Hypotension Vs Anemia

We always hear people saying, "Oh I am anemic" after getting a low blood pressure. Anemia (low Oxygen in the blood) is different from Hypotension(Low Blood Pressure). Blood pressure is defined as the amount of force exerted against the arterial wall per unit area in mm Hg. It has 2 components. Systolic Pressure is the peak arterial pressure. Averages about 120mmHg in healthy adults. 


Diastolic Pressure is the lowest arterial pressure. The normal is 70-80mmHg in healthy adults.


BP can be affected by the following factors: 


1. Blood volume- the amount of blood circulating in our body which is normally 4-5 liters.


2. Peripheral resistance- this refers to any hindrance to the blood flow to the different parts of the body.A common cause of increase peripheral resistance is an obstruction due to fats or lipids or clots. Another is the diameter of the blood vessel.Decreased diameter of the blood vessels or vasoconstriction increases peripheral resistance therefore increases BP while and increase in the diameter of the blood vessels or vasodilation decreases peripheral resistance therefore decreasing BP.


Anemia on the other hand, is identified by decreased hemoglobin in the blood. Hemoglobin is the pigment that gives the red blood cells its color and is the protein that carries Oxygen. The normal hemoglobin count is 120-140mg/dl for females and 140-180mg/dl for males. The reason for the difference is blood loss during pregnancy and menstruation. 


Anemia can be due to either defect in  RBC production or increased RBC destruction.  Defect in RBC production can be due to:

1. Aplastic anemia which is due to a defect in the Red Bone Marrow
2. Thalassemias are due to a genetic defect in the formation of the  RBC structure
3. Deficiency in Iron and Folate which is needed by the RBC in its development

Destruction in RBC can be due to:

1. Infections like Malaria or due to hemorrhagic toxin producing bacteria like Escherichia 
2. ABO incompatibility

Anemia due to defective RBC production may lead to decrease blood volume therefore hypotension. Hypotension on the other maybe due to a lot of causes not only anemia eg. dehydration or heart failure.