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Commentary
The cause and effects of neonatal/infantile thymectomy The thymus, primary source of circulating T-lymphocytes, is located in the superior portion of the anterior mediastinum behind the sternum and in front of the major vessels.[1] Congenital open heart operations are required aortic arterial cannulation. During these operations, a thymectomy is preferred in order to avoid innominate vein injury and for a safe aortic cannulation, especially in patients in the 1st year of life due to the large volume of the thymus. The development of thymus is almost complete at birth, and reaches sufficient size and weight in the first 6 months following birth. In course of time, it becomes a structure composed of fatty tissues due to degeneration. This natural process (involution) occurs relatively early period of life. However, importance of the thymopoiesis beyond the initial production of Treg cells still remains a matter of debate.[1] In neonates, removal of the thymus results in a loss of thymus-derived Treg cells and a reduced number of circulating Treg cells.[2] Turan et al.[3] revealed the significant differences in mean lymphocyte numbers, and CD2, CD4, CD5, CD8, CD16 ratios between the patients who had neonatal thymectomy and age-matched healthy controls. Also, a significant decrease in T-lymphocytes and Treg cell receptor excision circles were found in children who underwent neonatal thymectomy, consistent with cessation of thymopoiesis.[4] It is expected that neonatal thymectomy might lead to adverse consequences on immune system.[5] Therefore, total thymectomy should not be performed to avoid early immunosenescence, as reported in an article (The immune system in infants thymectomized during surgical correction of congenital heart defects) published in this issue of the journal. Although thymectomy is tolerated in patients older than 6 months without any known adverse consequences,[3] the long-term effects of total thymectomy under certain conditions such as malignancies or infections still have not been proven.[6] Congenital cardiac operations have been routinely performed over 30-40 years. For the moment, thymectomized individuals are still not in older age groups. Therefore, to obtain invaluable data, all patients undergoing 148
neonatal thymectomy should be followed up throughout the whole life. In conclusion, considering the possible adverse consequences of total thymectomy in the aging process, we suggest that partial thymectomy should be preferred instead of total thymectomy in neonates/infants undergoing open heart surgery.
Hasan Ekim, Meral Ekim1 Departments of Cardiovascular Surgery, Bozok University School of Medicine, Yozgat, 1Department of Biochemistry, Bozok University, School of Health, Yozgat, Turkey Address for correspondence: Dr. Hasan Ekim, Department of Cardiovascular Surgery, Bozok University School of Medicine, Yozgat, Turkey. E-mail:
[email protected]
References 1. Appay V, Sauce D, Prelog M. The role of the thymus in immunosenescence: Lessons from the study of thymectomized individuals. Aging (Albany NY) 2010;2:78-81. 2. Schadenberg AW, van den Broek T, Siemelink MA, Algra SO, de Jong PR, Jansen NJ, et al. Differential homeostatic dynamics of human regulatory T-cell subsets following neonatal thymectomy. J Allergy Clin Immunol 2014;133:277-80.e1-6. 3. Turan T, Turan A, Arslan C, Kinoglu B, Sarioglu T. How does neonatal thymectomy affect the immune system? Acta Cardiol 2004;59:511-3. 4. Mancebo E, Clemente J, Sanchez J, Ruiz-Contreras J, De Pablos P, Cortezon S, et al. Longitudinal analysis of immune function in the first 3 years of life in thymectomized neonates during cardiac surgery. Clin Exp Immunol 2008;154:375-83. 5. Eysteinsdottir JH, Freysdottir J, Haraldsson A, Stefansdottir J, Skaftadottir I, Helgason H, et al. The influence of partial or total thymectomy during open heart surgery in infants on the immune function later in life. Clin Exp Immunol 2004;136:349-55. 6. Kamali K, Ghahartars M, Amirghofran AA. Evaluation of thymic changes after median sternotomy in children. Iran J Med Sci 2014;39:289-92. This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.
© 2015 Medical Journal of Dr. D.Y. Patil University | Published by Wolters Kluwer - Medknow
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How to cite this article: Ekim H, Ekim M. The cause and effects of neonatal/infantile thymectomy. Med J DY Patil Univ 2016;9:148-9.
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DOI: 10.4103/0975-2870.167996
Anesthetic management of a case of congenital diaphragmatic hernia; delayed diagnosis Sir, To complement the case report Anesthetic management of a case of congenital diaphragmatic hernia (CDH); delayed diagnosis by Joshi and George,[1] we would like to highlight the importance of antenatal ultrasonography for diagnosis of CDH. Congenital diaphragmatic hernia occurs in approximately 1 of 2200 live births and is associated with high degree of morbidity and mortality.[2] Most babies born with CDH die after birth with a survival rate of 67%.[3,4] Therefore, antenatal diagnosis plays a vital role for its diagnosis and early intrauterine management to reduce mortality. In the prenatal period, antenatal ultrasonography has a high sensitivity (>70%) in the detection of CDH.[5] The key feature of note on the ultrasound images is presence of bowel loops peristalsis in the chest. Ultrasonographic lung size assessment is best undertaken by the use of the observed/expected lung-to-head ratio.[5] Singh et al. found in their studies that 50% of CDH patients which were diagnosed with antenatal diagnosis before 25 weeks survived.[6] O’Mahony et al. found that CDH is a potentially correctable anatomical defect that continues to represent a significant cause of stillbirth and neonatal death.[7] In the study by Adzick et al. they found that most fetuses with detectable CDH died in the neonatal period (80% mortality), despite optimal conventional therapy.[3] Adzick et al. also commented on presence of polyhydramnios, which was both a common prenatal marker for CDH (present in 76% of fetuses) and a predictor for poor clinical outcome (only 11% survived).[3] Polyhydramnious is easily detected on antenatal ultrasound and can alert the sonologist regarding associated congenital anomalies. Fetus with CDH and polyhydroaminos if surgically intervened before birth can lead to improvement of their survival.[3]
Bronshitein et al. in their study suggested that the timing of visceral herniation into the thoracic cavity is also a major indicator for the prognosis of fetuses. They stated 46% of them who were diagnosed CDH before 16 weeks were aborted while 13% which were diagnosed 21-23 weeks gestation died after surgical repair. In contrast, 40% of infants whose visceral herniation was diagnosed after 24 weeks of gestation, and whose sonographic studies at 15-23 weeks had been normal, were alive and well after corrective surgery.[8] Thus normal sonographic studies during the first half of pregnancy do not exclude the subsequent development of CDH, and thereby stating the importance of serial sonography examinations during the later stages of gestation. Kotecha et al. concluded that in all cases, delivery should be planned at a tertiary perinatal center; in those with a poor prognosis (e.g., having other congenital abnormalities), termination of pregnancy may be considered. And for isolated CDH, antenatal therapy is an option.[5] Therefore, antenatal counseling is essential and should be conducted by a multidisciplinary team. Amniocentesis and genetic consultation to screen for chromosomal anomalies are advised due to its association with other congenital anomalies.[5]
Medical Journal of Dr. D.Y. Patil University | January-February 2016 | Vol 9 | Issue 1
Dhaval K. Thakkar, Amit Kharat, Amarjit Singh, V. M. Kulkarni Department of Radiodiagnosis, Dr. D. Y. Patil Medical College, and Research Centre, Pimpri, Pune, Maharashtra, India Address for correspondence: Dr. Dhaval K. Thakkar, 403, Alaknanda, Neelkanth Valley, Ghatkopar East, Mumbai - 400 077, Maharashtra, India. E-mail:
[email protected] 149
