Discussion Topic 3: Cardiovascular System

Clinical Case: ER Trauma – Hemorrhage

During your clinical rotation in the ER, a patient in a car accident arrives and is experiencing hemorrhaging from injuries sustained during the accident.  From your studies of cardiovascular physiology, you know that hemorrhage is a serious, life-threatening situation for a patient due to its impact on MAP.

Discuss the following:

1. Beginning with your understanding that MAP = CO x TPR, which variable in this formula is directly decreased by the loss of blood during a hemorrhage? Remember that this variable is the direct reason why MAP decreases.
2. For the variable from part B, discuss the mechanism (list the steps with bullet points) which leads to the decreased MAP.
3. Reflex Arc: Compensatory mechanisms – discuss the body’s reflex compensatory mechanisms for the following MAP components which are initiated to try and keep MAP from decreasing any further: (*remember: identify the effector(s), inputs, and responses)

(i) CO: HR

(ii) CO: SV

(iii) TPR

Discussion Topic 3: Cardiovascular System Answer

1. The blood loss during a hemorrhage means that there is less blood circulating in the body. This means that there is also less blood pumped out by the heart or stroke volume (SV), which all in all decreases directly decreases the cardiac output (CO).