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Perfusion

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The term “perfusion” refers to the transportation of blood to a capillary bed in tissue through the circulatory or lymphatic systems to an organ or tissue. The volume of blood per unit time (blood flow) per unit tissue mass is used to calculate perfusion, which is the rate at which blood is given to tissue. Although perfusion of human organs is commonly recorded in ml/min/g, the SI unit is m3/(s-kg).

The word “perfusion” comes from the verb perfuser, which means to flow over or through in French. While the cardiac surgeon is doing open-heart surgery, perfusionists use artificial blood pumps to move the patient’s blood through their bodily tissue. It is known as extra-corporeal circulation (ECC)—outside-the-body blood circulation—when a patient’s blood is continually taken and returned through plastic tubing to allow medical experts to conduct an artificial organ function on the blood. Currently, a patient’s failing organs can be replaced with a variety of “artificial organs” that can be inserted into an ECC. Artificial hearts (blood pumps), artificial lungs (oxygenators), artificial kidneys (hemodialysis), and artificial livers are among the artificial organs now used in clinical settings.

An ECC can be constructed by perfusionists using sterile tubes and artificial organs to accommodate the needs of various medical experts treating patients with particular incurable disorders. Heart attacks, heart failure, heart valve disease, respiratory failure (smoker’s lung), kidney failure, and surgery to transplant hearts, lungs, and kidneys are a few conditions for which ECCs are prescribed by doctors. ECCs are also utilized to administer chemotherapy medications to the organs and/or limbs of cancer patients. A surgeon must insert special tubes known as “cannulas” into the patient’s bloodstream to attach an ECC to the patient. To assist the doctor in treating the patient, the perfusionist regulates the blood flow through the ECC devices.

The perfusionist builds circuits to treat various patient group demographics by fusing various ECC components. During numerous surgical and life-support operations, the perfusionist uses his training and understanding in anatomy, physiology, electronics, chemistry, and physics to maintain the patient’s vital functions.

Perfusionist 

Cardiovascular perfusionists are medical professionals who operate the heart-lung machine (cardiopulmonary bypass machine) during cardiac surgery and other procedures that call for a cardiopulmonary bypass to control the patient’s physiological status. They are also sometimes referred to as clinical perfusionists or perfusionists. The perfusionist, also known as the clinical perfusionist, is a member of the cardiovascular surgery team who uses a heart-lung machine to maintain blood flow to the body’s tissues and regulate blood oxygen and carbon dioxide levels.

Discovery

August Krogh received the Nobel Prize in Physiology or Medicine in 1920 for figuring out how to control capillaries in skeletal muscle. Krogh was the first to explain how arterioles and capillaries in muscle and other organs open and close in response to demands to alter blood flow.

History

The current effectiveness of perfusion in contemporary medical practice is the result of numerous noteworthy contributions.

Mid-18th century

The invention of perfusion dates to the 1800s. A closed-circuit perfusion system was created at this time, and bubble oxygenation was also invented. Evidence from 1858 revealed that perfusion was the source of the dying patients’ arms’ momentary response.

Mid-20th century

The development of the heart-lung machine was made possible by perfusion advancements. After testing on animals, these devices enabled successful operations on people. The first cardiopulmonary bypass operation was performed in the 1950s.

The heart-lung machine underwent advancements throughout the 1960s that made it possible for perfusion to last for longer periods to the invention of the bubble oxygenator in the 1970s. It eventually became the norm until the membrane oxygenator took its place in the 1990s.

Beyond the 21st Century

Perfusion tools and procedures are continually being improved nowadays. Additionally, advancements have produced fruitful outcomes that have the potential to save thousands of lives annually.

Blood Perfusion

The distribution of blood to tissues and organs is referred to as blood perfusion. Since cells cannot exist without the nutrients found in blood, it is crucial to preserve optimum health in many ways. Blood perfusion entails: 

  • Supporting the brain by supplying nutrients and maintaining cognitive function
  • Facilitating the presence of platelets and other wound-healing agents to aid in wound healing
  • Aiding the body fight infections with immune cells
  • Distributing hormones as chemical messengers
  • Maintaining bodily function
  • Giving skin a warm, healthy tone
  • Distributing digested nutrients to their right destination.

Concentration gradients and hydrostatic pressure are used to deliver oxygen and several other chemicals to tissues and organs. The buildup of material on one side of a membrane or biological partition is known as a concentration gradient. Concentrations frequently move from densely populated areas to sparsely populated ones.
The amount of pressure that blood exerts on blood arteries is known as hydrostatic pressure. Through fenestrations (holes or slits) in the capillary walls, blood enters the extracellular (tissue) space when it reaches the capillaries and uses its hydrostatic pressure to enter the tissue.

Treatment

A common definition of malperfusion is a reduction in blood flow to a particular location of the body. This typically happens as a result of a blood vascular occlusion or blockage. Among the signs are:

  • Swollen veins and arteries
  • Leg and foot heaviness
  • Numbness and tingling
  • Split and weeping skin
  • Pelvic pain and discomfort
  • Aches and leg pain.

Measurement 

In equations, perfusion is sometimes denoted by the letter Q when speaking of cardiac output. However, this nomenclature can be confusing because perfusion is measured as flow per unit tissue mass (mL/(min-g)), whereas cardiac output and the symbol Q refer to flow (volume per unit time).

Microspheres

  • Since the 1960s, radioactive isotope-labeled microspheres have been employed extensively. 
  • A radiation detector monitors the radioactivity in the target tissues after injecting the test subject with radioactively tagged particles. 
  • Radionuclide angiography, a technique for identifying cardiac issues, was developed using this approach.
  • Fluorescent microspheres were frequently used in place of radioactive particles in the 1990s.

Nuclear Medicine

  • Nuclear medicine, particularly positron emission tomography (PET) and single photon emission computed tomography makes it simple to monitor the perfusion of different tissues in vivo (SPECT). 
  • There are also numerous radiopharmaceuticals available, some of the most popular being:
  • Brain perfusion (rCBF) was explored using 99mTc-labeled HMPAO and ECD with SPECT 133Xe-gas for absolute quantification with SPECT 15O-labeled water for brain perfusion (rCBF) with PET. 

MRI

To determine tissue perfusion in vivo, there are two basic MRI types that can be utilized.

  • The first relies on the injection of a contrast agent, which modifies the blood’s magnetic susceptibility and, in turn, the MR signal that is repeatedly monitored throughout the bolus passage.
  • The other category is based on arterial spin labeling (ASL), in which arterial blood is magnetically tagged before it enters the tissue being studied. The amount of labeling is measured and labeled to a control recording that is acquired without spin labeling.

CT

Contrast-enhanced computed tomography can be used to evaluate brain perfusion (more accurately, transit durations).

Thermal diffusion

Measuring total thermal diffusion and dividing it into thermal conductivity and perfusion components will allow you to calculate perfusion. rCBF is often tested over time continuously. Periodically stopping the measurement is required to allow the material to cool before reevaluating the thermal conductivity.

FAQs on Perfusion

Question 1: What are the measurements of perfusion?

Answer: 

Measurements of perfusion are:

  • Microspores
  • Thermal diffusion
  • Nuclear medicine
  • CT
  • MRI

Question 2: Define perfusion?

Answer: 

The term “perfusion” refers to the transportation of blood to a capillary bed in tissue through the circulatory or lymphatic systems to an organ or tissue.

Question 3: What is malperfusion?

Answer: 

A reduction in blood flow to a particular location of the body is called malperfusion.

Question 4: Write the discovery of perfusion.

Answer: 

August Krogh received the Nobel Prize in Physiology or Medicine in 1920 for figuring out how to control capillaries in skeletal muscle. Krogh was the first to explain how arterioles and capillaries in muscle and other organs open and close in response to demands to alter blood flow.

Question 5: What is blood perfusion and mention what it entails?

Answer: 

The distribution of blood to tissues and organs is referred to as blood perfusion. Since cells cannot exist without the nutrients found in blood, it is crucial to preserve optimum health in many ways. Blood perfusion entails: 

  • Supporting the brain by supplying nutrients and maintaining cognitive function
  • Facilitating the presence of platelets and other wound-healing agents to aid in wound healing
  • Distributing hormones as chemical messengers
  • Maintaining bodily function.


Last Updated : 13 Jan, 2024
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