SINGLE-CENTRE RANDOMISED TRIAL OF RITODRINE HYDROCHLORIDE FOR PRETERM LABOUR

1293

SINGLE-CENTRE RANDOMISED TRIAL OF RITODRINE HYDROCHLORIDE FOR PRETERM LABOUR LEVENO DAVID S. GUZICK GARY D. V. HANKINS

KENNETH J.

VICTOR R. KLEIN DAVID C. YOUNG M. LYNNE WILLIAMS

of Maternal-Fetal Medicine, Department of Obstetrics and Gynecology, University of Texas Southwestern Medical School,

Division

Dallas, Texas, USA between 24 and 33 weeks’ and in preterm labour, rigidly gestation defined to include cervical dilatation plus regular uterine contractions, were randomly allocated to receive either intravenous ritodrine hydrochloride or no tocolytic treatment. Ritodrine treatment significantly delayed delivery for 24 hours or less but did not significantly modify the ultimate perinatal consequences of preterm labour.

Summary

106

women

Introduction EFFECTIVE methods for treatment of preterm labour have become major goals in modern obstetrics because preterm birth is the leading cause of neonatal morbidity and mortality. One cause of preterm birth, labour without ruptured membranes or other obstetrical complications requiring intervention, has been the focus during the past 15 - 20 years of pharmacological approaches aimed at inhibiting uterine contractions. Agents that have been employed include

ethanol, prostaglandin synthetase inhibitors,2 magnesium sulphate,3 various beta-adrenergic sympathomimetics,4 and calcium channel blocking drugs.5 A. TABOR AND OTHERS: REFERENCES 1.

Verp MS, Gerbie AB. Amniocentesis for prenatal diagnosis. Clin Obstet Gynecol 1981, 24: 1007-21.

2. Hook EB. Rates of chromosome abnormalities at different maternal ages. Obstet Gynecol 1981; 58: 282-85 3. Working party on amniocentesis. An assessment of the hazards of amniocentesis. Br J Obstet Gynaecol 1978; 85 (suppl 2): 1-41. 4. NICHD National Registry for amniocentesis study group. Mid-trimester amniocentesis for prenatal diagnosis Safety and accuracy JAMA 1976; 236: 1471-76. 5 Medical Research Council of Canada. Diagnosis of genetic disease by amniocentesis during the second trimester of pregnancy. Report no 5. Ottawa: Medical Research Council of Canada, 1977. 6. Obel EB. Risk of spontaneous abortion following legally induced abortion. Acta Obstet Gynaecol Scand 1980; 59: 131-37. 7. Nørgaard-Pedersen B, Bagger B, Bang J, et al Maternal serum-alphafetoprotein screening for fetal malformations in 28 062 pregnancies. A four-year experience from a low-risk area. Acta Obstet Gynaecol Scand 1985; 64: 511-14. 8. Hook EB. Spontaneous deaths of fetuses with chromosomal abnormalities diagnosed

prenatally. N Engl J Med 1978; 299: 1036-38. 9 Crandall

BF, Howard J, Lebherz TB, Rubinstein L, Sample WF, Sarti D. Follow-up of 2000 second-trimester amniocenteses. Obstet Gynecol 1980, 56: 625-28. 10. Elwood JM. Interpreting clinical trial results: Seven steps to understanding. Can Med Assoc J 1980; 123: 343-45 11. National Health Board. Medicinsk fødselsstatistik 1981. Copenhagen: S Jensen, Vitalstatistik 1985; 13: 1-110 12. Crane JP, Kopta MM. Genetic amniocentesis: Impact of placental position upon the risk of pregnancy loss. Am J Obstet Gynecol 1984, 150: 813-16. 13 Porreco RP, Young PE, Resnik R, et al. Reproductive outcome following amniocentesis for genetic indications. Am J Obstet Gynecol 1982, 143: 653-60. 14 Hanson FW, Tennant FR, Zorn EM, Samuels S. Analysis of 2136 genetic amniocenteses: Experience of a single physician. Am J Obstet Gynecol 1985; 152: 436-43. 15. Golbus MS, Loughman WD, Epstein CJ, Halbasch G, Stephens JD, Hall BD. Prenatal genetic diagnosis in 3000 amniocenteses. N Engl J Med 1979; 300: 157-63 16. Brock DJH, Barron L, Duncan P, Scrimgeour JB, Watt M Significance of elevated mid-trimester maternal plasma-alpha-fetoprotein values. Lancet 1979; i: 1281-82. 17 Wald NJ, Terzian E, Vickers PA, Weatherall JAC. Congenital talipes and hip malformation in relation to amniocentesis: A case-control study. Lancet 1983; ii: 246-49. 18. Hislop A, Fairweather DVI. Amniocentesis and lung growth: An animal experiment with clinical implications Lancet 1982; ii: 1271-72. 19. Vyas H, Milner AD, Hopkin IE. Amniocentesis and fetal lung development. Arch Dis Child 1982, 57: 627-28

Ritodrine hydrochloride, a beta-adrenergic substance, is the first and only agent approved for inhibiting uterine contractions in the United States. This approval was granted in October, 1980, by the Food and Drug Administration and we subsequently organised a programme for introduction of ritodrine at our institution. This programme included study of the metabolic effects of ritodrine’ and investigation of its clinical effectiveness in preventing preterm birth. We believed that a study of clinical effectiveness was prudent because of conflicting results between and within published multicentre investigations.’-9 We describe here the results of a prospective, randomised, single-centre trial in which ritodrine treatment was compared with no treatment in labour at between 24 and 33 weeks’ gestation. Patients and Methods

Subjects for this study were from the population of women presenting to the obstetrics service at Parkland Memorial Hospital, Dallas, Texas, between July 1, 1982, and Aug 30, 1985. Criteria for enrolment included: (1) preterm labour defined by regular uterine contractions associated with cervical dilatation of at least 1 cm but not more than 4 cm; (2) gestational age between 24 and 33 weeks; (3) intact fetal membranes; or (4) no other maternal or fetal complications such as hypertension, diabetes, hyperthyroidism, haemorrhage, cardiac disease, previous caesarean section, chorioamnionitis, and fetal growth retardation. Women meeting these criteria were asked to participate and those giving written informed consent were enrolled in the investigation which was performed under the auspices of the Institutional Review Board on Human Research for the University of Texas Health Science Center at Dallas and Parkland Memorial Hospital. Use of ritodrine for tocolysis at our hospital was restricted to this investigation. Pregnancies were randomly assigned to treatment or control groups by means of a random number table with group allocation predetermined and placed in sealed envelopes. Those assigned to the treatment group received ritodrine hydrochloride (150 mg in 500 ml physiological saline) via an infusion pump. The initial dose of ritodrine was 100 pg/min and the dosage was increased in 50 J..Ig/min increments every 10 min until uterine contractions ceased or until a maximum dose of 350 µg/min was reached. The tocolytic or maximum dose was continued for 24 h after cessation of contractions. 30 min before intravenous ritodrine therapy was discontinued, 10 mg oral ritodrine was given. This was followed by 20 mg of oral ritodrine every 3 h, which was continued until 36 weeks’ gestation. Women with recurrent preterm labour at a later date were eligible for a second treatment with intravenous ritodrine. Women assigned to the control group received intravenous physiological saline at a rate of 80 ml/h for 24 h. This volume of saline infused per hour for the control group was selected to parallel the volume administered during ritodrine infusion in the above regimen and previously reported by us to be 87±24(SD) ml/h.6 All women enrolled in this study had continuous electronic fetal heart rate monitoring for 12 - 24 h and were observed in the labour suite for 24 h. Similarly, all undelivered women in both groups were admitted until 34 weeks’ gestation to the high-risk antepartum unit. Premature births were attended by senior house-officers assigned to the neonatal intensive care unit and corticosteroids were not used to enhance fetal lung maturity. Laboratory studies obtained in all women included real-time ultrasound examination, urinalysis, haematocrit, plasma creatinine, glucose, and electrolytes. Electrolyte estimations were repeated serially in women randomised to ritodrine treatment and these women also had electrocardiograms before treatment. Failure of therapy was registered if the fetal membranes ruptured, if cervical dilatation progressed beyond 4 cm, if contractions persisted for more than 30 min at the maximum ritodrine dose with continued cervical dilatation, or if maternal side-effects required discontinuation of the drug. Maternal heart rates in excess of 150 beats per min prompted reduction in the ritodrine dosage. Similarly, chest pain, vomiting, symptomatic hypotension,

1294 TABLE I-COMPARISON OF SELECTED CHARACTERISTICS FOR THE WOMEN AND THEIR PREGNANCIES

TABLE III-GESTATIONAL AGE AT DELIVERY, DAYS GAINED IN UTERO, MEAN NUMBER OF ANTEPARTUM HOSPITAL DAYS, AND FREQUENCY OF CAESAREAN SECTION

*Previous

birthweight

<2500

g.

TABLE U-GESTATIONAL AGE, CERVICAL CONDITION AND CONTRACTION INTERVAL AT STUDY ENTRY

*p<0.02;

no

other differences

are

statistically significant.

randomised to ritodrine treatment, however, delivered during the first study day than during all subsequent days

(chi-square 4-65, p<0 . 02). Selected

cardiac palpitations unacceptable to the patient reduction of the ritodrine dosage. If progressive reduction in dosage was ineffective in relieving these side-effects,

dyspnoea, prompted

or

ritodrine was stopped. For comparison of entry characteristics and outcome variables we used Student’s t or chi-square tests (continuous and categorical data, respectively). Results in which the probability of a type I error was <0.05

were

judged significant. Results

During the 3-year study 106 pregnancies were enrolled, 52 being randomised to the control group and 54 to the ritodrine group. Table I shows the clinical characteristics of the two study groups. 2 women in the ritodrine group and 3 in the control group had twin gestations. There were no significant differences between the two groups with respect to mean maternal age, parity, racial composition, or social habits. Similarly, there were no significant differences with respect to a history of a previous preterm birth or to clinic attendance. Table II shows gestational age, cervical condition, and contraction interval at study entry for pregnancies randomised to ritodrine treatment or control groups: there were no significant differences. Shown in table III are gestational ages at delivery, time gained in utero, mean number of antepartum hospital days, and frequency of primary caesarean section. When mean values or categorical distributions are compared in the aggregate there are no significant differences in any of the measures of pregnancy outcome. Significantly fewer women

neonatal

outcomes according to maternal in table IV. All the infants summarised group were liveborn and the numbers of female infants in the two study groups were identical. Infants of women randomised to the ritodrine treatment or control groups did not differ significantly with respect to birthweight, Apgar score at 5 min, total hospital days, or number of days spent in the intensive care unit. Also compared in table IV are the rates of neonatal morbidity and mortality. There were no significant differences in the incidence of any index of neonatal morbidity associated with preterm birth. Two infants of women treated with ritodrine died and there were four neonatal deaths among women assigned to the control group. These six neonatal deaths are further analysed in table V. Two infants, one each in the ritodrine and control groups (case numbers 2 and 3) died shortly after birth. The gestational age of these infants was assessed to be 24 weeks and they were not treatment

are

TABLE IV—SELECTED NEONATAL OUTCOMES

1295 TABLE V-NEONATAL DEATHS

study. This fact underscores both the exigencies of performing randomised studies in human beings and the narrow application of ritodrine tocolysis when limited to a subset of women whose only discernible complication is early for

women

preterm labour between 24 and 33 weeks’ gestation.’On the basis ofaprevious survey of low birthweight at our hospital, 12 we estimate that, at most, about 800 pregnancies (2%) would have

been

investigation.

eligible

for

However,

randomisation during this patients commonly declined

randomisation, and clinical developments before written could be obtained frequently excluded potential candidates. Such difficulties have made multicentre trials of ritodrine tocolysis, although undesirable in some respects, virtually unavoidable. Indeed, 106 randomised pregnancies may seem like a paltry number, but this number represents the largest single-centre randomised study comparing ritodrine treatment with no treatment. These observations serve to emphasise the difficulty in performing trials such as we now report and the difficulty in assessing the clinical benefits of ritodrine tocolysis. In our view, one of the most striking results of this investigation concerns the vagaries of diagnosing preterm labour. It was our intention carefully to define preterm labour to include cervical dilatation and regular uterine contractions. Indeed, 94 (89%) of the 106 women studied had cervical dilatation of 2 cm or more and some cervical effacement with a mean contraction interval of5 min. Despite this definition, labour ceased within 24 h in 52% of the control group and more than half-of the women in whom intravenous ritodrine was discontinued because of sideeffects continued their pregnancies for more than one month. Clearly, the diagnosis of preterm labour must be held suspect, even when carefully and rigidly defined. Importantly, how can the tocolytic effectiveness of a substance be measured when preterm labour may frequently

consent

RDS= Respiratory distress syndrome;

NEC=necronsmg

enterocolittS-

given aggressive neonatal care. Factors implicated in the remaining four neonatal deaths included respiratory distress, necrotising enterocolitis, intraventricular haemorrhage, and Klebsiella sepsis (case 6) that developed on the ninth neonatal day. The mean maximum intravenous ritodrine dosage for the 54 women receiving this treatment was 242 I.lg/min. Pulmonary oedema did not develop in any of these women. Ritodrine infusion was discontinued in 17 (32%) pregnancies owing to persistent side-effects that included chesrpain (12), symptomatic hypotension (3), and dyspnoea (2). Electrocardiograms in 2 women with chest pain showed STsegment changes consistent with myocardial ischaemia. An additional 6 women requested that ritodrine infusion be discontinued because of unacceptable cardiac palpitations. The average duration of ritodrine infusion before discontinuation because of side-effects was about 6 h. Delivery occurred within one day in 10 of the women after intravenous ritodrine was discontinued. Another 2 women continued their pregnancies for 17 and 18 days. The interval to delivery for the remaining women in whom ritodrine was discontinued averaged 42.9 days with a range of 30 - 69 days. These women did not receive oral ritodrine.

Discussion Our interpretation of the outcome results is that ritodrine delayed delivery for 24 h or less while not modifying the ultimate perinatal consequences of premature labour. Specifically, there were no significant differences in several measures

cease

This work was presented in part at the sixth annual meeting of the Society of Perinatal Obstetricians, San Antonio, Texas, Jan 30 to Feb 2, 1986.

Correspondence should be addressed to K. J. L., Department of Obstetrics Gynecology, University of Texas Southwestern Medical School, 5323 Harry Hines Boulevard, Dallas, TX 75235, USA.

and

of neonatal outcome that included gestational age at

delivery, birthweight, time in hospital, six indices of neonatal morbidity, and neonatal death. These results are strikingly similar to those of a pooled analysis of all published placebocontrolled trials of beta-mimetic drugs completed by King et all0 for the Royal College of Obstetricians and Gynaecologists.lo They found that beta-mimetics delayed delivery for 24 h but did not significantly change the incidence of delivery before 37 weeks’ gestation, birthweight less than 2500 g, respiratory distress syndrome, and perinatal

REFERENCES 1. Zlatnick

2. 3. 4

5. 6

death.

The

spontaneously?

Before the start of this investigation, it was our view that the effectiveness of ritodrine in preventing preterm birth was not convincingly established. The results as well as difficulties encountered in this investigation and, in particular, the seemingly haphazard propensity of preterm labour to stop with or without tocolytic treatment, have reinforced our belief that the effectiveness of ritodrine is questionable. We have no doubt that ritodrine acutely interferes with uterine contractions, but we were unable to demonstrate that this is beneficial.

completion. of this investigation was frustrating because, during a period in which 36 707 women were delivered at our hospital, we were able to enrol only 106

7

FJ, Fuchs F. A controlled study of ethanol in threatened premature labor Am J Obstet Gynecol 1972; 112: 610-12 Zuckerman H, Reiss V, Rubeinstein I Inhibition of human premature labor by indomethacin Obstet Gynecol 1974, 44: 787-92 Steer CM, Petrie RH A comparison of magnesium sulfate and alcohol for the prevention of premature labour Am J Obstet Gynecol 1977, 129: 1-4 Barden TP, Peter JP, Merkatz IR Ritodrine hydrochloride. A betamimetic agent for use in preterm labor I. Pharmacology, clinical history, administration, side effects and safety Obstet Gynecol 1980; 56: 1-6. Ulmsten U, Anderson KE, Wingerup L Treatment of preterm labor with calcium antagonist nifedipine Arch Gynecol 1980; 229: 1-5 Young DC, Toofanian A, Leveno KJ Potassium and glucose concentrations without treatment during ritodrine tocolysis Am J Obstet Gynecol 1983, 145: 105-06 Hesseldahl H. A Danish multicentre study of ritodrine in the treatment of preterm labor Dan Med Bull 1979, 26: 116.

1296

RECIPIENT LYMPHOCYTE SENSITIVITY TO METHYLPREDNISOLONE AFFECTS CADAVER KIDNEY GRAFT SURVIVAL E. LANGHOFF

J. LADEFOGED

B. K. JAKOBSEN L. P. RYDER

P. PLATZ

A. SVEJGAARD J. H. THAYSEN Medical Department P, Division of Nephrology, and

Tissue Typing Laboratory, Department of Clinical Immunology, Rigshospitalet, Copenhagen, Denmark

In 42 recipients of mixed-lymphocyteculture (MLC) incompatible cadaver kidneys and conventional immunosuppressive treatment (azathioprine and steroids) the concentrations of methylprednisolone suppressing the in-vitro response of

Summary

Patients and Methods Patients In the first part of the study, the donor-specific MLC response5 was established in 79 recipients of kidney transplants carried out between September, 1982, and December, 1984. We included only subjects for whom frozen, living, pretransplant cells from both donor and recipient were available. 47 transplants were shown to be MLCincompatible ; in 42 (39 first and 3 second transplants) of these cases additional frozen cells were available for analysis of the

in-vitro sensitivity to methylprednisolone. The kidney transplants carried out by a conventional surgical technique. The immunosuppressive treatment was uniform and consisted of azathioprine (2 mg/kg daily) and prednisolone. In the second part of the study we included 42 recipients of transplants carried out between March, 1983, and December, 1984, who were receiving cyclosporin and prednisolone as immunosuppression. The donor-specific MLC response was established in 33 of these cases and found to be high in 23. In both groups, the dose of prednisolone was 2 mg/kg daily during the first 3 postoperative weeks, gradually tapering during the next 3 weeks to 0-5 mg/kg daily, then falling very slowly. Rejection crises were treated with high-dose prednisolone. Graft failure was defined as return to dialysis or death of the patient irrespective of cause. The observation period was at least 6 months. were

pretransplant lymphocytes to phytohaemagglutinin by 50% (ED50) were determined. 1-year graft survival was significantly higher in 21 recipients with methylprednisolone ED50 values below the median than in 21 patients with higher than median ED50s (86% v 29%; p<0·0002). Thus, the steroid sensitivity of recipients strongly influences the survival of MLC-mismatched kidneys. In 42 transplant recipients treated with cyclosporin and steroids, the effect of steroid sensitivity was also apparent (1-year graft survival 76% and 57% for recipients with low and high ED50, respectively), though not significant. Determination of the sensitivity to steroids may be valuable in determining which recipients can be given HLA-DR-mismatched kidneys and may serve as a guideline for determining the dose of

isolated from the supematant of the finely chopped spleen agitatedina bottle containing growth medium RPMI-1640 with 10 ug/ml gentamicin, 2 mmol/1 L-glutamine, and 10% fetal calf serum. All donor and recipient lymphocytes were stored in liquidnitrogen until

steroids to be used.

use.

Introduction SURVIVAL of cadaver kidney grafts is affected by various factors, such as HLA matching,l,2 pretransplant blood transfusions,3 and the immunosuppressive regimen used;2 the latter almost always consists of steroids in combination with azathioprine or cyclosporin. We have found4 substantial variability between individuals in the in-vitro lymphocyte sensitivity to steroids. This study was undertaken to see whether recipient sensitivity to steroids affects cadaver kidney graft survival. To minimise the effects of some of the other factors, we first studied a group of patients receiving only one, uniform immunosuppressive regimen

(azathioprineand steroids) whoreceivedmixed-lymphocyteculture (MLC) incompatible grafts, because in our experience MLC matching has the greatest effect on graft survival. We later studied a group of patients receiving cyclosporin and steroids to investigate the effect of sensitivity to steroids under this immunosuppressive regimen.

K.

J. LEVENO AND OTHERS: REFERENCES—continued

8. Merkatz

IR, Peter JB, Barden TP Ritodrine hydrochloride A betamimetic agent for preterm labor. II Obstet Gynecol 1980, 56: 7-12. Spellacy WN, Cruz AC, Birk SA, Buhi WC. Treatment of premature labor with ritodrine A randomized controlled study Obstet Gynecol 1979; 54: 220-23. King JF, Keirse JNC, Grant A, Chalmers I. Tocolysis-the case for and against In Sharp F, Beard RW, eds Research in perinatal medicine (III). Preterm labour and its consequences. London: Royal College of Obstetricians and Gynaecologists, use in

9 10.

1985: 199-208 11. Calder AA, Patel N. Are betamimetics worthwhile in preterm labour. In Sharp F, Beard RW, eds Research in perinatal medicine (III). Preterm labour and its consequences London Royal College of Obstetricians and Gynaecologists, 1985 209-24 12. Leveno KJ, Cunningham FG, Roark ML, Nelson SD, Williams ML Prenatal the low birthweight infant. Obstet Gynecol 1985, 66: 599-605.

care

and

Methods

Preparation of lymphocytes.-Recipient lymphocytes were from heparinised peripheral blood taken immediately before transplantation and before immunosuppressive therapy was started. Donor lymphocytes used for the MLC experiments were

isolated5

Mixed lymphocyte cultures were carried out in triplicate in microtitre plates (Nunc, Denmark). 5 x 104 responder cells (recipient) and 5 x 104 irradiated (2000 cGy) stimulator (donor) cells were added to each well. The plates were incubated in 5% carbon dioxide in humidified air at 370C for 5 days before addition of tritiated thymidine (1 pCi/well, Amersham, UK), harvesting on day 6, and counting. Large chequer-board MLC experiments were carried out, confronting in each experiment a group of 15 recipients as responders with their donors as stimulators. The donor-specific MLC reactivity of each recipient/donor combination was expressed as the stabilised relative response.6This method takes account of the different capacities of the cells to stimulate in MLC, as well as variations in the responses of the responder cells, and is based on the 75th centile as reference point of both stimulators and responders. A stabilised relative response value of 50 % was taken as the cut-off point between low and high donor-specific responses.5

Lymphocyte sensitivity to methylprednisolone.-Recipient peripheral blood lymphocytes were cultured in microtitre plates containing 5 x 104 cells/well. Phytohaemagglutinin (Difco, USA; 8 pg/well) was used in the mitogen-stimulated cultures. Methylprednisolone (’Urbason’, Hoechst, West Germany) was added to some of the phytohaemagglutinin-stimulated cultures.4 The concentrations used (0,0.06,0.3,0.6,1.2,3.0,and 12 µg/ml) included in-vivo physiological, pharmacological, and suprapharmacological concentrations. All the cultures were done in triplicate and incubated in parallel experiments for 72 h in a humidified atmosphere with 5 % carbon dioxide at 37°C before addition of carbon-14-labelled thymidine (20 nCi/well; Amersham, UK), harvesting after 96 h, and counting. The dose-response curves of the lymphocyte cultures to methylprednisolone in vitro were used to calculate for each recipient the ED50 of methylprednisolone-ie, the dose suppressing the phytohaemagglutinin response by 50%. Analyses.-The Mann-Whitney U test was used to compare the ED50 values of the patient groups. Life-table analysis was