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How to improve your amniocentesis technique
American]ournal of
Obstetrics and Gynecology Founded in 1920 volume 146
number 6
jULY
15. 1983
CLINICAL OPINION
This section reports opinion on the handling of clinical situations, i.e., the clinical diagnosis and manageme nt of certain disease entities. Papers should range from eight to twenty typed pages, including illustrations. tables. and figures which clarify the author's management. References are limited to sixteen citations. Mail to Frederick P. Zuspan, M.D., Editor.
How to improve your amniocentesis technique P. Jeanty, F. Rodesch, R. Rdtnero, I. Venus, and J. C. Hobbins Brussels, Belgium, and New Haven, Connecticut
Physicians have become dependent upon the information provided by amniocentesis, and each year more diagnostic uses for amniotic fluid are described. Initially amniocentesis was performed without knowledge about the position of the intrauterine contents. With the advent of ultrasound, however, the operator was allowed the luxury of selecting a pocket of amniotic fluid away from fetal vital parts and the placenta. Theoretically, ultrasound would lessen the incidence of fetal death,l- 5 fetal trauma,6 - 13 and subplacental hemorrhage. Although early reports 14 did not demonstrate a smaller incidence of procedure-related abortion when ultrasound was used , other reports 15 • 16 have demonstrated increased efficacy and safety with this modality . However, the commonly used term "ultrasonically guided" has meant that a site for amniocentesis was selected minutes befo re the tap, and during this interval the fetus could move into the selected site or change position in such a way as to redistribute the amniotic fluid volume . A technique is described here that will enable the operator to place the amniocentesis needle
into a desired area with simultaneous real-time direction, thereby obviating the above inherent liability.
From the Departments ofRadiology and Gynecology, Free University of Brussels, and the Department of Obstetrics and Gynecology, Yale University School of Medicine. Reprint requests: P. Jeanty, Yale University School of Medicine, Department of Obstetrics and Gynecology, New Haven, Connecticut 06510.
A rapid, nonsterile survey of the pregnancy is performed to check: (1) fetal age, (2) viability, (3) absence of gross abnormal conditions (fetal malformations), and (4) placental location. A pocket of amniotic fluid for
Fig. 1. The skin has been sterilized. The transducer is placed inside a sterile plastic bag (open arrow). On the sterile drape one or two 20 ml sy ringes are placed next to a 23-gauge needle and the plastic connecting tube (.
Methods
593
594 Jeanty et al. Am.
Fig. 2. A finger is slid between the transducer and the skin, causing decoupling of the skin (see Fig. 3).
Julyl5,1983 Gynecol.
J. Obstet.
Fig. 4. The needle is inserted parallel to and not at an angle with the transducer.
Fig. 5. The tip of the needle produces a bright echo, the tip echo that has to be monitored throughout the insertion of the needle .
Fig. 3. The technique described in Fig. 2 produces an acoustic shadow that demonstrates the future needle pathway.
needle insertion is ascertained, but the exact place of insertion is not defined. The skin is sterilized with very generous boundaries. A single sterile drape is placed to cover the pubic hair. Upon this drape two syringes, a plastic connecting tube, gauze, and the needle are placed. The real-time transducer is placed inside a plastic bag or sterile glove (Fig. l ), and sterile gel or oil is
applied on the patient's skin. The best window is then selected. To visualize the anticipated needle path, a finger is introduced between the transducer and the skin (Fig. 2). This causes decoupling of the skin by introducing air between the skin and the transducer, producing an acoustic shadow that demonstrates the needle pathway (Fig. 3). The needle is inserted alongside and parallel to the transducer (Fig. 4). After the first 2 em the needle enters the ultrasonic beam, resulting in a bright spot"the tip echo" (Fig. 5). The needle is advanced while the movement of the
How to improve amniocentesis technique
Volume 146 Number 6
595
Fig. 6. If the needle is inserted parallel to the transducer, only the tip will be represented. If the needle is inserted at an angle with the transducer, the beam will intersect the needle, but it will not demonstrate its tip, which could be in a harmful position. Notice that in both cases the image on the screen will be the same. Angling the needle is a dangerous procedure which ought to be avoided
tip echo is constantly monitored. When the insertion is very tangent to the endometrium, for instance, in the case of a large anterior placenta, one can usually see the needle pushing the chorion and separating it from the decidua instead of perforating it. The solution is to twist the needle so that the bevel can easily cut the chorion. Once in place, the transducer is left on the sterile drape, and the plastic tubing is fitted between the needle and the syringe. When the fluid has been obtained, the needle is withdrawn and disconnected from the plastic tubing, and the fluid from the plastic tubing is aspirated (±2 ml). The total procedure time (patient in, patient out) is usually less than 10 minutes.
Comment This technique has enabled us to obtain fluid in situations where we previously would not have succeeded, such as marked oligohydramnios, premature rupture of the membranes, and in all encompassing anterior placentas. With the use of this technique enough fluid has been aspirated to determine pulmonic maturity and the presence or absence of bacteria in 85% of patients with premature rupture of the membranes.' 7 In another group of second-trimester patients un-
Fig. 7. After withdrawal of the needle (in this case a 20 gauge), bleeding from the placenta into the amniotic cavity is evident.
dergoing genetic amniocentesis, we have compared our results with those obtained by the standard ultrasound techniqueY The method has also been adapted for use in intrauterine transfusiOiis and intervening intrauterine therapy.
596 Jeanty et al.
July 15, 1983
Am.]. Obstet. Gynecol.
Needles of smaller bore are less painful for the patient and are probably safer. The main disadvantage is that aspiration time is somewhat lengthened. In cases of an anterior placenta which is impossible to avoid, a 25-gauge needle is recommended. Otherwise, the 23gauge needle is the preferred choice. The plastic connector avoids operator movement of the syringe and allows the needle to lie passively in the amniotic cavity. With this "soft" method fetal puncture is unlikely. In fctet, on occasion, we have observed the fetus to hit the needle gently. It is extremely important to monitor the fetal position constantly during the insertion of the needle. In the second trimester fetuses are very active, and an insertion site that was safe minutes previously may not be at the time of the procedure. Special "puncture transducers" are expensive, cumbersome, and have to be resterilized. In addition, some linear-array aspiration transducers have inferior resolution. We have found it easier simply to use a sterile plastic (sandwich) bag. The plastic bags are packed individually and gas sterilized in the hospital. This technique is faster and permits many procedures to be performed on the same day. The needle has to be introduced parallel to the transducer and not at an angle. In the latter case only a section of the needle can be imaged and the tip might be in an unexpected and harmful position (Fig. 6).* If the placenta is penetrated, the duration of the bleeding into the amniotic cavity can be observed at the time of needle withdrawal (Fig. 7). The duration of this bleeding is a function of the gauge of the needle. Thus, when transplacental insertion is unavoidable, the 25gauge needle is ideal. In addition, when these small needles are used, local anesthesia is not required.
REFERENCES I. Goodlin, R. C., and Clewell, W. H.: Sudden fetal death following diagnostic amniocentesis, AM. J. 0BSTET. GYNECOL. 118:285, 1974. *For those who want to practice "tip echo tracking," training on a large beefliver is an easy way to get some experience.
2. Stock, R. J.: Fetal death secondary to needle laceration during 2nd trimester amniocentesis: a case report. Prenatal Diagn. 2:133, 1982. 3. Robertson, R. D., Rubinstein, L. N., and Wolfson, W. L.: Constriction of the umbilical cord as a cause of fetal demise following mid trimester amniocentesis, J. Reprod. Med. 26:325, 1981. 4. Romero, R., Chervenak, F. A., and Coustan, D.: Antenatal sonographic diagnosis of umbilical cord laceration, AM. J. OBSTET. GYNECOL. 143:719, 1982. 5. Park, I. J., Heller, R. H., and Kaiser, R. N .: Spontaneous abortion after midtrimester amniocentesis, Obstet. Gynecol. 53:190, 1979. 6. Therkelsen, A. ]., and Redher, H.: Intestinal atresia caused by second trimester amniocentesis: case report, Br. J. Obstet. Gynaecol. 88:559, 1981. 7. Epley, S. L., Hanson, J. W., and Cruikshank, D. P.: Fetal injury with midtrimester diagnostic amniocentesis, Obstet. Gynecol. 53:77, 1979. 8. Sadovsky, E., Eyal, F. G., and Perlman, R.: Decreased fetal activity and fetal heart rate changes after amniocentesis complicated by fetal hemorrhage. Int. J. Gynaecol. Obstet. 19:395, 1981. 9. Neldam, S., and Pederssen, J. F.: Fetal heart rate response to amniocentesis in early pregnancy, J. Perinat. Med. 8:209, 1980. 10. Lele, A. S., Carmody, P.J., and Hurt, M. E.: Fetomaternal bleeding following diagnostic amniocentesis, Obstet. Gynecol. 60:60, 1982. 11. Report to the Medical Research Council by their working party on amniocentesis: An assessment of the hazards of amniocentesis, Br. J. Obstet. Gynaecol. (Suppl. 2) 85:1, 1978. 12. Mennuti, M. T., Brummond, W., and Cromb1eholme, W. R.: Fetal maternal bleeding associated with genetic amniocentesis, Obstet. Gynecol. 55:48, 1980. 13. Sneider, P.: Ultrasound aspiration biopsy transducer amniocentesis, S. Afr. Med. J. 55:829, 1979. 14. Golbus, M.S., Loughman, W. D., and Epstein, C.J.: Prenatal genetic diagnosis in 3000 amniocenteses, N. Engl. J. Med. 300:157, 1979. 15. Chandra, P., Nitowsky, H. M., and Marion, R.: Experience with sonography as an adjunct to amniocentesis for prenatal diagnosis of fetal genetic disorders, AM. J. 0BSTET. GYNECOL. 133:519, 1979. 16. Crandon, A. J., and Peel, K. R.: Amniocentesis with and without ultrasound guidance, Br. J. Obstet. Gynaecol. 86:1, 1979. 17. Romero, R., Jeanty, P., and Grannum, P.: A comparison of two techniques of sonographically guided amniocentesis. In preparation.
Obstetrics and Gynecology Founded in 1920 volume 146
number 6
jULY
15. 1983
CLINICAL OPINION
This section reports opinion on the handling of clinical situations, i.e., the clinical diagnosis and manageme nt of certain disease entities. Papers should range from eight to twenty typed pages, including illustrations. tables. and figures which clarify the author's management. References are limited to sixteen citations. Mail to Frederick P. Zuspan, M.D., Editor.
How to improve your amniocentesis technique P. Jeanty, F. Rodesch, R. Rdtnero, I. Venus, and J. C. Hobbins Brussels, Belgium, and New Haven, Connecticut
Physicians have become dependent upon the information provided by amniocentesis, and each year more diagnostic uses for amniotic fluid are described. Initially amniocentesis was performed without knowledge about the position of the intrauterine contents. With the advent of ultrasound, however, the operator was allowed the luxury of selecting a pocket of amniotic fluid away from fetal vital parts and the placenta. Theoretically, ultrasound would lessen the incidence of fetal death,l- 5 fetal trauma,6 - 13 and subplacental hemorrhage. Although early reports 14 did not demonstrate a smaller incidence of procedure-related abortion when ultrasound was used , other reports 15 • 16 have demonstrated increased efficacy and safety with this modality . However, the commonly used term "ultrasonically guided" has meant that a site for amniocentesis was selected minutes befo re the tap, and during this interval the fetus could move into the selected site or change position in such a way as to redistribute the amniotic fluid volume . A technique is described here that will enable the operator to place the amniocentesis needle
into a desired area with simultaneous real-time direction, thereby obviating the above inherent liability.
From the Departments ofRadiology and Gynecology, Free University of Brussels, and the Department of Obstetrics and Gynecology, Yale University School of Medicine. Reprint requests: P. Jeanty, Yale University School of Medicine, Department of Obstetrics and Gynecology, New Haven, Connecticut 06510.
A rapid, nonsterile survey of the pregnancy is performed to check: (1) fetal age, (2) viability, (3) absence of gross abnormal conditions (fetal malformations), and (4) placental location. A pocket of amniotic fluid for
Fig. 1. The skin has been sterilized. The transducer is placed inside a sterile plastic bag (open arrow). On the sterile drape one or two 20 ml sy ringes are placed next to a 23-gauge needle and the plastic connecting tube (.
Methods
593
594 Jeanty et al. Am.
Fig. 2. A finger is slid between the transducer and the skin, causing decoupling of the skin (see Fig. 3).
Julyl5,1983 Gynecol.
J. Obstet.
Fig. 4. The needle is inserted parallel to and not at an angle with the transducer.
Fig. 5. The tip of the needle produces a bright echo, the tip echo that has to be monitored throughout the insertion of the needle .
Fig. 3. The technique described in Fig. 2 produces an acoustic shadow that demonstrates the future needle pathway.
needle insertion is ascertained, but the exact place of insertion is not defined. The skin is sterilized with very generous boundaries. A single sterile drape is placed to cover the pubic hair. Upon this drape two syringes, a plastic connecting tube, gauze, and the needle are placed. The real-time transducer is placed inside a plastic bag or sterile glove (Fig. l ), and sterile gel or oil is
applied on the patient's skin. The best window is then selected. To visualize the anticipated needle path, a finger is introduced between the transducer and the skin (Fig. 2). This causes decoupling of the skin by introducing air between the skin and the transducer, producing an acoustic shadow that demonstrates the needle pathway (Fig. 3). The needle is inserted alongside and parallel to the transducer (Fig. 4). After the first 2 em the needle enters the ultrasonic beam, resulting in a bright spot"the tip echo" (Fig. 5). The needle is advanced while the movement of the
How to improve amniocentesis technique
Volume 146 Number 6
595
Fig. 6. If the needle is inserted parallel to the transducer, only the tip will be represented. If the needle is inserted at an angle with the transducer, the beam will intersect the needle, but it will not demonstrate its tip, which could be in a harmful position. Notice that in both cases the image on the screen will be the same. Angling the needle is a dangerous procedure which ought to be avoided
tip echo is constantly monitored. When the insertion is very tangent to the endometrium, for instance, in the case of a large anterior placenta, one can usually see the needle pushing the chorion and separating it from the decidua instead of perforating it. The solution is to twist the needle so that the bevel can easily cut the chorion. Once in place, the transducer is left on the sterile drape, and the plastic tubing is fitted between the needle and the syringe. When the fluid has been obtained, the needle is withdrawn and disconnected from the plastic tubing, and the fluid from the plastic tubing is aspirated (±2 ml). The total procedure time (patient in, patient out) is usually less than 10 minutes.
Comment This technique has enabled us to obtain fluid in situations where we previously would not have succeeded, such as marked oligohydramnios, premature rupture of the membranes, and in all encompassing anterior placentas. With the use of this technique enough fluid has been aspirated to determine pulmonic maturity and the presence or absence of bacteria in 85% of patients with premature rupture of the membranes.' 7 In another group of second-trimester patients un-
Fig. 7. After withdrawal of the needle (in this case a 20 gauge), bleeding from the placenta into the amniotic cavity is evident.
dergoing genetic amniocentesis, we have compared our results with those obtained by the standard ultrasound techniqueY The method has also been adapted for use in intrauterine transfusiOiis and intervening intrauterine therapy.
596 Jeanty et al.
July 15, 1983
Am.]. Obstet. Gynecol.
Needles of smaller bore are less painful for the patient and are probably safer. The main disadvantage is that aspiration time is somewhat lengthened. In cases of an anterior placenta which is impossible to avoid, a 25-gauge needle is recommended. Otherwise, the 23gauge needle is the preferred choice. The plastic connector avoids operator movement of the syringe and allows the needle to lie passively in the amniotic cavity. With this "soft" method fetal puncture is unlikely. In fctet, on occasion, we have observed the fetus to hit the needle gently. It is extremely important to monitor the fetal position constantly during the insertion of the needle. In the second trimester fetuses are very active, and an insertion site that was safe minutes previously may not be at the time of the procedure. Special "puncture transducers" are expensive, cumbersome, and have to be resterilized. In addition, some linear-array aspiration transducers have inferior resolution. We have found it easier simply to use a sterile plastic (sandwich) bag. The plastic bags are packed individually and gas sterilized in the hospital. This technique is faster and permits many procedures to be performed on the same day. The needle has to be introduced parallel to the transducer and not at an angle. In the latter case only a section of the needle can be imaged and the tip might be in an unexpected and harmful position (Fig. 6).* If the placenta is penetrated, the duration of the bleeding into the amniotic cavity can be observed at the time of needle withdrawal (Fig. 7). The duration of this bleeding is a function of the gauge of the needle. Thus, when transplacental insertion is unavoidable, the 25gauge needle is ideal. In addition, when these small needles are used, local anesthesia is not required.
REFERENCES I. Goodlin, R. C., and Clewell, W. H.: Sudden fetal death following diagnostic amniocentesis, AM. J. 0BSTET. GYNECOL. 118:285, 1974. *For those who want to practice "tip echo tracking," training on a large beefliver is an easy way to get some experience.
2. Stock, R. J.: Fetal death secondary to needle laceration during 2nd trimester amniocentesis: a case report. Prenatal Diagn. 2:133, 1982. 3. Robertson, R. D., Rubinstein, L. N., and Wolfson, W. L.: Constriction of the umbilical cord as a cause of fetal demise following mid trimester amniocentesis, J. Reprod. Med. 26:325, 1981. 4. Romero, R., Chervenak, F. A., and Coustan, D.: Antenatal sonographic diagnosis of umbilical cord laceration, AM. J. OBSTET. GYNECOL. 143:719, 1982. 5. Park, I. J., Heller, R. H., and Kaiser, R. N .: Spontaneous abortion after midtrimester amniocentesis, Obstet. Gynecol. 53:190, 1979. 6. Therkelsen, A. ]., and Redher, H.: Intestinal atresia caused by second trimester amniocentesis: case report, Br. J. Obstet. Gynaecol. 88:559, 1981. 7. Epley, S. L., Hanson, J. W., and Cruikshank, D. P.: Fetal injury with midtrimester diagnostic amniocentesis, Obstet. Gynecol. 53:77, 1979. 8. Sadovsky, E., Eyal, F. G., and Perlman, R.: Decreased fetal activity and fetal heart rate changes after amniocentesis complicated by fetal hemorrhage. Int. J. Gynaecol. Obstet. 19:395, 1981. 9. Neldam, S., and Pederssen, J. F.: Fetal heart rate response to amniocentesis in early pregnancy, J. Perinat. Med. 8:209, 1980. 10. Lele, A. S., Carmody, P.J., and Hurt, M. E.: Fetomaternal bleeding following diagnostic amniocentesis, Obstet. Gynecol. 60:60, 1982. 11. Report to the Medical Research Council by their working party on amniocentesis: An assessment of the hazards of amniocentesis, Br. J. Obstet. Gynaecol. (Suppl. 2) 85:1, 1978. 12. Mennuti, M. T., Brummond, W., and Cromb1eholme, W. R.: Fetal maternal bleeding associated with genetic amniocentesis, Obstet. Gynecol. 55:48, 1980. 13. Sneider, P.: Ultrasound aspiration biopsy transducer amniocentesis, S. Afr. Med. J. 55:829, 1979. 14. Golbus, M.S., Loughman, W. D., and Epstein, C.J.: Prenatal genetic diagnosis in 3000 amniocenteses, N. Engl. J. Med. 300:157, 1979. 15. Chandra, P., Nitowsky, H. M., and Marion, R.: Experience with sonography as an adjunct to amniocentesis for prenatal diagnosis of fetal genetic disorders, AM. J. 0BSTET. GYNECOL. 133:519, 1979. 16. Crandon, A. J., and Peel, K. R.: Amniocentesis with and without ultrasound guidance, Br. J. Obstet. Gynaecol. 86:1, 1979. 17. Romero, R., Jeanty, P., and Grannum, P.: A comparison of two techniques of sonographically guided amniocentesis. In preparation.