Operative Vacuum-Assisted Vaginal Delivery

Sep 07, 2006


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Dr. Dean Wallace:  “We’re going to discuss vacuum assisted deliveries and some of the problems and issues that we’ve seen here in the United States and actually throughout the world. I have with me Dr. Arulkumaran, and I’d like to ask him a question about what in his opinion are some of the problems and issues that faces us today on vacuum extraction?”

Professor. S. Arulkumaran:  “Thank you, it’s a very important topic. As you know, in the United Kingdom about 12% are assisted vaginal deliveries and this could be vacuum delivery or it could be forceps deliveries. There have been a number of concerns raised about fetal injuries and the failure of vacuum deliveries; these are the two main concerns and I think it’s mainly due to the problems with training. The doctors who come for training are not properly trained and they’re not given an explanation as to how they should use the equipment. So I would like to just demonstrate first one or two issues, and perhaps, I’ll start with the model of the baby’s head. If you look at the baby’s deflexed head the longitudinal diameter is long. If a vacuum cup is put straight onto the baby’s head, then we will be pulling a larger diameter through the pelvis. The vacuum cup has to be on the flexion point which is just in front of the posterior fontanel so the head comes down like an egg with it’s shortest saggital diameter along the axis of the pelvis. In the occipital posterior and, occipital transverse positions the head might be slightly deflexed and the cup has to be applied further back and laterally. The cups obviously have to be made in such a way that the cup could reach the flexion point. The cups that has a slim design and where the tube to create the vacuum does not interfere to allow the cup to be slipped through the vagina posteriorly and laterally to the flexion point will give the best results with occipito posterior and lateral positions of the head. With traction the head will flex and rotate permitting the smallest diameters of the head to descend. 

The reasons for failure are because the cups are applied directly to whatever area of the head within the vaginal introitus. This could be a deflexing paramedian application rather than a flexing median application. The center of the cup has to go on the flexion point, which is about 3 cm in front of the posterior fontanel. The sagital suture should bisect the cup indicating it is a median application. When the head comes down, the pull should be directed posteriorly and downwards for the head to follow the axis of the pelvis. There’s a tendency to pull upwards and anteriorly to keep the tube handle of the cup perpendicular to the cup to prevent it from ‘popping off’. This may bring the largest transverse diameter of the head behind the narrow arch of the symphysis pubis preventing the head from coming down and the cup ‘pops’ off. To prevent the cup detaching whilst pulling at an angle counter pressure should be applied on the opposite side of the cup. Too much force and pulling the head when there is disproportion also allows the cup to detach. In summary there are few reasons for the cups to slip; application of the wrong design of the cup, incorrect application, wrong direction of traction, too much traction and traction when there is disproportion. The cups specially designed for vertex in the occipito-posterior lateral position should be used for such positions. Any cup could be used for an occipito-anterior position with the flexed head.”

Dr. Dean Wallace:  “Dr. Arulkumaran, what kind of problems do we see if the cup is applied wrong or improperly?”

Professor. S. Arulkumaran:  “If it is a deflexing paramedian application, then a larger diameter is pulled down. As a result, the cup tends to either pop off or there is a greater force between the scalp aponeurosis and the bone and there is a possibility of a cephalhaematoma or rarely subgaleal hemorrhage. In a cephalhaematoma the blood that leaks is collected within the suture margins of the piece of bone that forms the skull like the parietal bone. The minor injuries are abrasion around the cup, which tends to disappear in 24-48 hours. The minor abrasions are not a problem. The main concerns are cephalhematoma and subgaleal hemorrhage. The most important thing is training. Training is about selection of appropriate cases, cups, placement, and direction of traction and to realise the limitations in each case. I would emphasize training all the time because that is the most crucial aspect in any operative delivery. Thank you.”

Dr. Dean Wallace

:  “Thank you very much.”