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Abstract
Preoperative cervical ripening reduces the morbidity of surgical termination, including haemorrhage, incomplete uterine evacuation, uterine perforation, and cervical trauma (mackenzie and Fry, 1981).
Cervical ripening is commonly stimulated in induction of labour or to enable surgical evacuation of uterus (Shultz et al., 1983).
Prostaglandins are the current pharmacological method of choice for induction of cervical ripening and are usually administered into the posterior fornix of the vagina. Prostaglandins act on the connective tissue stroma and lead to disintegration and dissolution of collagen as evidenced by proline uptake (El-Refaey et al., 1994).
The ideal cervical ripening agent would induce cervical remodeling without stimulating uterine activity and nitric oxide donors are such agents. Nitric oxide donors relax the myometrium while inducing cervical ripening (Norman, 1996). These agents could therefore be used as an alternative to prostaglandins to induce cervical ripening before intrauterine procedures in the first trimester, thereby avoiding the side effects associated with prostaglandins (Thomson et al., 1997).
Nitric oxide (NO) releasing drugs are a novel class of effective and safe agents for cervical ripening. Several chemical donors of NO are currently being used in a various types of experimental and therapeutic studies (Anggard, 1994).
The NO donor, isosorbide dinitrate is effective at inducting cervical ripening during first trimester, prior to surgical termination of pregnancy (Thomson et al., 1997).
There is a clinical evidence of cervical ripening in women with missed abortions in response to administration of 80mg isosorbide dinitrate with a clear therapeutic benefits and less non-serious adverse events than prostaglandin analogues (Troncoso et al., 2005).
The aim of this study was to compare between vaginally administrated isosorbid dinitrate (NO donor) and misoprostol prior to surgical evacuation of first trimesteric missed abortion as regards efficiency and safety.
This study was performed at Ain Shams University, Maternity Hospital from March to September 2006. Sixty women with missed abortion admitted from outpatient clinic and reception room and referred for evacuation of retained products of conception were included in the study. Written informed consent was obtained from every patient and this randomized clinical trial was approved by the ethics committee of the hospital.
Women with the following characteristics were included: a first trimester pregnancy, no evidence of cervical change, no history of hypotension and ultrasound evidence of a gestation sac and a non-viable embryo.
The patients involved in this study were subdivided randomly into 2 equal groups each group 30 patients.
Group I: (isosorbide dinitrate group) in which 80mg iosorbide dinitrate 4 tablets (dinitra, E.I.P.C.O.) were applied deeply in the posterior vaginal fornix 6 hours prior to surgical evacuation and curettage.
Group II: (Misoprostol group) in which 800g misoprostol (Misotac, Segma) (4 tablets) were applied deeply in the posterior vaginal fornix 6 hours prior to surgical evacuation and curettage.
During these 6 hours, the patient was kept under close observation for the vital data and development of vaginal bleeding or lower abdominal colicky pain or headache.
After 6 hours (or if active vaginal bleeding developed) the patients (of both groups) were admitted to the theatre for dilatation and evacuation operation under general anesthesia. The pre-operative (post-treatment) cervical canal diameter was measured using the greatest diameter of Hegar dilator that could be introduced through internal Os without resistance.
In this study it was found that there was a significant statistical difference between the two groups as regards the post treatment internal Os diameter (the mean post treatment internal Os diameter was 5.47mm and 8.85mm in group I and group II respectively). On the other hand, there was a significant statistical difference between the two groups as regards the consistency of the cervix which was found to be more soft if it was pretreated with isosorbide dinitrate (group I).
The explanation of these results is that, although the NO donors considered as ideal ripening agents which induce cervical remodeling without stimulating the uterine activity, the relaxing effect on the uterus is not desirable in the first trimester prior to surgical evacuation when uterine contractions help in dilatation of the cervix and expulsion of the products of conception up to even the occurrence of inevitable abortion.
The current study shows that the incidence of occurrence of inevitable abortion was significantly higher in misoprostol group and in contrast to isosorbide dinitrate the uterotonic effect of misoprostol in the first trimester plays an important role in cervical dilatation.
It was concluded that vaginal administration of 800g misoprostol is more effective than 80mg isosorbide dinitrate in achieving cervical dilatation