Saturday, July 28, 2012
A Step By Step Guide To The IVF Process: Steps Three And Four--Egg Retrieval
This is the fourth part in the series I have begun to help answer what In Vitro Fertilization (IVF) is and how it works with my world-wide Blog audience. What you read here is what I also provide my patients with on a daily basis. I plan on going into some detail but in a way that is understandable to the normal (lay) audience, and not the medical or scientific one. I also hope that this will not only clarify what you will go through, but explain why things are done a certain way and what the goals of each step are. I also want to convey that IVF is actually a replacement for some of the “natural” steps required to get pregnant and not some miraculous high tech fertility treatment that gets patients pregnant artificially, as many think it is. It is somewhat of a miracle that we can do as much as we can, but there are still lots of things/steps that we cannot do or influence. I hope this discussion will benefit you. This series will continue to be posted over the next few weeks in installments.
STEPS THREE AND FOUR: EGG RETRIEVAL
Thus far, we have covered the first two steps in the reproductive process. In the natural process, the brain has sent signals to the ovaries to recruit and grow the follicle and mature an egg within. The same process has been done in IVF through stimulation by the fertility medications. The follicles have grown and the eggs within have gone through their maturation process. In a natural cycle, one follicle will rupture and the fluid will rush out, taking the egg with it, and empty into the cul-de-sac. The egg will then have to find its way to the fimbriated end of one of the fallopian tubes. Follicular aspiration is the way that IVF accomplishes the ovulation step so that the egg can be retrieved. It is also the method that the egg and sperm are brought together, and therefore, a substitute for finding and being picked up by the tube.
Egg retrieval is technically known as "transvaginal ultrasound guided oocyte (egg) or follicular aspiration". It is a relatively safe procedure and simply put, just a needle poke, like drawing blood. There are some potential risks to this procedure, as with all medical procedures, such as causing bleeding, infection, organ injury or pain but these risks are very minimal and rarely occur. As with all surgeries or procedures, the experience of the physician directly influences the risks. The more experience a physician has doing the procedure, the lower the risks. In many centers, some form of conscious sedation is used so that the patient does not move or feel pain. Despite the quick duration of the procedure, the ovaries are very sensitive and can elicit a large amount of pain. There are some clinics that do not use any sedation, however, and a few that still use general anesthesia where the patient is intubated.
Some clinics will use an Anesthesiologist or Nurse anesthetist to give the conscious sedation and monitor the patient during the procedure. The safety of this set-up is that the physician doing the procedure does not have to be distracted by constantly thinking about the patient’s vital signs, and thus will be able to concentrate fully on just the aspiration part of the procedure. Also if the patient has any difficulties, such as difficulty breathing, bronchospasm, inadequate sedation or increased movement, the Anesthesiologist can attend to it without the fertility physician having to stop the aspiration procedure. The procedure takes 5-20 minutes to perform depending on the skill of the physician, the number of follicles to be aspirated and whether or not the physician uses a technique of follicular flushing (rinsing out the follicle with culture media after the initial aspiration).
The procedure proceeds as follows:
The patient is placed into an operating suite or procedure room, vital sign monitors are placed, the patient is put into the lithotomy (or pap smear type) position and the sedation medication given. In some cases, sterile drapes are put in place, but this is not absolutely necessary. In most clinics, a vaginal speculum is placed and the vagina irrigated with sterile water. Betadine or similar antiseptics are NOT used because they could be lethal to the egg if the solution contaminates the aspiration needle. Local anesthesia is not used in this procedure. Once the vagina has been thoroughly irrigated, the speculum is removed. Just as was done with a vaginal probe to view and monitor the follicular growth, a vaginal probe is used to visualize each ovary, but in this case, a needle guide has been mounted to the probe. This needle guide is so that a needle can be directed to where the probe is pointing. The vaginal ultrasound probe, with the needle guide mounted, is then placed into the vagina once the patient is sedated, and a quick inspection of the ovaries are carried out to verify position and confirm that the follicles are intact. If ovulation had occurred prematurely, the follicles would be absent. The probe is placed toward one side so that it can clearly see one ovary.
With IVF, the ovaries usually fall into the cul-de-sac, a space behind the uterus, which is located just on the other side of the vaginal wall, so the probe is actually millimeters away from the ovary and the ovary can be seen clearly. In addition, the probe is almost in direct contact with the ovary. There is only a small amount of vaginal wall between the probe and the ovary. The needle can then be easily passed through the vaginal wall, into the ovary and into the first follicle to be aspirated. Once within the ovary, it can then be moved from follicle to follicle to aspirate (or vacuum extract) the fluid within the follicle. It does not need to be removed and reinserted for each follicle. Basically the physician will move from follicle to follicle aspirating each follicle until all the fluid is removed. If the physician uses a flushing technique, the fluid will first be aspirated then culture media is injected back into the follicle and aspirated. This is done several times. Some physicians use this technique because that is how they were trained. There is no advantage of using flushing over not using flushing on pregnancy rates, but flushing may help to make sure that an egg is either retrieved or not present, especially if there are only few follicles as occurs with poor responders. The downside of this techniques is that is lengthens the retrieval procedure and so more sedation medication is required.
If the egg within the follicle has matured, and assuming that there was an egg within the follicle because not all follicles have eggs, the egg releases from the follicle wall and is floating within the follicular fluid. The exact physiologic process is more detailed than can be explained here, but suffice it to say that the egg is surrounded by a layer that is congruent with the wall of the follicle. As it matures that connection slowly gets pinched off and the egg is released from the wall. If the egg does not reach maturity, it will usually stay attached to the wall. That is why it is important for the physician to determine when is the appropriate time to trigger the follicle with HCG and schedule the aspiration/retrieval. This is another place where the “art” of IVF comes into play and experience plays an important role. Usually once the appropriate follicle size has been reached, the trigger is scheduled so that it is 34-39 hours prior to the time of the retrieval. Most clinics will schedule the retrieval to be at 36-37 hrs.
So by aspirating the follicular fluid, the egg is retrieved from that follicle. The physician will work on one ovary at a time and aspirate each follicle on that side. Once that is completed, then he or she will move to the second ovary and aspirate all the follicles on that side. The follicular fluid with the egg is aspirated, using a specialized aspiration machine with a low aspiration pressure, into a tube that has been prepared with a special culture media. A special 16 or 17 gauge aspiration needle is also used. As the needle is placed into the follicle, the end of the needle can be seen via the ultrasound as a bright echo. This allows the physician to know where the needle tip is at all times to prevent injury to other structures.
The aspirated fluid, collected in a test tube (hence the name “test tube baby” ) is then passed to the embryologist. The embryologist empties the fluid into a small plastic dish and looks for the egg using a high powered microscope. Some of the tubes will not have an egg within because either the egg did not mature and release from the follicle wall, or there was no egg within the follicle i.e. the follicle was empty. Once an egg is identified, the embryologist will move it into a special petri dish or other prepared dish with culture media. This is the dish that the eggs will stay in as it develops into an embryo. The eggs will then be placed into an incubator that has a set temperature, humidity and gas content within so that there is a stable and idealized environment for embryo growth. Fertilization is then the next step in the process.
In the meantime, the patient is awakened, most don’t remember anything that has occurred and enjoyed a short sleep, and moved to a recovery bed or returned to her recovery area. My clinic has individual rooms where the patient is prepared for the procedure and then returned to for her post-procedure care. Many clinics have an open recovery room area, and each patient is separated by a curtain. She is then closely watched by a nurse for 30 minutes to 1 hour to make sure that the sedation has cleared her system, that she remains stable and that there are no signs of any complications. She can take fluids orally at this point (we don’t allow food or drink prior to the procedure).
Once she has met criteria for discharge, she is allowed to go home. My criteria for discharge is that she will need to be able to take and keep down oral fluids, that her vital signs, especially the pulse, remain stable and within normal limits, that she is able to sit upright without getting dizzy and that she can urinate prior to leaving the recovery area. Because we place an intravenous catheter and run IV fluids in our patients, she will receive sufficient fluid to have an urge to urinate by the end of her stay. Most patients will be able to walk out of the clinic on her own after this procedure. From a pain perspective, there is some cramping that occurs immediately after the procedure, but by 30 minutes it is mostly gone. It usually does not need anything more than a warm pad on the stomach or mild nonsteroidal pain medication to relieve the pain. Most patients will not need a pain medication prescribed when they go home. Patients are directed to remain at very light activity, what I call “couch potato rest”, for the duration of the day. They do not need to remain in bed, and I do not encourage it. They should not engage in any strenuous activities, even long walks, or intercourse for 24-48 hours. I usually will prescribe antibiotics for a short course to reduce the chances of pelvic infection, but not all clinics do this. It is also at this point that patients will start their progesterone supplementation which starts the luteal phase of the endometrium in preparation for implantation.
We will continue this discussion soon with the next installment, "Step Five: "Fertilization". Thank you for joining me today! Edward J. Ramirez, M.D. F.A.C.O.G. Medical Director, Monterey Bay IVF Monterey, CA http://www.montereybayivf.com/