Scaling of physiological responses: a new approach for hemorrhagic shock

Abstract

Standard protocols used to study hemorrhagic shock involve sampling at fixed time intervals and generating a time-based composite curve from each experiment. Although each animal may show the same sequence of responses, the time, rate, and size of the response varies from animal to animal. As a result, sampling times may be inappropriate to identify sharp transitions in the measured parameters, and the composite curves do not reflect the size and shape of the individual responses. This report evaluates several approaches to normalizing hematocrit and blood glucose data obtained from a constant-pressure model of hemorrhagic shock in fed and fasted and dehydrated animals to see if phase relationships and fractional responses from individual animals can be made coherent. Scaling for fractional blood loss on the x-axis and maximal response on the y-axis resulted in convergence of the results from individual animals and different experimental series. Data from a constant rate of hemorrhage model also converged after scaling. A method for prospectively defining the scale and adjusting sampling frequency for individual animals is given.