Cardiac Output Variability during Induction of Hypovolemic Shock

Joyce da Silva Bevilacqua [1] Centro Universitário Senac – Campus Santo Amaro. Av. Eng. Eusébio Stevaux, 823, 04696-000, São Paulo, SP, Brasil. [email protected] [2] Instituto de Matemática e Estatística da Universidade de São Paulo. Rua do Matão, 1010, 05508-900, São Paulo, SP, Brasil. [email protected] Gislaine Silva Vieira Duarte Instituto de Matemática e Estatística da Universidade de São Paulo. Rua do Matão, 1010, 05508-900, São Paulo, SP, Brasil. [email protected] Abstract. Hypovolemic shock was induced in fourteen male rats by successive bleeding. During 30 minutes, after base signal acquisition, 3.1ml of blood for each 100g of weight has been collected. After this period,a treatment was initiated with isotonic saline solution (7.5%NaCl each 0.4ml/g of weight) or hypertonic (0.9% NaCl each 0.4ml/g of weight). The arterial pressure signal was captured during all the experiment. The goal of this work is to analise the variability of the cardiac debit during the induction of shock and identify whether the physiologic mechanism to compensate the loss of volume is working. The analysis is foccused on the cardiac debit, because it depends linearly on systolic volume and heart rate. A non-invasive method was implemented to calculate the systolic volume directly from the arterial pressure signal. Wavelet analysis was used to find the main frequencies and also their variability during each stage. The cardiac debit stability was expected, because the heart rate must increase to compensate the lost of volume. In both cases was observed that the frequency increase in the stage E1 followed by a significant decrease. As a consequence the cardiac debit descreases during the intermediat stages, showing that the compensation mechanism was not working propely. In three experiments the frequencies increase only in the final stage. This anomalie suggests a deeper investigation including response to treatment and shock evolution.