Treatment of preterm labor with the beta-adrenergic agonist ritodrine

BACKGROUND

Beta-adrenergic agonists are commonly used to arrest premature labor. Although treatment of preterm labor with these agents can delay delivery by 24 to 48 hours, the potential risks and benefits to the mother and infant before and after delivery have not been adequately assessed.

METHODS

We randomly assigned 708 women with preterm labor at six hospitals to receive an intravenous infusion of either the beta-adrenergic agonist ritodrine (n = 352) or placebo (n = 356). Assignment was made with stratification according to four categories of gestational age (20 to 23 weeks, 24 to 27 weeks, 28 to 31 weeks, and 32 to 35 weeks). The primary objective was to assess the effect of ritodrine on perinatal mortality. Secondary objectives were the evaluation of the causes of perinatal death, the extent to which delivery was delayed with ritodrine, and the effects on birth weight, maternal morbidity, neonatal morbidity, and infant morbidity at 18 months of postnatal age, corrected for preterm delivery.

RESULTS

Among the 771 infants born to the women in the study (including 63 pairs of twins), there were 23 deaths (6.1 percent) in the ritodrine group and 25 deaths (6.4 percent) in the placebo group (event-rate difference, -0.3 percent; 95 percent confidence interval, -3.7 percent to 3.1 percent). There was no difference between the groups in the extent of delay of delivery, the incidence of delivery before 37 weeks' gestation, the proportion of babies weighing less than 2500 g, or measures of neonatal morbidity. Maternal morbidity (such as chest pain and cardiac arrhythmias) occurred more frequently but not exclusively in the ritodrine group. One infant born to a woman in the ritodrine group and five infants born to women in the placebo group had cerebral palsy (P = 0.09). There was a slight but not significant trend toward an improved score on the Bayley Psychomotor Development Index at 18 months of age among the infants of the ritodrine-treated women.

CONCLUSIONS

We found that the use of ritodrine in the treatment of preterm labor had no significant beneficial effect on perinatal mortality, the frequency of prolongation of pregnancy to term, or birth weight.

Ritodrine-induced agranulocytosis

This is the first reported case of development of agranulocytosis induced by continuous intravenous infusion of a large quantity of ritodrine hydrochloride for tocolysis. It is suspected that the pathophysiological mechanism is a dose-related toxic reaction and a cell loss maturation process of myelocytes.

[Effect of some drugs on physiological icterus in the newborn]

The Authors have correlated neonatal jaundice with the administration of oxytocin and prifinium bromide to the mother either alone or in association during labour. The percentage of neonatal jaundice in women treated with ritodrine hydrochloride during the second and third trimester of pregnancy was also calculated. A total of 1.101 deliveries were taken into consideration between January 1984 and June 1986. Thirty-three patients were treated with oxytocin alone; 444 patients with oxytocin and prifinium bromide; 81 patients with ritodrine hydrochloride during the second and third trimesters of pregnancy, and 192 patients were untreated. This study indicates that all drugs may contribute to producing neonatal jaundice, as shown in the graphs, and drugs during labour should be used with extreme caution and be limited in quantity and period.

Comparison of nifedipine and ritodrine for the treatment of preterm labor

Treatment of preterm labor with beta-sympathomimetics has been questioned because of the many maternal and fetal complications associated with its use. Nifedipine, a calcium antagonist, has been shown to suppress uterine activity in vitro and in vivo. A randomized prospective study was performed to compare the efficacy of nifedipine to ritodrine in the suppression of preterm labor. Data obtained from 42 women, of which 19 were randomized to the ritodrine group and 23 to the nifedipine group, were analyzed. Ritodrine and nifedipine proved to be equally effective in the suppression of preterm labor. However, the nifedipine group had fewer maternal and fetal complications.

Acute cutaneous vasculitis associated with prolonged intravenous ritodrine hydrochloride therapy

A patient with twin gestation was hospitalized because of preterm labor and treated with intravenous ritodrine hydrochloride (Yutopar, Astra Pharmaceutical Products, Westborough, Mass.). After greater than 4 weeks of therapy, the patient had a petechial rash and prolonged bleeding time, which were diagnosed and confirmed by skin biopsy at cesarean section as vasculitis. This is the first documented case of vasculitis associated with ritodrine use.

Outcome of very-low-birth-weight infants exposed to beta-sympathomimetics in utero

In this study we examined neonatal and early childhood outcomes after intrauterine exposure to beta-sympathomimetic agents on infants with birth weights less than or equal to 1500 gm. The hospital courses and anthropomorphic, developmental, and neurologic development of 201 infants exposed to one or more beta-sympathomimetic agents (isoxsuprine, 33; ritodrine, 70; terbutaline, 43; combination, 55) were analyzed and compared with those of 130 control infants of similar birth weight. One hundred and seventy-seven infants had follow-up to 1 year of age, 101 to age 3, and 58 to age 4. When treatments consisting of a single beta-sympathomimetic or no treatment were compared, there were no statistically significant overall differences found in growth and development or in most of the short-term measures of infant well-being. However, significant overall differences with no evidence of confounding by time-related effects were found for the following; mortality, none greater than terbutaline; maximum positive inspiratory pressure when respiratory distress syndrome was present, none greater than terbutaline; neonatal trauma, terbutaline greater than ritodrine. Other differences were found in conjunction with evidence of time-related confounding, or within specific time intervals. It should be noted that these differences are not necessarily due to effects of the different treatments, as the data are observational.

Effect of left-lateral position on maternal hemodynamics during ritodrine treatment in comparison with supine position

Pregnant women are generally recommended to rest in the left-lateral position (l-lat.) to avoid caval compression. We studied the influence of postural change from the supine position (sup.) to the l-lat. on maternal hemodynamics and tocolysis. The cardiac output (CO) was measured by impedance cardiography, while the pulsatility index of the uterine artery (PIUtA) was determined by the pulsed Doppler method. When the maternal posture was changed from sup. to l-lat, the following results were obtained. (1) The frequency of uterine contractions (UC) (preterm labor = 92) was significantly reduced (p less than 0.01). (2) The resting uterine tonus (n = 5) was also significantly decreased (p less than 0.05). (3) In the cases showing a decrease in the frequency of UC, the CO value was significantly increased (p less than 0.01), whereas PIUtA was significantly decreased (p less than 0.01). It is concluded that the postural change from sup. to l-lat. resulted in a decrease in the frequency of UC and the resting uterine tonus and at the same time an increase in the CO and decrease in the vascular resistance of the uterine artery.

Randomized comparative trial of indomethacin and ritodrine for the long-term treatment of preterm labor

A randomized prospective trial was performed to compare the efficacy and safety of ritodrine and indomethacin in the long-term treatment of preterm labor. Forty patients with intact membranes in preterm labor at 23 to 34 weeks' gestation were randomized to receive either intravenous ritodrine or oral indomethacin as the first-line tocolytic agent. Successful intravenous ritodrine therapy was followed by oral terbutaline therapy, and indomethacin-treated patients continued to receive oral indomethacin. Treatment failures were defined as progressive preterm labor or patient intolerance, and these patients were treated with intravenous magnesium sulfate. Ritodrine and indomethacin were equally successful in delaying preterm birth as defined by interval to delivery, gestational age at delivery, delivery delayed greater than 7 days, attainment of 35 weeks of gestation, percentage of patients who required magnesium sulfate therapy, percentage of patients who were readmitted with premature rupture of membranes, absence of recurrent preterm labor, and infant birth weight. More than 80% of mothers who received ritodrine voiced complaints of beta-sympathomimetic side effects, and one patient discontinued treatment as the result of intolerance. There were minimal patient complaints with indomethacin use. No statistically significant differences were noted in neonatal outcome as defined by Apgar scores, umbilical cord pH, intensive care days, ventilator days, or neonatal deaths. However, three cases of primary pulmonary hypertension were observed in the indomethacin group. We had not previously observed this problem with short-term (24 to 48 hours) indomethacin therapy.

Type I second-degree AV block (Mobitz type I, Wenckebach AV block) during ritodrine therapy for preterm labor

A patient, while on intravenous ritodrine therapy for preterm labor, experienced an episode of acute chest pain. The electrocardiogram (ECG), which was read as normal prior to ritodrine infusion, demonstrated a type I second-degree AV block which disappeared upon discontinuation of ritodrine therapy. This case illustrates the need for close ECG monitoring during ritodrine treatment when clinical symptoms arise.

[Neurological manifestations in the vertebro-basilar system suggesting pregnancy toxemia]

Early CT scan showed a large hypodensity throughout midbrain. Brainstem auditory evoked potential showed initially an abolition of III and V pikes suggesting brainstem injury. Two days later neurologic examination and brain stem auditory evoked potential returned to normal. CT scan performed three weeks after the onset was normal. These finding suggest a vasospasm; in this case betasympathomimetic agents given two weeks before the onset of toxemia for preterm labor could lead to the vasospasm.

Safety and efficacy of combined ritodrine and magnesium sulfate for preterm labor: a method for reduction of complications

Ritodrine hydrochloride and magnesium sulfate used in combination for preterm labor tocolysis have been cited for yielding excessively high complication rates. A retrospective chart review was performed to assess the frequency of these complications and to determine whether tocolysis can be continued despite complications. Of 95 patients managed with dual tocolytics, 61 had side effects sufficiently serious to warrant cessation of tocolytic therapy for an overall complication rate of 64%. After evaluation for objective evidence of pathologic conditions, 41 (67%) patients were restarted on dual tocolytics without further complication. It was deemed inappropriate to restart tocolysis in 20 patients, resulting in a 21% rate of complications. This allowed a significant increase in the number of patients delivering after 36 weeks (19.5% versus 50%, p less than 0.02) and a decrease in neonatal intensive care unit days per infant (3 versus 15.5 days, p less than 0.02). This suggests that aggressive continued tocolysis with multiple agents can be safe and efficacious with appropriate evaluation.

Pulmonary edema during ritodrine tocolysis--a case report

A case of maternal pulmonary edema is presented as a late complication after intravenous administration of ritodrine in combination with dexamethasone for the suppression of premature uterine contraction and for the stimulation of fetal lung maturity. Swan-Ganz catheterization showed normal pulmonary capillary wedge pressures. Two-dimensional echocardiography disclosed good ventricular performance. The patient recovered very soon in 2 days post termination of pregnancy. Relative fluid overload might probably be responsible for the development of pulmonary edema in this case.

A comparison of tocolysis with nifedipine or ritodrine: analysis of efficacy and maternal, fetal, and neonatal outcome

Nifedipine, a dihydropyridone calcium entry blocker, has been used with increasing frequency in the treatment of preterm labor. We studied 66 patients in this prospective, randomized trial to evaluate the efficacy and maternal, fetal, and neonatal outcome associated with tocolysis with nifedipine or ritodrine. Delivery was delayed for 48 hours, 7 days, and until the thirty-sixth week of gestation in 84%, 70%, and 41%, respectively, of patients in the nifedipine group, compared with 72%, 63%, and 52% of patients in the ritodrine group (difference not significant). Maternal side effects were more common and more serious in the group of patients who received ritodrine compared with those who received nifedipine (18 of 38 versus 5 of 38, p less than 0.01); however, fetal and neonatal outcome appeared to be similar when the groups were compared. On the basis of this study, it appears that tocolysis with either nifedipine or ritodrine is equally efficacious; however, maternal side effects are less common with nifedipine treatment. We conclude that nifedipine may have a role in the treatment of preterm labor but suggest further careful evaluation of this agent before it is considered for routine clinical use.

Nifedipine versus ritodrine for suppressing preterm labor

Fifty-eight women in preterm labor were selected randomly to receive either oral nifedipine or intravenous ritodrine hydrochloride. In comparison to ritodrine, nifedipine had similar tocolytic efficacy with fewer adverse maternal and fetal side effects. On Doppler studies nifedipine had an insignificant effect on umbilical blood flow. Preliminary data suggest that nifedipine is a safe, effective and well-tolerated tocolytic agent. It may prove to be a suitable alternative to ritodrine hydrochloride, especially for women in whom beta-sympathomimetics are contraindicated.

Effects of epinephrine and ritodrine in dogs with acute hyperkalemia

As plasma potassium concentrations, whether normal or elevated, can be reduced by intravenous administration of either epinephrine or ritodrine, the effects of these drugs were examined during acute hyperkalemia. Six anesthetized dogs were studied every 2 wk, on 18 separate occasions. Hyperkalemia was induced by intravenous infusion of potassium chloride, resulting in plasma potassium concentrations of 9.6 +/- 0.3 mEq/L (mean +/- SEM), bradycardia, and idioventricular rhythm. Dogs were then given slow intravenous injections every 30 min of either saline (controls), epinephrine, or ritodrine. Epinephrine doses were 0.01, 0.1, 1.0, 10, or 100 micrograms/kg; ritodrine doses were 0.1, 1.0, 10, 100, or 1000 micrograms/kg. At the highest does, both epinephrine and ritodrine caused clinically important decreases in plasma potassium, reducing concentrations to below 7.0 mEq/L. Ritodrine had a significantly greater effect than epinephrine. Side effects included hypertension and dysrhythmias with epinephrine, serious hypotension with ritodrine, and tachycardia with both drugs. For both drugs, the doses that caused a decrease in plasma potassium also caused an increase in heart rate and there was a correlation between plasma potassium levels and heart rate. Epinephrine and ritodrine may be useful in treating acute hyperkalemia, but cardiovascular side effects may occur. Increased heart rate could be used as an indicator of therapeutic effect and the magnitude of the increase in heart rate may be helpful in predicting the level of response.

Single doses of ritodrine delay orocaecal transit in patients with irritable bowel syndrome

The lactulose hydrogen breath test was used to assess the effect of a single dose of the beta 2-adrenoceptor agonist ritodrine on orocaecal transit time in 11 patients (three men) with irritable bowel syndrome. Transit time (median values, range) was significantly longer (P less than 0.01) after ritodrine than after placebo (120, 50-200 vs 75, 40-100 min). Median heart rate was similar before treatments whereas the maximal increase in heart rate was significantly greater (P less than 0.01) after ritodrine than after placebo.

Efficacy, safety and tolerance of oral sustained-release ritodrine given after intravenous administration in the treatment of premature labor

45 patients in premature labor entered the study, four dropped out for administrative reasons. The remaining 41 patients started all with an intravenous treatment followed by oral treatment with sustained-release ritodrine at a daily dosage of 120 mg per day until the 36th week of gestation. The mean gestational age at entry was 31.26 weeks +/- 3.27 and at delivery 37.76 weeks +/- 2.11 or a mean gain in days of 44.61 days +/- 20.85. A cluster analysis splitting the patients into four groups regarding the gestational age at entry and the Baumgarten tocolytic index showed that even the high-risk patients benefit remarkably by the treatment. The side effect rate was low as well for palpitation as for tremor. The patient compliance was excellent. No neonatal deaths or stillborns occurred during this study.

Pharmacokinetics of ritodrine administered intravenously: recommendations for changes in the current regimen

We define the pharmacokinetics of ritodrine in 13 pregnant women who received the drug intravenously. With constant infusion of 50 micrograms/minute, steady state ritodrine concentrations reached 28 +/- 11 ng/ml (SD) with a range of 15 to 45 ng/ml. This wide variation is a result of differences in plasma clearance, which ranged from 1.0 to 3.3 L/min, mean 1.94 +/- 0.71 L/min. The apparent volume of distribution was 6.95 +/- 3.54 L/kg, indicating that ritodrine is extensively bound to extravascular tissue. When an infusion of ritodrine is stopped, plasma concentrations fall rapidly initially with a distribution half-life of 5.9 +/- 6.0 minutes. After the initial rapid fall, plasma concentrations decrease more slowly with a mean disposition half-life of 156 +/- 51 minutes. On the basis of the pharmacokinetic parameters defined, we recommend that the current infusion regimen for ritodrine be changed. The infusion rate of ritodrine should start at 50 micrograms/minute rather than 100 micrograms/minute. The maximal infusion rate of 350 micrograms/minute should be increased and once labor is inhibited, the infusion rate should be reduced.

[Combination therapy of intravenous ritodrine and magnesium sulfate to inhibit premature labor]

Thirty-seven patients in premature labor with intact membranes were treated as follows. Ritodrine was given as a primary tocolytic agent and magnesium sulfate was added adjunctively when the uterine contractions could not be controlled even when the administration of ritodrine exceeded 250mmg/min (14 of 37 cases) (combination therapy group). Prolongation of pregnancy for more than 48 hours and delivery beyond 37 weeks were achieved in 89% and 68% respectively. These results were more satisfactory than those obtained with the isoxsuprine treated group (122 cases). The incidence of discomfort due to nasal obstruction was low in the ritodrine group, but side effects such as palpitation and hot flush occurred more commonly in the combination group. No life-threatening side effects were observed throughout this study. Twelve out of 37 cases (32%) were delivered before 37 weeks. Neonatal morbidity was more frequent in this group delivered before 33 weeks of gestation. These included respiratory distress, hypotension, hypoglycemia, and hypocalcemia. Moreover, two babies born from mothers treated with ritodrine and magnesium had ileus-like symptoms. These data suggest that this combination therapy is effective as far as the tocolytic purpose is concerned. However, special attention must be paid to adverse maternal and neonatal effects as well.

Efficacy and safety of indomethacin versus ritodrine in the management of preterm labor: a randomized study

One hundred six patients in preterm labor with intact amniotic membranes and gestational age less than or equal to 32 weeks were randomized to receive either ritodrine hydrochloride or a 48-hour course of indomethacin for tocolysis. The relative efficacy, maternal and neonatal safety, and costs were evaluated to determine which may be the more appropriate first-line pharmacologic agent used to manage preterm labor. Fifty-four patients and 52 patients were randomized to receive ritodrine hydrochloride or indomethacin, respectively. Ritodrine hydrochloride and indomethacin were equally effective in inhibiting uterine contractions and delaying delivery. Delivery was delayed for at least 48 hours in 83 and 94%, and for at least 7 days in 70 and 75% of patients receiving ritodrine or indomethacin, respectively. Tocolysis with indomethacin was associated with no maternal side effects, whereas tocolysis with ritodrine hydrochloride was associated with a 24% incidence of serious cardiovascular and metabolic adverse effects prompting discontinuation of the drug. There were no differences in outcome between the infants exposed to indomethacin versus ritodrine hydrochloride when delivered either remote from therapy or during therapy, except for a statistically higher serum glucose in the infants exposed to ritodrine hydrochloride when delivered during tocolytic therapy. There were no cases of premature closure of the ductus arteriosus or pulmonary hypertension. Tocolysis with indomethacin was 17 times less costly than tocolysis with ritodrine hydrochloride. For gestations less than or equal to 32 weeks complicated by preterm labor, indomethacin may be an appropriate alternative as a first-line tocolytic agent.

[Heart-specific L-myosin in pregnancy and tocolysis therapy]

Determination of light-chain (L-)myosin represents the currently most sensitive and specific method for detection of myocardial damage, which often was reported during tocolysis with betamimetics. Compared with 51 healthy pregnant subjects, it was not possible to demonstrate any pathologic increase in 14 patients, who underwent a tocolytic treatment with ritodrine-verapamil.

Cardiac isoenzymes and electrocardiographic changes during ritodrine tocolysis

To investigate the potential myocardial ischemic effects of ritodrine, we studied 36 singleton and four twin preterm pregnancies during ritodrine therapy. We serially determined serum creatinine phosphokinase (CPK-MB fraction) and lactic dehydrogenase isoenzymes and performed electrocardiography before and during ritodrine infusion and again within the first 24 hours of oral drug therapy. We observed that serum CPK-MB and lactic dehydrogenase isoenzymes remained within the normal range during therapy periods. The incidence of sinus tachycardia and non-specific T wave changes were 100% and 25%, respectively. In three of four twin pregnancies, ST-T segment depression in leads I, V4, V5, and V6 of the electrocardiogram was noted. Our study suggests that (1) the recommended ritodrine regimen does not produce direct myocardial damage, and (2) ritodrine may cause cardiac ischemia as determined by electrocardiography, which theoretically would progress to myocardial damage if not treated properly.

Dilemmas in the pharmacological management of preterm labor

It is the thesis of the author that the use of Ritodrine in the treatment of premature labor is potentially dangerous and possibly even lethal. Ritodrine is being overused in the attempt to control and delay premature labor. Only 25 to 50 per cent of patients complaining of premature labor pains actually proceed to true preterm labor. Because there is no definitive screening test to firmly establish the diagnosis of preterm labor, many women are treated unnecessarily with a drug that many obstetricians question as to its efficacy, safety, and cost. If it is used, it must be in a hospital with adequate facilities both in manpower and the ability to identify and treat the medical and obstetrical complications. Ritodrine is too potentially dangerous to be used as an attempt to "do something" it there are questionable indications.

Asthma in pregnancy complicated by iatrogenic pulmonary oedema

We report a unique case of near fatal acute pulmonary oedema developing with intravenous ritodrine, given in an attempt to suppress premature labour. The novel aspect of the case is that the patient had also been treated in the previous week with high dose nebulized beta-agonists for an episode of acute severe asthma, demonstrating that this idiosyncratic reaction to beta-adrenergic agents only occurs with the intravenous route of administration. The management of acute severe asthma occurring in pregnancy is discussed with a review of previous literature regarding possible mechanisms of beta 2-agonist-induced pulmonary oedema.

Umbilical cord prolapse: a true obstetrical emergency

The case of a 23-year-old woman with umbilical cord prolapse and fetal distress is described. This serious obstetrical complication is unfamiliar to many emergency physicians although it represents an acute emergency with high mortality. Appropriate prehospital, emergency department, and obstetrical suite care is discussed including a bladder-filling technique and tocolysis that can buy valuable time by temporarily relieving pressure on the cord.

Randomized comparison of oral terbutaline and ritodrine for preventing recurrent preterm labor

We compared oral ritodrine and terbutaline for the prevention of recurrent preterm labor. Women between 20 and 35 weeks' gestation who successfully completed a course of intravenous tocolysis were eligible for inclusion. One hundred two patients were randomized to oral ritodrine (20 mg every four hours) or oral terbutaline (5 mg every four hours). The groups showed no significant differences with respect to recognized risk factors for preterm labor or prognostic factors for the failure of tocolysis. Initial treatment failures occurred more frequently in the ritodrine group (nine vs. two, P = .0527). There were no statistically significant differences in the treatment results or frequency of side effects. We conclude that ritodrine appears to be less effective than terbutaline upon the initiation of oral therapy and that oral ritodrine and terbutaline are equivalent in safety and efficacy when used on a long-term basis for preventing recurrent preterm labor.

Acute pulmonary edema associated with the use of oral ritodrine for premature labor

We describe a patient who developed acute pulmonary edema while taking oral ritodrine for the treatment of premature labor and recovered after its discontinuation. The mechanism of development of pulmonary edema associated with beta-sympathomimetic agents is still not fully understood. Patients taking oral ritodrine should be observed for cardiopulmonary signs and symptoms.

Efficacy and side effects of magnesium sulfate and ritodrine as tocolytic agents

Ritodrine as the first-line drug in the treatment of established preterm labor has been supplanted in some centers by magnesium sulfate. To assess the relative efficacy and rates of side effects of these two agents, 120 patients were randomly assigned to receive one of these two drugs. Patients were included if they had intact membranes and met strict criteria for the definition of labor. In both groups excellent outcome was achieved, with 96.3% and 92.3% of patients receiving ritodrine and magnesium sulfate, respectively, obtaining a delay in delivery of greater than 48 hours. Side effects were comparable in both groups, although they tended to be more serious in the patients receiving ritodrine. In patients receiving both drugs together, the rate of side effects was 77% without a demonstrable benefit over a single agent. We conclude that ritodrine and magnesium sulfate are tocolytics of comparable efficacy and when used aggressively are highly successful in delaying delivery.

ST segment depression in paired electrocardiograms and serum electrolytes in pregnant women receiving intravenous ritodrine

Forty-three women admitted for preterm labor had electrocardiograms and serum potassium and glucose levels determined before and two and four hours after the initiation of intravenous ritodrine tocolysis. The ST segment depression found at two and four hours was significant but not dependent upon a fall in potassium or increase in the heart rate or glucose level. Such symptoms as chest pain and dyspnea were also not dependent upon potassium, glucose or heart rate changes. These findings support the concept of an intrinsic drug effect.

Pharmacodynamics and tolerance of oral sustained release ritodrine

A new oral sustained release formulation of ritodrine was tested for patient tolerance in this open study. The doses tested were 120 mg/day, 240 mg/day, and 360 mg/day. No objective toxicity was seen at any level. Doses of 120 mg/day and 240 mg/day were well-tolerated. Of the subjects who received the 360 mg/day dose, most tolerated it well.

Ritodrine-induced pulmonary edema unmasking underlying peripartum cardiomyopathy

Pulmonary edema was induced by an increase in the dose of ritodrine in a patient receiving the drug for 28 days because of preterm contractions. After initial therapy, the cardiologic evaluation revealed peripartum cardiomyopathy. This is the first report of ritodrine causing pulmonary edema by unmasking underlying asymptomatic cardiomyopathy. This may have been the cause of some of the previously reported cases of ritodrine-induced heart failure.

Anaesthesia for caesarean section in a parturient with quintuplet gestation, pulmonary oedema and thrombocytopaenia

The case of a 32-year-old parturient with a quintuplet pregnancy is described. The pregnancy had been complicated by premature labour which was treated with ritodrine tocolysis. Betamethasone was administered to hasten fetal lung maturation. The ritodrine therapy was complicated with fluid overload and pulmonary oedema requiring intravenous diuretic treatment. The patient presented urgently for Caesarean section, with fluid overload and worsening thrombocytopaenia. Life-threatening pulmonary oedema was manifest in the immediate preinduction period, following insertion of a pulmonary artery catheter and surgery was delayed to improve the mother's condition with intravenous diuretic therapy. Induction was carried out with the patient in the sitting position, with cricoid pressure maintained to protect the airway as the patient was lowered to a wedged, supine position. Intravenous nitroglycerin was used to control blood pressure. Low pressure mask-bag ventilation was utilized to maintain oxygen saturation and the patient was intubated and ventilated with positive end-expiratory pressure. Positive pressure ventilation was continued for 24 hours postoperatively. The perioperative course is reviewed and followed by a discussion of the anaesthetic considerations for multiple gestation pregnancies.

Comparison of oral ritodrine and magnesium gluconate for ambulatory tocolysis

Magnesium sulfate has been administered intravenously to arrest preterm labor but the oral form of this drug cannot be used for continual tocolysis. This trial involved the administration of oral magnesium gluconate to determine its effectiveness compared with that of ritodrine hydrochloride in 50 patients whose labor had been arrested by parenteral therapy. Group A (n = 25) received 1 gm of oral magnesium gluconate every 2 to 4 hours for tocolysis and group B (n = 25) received 10 mg of ritodrine every 2 to 4 hours. The number of patients who progressed to 37 weeks' gestation was similar (group A, 21 versus group B, 19) and the time gained in utero was not different (group A, 6.4 weeks versus group B, 5.9 weeks). There was a trend toward more side effects with the use of ritodrine (40%) compared with magnesium gluconate (16%), but the numbers were too small to reveal a significant difference. These data suggest that magnesium gluconate used as an oral tocolytic is as effective as a beta-agonist in patients whose labor is arrested initially with intravenous therapy.

Ventricular tachyarrhythmias during cesarean section after ritodrine therapy: interaction with anesthetics

This case illustrates that patients receiving ritodrine for preterm labor may risk interactions between the residual betamimetic effects of ritodrine and the effects of anesthetics during cesarean section. Such interactions may result in serious cardiovascular complications even after cessation of an infusion of ritodrine. Preoperative assessment should focus on cardiovascular status and serum potassium level. Delaying induction of anesthesia should be considered whenever possible. Careful fluid administration and cautious use of titrated doses of ephedrine are advised. After delivery of the infant, there should be no contraindication to the use of an alpha-adrenergic vasopressor such as phenylephrine to treat hypotensive patients with tachycardia.

Detection of cardiac events by continuous electrocardiogram monitoring during ritodrine infusion

Cardiac events in 30 patients in preterm labor on ritodrine therapy were examined continuously on a Holter monitor. Unsuspected events, such as persistent severe tachycardia, premature ventricular contractions, and supraventricular premature contractions, were observed. These events did not occur more frequently in patients with cardiac symptoms. None of these changes were observed by standard monitoring methods. Continued beta-mimetic stimulation in the presence of these events may lead to the serious cardiopulmonary complications that have been reported during ritodrine infusion.

A glycopyrrolate-ritodrine drug-drug interaction

This is a case report of a 39-year-old patient who developed supraventricular tachycardia secondary to a ritodrine-glycopyrrolate interaction. The cardiovascular effects of ritodrine as well as the possible mechanism for this interaction are discussed. Suggested treatment for ritodrine-induced tachycardia in the parturient are presented.

Intravenous ritodrine as a possibly provocative predictive test in gestational diabetes. A case report

A 24-year-old, nonobese, gestational diabetic woman developed diabetic ketoacidosis while receiving intravenous ritodrine therapy to suppress premature labor. This case emphasizes the necessity for close observation of any gestational diabetic during intravenous ritodrine tocolysis and suggests the possibility of predicting diabetes in pregnant patients exhibiting marked glucose intolerance during therapy.

Peripartum congestive cardiomyopathy and endocardial fibroelastosis associated with ritodrine treatment. A case report

Congestive cardiomyopathy from endocardial fibroelastosis occurred in a 24-year-old primigravida with a twin gestation and preeclampsia. The patient was taking ritodrine for premature labor. Cardiovascular evaluation should be performed during the course of ritodrine treatment, and no patient should be discharged if she does not have normal cardiovascular function.

Fasting hyperinsulinemic hypoglycemia after ritodrine therapy for premature labor

A 26-year-old woman with a triplet pregnancy was treated prophylactically with ritodrine beginning at 15 weeks' gestation. At 32 weeks, she was admitted in preterm labor, and over the next 12 days received high-dose oral or intravenous ritodrine. Three female infants were delivered by cesarean section after spontaneous rupture of the membranes. Postoperatively, she developed profound hypoglycemia with inappropriately high insulin levels. Maternal hypoglycemia after ritodrine therapy in pregnancy has not been reported previously. We discuss possible mechanisms.

Pulmonary edema as a delayed complication of ritodrine therapy. A case report

Pulmonary edema occurred 24 hours after intravenous ritodrine therapy and 10 hours after subcutaneous terbutaline therapy. Standard therapy directed at volume overload quickly cleared the pulmonary congestion, and the pregnancy progressed uneventfully to term. A retrospective review incriminated transfusion therapy and volume overload as the etiology.