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INTRODUCTION
Laparoscopy
Before the era of clinical in vitro fertilization (IVF), oocytes were acquired by parotomy . Aside from the escalating scientific interest in fertilizing and culturing human oocytes in vitro, the development of laparoscopic surgery also facilitated the use of IVF in treatment of infertile couples. At the end of 1960, the laparoscopic technique made it possible to retrieve human oocytes quite simply for both research and clinical purposes. The technique played a key role in the start of collaboration between Edwards, the scientist with the knowledge of how to fertilize and culture human oocytes in vitro, and Steptoe, a clinician mastering a technique that could be used to harvest oocytes in women with tubal infertility . Subsequently, laparoscopy became the technique of choice for oocyte aspiration during the first 10 years of this clinical IVF era. Different technical aspects surrounding this technique were published at that time by those groups involved in the early clinical practice of IVF . Retrieving oocytes under the guidance of a laparoscope was a fairly simple technique with a high oocyte recovery rate.
However, general anesthesia was routinely needed and only in certain patients was it performed with local anesthesia. Furthermore, laparoscopy exposes healthy women to risks that are not negligible and it is rather an expensive method. In order for IVF to evolve into a procedure that could be afforded by many women, there was a need to find a technique for oocyte retrieval that could be performed as an outpatient surgical procedure. Even in those cases when laparoscopy was performed using local anesthesia, it was still quite a technically demanding technique using expensive instruments and unsuitable to performing multiple oocyte collections on the same day . With the introduction of ultrasound in monitoring follicular maturation and the knowledge that ultrasound could be used for guiding puncturing procedures, it is not surprising that ultrasound-guided follicle aspiration became a very interesting alternative technique.
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Ultrasound
Clinical IVF started at the time when ultrasound imaging in obstetrics and gynecology developed rapidly. This was due to a rapid technical development within diagnostic ultrasound. Ultrasound was applied early for ovarian imaging and in some early studies it was elegantly shown that the technique could be used for monitoring follicular maturation. Furthermore, one of the Danish pioneers within diagnostic ultrasound proved earlier that the technique could be used safely and accurately for guidance of percutaneous puncture of cystic as well as homogenous tumors within different organs of the body
. With the experience of ultrasound-guided puncture developed by Holm et al.,
it is not surprising that another Danish group lead by Lenz demonstrated the first successful oocyte collection under the guidance of ultrasound. Parallel to Lenz et al., our own group in the beginning of 1980 started to use a similar technique for ultrasound guided follicle aspiration. The technique used at that time utilized abdominal ultrasound scanning and Tran abdominal, transvesical puncture of follicles. This technique had to be performed in light general anesthesia with a full urinary bladder
. Although it was not as technically demanding as laparoscopy, it was still
preferable to perform in general anesthesia and as such the advantages in
comparison to laparoscopy were not widely appreciated. However, many IVF
groups did adopt the technique and some tried new approaches that could be
used with local anesthesia. One such interesting development was the
introduction of the puncturing needle through a urinary catheter to the
urinary bladder. By scanning abdominally, the needle could be directed to the
follicles .
In 1983, our group started to work on vaginal ultrasound scanning. At that time, we used small abdominal mechanical sector transducers that after some modification could be used for vaginal scanning. However, those probes were not ideal for puncturing transvaginally. We,therefore, started a collaboration with the Danish ultrasound company Bryel and Kjaer. They had developed a probe for cranial scanning during neurosurgical procedures.
After minor modifications of this probe, it could be used as a vaginal transducer. Ovaries could now easily be scanned without the full bladder 118 Wikland technique and oocyte aspiration could be performed as an outpatient procedure with local anesthesia
. Manufacturers of diagnostic ultrasound very soon realized the potential of
vaginal sonography for gynecological diagnostic and interventional procedures
and consequently started to produce vaginal probes. It did not take long for
other IVF groups to realize the potential of this new technique.One group that
begun early was Dellenbach et al. in France and they published their
initial experiences already in 1984. Another group that contributed early on
to the development of this technique was Feichtinger and Kemeter.
Transvaginal ultrasound-guided oocyte retrieval (TVOR) has since then become the gold standard for oocyte aspiration in assisted reproductive technology (ART). Even though no large prospective-controlled, randomized trial comparing laparoscopic-guided and transvaginal-guided oocyte retrieval has ever been performed, the latter has become the method of choice. The reason for this is probably that TVOR is such a simple method and does in the majority of patients result in enough oocytes to guarantee a good chance of becoming pregnant.
The technique has, over the years, in many ways been improved. The ultrasound equipment has become more sophisticated; resulting in extremely refined images as compared to the equipment used more than 20 years ago. This has meant a lot for the safety of this technique and the ease with which it can be used.
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TECHNICAL ASPECTS
Equipment
Today most ultrasound equipment with a vaginal transducer can be used for safe and accurate puncture of follicles via the vaginal route. It is, however, important to chose a fairly long (total length 40–50 cm) transducer, which makes it easy to handle during the scanning and puncture procedure. A frequency of 5–7MHz gives a sufficient penetration depth and enough resolution for accurate scanning of the lower pelvis. The transducer should have a shape that is easy to put into a slim sterile cover or a finger of a sterile surgical glove. The needle guide should be easy to attach to the transducer when it has been placed in a sterile cover (Fig. 1).
There are today many different needles that are specially designed for oocyte
aspiration. Most companies, like Cook Ltd., Swemed International Lab, and
Wallas Ltd., which have specialized in equipment for IVF, offer different
types of needles for oocyte retrievals. Our opinion after nearly 20 years of
experience with TVOR and having tested most of the available needles on the
market is that the sharpness of the needle is the most important factor. A
sharp needle means less pain if the puncture is performed in analgesia.
Furthermore, it is important that the surface of needle tip has some kind of
preparation that will increase the ultrasound echo, making it easier to
identify the position of the needle tip. Most needles used for ultrasound-
guided puncture do have such a preparation. The diameter of the needle is
important for two reasons. A thin needle 18–20 gage means less pain when the
analgesia only is used. The other is that a needle with too small inner
diameter may be harmful to the oocyte cumulus complex .
As long as the inner diameter of the needle is 0.8–1 mm, it seems as if the oocyte cumulus complex is unaffected, provided that the aspiration pressure is <120 mmHg. A needle too thin often causes problems by deviating away from the puncturing line, particularly if the ovary is situated high up in the pelvis. A nicely shaped fingertip handle on the distal end of the needle is preferable because it makes it possible to puncture with good clinical touch.
To increase the recovery, it was shown earlier that Teflon tubing between the needle and the sampling tube was important. Commercially available follicle aspiration needles do have such tubing as well as a sampling tube. Today, manufactures provide sterile and mouse embryo tested follicle aspiration sets including needle, tubing, and sampling tubes. The set is ready to use and only needs to be connected to the suction pump. The set is made for single use and thereby guarantees sterility and non-toxicity to the oocyte. Over the last 15 years, our group has used such follicle aspiration sets and found them to be very convenient. In our opinion, an 18 gage needles (outer diameter) thin walled with an inner diameter of 20 gages is ideal.
Suction of follicular fluid can be performed either with a syringe or a suction pump creating the negative pressure needed. It was shown earlier that a negative pressure of 90–120mmHg seems to be optimal for a good recovery and exerts no harm on the oocyte cumulus complex when aspirating mature follicles. However, aspirating immature oocytes from follicles of 5mm diameter with very small volume needs much less pressure, 40–60mmHg.
Creating a negative pressure by means of a suction pump where the pressure can
be controlled in a standardized manner is probably the safest and the best
way. Today there are several such suction pumps available specifically
manufactured for oocyte aspiration. In the early days, aspiration of
follicular fluid was often performed by means of a syringe connected to the
puncturing needle. This is a risky alternative because it is difficult to
control the negative pressure and it was earlier shown that the effect of a
high negative pressure in the system might cause damage to the oocyte cumulus
complex .
In conclusion, one should use a ready-to-use follicle aspiration set and connect it to a calibrated suction pump using a negative pressure of 100mmHg for retrieval of mature oocytes and 50mmHg for immature oocytes.
Figure 1 Schematic illustration of transvaginal ultrasound-guided oocyte retrieval.
The needle is inserted through the needle guide that is mounted on the vaginal transducer.
The ultrasound image shows a punctured follicle, and the needle tip is presented as a white echo inside the follicle.
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Aspiration technique
The actual TVOR technique has been described extensively over the years and in principle has not changed very much (Fig. 1) . I will, therefore, in this part only focus on the following: anesthesia/analgesia; flushing follicles or not, and complications.
The first two topics are interesting because almost all IVF clinics have their own methods of management. It is also very important to discuss updates related to complications within a technique. The longer a technique has been in use, the more information we will acquire about its safety.
Anesthesia or Analgesia Already from the beginning our group performed TVOR combined with conscious sedation. Our reason was driven by the belief that if TVOR could be accepted by the patients and performed under local anesthesia, it would bring down the cost of the whole IVF treatment.
Oocyte retrieval is supposed to be physically the most painful part of the IVF procedure, and various methods of analgesia have been tried over the years. Many groups therefore use general anesthesia. In our opinion, one of the leading advantages of transvaginal follicle puncture is then lost. A good analgesic method for oocyte retrieval has to give a satisfactory pain relief with rapid onset, rapid recovery, and ease of administration and monitoring. It is also important that it is safe and has no toxic effect on the oocytes.
Conscious sedation appears to be the most commonly used method of pain relief
for oocyte retrieval in the United Kingdom and in the United States.
Randomized, controlled trials (RTC) suggest that pain relief is superior when a paracervical block (PCB) is used combined with sedation Oocyte Retrieval 121 as compared to sedation alone . It has also been shown that patients who received only a PCB during egg collection experienced 2.5 times higher levels of vaginal and abdominal pain as compared to those who received both PCB and conscious sedation. With the PCB, the local anesthetic is usually deposited in four locations around the cervix in the vaginal mucosa. Accordingly, today we use in total 100 mg lidocaine (10 ml of 1% lidocaine, XylocaineTM 10 mg/ml, AstraZeneca Sverige AB, So¨derta¨lje, Sweden) injected at four points around the cervix and alienating 0.5 mg IV. If needed, a supplementary 0.25 mg alfentanil (Rapifen 0.5 mg/ml; Janssen-Cilag AB, Sollentuna, Sweden) is given once or twice during the procedure. With this combination, 99.5% of our oocyte aspirations are performed.
The majority of our patients seem to have sufficient pain relief .
An interesting method for pain relief during oocyte aspiration is electro- acupuncture. The reason for exploring this method arose from an earlier study from our group where we tried to evaluate a possible positive effect of electro-acupuncture on ovarian blood flow
. This study led us to also explore the possible positive effect on pain
during oocyte aspiration.
A recently published study comparing electro-acupuncture and conventional medical analgesia during oocyte aspiration showed, however, that no method seems to be superior to another . Hence, our experience is that electro-acupuncture can in many patients be a good alternative for pain relief during oocyte aspiration
.
Flushing Follicles or Not
Flushing follicles or not has been debated for years. The rationale is that flushing of the follicle offers an advantage to the patient, with a larger number of oocytes being collected and therefore a higher potential for pregnancy. Kingsland et al. were the first to perform a randomized trial. They demonstrated that when performing transvaginal ultrasonically guided oocyte recovery, there were no significant differences in number of oocytes retrieved, fertilization rate, or pregnancy rate between those where flushing had been used as compared to no flushing. However, they could show that the operating time was significantly shortened in the non-flushing group . Similar results were later demonstrated in another prospective randomized study . In a recent publication, a study by Bagtharia and Haloob found that 40% of the oocytes were retrieved in the primary aspirate, whereas up to 82% of oocytes were retrieved with two flushes and 97% of oocytes were retrieved in up to four flushes. Based on this study, they concluded that the optimum number of follicular flushings was four times . It could be argued that in this particular study it is not known if the oocytes were trapped in the needle or the tubing after the first aspiration. In our IVF program, we do not flush follicles and have had a recovery rate of 70% per punctured follicle over the last 10 years. Based on our own experience and of 122 Wikland published prospective randomized studies, in our opinion routine flushing would seem superfluous in ART.
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COMPLICATIONS
In this part, I will only deal with complications related to TVOR because this is the gold standard today for oocyte collection in ART. Complications related to laparoscopic procedures are dealt with elsewhere. Despite all the advantages with TVOR during IVF treatment, the aspiration needle may injure pelvic organs and structures leading to serious complications. The mostcommon
complications are hemorrhage, trauma, and injury of pelvic structures and
pelvic infection. Other complications described include adnexal torsion,
rupture of endometriotic cysts, and even vertebral osteomyelit.
Bleeding from the vaginal vault is the most common consequence and has been reported to occur between 1.4% and 18.4% . However, such a bleeding generally ceases spontaneously at the end of the procedure. Sometimes, the bleeding site needs to be identified and application of a sponge is necessary.
Injuries to intraperitoneal or retroperitoneal pelvic blood vessels and
subsequent bleeding have been reported to occur from 0% to 1.3% .
Retroperitoneal bleeding can be difficult to diagnose due to the absence of
free fluid in the pouch of Douglas and can be present several hours after
oocyte pickup .
Acute severe intraabdominal bleeding is often detected by symptoms immediately after the OPU. Such symptoms are weakness, dizziness, dyspnea, abdominal pain, tachycardia, and low blood pressure typical for any severe bleeding. In such cases, early hemodynamic monitoring with serial measurement of hemoglobin concentrations should be performed.
A drop in hemoglobin indicates intraabdominal bleeding and should be regarded as such until the opposite is proved. With the wide variation in TVOR and how it is performed today, one has to be aware that intraabdominal bleeding can always occur and any sign indicating bleeding should be taken seriously.
Pelvic infections after TVOR have been reported to occur between 0.2% and 0.5% . Symptoms such as lower abdominal pain more than a week after TVOR, dysuria, and fever should always make one suspicious of a pelvic infection. If endometrioma has been punctured during TVOR, there is always a risk for an infection. There are reports about tubo-ovarian or abscess after OPU . Owing to the risk for pelvic infections after OPU, it has been debated if prophylactic antibiotics should be given. However, even though the role of prophylactic antibiotics is controversial, they should be considered in the presence of risk factors . Our group does not use Oocyte Retrieval 123 any prophylactic antibiotics. Over the years, we have had four cases of pelvic abscess in almost 12,500 OPU. Of course, the risk of pelvic infection is related to many things such as if the patient is at risk for PID or not.
Another important factor is the type of vaginal cleaning performed before the OPU. Over the years, we have only used sterile saline for washing of the vagina before OPU and still have had very few proven pelvic infections.
However, one has to be aware of the risk of infection and if the patient presents herself with symptoms before embryo transfer, it is recommended to freeze the embryos for later transfer when the infection has been treated.
CONCLUSION
For more than 20 years, oocyte aspiration has been performed under the guidance of transvaginal ultrasound. The technique has proved to be a simple and safe procedure that is well accepted by the patients even if it is performed under local anesthesia with conscious sedation. It can thus be performed as an outpatient procedure. Since it was introduced and till today the technique has been refined in many ways and is regarded as the gold standard for oocyte pickup. The simplification that transvaginal ultrasound-guided oocyte retrieval has meant for the IVF procedure has probably given more patients access to ART.
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