Effects of paraquat on cardiac function *
Background and Objective : Although in acute phase of the paraquat poisoning, many patients die because of irreversible circulatory shock, the effects of paraquat on hemodynamics have not been clarified well, and specifically, only a few studies have investigated cardiac contractility in vivo. We measured left ventricular volume and pressure serially after the paraquat administration in rats using a conductance catheter and a micromanometer. Using these parameters cardiovascular indices were obtained for cardiac contractility, preload, afterload and cardiac output. Since the end-systolic pressure-volume relationship (ESPVR) in small animals is not linear, a traditional index such as end-systolic elastance (Ees) or Emax is inappropriate. Therefore, PVAmLvv, the integrated ESPVR from Vo to the mid-range of left ventricular volume during afterload change, was used as an index of cardiac contractility in this study, Method : Eighteen rats were divided into three groups (six in each group). The animals in the P100 group were administrated 100 mg/kg of paraquat, while those in the P200 group received 200 mg/kg. No paraquat were administrated to the animals in the control group. A conductance catheter and a micromanometer were inserted into the left ventricle after thoracotomy. PVAmLw was calculated from the end-systolic pressure-volume relationship as an index of cardiac contractility. Similarly, end-diastolic volume (Ved) was used as an index of preload. Effective arterial elastance (Ea) , which is end-systolic pressure divided by stroke volume, was used as an index of afterload. PVAmLvv, cardiac output, Ved and Ea were measured before paraquat administration and 10, 15, 20, 25, 30 minutes after administration terminated. In the control group, only 5 % glucose solution was given. Results : PVAmLW rose in both the P 100 and P200 groups. Ved and cardiac output decreased, and Ea increased in the P200 group. These hemodynamic changes resembled those in hypovolemia. Ea tended to increase in the P100 group, but it was not statistically significant. Ved and cardiac output in the P100 group did not vary significantly. Heart rate decreased in both the P100 and P200 group. Conclusion '. Cardiac contractility is elevated in the early phase of paraquat poisoning. Changes in Ved, cardiac output, and Ea are similar to hypovolemia. (Accepted on October 21, 2003)
