Different patterns of pulse spectrum between survivors and non-survivors during progressive hemorrhage in rats

Previous work from our laboratory has demonstrated that the percentage differences of 2nd (C2) and 3rd (C3) pulse harmonics related to Kidney and Spleen were both increased toward another steady state in rats after acute hemorrhage. Therefore, it is suggested that changes in pulse spectra might represent the ability of animals to survive a model of progressive hemorrhage. In this study, the difference of the pulse spectra patterns between survivors and non-survivors after progressive hemorrhage (by loss of 5%, 10% or 20% of the estimated blood volume) in anesthetized rats is determined. Seven rats, dead within 2 hours after a loss of 20% of the estimated blood volume hemorrhage, were defined as 'non-survivors'. The other eleven rats, more than 2 hours after hemorrhage, were defined as 'survivors'. Pulse waves of arterial blood pressure before and after the hemorrhage were measured in parallel to the pulse spectrum analysis. Data among different phases were analyzed using one-way analysis of variance (ANOVA) with Duncan's test for pairwise comparisons. Differences between survivor and non-survivor groups at each phase were analyzed using Student's t-test. A mixed-effects linear regression model was applied to evaluate the relationship in harmonics, which significantly differed between the two groups. The study results showed that in rats, during progressive hemorrhage, the percentage differences of 2nd harmonic proportion increased significantly; however, the result failed to show any significant difference between survivors and non-survivors. After the third blood withdrawal process, the percentage differences of 3rd harmonic proportion increased more significantly in the survivors. In addition, the percentage differences of 1st harmonic proportion related to the Liver for the survivor group was significantly lower than that of the non-survivors. After analysis with the mixed linear regression model, C3 and C1 demonstrated a linear regression relationship, and there existed significant differences between survivors and non-survivors. These results suggest that C3 might play an important role in physiology regarding surviving capability after progressive hemorrhage.