Hemodynamic Monitoring in Septic Shock

Abstract

Septic shock is the ultimate consequence of overwhelming, predominantly Gram negative infection, and carries a high mortality rate ( = 50%) [1-8]. Hemodynamic changes play a central role in septic shock, so that monitoring of the circulation might allow evaluation of the severity and course of the syndrome and its response to treatment. Conventional hemodynamic monitoring in septic shock pertains to invasive, mostly continuous measurements of arterial blood pressure and pressures in the lesser circulation (central venous, pulmonary arterial and capillary wedge pressures) and to intermittent determinations of cardiac output. In order to obtain the latter variables, insertion of a thermistor, balloon tipped pulmonary artery catheter is required. In conjunction with determinations of arterial and mixed venous oxygen contents, cardiac output measurements with the thermodilution technique allow assessment of peripheral oxygen delivery, extraction and uptake. The indications and implications of hemodynamic monitoring in septic shock are to a large extent dictated by the circulatory pathophysiology involved. Difficulties in the diagnosis and treatment of septic shock may constitute indications for insertion of a pulmonary artery catheter and measurements of filling pressures, pulmonary arterial pressures and blood flow. However, problems may arise in the proper interpretation of hemodynamic and metabolic measurements in septic shock. The impact of these variables on treatment and prognosis is difficult to prove. Hence, it has been doubted whether the benefits of a pulmonary artery catheter outweigh the risks of insertion and whether the use of the catheter improves outcome. Finally, some additional (non-invasive) monitoring devices have been developed, that may be useful in the treatment of septic shock. Before discussing these issues, we will briefly outline the hemodynamic characteristics of septic shock. A discussion of techniques of catheter insertion, maintenance, measurements of blood flow and pressures is provided elsewhere [9–12].