The main reason that the cardiovascular system exists is to pump blood around the body through the heart. Blood is the primary substance in every nook and cranny of our body, flowing through us constantly, and blood helps with several functions such as controlling cardiac output and vascular resistance. In cardiology, bloodletting, transfusion and circulation show exactly how much medicine has evolved recently, seeing as just a few centuries ago blood transfusion was only a theory.
To start if off, circulation is defined by the movement o blood through a closed loop system driven by cardiac output which is the result of heart rare and stroke value. Precise circulation doesn’t actually rely that much on cardiac output as it does on systemic vascular resistance (resistance that the left ventricle of the heart must overcome to eject blood into systemic circulation) and the oxygen content of the blood. The modern understanding of the circulatory system is more or less enhanced by the work of William Harvey in the seventeenth century. He proposed that circulation works in a dual cycle, where the blood is driven around the body in a circular motion and passes through the heart twice. Another major aspect in circulation would be the importance of efficient oxygen delivery, which is the cardiac output and arterial oxygen content, which itself is also dependent on hemoglobin circulation. Even with preserved cardiac function, a low amount of hemoglobin can significantly impair tissue oxygenation.
On the other hand, blood transfusion is used to replication oxygen carrying capacity and intro vascular volume, especially in patients that suffered from acute blood loss. In cardiology, this is especially relevant, particularly in acute coronary syndromes or decompensated heart failure. Doctors who actually perform blood transfusion usually prefer a more restrictive approach. In stable patients, transfusion is only considered when the patients hemoglobins level decrease lower than 7 g/dL. The main goal is to improve oxygen delivery and prevent potential adverse effects.
Now last but not least, bloodletting was first based on homunal theory and was before widely used across nearly every medical condition, while now it’s generally not a common treatment, and it’s more recent counterpart (therapeutic phlebotomy) remains quite relevant, particularly in hematologic disorders. In certain specific conditions such as “polycythemia Vera” and “hemochromarasis”, phlebotomy actually removes iron burden and blood viscosity. From a cardiovascular perspective, the lowering of a hematocrit helps improve micro vascular flow and reduce the risk of thrombosis as a whole, supporting circulatory efficiency. Phlebotomy is the perfect example of how older practices can be reintergrated to more modern treatments and used more effectively.
In conclusion, blood circulation, transfusion and removal are some of the most dire and necessary aspects of cardiology and cardiovascular management in general. They defined how we treat cardiology as a speciality and is the building blocks of the whole system.
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