Measurement of pulmonary capillary pressure during ritodrine tocolysis in twin pregnancies: a new noninvasive technique.

Five twin pregnant women were studied during treatment of preterm labor with ritodrine. Maternal pulmonary capillary pressure (PCP) and cardiac function were measured by noninvasive simultaneous recordings of the indirect carotid pulse, electrocardiography, phonocardiography, and M-mode echocardiography. Pulmonary capillary pressure significantly increased from the control value of 9 +/- 3.0 to 18 +/- 2.2 mmHg during the infusion period of therapy. Cardiac index and preejection period to left ventricular ejection time ratio were also increased during treatment with ritodrine. Our findings suggest that noninvasive measurement of PCP and cardiac function may be useful in monitoring twin pregnancies that develop cardiovascular side effects during tocolytic therapy.