Thermodilution Qp/Qs: an indicator dilution method.
The pulmonary-to-systemic blood flow ratio (Qp/Qs) is critical in the appraisal of the need for surgery in patients with left-to-right shunts. Because of the drawbacks present with conventional Fick, indicator dilution, and radionuclide techniques of Qp/Qs measurement, we sought to determine whether an extension of thermodilution technology could accurately predict Qp/Qs. We studied 30 children with clinically suspected or postoperative atrial or ventricular septal defects. The thermodilution temperature curves from the pulmonary artery were printed on a strip chart recorder after right atrial injection of iced solution. Gamma variate curve fitting and area analysis were used to determine Qp/Qs. The correlation between Fick and thermodilution Qp/Qs values was excellent (r = 0.95). The thermodilution technique was rapid, and did not require either arterial entry, radiation after venous catheter placement, or multiple sampling.
D006328:Cardiac Catheterization / Q000295:instrumentation; D002302:Cardiac Output; D002648:Child; D002675:Child, Preschool; D005260:Female; D006343:Heart Septal Defects / Q000503:physiopathology*; D006801:Humans; D007223:Infant; D008297:Male; D011651:Pulmonary Artery / Q000503:physiopathology; D011652:Pulmonary Circulation; D013815:Thermodilution / Q000379:methods*