ajog.org
Letters to the Editors Elyce Cardonick, MD Cooper Medical School at Rowan University Camden, NJ [email protected]
The authors report no conflict of interest.
Marcy Gringlas, PhD Nemours/Alfred I. DuPont Hospital for Children Wilmington, DE [email protected]
1. Hunt E. Human intelligence. Cambridge: Cambridge University Press; 2001.
REFERENCE
ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ajog. 2015.01.036
RE: Cerebral autoregulation in different hypertensive disorders of pregnancy TO THE EDITORS: Because hypertension is one of the major complications linked to maternal death, there is a clear need for continued investigation. van Veen et al1 must be commended for their appropriate statistical analysis of the data on the subject. The transformations of the cerebral blood flow velocity are consistent with reliable standard methods.2 It was also relevant to measure the bilateral cerebral blood flow velocity to control for variation between the left and right hemispheres.2 Although the statistical analysis methods of the authors are appropriate for the tests, the issues with the study are due to data collection. To access the effects of pregnancy on chronic conditions accurately, several measurements spanning the maximal allowable proportion of the pregnancy should have been taken. The patients underwent testing only for a single 7-minute period. The importance of taking into account the temporal factor is only further validated by the number of patients with gestational hypertension and chronic hypertension that developed the more severe preeclampsia during the course of the study.1 This limitation is noted briefly in the discussion but could have been addressed easily by increasing the number of data collection points as permitted by the duration of the pregnancy. The second major methodologic shortcoming is that the researchers give little attention to a variety of additional confounders that complicate comparisons between groups. The hypertensive groups contained more patients with underlying diabetes mellitus than did the control group. This is problematic because type II diabetes mellitus has been shown to affect cerebral autoregulation even early in the disease,3 although there have been no comprehensive studies on the effects of gestational diabetes mellitus. The difference in the number of twin pregnancies between the groups further complicates analysis because differences in circulating angiogenic factors have been found between single and multiple fetus pregnancies.4 Little is known about how these factors affect the mother’s cerebral vasculature. Because the pathophysiologic condition of impaired cerebral autoregulation is largely undetermined, it is important that researchers implement stringent controls in studies that access its relationship to other conditions. These issues could have 832 American Journal of Obstetrics & Gynecology JUNE 2015
been avoided with stricter enrollment criteria that would have come at no additional cost to the researchers. Although clinical studies that lack substantial funding are often subject to limitations, it is important to address these shortcomings. The authors should consider addressing these issues more completely in any future investigational studies on the topic. Alyssa J. Rolfe, BS Florida State University College of Medicine Biomedical Sciences Tallahassee, FL [email protected] The authors report no conflict of interest.
REFERENCES 1. van Veen TR, Panerai RB, Haeri S, et al. Cerebral autoregulation in different hypertensive disorders of pregnancy. Am J Obstet Gynecol 2015;212:513.e1-7. 2. Brodie FG, Atkins ER, Robinson TG, Panerai RB. Reliability of dynamic cerebral autoregulation measurement using spontaneous fluctuations in blood pressure. Clin Sci 2009;116:513-20. 3. Kim YS, Immink RV, Stok WJ, Karemaker JM, Secher NH, van lieshout JJ. Dynamic cerebral autoregulatory capacity is affected early in Type 2 diabetes. Clin Sci 2008;115:255-62. 4. Maynard SE, Moore Simas TA, Solitro MJ, et al. Circulating angiogenic factors in singleton vs multiple-gestation pregnancies. Am J Obstet Gynecol 2008;198:200.e1-7. ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ajog. 2015.01.037
REPLY We thank Ms Rolfe for her comments. With respect to her suggestion of a need for increasing the number of data collection points, we agree and did mention this limitation within the article. Unfortunately, the length of time required to recruit, obtain informed consent, set-up, and complete data collection was nearly 30 minutes long. Given that the patients all volunteered for the study and were not compensated, coupled with balancing the time/financial burden on the participants, we chose to perform only this
Letters to the Editors Elyce Cardonick, MD Cooper Medical School at Rowan University Camden, NJ [email protected]
The authors report no conflict of interest.
Marcy Gringlas, PhD Nemours/Alfred I. DuPont Hospital for Children Wilmington, DE [email protected]
1. Hunt E. Human intelligence. Cambridge: Cambridge University Press; 2001.
REFERENCE
ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ajog. 2015.01.036
RE: Cerebral autoregulation in different hypertensive disorders of pregnancy TO THE EDITORS: Because hypertension is one of the major complications linked to maternal death, there is a clear need for continued investigation. van Veen et al1 must be commended for their appropriate statistical analysis of the data on the subject. The transformations of the cerebral blood flow velocity are consistent with reliable standard methods.2 It was also relevant to measure the bilateral cerebral blood flow velocity to control for variation between the left and right hemispheres.2 Although the statistical analysis methods of the authors are appropriate for the tests, the issues with the study are due to data collection. To access the effects of pregnancy on chronic conditions accurately, several measurements spanning the maximal allowable proportion of the pregnancy should have been taken. The patients underwent testing only for a single 7-minute period. The importance of taking into account the temporal factor is only further validated by the number of patients with gestational hypertension and chronic hypertension that developed the more severe preeclampsia during the course of the study.1 This limitation is noted briefly in the discussion but could have been addressed easily by increasing the number of data collection points as permitted by the duration of the pregnancy. The second major methodologic shortcoming is that the researchers give little attention to a variety of additional confounders that complicate comparisons between groups. The hypertensive groups contained more patients with underlying diabetes mellitus than did the control group. This is problematic because type II diabetes mellitus has been shown to affect cerebral autoregulation even early in the disease,3 although there have been no comprehensive studies on the effects of gestational diabetes mellitus. The difference in the number of twin pregnancies between the groups further complicates analysis because differences in circulating angiogenic factors have been found between single and multiple fetus pregnancies.4 Little is known about how these factors affect the mother’s cerebral vasculature. Because the pathophysiologic condition of impaired cerebral autoregulation is largely undetermined, it is important that researchers implement stringent controls in studies that access its relationship to other conditions. These issues could have 832 American Journal of Obstetrics & Gynecology JUNE 2015
been avoided with stricter enrollment criteria that would have come at no additional cost to the researchers. Although clinical studies that lack substantial funding are often subject to limitations, it is important to address these shortcomings. The authors should consider addressing these issues more completely in any future investigational studies on the topic. Alyssa J. Rolfe, BS Florida State University College of Medicine Biomedical Sciences Tallahassee, FL [email protected] The authors report no conflict of interest.
REFERENCES 1. van Veen TR, Panerai RB, Haeri S, et al. Cerebral autoregulation in different hypertensive disorders of pregnancy. Am J Obstet Gynecol 2015;212:513.e1-7. 2. Brodie FG, Atkins ER, Robinson TG, Panerai RB. Reliability of dynamic cerebral autoregulation measurement using spontaneous fluctuations in blood pressure. Clin Sci 2009;116:513-20. 3. Kim YS, Immink RV, Stok WJ, Karemaker JM, Secher NH, van lieshout JJ. Dynamic cerebral autoregulatory capacity is affected early in Type 2 diabetes. Clin Sci 2008;115:255-62. 4. Maynard SE, Moore Simas TA, Solitro MJ, et al. Circulating angiogenic factors in singleton vs multiple-gestation pregnancies. Am J Obstet Gynecol 2008;198:200.e1-7. ª 2015 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.ajog. 2015.01.037
REPLY We thank Ms Rolfe for her comments. With respect to her suggestion of a need for increasing the number of data collection points, we agree and did mention this limitation within the article. Unfortunately, the length of time required to recruit, obtain informed consent, set-up, and complete data collection was nearly 30 minutes long. Given that the patients all volunteered for the study and were not compensated, coupled with balancing the time/financial burden on the participants, we chose to perform only this
