Currently used oxytocin regimen outcome measures at term & postterm. II: Outcome indicators in relation to Bishop Score & other covariates

BACKGROUND

The effect of Bishop Score on labour induction outcome is extensively studied and partly known. However, the length of induction before failed induction declared is a controversial issue. Furthermore, to our knowledge, stratified Bishop Score in relation with stratified mode of delivery, induction initiation to vaginal delivery time, and variable cervical dilatation change among failed inductions were not assessed before. In literature, the maximum oxytocin in milliunit/minute also does vary from 20 to 42 milliunit/minute. Lack of published study assessing the separate oxytocin dose regimen for nulliparas and multiparas in Ethiopia, for which we could not find such regimen in literature, motivated us to review a two year case-series at term and post term.

OBJECTIVE

To evaluate the relation of Bishop Score and induction outcome measured by length of induction initiation-vaginal delivery time and modes of delivery in Gandhi and St. Paul's hospitals.

METHODS

Time lapsed to deliver vaginally or to declare failed induction, the maximum oxytocin level in milliunit/ minute infused before subjecting for abdominal delivery, length of induction and mode of delivery were some of the variables assessed.

RESULT

The Bishop score of 42.0% and 42.4% of the 552 women medically induced were assessed to have 0-5 and 6-8, respectively. Over all, among the 0-5 Bishop Score group, 45.7% were induction failures. To be specific, out of 157 total failures, 0-5 Bishop Score group accounted for 67.5% (P < 0.0001). Bishop score was found to have an inverse relation with failed induction, and negative correlation (r = -0.22) with length of labour among vaginal deliveries. Failure to bring about cervical dilatation and unable to establish adequate uterine contractions (45.2% and 54.8%, respectively) were the two reasons for failed inductions. Although the range was wide (2:50 - 21:0), the mean length of induction in hours in both nulliparas and multiparas prior to decision for failed induction was comparable (9:45 +/- 3:20 vs 9:25 +/- 2:55). The maximum oxytocin infused in mu/min for nulliparas and multiparas was 73.4 and 36.7 but was not linear; stepwise increase with each increase in the infusion rate was not the finding.

CONCLUSION

currently used oxytocin regimen protocol was associated with high induction failure.

Currently used oxytocin regimen outcome measures at term & postterm. I: Outcome indicators in relation to parity & indication for induction

INTRODUCTION

Although induction of labour with oxytocin is a daily practice at public as well as private health institutions, to the best of our knowledge, there is no published study on induction in Ethiopia.

OBJECTIVE

To assess the oxytocin dose required to achieve adequate uterine contraction, the time interval between initiation of oxytocin and adequate contraction achieved and the time lapsed between initiation of induction and vaginal delivery.

METHODOLOGY

A two-year retrospective case-series study was done to evaluate the currently used oxytocin regimen outcome measures at Gandhi and St. Paul's hospitals. Oxytocin level in milliunit/minute to achieve adequate uterine contraction, time lapsed to establish labour and deliver vaginally, Bishop Score, and indications for induction were some of the variables included.

RESULTS

Five hundred fifty two women induced at term and post term (55.8% nulliparas and 44.2% multiparas) were reviewed with overall elective to emergency induction ratio about 1:1. The first three indications for induction were post term (P < 0.05), term premature rupture of fetal membranes and hypertension (P = 0.005). Spontaneous vertex delivery (46.4%), caesarean section for failed induction (28.4%) and fetal distress (9.6%) were the top modes of delivery in both nulliparas and multiparas. Equal proportion of nulliparas and multiparas established labour (84.1% vs 84.8%) with mean oxytocin level in mu/min 33.6 +/- 21.9 and 17.2 +/- 11.4 and mean time lapsed in hours 2:10 +/- 1:30 and 2:10 +/- 1:10 between initiation of induction and adequate uterine contraction, respectively. More than two-thirds of multiparous and half of nulliparous women achieved adequate uterine contractions with 20-mu/min and less oxytocin infusion among the total women (84.4%) who were diagnosed to have adequate uterine contractions.

CONCLUSION

Although the starting, increment and maximum oxytocin regimen for nulliparas and multiparas were different but with parallel Bishop Score, the induction initiation to vaginal delivery time was almost comparable. Very high oxytocin dose for nulliparas wasn't superior to multiparas dose.

Critical appraisal of currently used oxytocin regimen and prospects

About half a century passed since synthetic oxytocin use to induce or augment labour came in to clinical practice; however, so far there is no international consensus on the dose regimen. In most studies, high dose regimen and long increment interval were found to have much desirable obstetric outcomes (short induction-to-delivery time, low caesarean section rate, less fetal and maternal risk). Although different centres use different starting and increment dose regimen, the stepwise increment till the maximum dose achieved (20 mu/min for low-dose and 42 mu/ min for high dose regimen) is the common feature. The oxytocin regimen practiced in Ethiopia is unique: different regimen is used for nulliparas and multiparas; half dose of induction is for augmentation; the maximum dose achieved at the middle of the cycle is nearly twice (74.3-85.4 mu/min) the maximum dose other centres use (42 mu/ min). Dose increment is also so bizarre and swinging. The maximum dose achieved at the middle of the three cycles is not maintained In general, to the best of author's accessible resources, the origin of this regimen is not clear and can not be traced to any scientific literature. Therefore, easily applicable regimen for Ethiopian set up is presented for clinical trail.