1152
Letters
meter, as suggested to reduce bipolar sterilization failure: is not only unnecessary and nonscientific but can be counterproductive in closure of blood vessels. IO The majority of gynecologists do not use the ammeter. In our extensive experience we have not had any complications related to inadequate hemostasis. Finally, there is much science surrounding electrosurgery, but the techniques used and the instruments chosen by the individual surgeon will greatly determine the success or failure of a given procedure. In addition, many other variables influence the successful use of electrosurgery. These variables include power setting, wave form, electrode size, time, technology used, and tissue impedance. With so many variables, absolute answers are not possible. Reich suggests that end-point desiccation is a scientific measurement of complete coaptive desiccation, allowing the surgeon to make an objective decision of how much current is enough and when it is safest to divide the tissue. This implies an absolute answer. However, it is our opinion that it is possible to reach the impedance level that cuts off the current flow while viable tissue remains in the center. The ammeter simply measures the total impedance present within the circuit. It does not measure the viability of tissue. Whether a surgeon incorporates a visual end point or chooses to use the ammeter is more a question of personal preference and not one of absolute science. The greater concern is adequacy of training and experience. Neither technique is infallible. Camran Nezhat, MD, and Farr Nezhat, MD Center for Special Pelvic Surgery, Fertility and Endoscopy Center, Endometriosis Clinic, 5555 Peachtree Dunwoody Road, Atlanta. GA 30342
1.
2. 3. 4. 5. 6. 7. 8. 9. 10. II.
REFERENCES Shapiro HI, Adler DH. Excision of an ectopic pregnancy through the laparoscope. AM J OBSTET GYNECOL 1973;117:290-1. Gomel V. Laparoscopy in the diagnosis and treatment of ectopic gestation. Ginecol Dips 1975;2:85-7. Soderstrom RM, Levy BS, Engel T. Reducing bipolar sterilization failures. Obstet Gynecol 1989;74:60-3. Fontaine R, Herrmann LG. Clinical and experimental basis for surgery of pelvic sympathetic nerves in gynecology. Surg Gynecol Obstet 1932;54:133-63. Nezhat C, Nezhat F. Safe laser excision or vaporization of peritoneal endometriosis. Fertil Steril 1989;52: 149-51. Nezhat C, Nezhat F, Winer W. Salpingectomy via laparoscopy: a new surgical approach. J Laparosc Surg 1991;1:91-5. Nezhat C, Crowgey S, Garrison C. Surgical treatment of endometriosis via laser laparoscopy. Fertil Steril 1986;45:778-83. Nezhat C. Videolaseroscopy: a new modality for the treatment of endometriosis and other diseases of reproductive organs. Colposc Gynecol Laser Surg 1986;2:221-4. Nezhat C, Nezhat F. Incidental appendectomy during videolaseroscopy. AMJ OBSTET GYNECOL 1991;165:559-64. Sigel B, Dunn MR. The mechanism of blood vessel closure by high frequency electrocoagulation. In: Surg Gynecol Obstet 1965;121:823-31. Reich H. Laparoscopic oophorectomy without ligature or morcellation. Contemp Ob/Gyn 1989;34:34-46.
October 1992 Am J Obstet Gyneco1
Is the glucose challenge test really unnecessary? To the Editors: We have read with great interest the article by Neilson et al. (Neilson DR Jr, Bolton RN, Prins RP, Mark C, III. Glucose challenge testing in pregnancy. AM J OBSTET GVNECOL 1991; 164: 1673-9). The authors concluded that there was no benefit for glucose challenge testing. We have some concerns regarding possible methodologic flaws in the design of this study: 1. A high threshold value (150 mg/dl) was chosen for the glucose challenge test. This possibly resulted in allocation of patients with gestational diabetes into the control group, thus diminishing the difference (if any) between the control group and the study groups. This may explain the high incidence (14%) of macrosomia in the "normal" group. 2. All patients with abnormal glucose tolerance tests were treated. Therefore the negligible difference in macrosomia and cesarean deliveries may reflect successful treatment and not poor screening. 3. Interestingly enough, in their borderline group of patients (one abnormal value), the average birth weight was actually lower than in those with a normal glucose tolerance test. This is in contrast with two previous studies,,2 reporting an increased incidence of macrosomia and improvement with treatment. Is it possible that the obstetricians caring for these patients were familiar with these studies and informally prescribed a diet to these patients? We have also conducted a retrospective study comparing macrosomia in women with normal and borderline glucose tolerance test results. We had more patients (n = 32) with borderline values than in Neilson's study (n = 14). There were six neonates above the 90th percentile and one that weighed >4 kg. As in Neilson's study, our study did not demonstrate a significant difference in macrosomia. However, both studies did not have the power to show a difference. A sample of 400 patients in each group would be required to demonstrate a relative risk reduction of >25% (based on a error = 5%, ~ error = 20%, macrosomia in control group 7%, macrosomia in borderline group 14%). The authors' conclusion that postprandial glucose monitoring can be done in lieu of challenge testing is not supported by their data. In conclusion, we suggest that a large, well-designed prospective study is required to assess the value of glucose challenge testing. Debbie Butler, MD, Dan Farine, MD, and Denice S. Feig, MD Mount Sinai Hospital, University of Toronto, 600 University Ave., Toronto, Ontario, Canada M5G lX5
Reply To the Editors: We wish to thank Butler, Farine, and Feig for their interest in our article on glucose challenge testing. We specifically selected a high threshold value (150 mg/dl) because we believed this would increase specificity and should exaggerate the difference be-
Letters
meter, as suggested to reduce bipolar sterilization failure: is not only unnecessary and nonscientific but can be counterproductive in closure of blood vessels. IO The majority of gynecologists do not use the ammeter. In our extensive experience we have not had any complications related to inadequate hemostasis. Finally, there is much science surrounding electrosurgery, but the techniques used and the instruments chosen by the individual surgeon will greatly determine the success or failure of a given procedure. In addition, many other variables influence the successful use of electrosurgery. These variables include power setting, wave form, electrode size, time, technology used, and tissue impedance. With so many variables, absolute answers are not possible. Reich suggests that end-point desiccation is a scientific measurement of complete coaptive desiccation, allowing the surgeon to make an objective decision of how much current is enough and when it is safest to divide the tissue. This implies an absolute answer. However, it is our opinion that it is possible to reach the impedance level that cuts off the current flow while viable tissue remains in the center. The ammeter simply measures the total impedance present within the circuit. It does not measure the viability of tissue. Whether a surgeon incorporates a visual end point or chooses to use the ammeter is more a question of personal preference and not one of absolute science. The greater concern is adequacy of training and experience. Neither technique is infallible. Camran Nezhat, MD, and Farr Nezhat, MD Center for Special Pelvic Surgery, Fertility and Endoscopy Center, Endometriosis Clinic, 5555 Peachtree Dunwoody Road, Atlanta. GA 30342
1.
2. 3. 4. 5. 6. 7. 8. 9. 10. II.
REFERENCES Shapiro HI, Adler DH. Excision of an ectopic pregnancy through the laparoscope. AM J OBSTET GYNECOL 1973;117:290-1. Gomel V. Laparoscopy in the diagnosis and treatment of ectopic gestation. Ginecol Dips 1975;2:85-7. Soderstrom RM, Levy BS, Engel T. Reducing bipolar sterilization failures. Obstet Gynecol 1989;74:60-3. Fontaine R, Herrmann LG. Clinical and experimental basis for surgery of pelvic sympathetic nerves in gynecology. Surg Gynecol Obstet 1932;54:133-63. Nezhat C, Nezhat F. Safe laser excision or vaporization of peritoneal endometriosis. Fertil Steril 1989;52: 149-51. Nezhat C, Nezhat F, Winer W. Salpingectomy via laparoscopy: a new surgical approach. J Laparosc Surg 1991;1:91-5. Nezhat C, Crowgey S, Garrison C. Surgical treatment of endometriosis via laser laparoscopy. Fertil Steril 1986;45:778-83. Nezhat C. Videolaseroscopy: a new modality for the treatment of endometriosis and other diseases of reproductive organs. Colposc Gynecol Laser Surg 1986;2:221-4. Nezhat C, Nezhat F. Incidental appendectomy during videolaseroscopy. AMJ OBSTET GYNECOL 1991;165:559-64. Sigel B, Dunn MR. The mechanism of blood vessel closure by high frequency electrocoagulation. In: Surg Gynecol Obstet 1965;121:823-31. Reich H. Laparoscopic oophorectomy without ligature or morcellation. Contemp Ob/Gyn 1989;34:34-46.
October 1992 Am J Obstet Gyneco1
Is the glucose challenge test really unnecessary? To the Editors: We have read with great interest the article by Neilson et al. (Neilson DR Jr, Bolton RN, Prins RP, Mark C, III. Glucose challenge testing in pregnancy. AM J OBSTET GVNECOL 1991; 164: 1673-9). The authors concluded that there was no benefit for glucose challenge testing. We have some concerns regarding possible methodologic flaws in the design of this study: 1. A high threshold value (150 mg/dl) was chosen for the glucose challenge test. This possibly resulted in allocation of patients with gestational diabetes into the control group, thus diminishing the difference (if any) between the control group and the study groups. This may explain the high incidence (14%) of macrosomia in the "normal" group. 2. All patients with abnormal glucose tolerance tests were treated. Therefore the negligible difference in macrosomia and cesarean deliveries may reflect successful treatment and not poor screening. 3. Interestingly enough, in their borderline group of patients (one abnormal value), the average birth weight was actually lower than in those with a normal glucose tolerance test. This is in contrast with two previous studies,,2 reporting an increased incidence of macrosomia and improvement with treatment. Is it possible that the obstetricians caring for these patients were familiar with these studies and informally prescribed a diet to these patients? We have also conducted a retrospective study comparing macrosomia in women with normal and borderline glucose tolerance test results. We had more patients (n = 32) with borderline values than in Neilson's study (n = 14). There were six neonates above the 90th percentile and one that weighed >4 kg. As in Neilson's study, our study did not demonstrate a significant difference in macrosomia. However, both studies did not have the power to show a difference. A sample of 400 patients in each group would be required to demonstrate a relative risk reduction of >25% (based on a error = 5%, ~ error = 20%, macrosomia in control group 7%, macrosomia in borderline group 14%). The authors' conclusion that postprandial glucose monitoring can be done in lieu of challenge testing is not supported by their data. In conclusion, we suggest that a large, well-designed prospective study is required to assess the value of glucose challenge testing. Debbie Butler, MD, Dan Farine, MD, and Denice S. Feig, MD Mount Sinai Hospital, University of Toronto, 600 University Ave., Toronto, Ontario, Canada M5G lX5
Reply To the Editors: We wish to thank Butler, Farine, and Feig for their interest in our article on glucose challenge testing. We specifically selected a high threshold value (150 mg/dl) because we believed this would increase specificity and should exaggerate the difference be-
