Linear and nonlinear dynamics and the pathophysiology of shock

Rapid progress has been made in the use of linear and nonlinear time series analysis of heart rate and blood pressure variability as an indicator of disease severity and prognosis for patients in shock. Clinical and experimental studies have demonstrated the potential for linear and nonlinear measurements as a method for quantifying changes in neuroautonomic cardiovascular regulatory mechanisms. These measures have been demonstrated to correlate with severity of illness and outcome for critically ill and injured patients, including those with shock. These powerful mathematical techniques may allow for new insights into the pathophysiology of shock. In addition, these measures may also enable detection of early changes in neuroautonomic cardiovascular regulatory mechanisms during the development of shock before the onset of overt hypotension and inadequate tissue perfusion or may be used to assess the response to therapy. Further studies are needed to establish the role of these tools in clinical use.