Changes Of Cardiac Reserve Function Of Pregnant Woman During Using Of Ritodrine To Prevent Uterine Contraction

Objective To investigate changes of cardiac reserve function of patientsreceiving ritodrine tocolysis.Methods Gravid patients between23and33weeks’gestation admittedfrom march and September2010to The first affiliated hospital of ChongqingMedical University for preterm labor were involved in this study. onehundred and one pregnant women were included in our study.The study andcontrol groups were composed of patients with preterm labor (studygroup,N=51) and patients with uneventful pregnancies (controlgroup,N=50),respectively. The digital technique of heart sound signalprocessing was used to measure cardiac reserve function parametersincluding the heart rate (HR), the ratio of the amplitude of the first heartsound to the second heart sound (S1/S2) and the ratio of diastolic to systolicduration (D/S) of pregnant women.While the patients in study group wereevaluated before and during treatment (5minutes、30minutes、1hours、2hours、4hours、8hours and24hours after initiation of ritodrine infuseon),those in control group were evaluated only once.Results At the4hours after receiving treatment,the heart rates of thepregnant women increased significantly from83±9beats/min to124±13beats/min, and significantly higher than the control group(78±6beats/min)（P<0.01）, The ratio of S1/S2during treatment(4.2±1.8) was significantlyhigher than before treatment (2.5±0.9)and the control group(2.7±1.5)（P<0.01）, The ratio of D/S during treatment(1.0±0.2) was significantlylower than before treatment (1.3±0.2)and the control group(1.3±0.4)（P<0.01）, at the4hours after receiving treatment, the maternal heart ratesand S1/S2were positively correlated (r=0.466, P=0.01), maternal heartrates and D/S were negatively correlated (r=0.68, P <0.01),Whenmaternal heart rates>120bpm,the incidence rate of D/S≤1was74%,Weobserved4pregnant women who heart rates≥140bpm,all of themD/S≤0.8.By the24hours of treatment,the diastolic blood pressures of thepregnant women(60±4mmHg) was significantly lower than before treatment(67±6mmHg)and the control group(70±4mmHg)（P<0.05）.The highestpeak of the change from baseline in maternal heart rates always occurred atthe4hours after initiation of ritodrine infusion and basically stable by24hours.Conclusions The cardiac reserve function of pregnant woman during useof ritodrine hydrochloride，especially within the first four hours, decreasedalong with the increase of maternal heart rates.