Cardiovascular markers for the early detection of hemorrhagic shock

Abstract

Hypovolemic shock is characterized by an acute failure of the cardiovascular system to perfuse the body tissues adequately. If the patient is not resuscitated appropriately, it can lead to organ failure and death. It is well known that the body’s compensatory responses often maintain an almost normal blood pressure while hemorrhaging. When the blood pressure finally decreases, management is much more difficult. Due to high variability, the vital signs heart rate and blood pressure is therefore not very sensitive markers of evolving hemorrhage. In this project we wanted to simulate the development of a hemorrhagic shock by using a lower body negative pressure chamber. Simultaneously we recorded several cardiovascular variables at a high sampling rate (100 Hz). The idea was to investigate whether any of these variables could be used to predict a cardiovascular collapse on an early stage. 10 healthy non-smoking subjects (5 female) were investigated. They were instrumented with different cardiovascular and respiratory instruments recording variables like heart rate, stroke volume, cardiac output, blood pressure, skin blood flow, respiratory movements, concentration of expiratory CO2 and O2 and skin temperature. In addition many variables could be calculated, like cardiac output and total peripheral resistance. This was a large project involving 6 researchers. More than 6.4 million unique data points were collected. In this paper only preliminary results are presented. MAP and HR were confirmed to be unreliable as an early marker. SV fell almost linearly and can be used, but is difficult to measure. Further investigation of data is necessary before conclusions can be drawn.