examination of the vaginal opening and cervix is performed. Any lacerations are repaired with absorbable suture (stitches that do not need to be removed). For a complete discussion about vaginal lacerations and repairs, please refer to the.
It is common for a pediatrician or neonatologist to attend vacuum-assisted vaginal deliveries because many of the indications for assisted vaginal delivery can pose problems for the baby (non-reassuring fetal status, concerning findings on the fetal heart rate monitor, or prolonged labor). The pediatrician evaluates the baby to ensure there is no acute problems. Once the infant has been cleaned and the initial evaluation is complete, the baby is given to the new mother.