Repercusión de las características de la episiotomía en los desgarros obstétricos del esfinter anal en los partos instrumentales

Abstract

INTRODUCTION AND OBJECTIVES Episiotomy is a surgical incision made in the perineum during delivery to facilitate expulsion. Liberal use in operative vaginal deliveries to prevent obstetric anal sphincter injuries (OASIs) is supported by large observational studies. There are three parameters that defined it: the distance from its introitus start to the vulvar fourchette, the angle, and its length; and exact placement is a modifiable risk factor for OASIs. Our objectives were to establish a correlation between the characteristics of the episiotomy at the time of incision and after suturing, select the suture pattern associated with a lower risk of OASIs in operative vaginal deliveries, and assess whether optimization with the use of Triepi-45 can prevent OASIs. MATERIAL AND METHODS This doctoral thesis is presented as a compendium of three published reports. Firstly, a prospective descriptive study with 45 primiparas, in which changes in the pre-marked perineum were analyzed using two digital photographs, one at rest and the other with the head crowning. Secondly, a retrospective case-control study with 958 operative vaginal deliveries that was reviewed in the puerperium, including those deliveries with an OASIs in the case group. And finally, a retrospective-prospective cohort study after the implementation of the use of Triepi-45, a device that allows marking with a 45º angle of the perineum at rest, with 986 instrumental deliveries in each group. RESULTS When the perineum is stretched during the expulsion, each marked line as well as its starting point at the vulvar fourchette moves laterally linearly, and without significant changes in angle and distance to points A and B. However, if we compared the original linear configuration at rest with imaginary lines from the fourchette to points A and B before delivery, the angle and distance increase statistically significantly. In the second study, we found that nulliparity, persistent occipitoposterior position, birthweight >3500g, an angle of episiotomy <30º, a distance episiotomy-fourchette <5mm and a distance of perineal body <30mm are independent risk factors for OASIs. Furthermore, only multiparous women do not benefit from any characteristic of the episiotomy, and an angle greater than 30º and a distance episiotomy-fourchette >5 mm are associated with a risk reduction of OASI in nulliparous, perineal bodies <30 mm and occipitoanterior position. In the last study, the intervention cohort had a lower incidence of OASIs than the preintervention cohort (7.1% Vs 9.4%), but the difference was not significant, owing to the low use of Triepi-45 in the intervention cohort (38% ). However, the OASIs incidence was significantly lower in the Triepi-45 cohort than in the pre-intervention cohort (4.8% vs. 9.4%; OR 0.47, CI: 0.26-0.86). CONCLUSIONS The distension caused by the fetal head during the expulsion causes a linear displacement of the perineum causing differences in the characteristics of the episiotomy between the incision and its suture. In order to reduce the risk of OASIs in instrumental deliveries, it is necessary to achieve an episiotomy suture angle of at least 30º; and in those nulliparous women, with perineal bodies less than 30 mm and with fetal positions in the occipitoanterior, they can also benefit from a lateralization of the episiotomy (increasing the distance to the vulvar fork to> 5mm). Use of Triepi-45 had a positive impact on reducing of up to 50% of OASIs in operative vaginal deliveries.