Use of nitroglycerin for uterine relaxation

General Surgery During Pregnancy and Gynecologic Emergencies

Nonobstetrical surgical emergencies can occur throughout pregnancy but are often difficult to diagnose due to the physiologic and anatomical changes that occur during pregnancy. Medical providers should have insight into these changes and be familiar with options for the diagnosis and management of common nonobstetrical surgical emergencies, such as appendicitis, cholecystitis, and small bowel obstruction. Surgeons should also be aware of obstetrical emergencies, such as ectopic pregnancy and severe vaginal bleeding, which may be life threatening to mother and the fetus. Intraoperatively, surgeons should be familiar with minimally invasive approaches for surgical diseases and special anesthetic considerations for pregnant patients.

A case of asymptomatic uterine incarceration in a patient undergoing dilation and evacuation

Uterine incarceration is a rare pregnancy complication that occurs when the uterine fundus becomes trapped beneath the sacral promontory. We present a case of incarceration in a patient seeking dilation and evacuation and a discussion of strategies for uterine reduction and cervical preparation.

Interventions of Postpartum Hemorrhage

Postpartum hemorrhage is a common and potentially life-threatening obstetric complication, with successful management relying heavily on early identification of hemorrhage and prompt intervention. This article will review the management of postpartum hemorrhage, including initial steps, exam-specific interventions, medical therapy, minimally invasive, and surgical interventions.

Subacute uterine inversion following an induced abortion in a teenage girl: a case report

Background

Subacute uterine inversion is a very rare complication of mid-trimester termination of pregnancy that should be considered in a situation where unsafe abortion occurs.

Case presentation

We present a case of subacute uterine inversion complicated by hypovolemic shock following an unsafe abortion in a 17-year-old nulliparous unmarried girl. She presented with a history of collapse, mass protruding per vagina that followed Valsalva, and persistent lower abdominal pain but not vaginal bleeding. This followed her second attempt to secretly induce an abortion at 18 weeks amenorrhea. On examination, she was agitated, severely pale, cold on palpation, with an axillary temperature of 35.8 °C, a tachycardia of 143 beats per minute and unrecordable low blood pressure. The abdomen was soft and non-tender with no palpable masses; the uterine fundus was absent at its expected periumbilical position and cupping was felt instead. A fleshy mass with gangrenous patches protruding in the introitus was palpated with no cervical lip felt around it. We made a clinical diagnosis of subacute uterine inversion complicated with hypovolemic shock and initiated urgent resuscitation with crystalloid and blood transfusion. Non-operative reversal of the inversion failed. Surgery was done to correct the inversion followed by total abdominal hysterectomy due to uterine gangrene.

Conclusion

Our case highlights an unusual presentation of subacute uterine inversion following unsafe abortion. This case was managed successfully but resulted in significant and permanent morbidity.

Development and characterization of polymer-coated liposomes for vaginal delivery of sildenafil citrate

Vaginal administration of sildenafil citrate has shown recently to develop efficiently the uterine lining with subsequent successful embryo implantation following in vitro fertilization. The aim of the present study was to develop sildenafil-loaded liposomes coated with bioadhesive polymers for enhanced vaginal retention and improved drug permeation. Three liposomal formulae were prepared by thin-film method using different phospholipid:cholesterol ratios. The optimal liposomal formulation was coated with bioadhesive polymers (chitosan and HPMC). A marked increase in liposomal size and zeta potential was observed for all coated liposomal formulations. HPMC-coated liposomes showed the greater bioadhesion and higher entrapment efficiency than chitosan-coated formulae. The in vitro release studies showed prolonged release of sildenafil from coated liposomes as compared to uncoated liposomes and sildenafil solution. Ex vivo permeation study revealed the enhanced permeation of coated relative to uncoated liposomes. Chitosan-coated formula demonstrated highest drug permeation and was thus selected for further investigations. Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) confirmed the successful coating of the liposomes by chitosan. Histopathological in vivo testing proved the efficacy of chitosan-coated liposomes to improve blood flow to the vaginal endometrium and to increase endometrial thickness. Chitosan-coated liposomes can be considered as potential novel drug delivery system intended for the vaginal administration of sildenafil, which would prolong system's retention at the vaginal site and enhance the permeation of sildenafil to uterine blood circulation.

Prehospital Breech Delivery with Fetal Head Entrapment -A Case Report and Review

We present a case in which an emergency medical services (EMS) crew was called for a precipitous breech delivery with fetal head entrapment that was unrelieved following standard prehospital interventions and eventually resulted in neonatal cardiac arrest and death. Although this is a rare occurrence, EMS responders must have adequate training and guidelines on how to assist with vaginal delivery of breech presentation and how to appropriately manage fetal head entrapment in the field. There is little literature to provide guidance but it appears that standard EMS teaching does not represent current best obstetrical practice. We review the available literature, make expert recommendations, and provide a sample new treatment guideline for basic life support, advanced life support, and EMS physician response.

The Effect of Glyceryl Trinitrate on Hypertension in Women with Severe Preeclampsia, HELLP Syndrome, and Eclampsia

OBJECTIVE

The goal of this study is to evaluate the effect of glyceryl trinitrate (GTN) in the management of hypertension in women with preeclampsia, eclampsia, and HELLP syndrome.

STUDY DESIGN

Fifty five women with preeclampsia, eclampsia, and HELLP syndrome administered GTN infusion for the management of hypertension were studied. Demographic, clinical, and perinatal outcome findings were collected for analyses. We recorded initial and maintenance doses of GTN, and duration of its use in prepartum and postpartum periods. We collected systolic and diastolic blood pressures (BPs) at admission and before the administration of GTN infusion. During the GTN infusion, we calculated average diastolic and systolic blood pressures 6 hours apart on the first day, 12 hours apart on the second day, and 24 hours apart on the third day.

RESULTS

Of 55 women, 24 with severe preeclampsia, 16 with HELLP syndrome, and 15 with eclampsia were included in this study. In severe preeclampsia group, GTN infusion significantly reduced systolic and diastolic BPs beginning from the second quarter and third quarter, respectively, of first day (p < 0.05). In the HELLP syndrome group, GTN infusion significantly decreased systolic and diastolic blood pressures beginning from the third quarter and second quarter, respectively, of the first day (p < 0.05). In the eclampsia group, GTN infusion significantly reduced systolic and diastolic blood pressures beginning from the third quarter and first quarter, respectively, of the first day (p < 0.05).

CONCLUSION

In women with severe preeclampsia, eclampsia, and HELLP syndrome, infusion of GTN can be used as an alternative agent to well-known drugs and causes no significant adverse effect to the mother and fetus.

Obstetric emergencies

Uterine rupture, uterine inversion, and pelvic lacerations/hematomas are all associated with increased risk for hemorrhage at the time of delivery. Certain clinical factors will increase the likelihood that these complications will occur, and clinical management can be adapted to reduce risk. Prior cesarean section is a significant risk factor for uterine rupture, with the degree of risk directly related to the location and quantity of prior uterine incisions. Obstetric trauma is another independent risk factor for uterine rupture. In turn, uterine inversion has traditionally been associated with overly aggressive management of the third stage of labor. The forces of normal labor and delivery will sometimes result in lacerations and hematomas of the lower genital tract. Except for the most superficial tears, these lacerations require surgical repair to restore proper anatomical appearance and support and to limit blood loss. Trauma in pregnancy remains one of the major contributors to maternal and fetal morbidity and mortality.

Randomized double-blind placebo-controlled trial of transdermal nitroglycerin for preterm labor

OBJECTIVE

Despite advances in perinatal medicine, the incidence of preterm birth continues to increase. The primary goal of tocolytic therapy is to reduce neonatal morbidity and mortality. While studies have demonstrated a prolongation of pregnancy, no tocolytic has been shown to improve neonatal outcomes. The objective of this randomized placebo-controlled trial was to determine the effect of transdermal nitroglycerin on neonatal outcomes in women who present in preterm labor.

STUDY DESIGN

We randomized 153 women in labor between 24 and 32 weeks to receive either transdermal nitroglycerin or placebo patches. The primary outcome was a composite of neonatal morbidity (chronic lung disease, intraventricular hemorrhage, periventricular leukomalacia, necrotizing enterocolitis) and mortality. Secondary outcomes included birth within 48 hours, birth before 28, 34, and 37 weeks, number of doses of antenatal corticosteroids received, side effects, and adverse events.

RESULTS

Infants born to transdermal nitroglycerin treated mothers (n = 74) had a statistically significantly reduced composite outcome compared to placebo treated mothers (n = 79) (relative risk 0.29 [95% confidence interval 0.08, 1.00] [p = 0.048]; risk difference -0.10 [95% confidence interval -0.19, -0.01); number needed to treat 10 [95% confidence interval 5, 100]). Birth prior to 28 weeks was reduced (relative risk 0.50, 95% confidence interval 0.23, 1.09). Transdermal nitroglycerin caused significantly more maternal side effects (relative risk 1.41, 95% confidence interval 1.06, 1.86).

CONCLUSION

Transdermal nitroglycerin may reduce neonatal morbidity and mortality as a result of decreased risk of birth before 28 weeks.

Frequently asked questions on tocolytics

The majority of drugs that are used today for tocolysis have been developed for clinical conditions other than preterm labour. Obstetricians started to use these drugs as tocolytics because of their additional influence on uterine smooth muscle relaxation, accepting their cardiovascular (side) effects. Because the majority of these drugs are used off label, today's strict criteria to evaluate drugs for their predominant use in pregnancy have not been applied; therefore, we also lack sufficient peri- and neonatal follow up data for these drugs. This problem is compounded as our understanding of the regulation of myometrial smooth muscle contraction and relaxation is still incomplete.

Therapeutic interventions targeting the nitric oxide system: current and potential uses in obstetrics, bone disease and erectile dysfunction

Nitric oxide is involved in a countless number of physiological processes and is known to have cytoprotective as well as cytotoxic effects. Increased knowledge about the multifaceted role of nitric oxide in a variety of disease states has led to the design of multiple treatment strategies involving the nitric oxide system. The current review focuses on recent research advances in the fields of obstetrics, bone disease and erectile dysfunction that have led to current or potential future therapies involving nitric oxide.

Sublingual nitroglycerin versus placebo as a tocolytic for external cephalic version: a randomized controlled trial in parous women

OBJECTIVE

The purpose of this study was to evaluate the efficacy of sublingual nitroglycerin as a tocolytic agent for external cephalic version in parous women.

STUDY DESIGN

A double-blinded randomized controlled trial was performed. Patients with parity of >or=1 at 36 to 40 weeks of gestation who were eligible for external cephalic version were included. Patients were randomized to receive either two sublingual sprays of 400 mug of nitroglycerin or two sprays of placebo 3 minutes before the trial of external cephalic version. Rates of successful external cephalic version and side effects were compared between groups.

RESULTS

Of 99 patients in the study, 50 patients received sublingual nitroglycerin, and 49 patients received placebo. There were no differences in maternal age, gestational age, estimated fetal weight, amniotic fluid index, and placental location between the two groups. The success rate of external cephalic version was 48% in the nitroglycerin group compared with 63% in the placebo group (P=.13). There was a higher incidence of headaches in the nitroglycerin group (42% vs 4%, P<.001).

CONCLUSION

Sublingual nitroglycerin was associated with a higher rate of headache and did not improve the rate of successful external cephalic version.

Steady-state maternal and fetal plasma concentrations of glyceryl trinitrate (GTN) in the preterm sheep

The administration of glyceryl trinitrate (GTN; nitroglycerin) is increasing during preterm pregnancies, yet its disposition and, importantly, the extent of fetal exposure remain to be elucidated. When used as a tocolytic (pharmacological agent that stops uterine contractions), it is administered transdermally (24–48 h). Here, we quantified the maternal and fetal steady-state plasma concentrations of maternal intravenous GTN in preterm sheep and continuously monitored maternal and fetal vascular parameters to observe possible dose-dependant vascular effects. Preterm (120 days gestation) pregnant sheep (n = 6) were instrumented with maternal femoral arterial (MA) and venous (MV) and fetal femoral arterial (FA) and umbilical venous (UV) polyethylene blood-sampling catheters. During maternal GTN infusion (3.0 µg·kg–1·min–1, 60-min duration) the steady-state GTN concentrations ([GTN]) were as follows: MA, 98.6 ± 9.0 nM; UV, 17.4 ± 7.6 nM; and FA, <5 nM. There were no changes in maternal and fetal mean arterial pressure and heart rate or in uterine activity. Overall, the steady-state [GTN] was established by 5 min, and the UV/MA ratio of [GTN] was 0.18. The FA [GTN] (<5 nM) indicates that the fetus cleared essentially all GTN in the UV, and the maternal and fetal heart rate and mean arterial pressure appear to be independent of maternal GTN infusion.Key words: nitroglycerin, pharmacokinetics, maternal-fetal exchange, pregnancy, cardiovascular.

Sublingual nitroglycerin versus intravenous ritodrine as tocolytic for external cephalic version: a double-blinded randomized trial

OBJECTIVE

The purpose of this study was to compare the efficacy of sublingual nitroglycerin with that of intravenous ritodrine as a tocolytic agent for external cephalic version in nulliparous women.

STUDY DESIGN

We performed a double-blinded, randomized trial. Nulliparous patients, between 36 and 40 weeks of gestation, were assigned randomly to receive either (1) an intravenous infusion of ritodrine (111 microg/min) for 20 minutes, followed by two puffs of sublingual placebo or (2) an intravenous infusion of sodium chloride 0.9% (placebo) for 20 minutes, followed by two puffs of sublingual 0.4 mg of nitroglycerin. Three minutes after the administration of the sublingual spray, an external cephalic version was attempted. The rate of successful external cephalic version and side effects was compared between groups.

RESULTS

Of 74 randomly assigned patients, 38 patients received intravenous ritodrine, and 36 patients received sublingual nitroglycerin. Although not statistically significant, the rate of the successful external cephalic version was higher in the ritodrine group compared with the nitroglycerin group (45% vs 25%, P =.075). The rate of headaches was higher in patients who received nitroglycerin (28% vs 8%, P =.02). Mean blood pressure and maternal heart rate were lower in the nitroglycerin group 10 minutes after the administration of the medication. However, there was no significant difference in the rate of palpitations, hypotension, or fetal bradycardia between the two groups.

CONCLUSION

When compared with intravenous ritodrine, sublingual nitroglycerin was associated with a higher rate of headache, lower blood pressure, and a trend toward a lower rate of successful external cephalic version.

The pharmacokinetics of glyceryl trinitrate with the use of the in vitro term human placental perfusion setup

OBJECTIVE

The purpose of this study was to determine the pharmacokinetics of glyceryl trinitrate across the in vitro term human perfused placenta.

STUDY DESIGN

Peripheral placental lobules (n = 6) were dually perfused. The maternal side was perfused with glyceryl trinitrate (100 nmol/L) for 90 minutes. Serial samples from the fetal venous and maternal venous catheters were collected and assayed for glyceryl trinitrate and its vasoactive metabolites (1,2- and 1,3-glyceryl dinitrate) with gas chromatography. Fetal arterial perfusion pressure was continuously measured throughout. Data are expressed as the mean +/- SEM, with 1-way analysis of variance followed by a Newman-Keuls post-hoc test (P <.05).

RESULTS

The mean steady-state fetal venous:maternal side ratio of glyceryl trinitrate concentration was 18.5% +/- 3.7%. The 1,2-glyceryl dinitrate and 1,3-glyceryl dinitrate levels in the fetal venous samples and maternal venous samples were less than the lower end of the sensitivity range of the assay (<5 nmol/L). Fetal arterial perfusion pressure did not change with glyceryl trinitrate administration.

CONCLUSION

The glyceryl trinitrate in the fetal venous sample was approximately 18.5% of the glyceryl trinitrate in the maternal side in this preparation. The presence of glyceryl dinitrates in the maternal venous samples and the fetal venous samples indicates the capacity for placental biotransformation of glyceryl trinitrate. The data demonstrate that glyceryl trinitrate, at a tocolytic concentration, has the ability to cross the placenta but was not found to affect fetal arterial perfusion pressure.

The management of breech presentation at term

Three to four percent of singleton pregnancies at term are complicated by breech presentation. The management options are to offer external cephalic version, to perform planned caesarean section or to aim for vaginal birth. There has been an increasing reluctance, in many centres, to allow vaginal birth. The publication of the Term Breech Trial will almost certainly accelerate this trend. For many, the choice now lies between external cephalic version and elective caesarean section. Perhaps the focus should now be on increasing the rate of offering external cephalic version, increasing its uptake and also its success.

Glyceryl trinitrate and acute uterine relaxation: a literature review

The use of nitro-vasodilators for achieving rapid uterine relaxation in the resolution of obstetric emergencies has been documented for nearly 120 years. Glyceryltrinitrate (GTN) is the most commonly used nitro-vasodilator for this purpose, with the presumed mechanism of action being via nitric oxide and cyclic guanosine monophosphate (cGMP) mediated processes. GTN is known to release nitric oxide to effect smooth muscle relaxation and some dose response data is available for its vasodilator activity. Human myometrium is known to synthesize and respond to nitric oxide, with changes in the production of and sensitivity to nitric oxide being subject to the cyclical and gestational state of the uterus. Experimental data on the efficacy of GTN in reliably producing uterine relaxation is conflicting and inconsistent. A total of 32 studies and case reports on the use of GTN in achieving rapid uterine relaxation have appeared in the English language literature. Case reports are subject to reporting bias and prospective randomized controlled trials are not without design flaws. Indications for the use of GTN in achieving rapid uterine relaxation cover the antepartum, intrapartum and postpartum periods. The safety of GTN during obstetric emergencies appears high, with no adverse maternal or neonatal outcomes. To establish the efficacy of GTN in reliably achieving uterine relaxation, well designed randomized controlled trials in labouring women are required.

Delayed-interval delivery: extended series from a single maternal-fetal medicine practice

OBJECTIVE

Our purpose was to review the extended experience of a single maternal-fetal medicine practice with delayed-interval delivery.

STUDY DESIGN

We completed a retrospective review of our maternal-fetal medicine practice database from January 1991 through March 1999. Patients were derived from both primary and consultative practices. All patients were managed with tocolysis, antibiotics, and cerclage after delivery of the first fetus(es). Retained siblings were investigated by amniocentesis to exclude intra-amniotic infection.

RESULTS

Twenty-four consecutive patients had attempted delayed-interval delivery. Exclusion criteria for delayed-interval delivery included monochorionicity, abruptio placentae, severe preeclampsia, and the need for hysterotomy. The mean latency interval was 36 days, with a range of 3 to 123 days. Additionally, patients with previous cerclage(s) had significantly shorter mean latency intervals than patients without previous cerclage(s). Patients with long latency intervals (> or =49 days) had earlier births of the first fetus.

CONCLUSION

Selected multichorionic pregnancies may benefit from delayed-interval delivery. Patients with previous cervical cerclage(s) during the index pregnancy are less likely to achieve significant latency intervals. Even modest intervals between births of siblings at critical gestational ages can improve neonatal survival and decrease neonatal morbidity.

Three-week delayed delivery in a triplet pregnancy at full dilatation with aggressive tocolysis

We describe our aggressive management of a woman with a triplet pregnancy resulting from in vitro fertilization who presented at 22 weeks' gestation in labor with full cervical dilation. Successful multiagent tocolysis and delayed delivery of the two remaining fetuses after delivery of the presenting fetus led to an improved outcome for all three babies.

Regulation of uterine contraction: mechanisms in preterm labor

Preterm labor (PTL) is defined as uterine irritability accompanied by cervical dilation and/or effecement that occurs before 37 weeks gestation. In most cases, PTL becomes preterm delivery (PTD), accounting for 8% to 10% of births in the United States. Fetuses born before 37 weeks' gestation are at risk for a multitude of health and developmental problems. Most perinatal morbidity and mortality in the United States are caused by PTL. It is a costly problem, in both monetary and human terms. Although some risk factors have been identified, they by no means identify, in advance, every case of PTL and PTD. Despite the understandable emphasis on attempts to find and test risk factors that predict PTL, the ultimate benefit--preventing PTD--will come only from an understanding of the physiologic mechanisms of parturition and how to halt those processes when they occur too early. This article reviews current approaches to preventing PTD, describes the biology of myometrial contraction, and discusses recent progress from several laboratories including the authors' that may shed light on approaches to inhibit uterine contractility in the setting of PTL.

Controversies in tocolytic therapy

In general, tocolytic agents are effective in stopping uterine contractions and in temporarily delaying delivery. The benefit of stopping uterine contractions is dependent on the fetal status and gestational age. The rationale for stopping preterm labor is to improve neonatal outcome. At this time, the best way to improve neonatal outcome would be to assure delivery in a center capable of caring for a preterm infant and prescription of glucocorticoids to decrease the risk of respiratory distress syndrome and other neonatal complications. Intravenous tocolysis for premature labor has found a prominent place in the obstetrician's armamentarium. We recommend the use of magnesium sulfate as first-line therapy. When comparing maternal and fetal risks, side effects, and the safety profile, magnesium sulfate is superior to beta-mimetics; however, there are still significant problems with potential morbidity and mortality for both mother and fetus with any tocolytics. Adjunctive use of indomethacin with magnesium sulfate may be used through 32 weeks for up to 48 hours at a time. Most tocolytics are effective in stopping labor for 48-72 hours. None have been shown to decrease the rate of preterm delivery. Once the uterus is quiescent and intravenous tocolytics are stopped, prolonged use of tocolytics has not been shown to be effective in preventing preterm birth. Tocolytics have significant long-term side effects to the mother's cardiovascular system, carbohydrate metabolism, and the fetal cardiovascular system. Thus, the prolonged use of prophylactic tocolytics after cessation of intravenous medications is not recommended. Tocolytics may be an appropriate therapy during preterm labor vaginal bleeding, ruptured membranes, multiple gestation, or advanced cervical dilatation. In all situations, however, careful guidelines must be observed. These guidelines include: (1) maternal and fetal well-being must be established before tocolytic therapy; (2) causes of preterm labor should be evaluated and treated when possible; (3) the risk/benefit ratio for both the mother and fetus must be re-evaluated on an ongoing basis; (4) when tocolytics are given before pulmonary maturity, then antenatal corticosteroids also should be considered in every case; (5) long-term use of tocolytics is difficult to justify at this time; (6) the safest tocolytic should be used for the shortest amount of time possible. It is doubtful, because of the nature of tocolytics, that newer tocolytics will be developed that will eliminate the problems of preterm delivery. Preterm delivery is an end-stage symptom of a multifactorial disease. Preterm labor is one of the last symptoms in a cascade of biochemical events that lead to preterm delivery. The most appropriate way to end preterm delivery would be to prevent the causes that initiate the cascade that ends in preterm labor. Authors' Note: Literally hundreds of papers have been written in the last 30 years on tocoloysis. For the purposes of space, when studies are summarized in peer-reviewed articles, we have referenced the reviews instead of the individual studies.

Randomised, double-blind, placebo controlled pilot study assessing nitroglycerin as a tocolytic

Thirty-three women in preterm labour were randomised in a double-blind fashion to receive either transdermal nitroglycerin (n = 17) or placebo (n = 16). Both groups had significant (P < 0.001) change in the cervix prior to randomisation. The primary outcome measure was delivery within 48 hours of randomisation. Fewer women randomised to nitroglycerin treatment (6/17) were delivered within 48 hours, compared with the placebo treatment (10/16) (RR 0.56, 95% CI 0.27 to 1.19). This pilot study lends support to two case series published that suggest that transdermal nitroglycerin may be promising as a safe, effective means for tocolysis.