perfusion

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(pər-fyū'zhən) pronunciation
n.
  1. The act of perfusing.
  2. The injection of fluid into a blood vessel in order to reach an organ or tissues, usually to supply nutrients and oxygen.

The flow of fluid, usually blood through the vessels of an organ.

1. the act of pouring through or over; especially the passage of a fluid through the vessels of a specific organ.
2. a liquid poured through or over an organ or tissue.

  • p. pressure — the gradient between arterial blood pressure and venous pressure in a comparable location in the vascular tree.
  • pulmonary p. — blood flow through the pulmonary capillaries.
  • renal p. — the rate of perfusion in the kidney is much higher than in any other organ. The rate of formation of urine depends to a large extent on the perfusion rate.
  • p. scan — using pulmonary scintigraphy, radionucleotide agents injected into a peripheral vein can be detected where it is trapped in the pulmonary capillary bed. Used to assess pulmonary blood flow.
  • p. technique — maintenance of blood circulation to tissues during cardiopulmonary bypass.
  • p.:ventilation ratio — see ventilation: perfusion ratio.

n

A therapeutic measure whereby a drug intended for an isolated part of the body is introduced via the bloodstream.

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categories related to 'perfusion'

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Random House Word Menu by Stephen Glazier
For a list of words related to perfusion, see:

A perfusion pump, c. 1935, an early device for simulating natural perfusion

In physiology, perfusion is the process of delivery of blood to a capillary bed in the biological tissue. The word is derived from the French verb "perfuser" meaning to "pour over or through."

Tests of adequate perfusion are a part of the patient assessment process performed by medical or emergency personnel. The most common methods include evaluating skin color, temperature, condition and capillary refill.

Contents

Overperfusion and underperfusion

The terms "overperfusion" and "underperfusion" are measured relative to the average level of perfusion across all tissues in an individual body, and the terms should not be confused with hypoperfusion and "hyperperfusion", which measure the perfusion level relative to the tissue's current need.

Tissues like the heart are considered overperfused and receive more blood than would be expected to meet the metabolic needs of the tissue. In the case of the skin, extra blood flow is used for thermoregulation. In addition to delivering oxygen, the blood helps dissipate heat by redirecting warm blood close to the surface where it can cool the body through sweating and thermal dissipation.

Discovery

In 1920 August Krogh was awarded the Nobel Prize in Physiology or Medicine for the discovery of the mechanism of regulation of the capillaries in skeletal muscle. Krogh was first to describe the adaptation of blood perfusion in muscle and other organs according to demands through opening and closing the arterioles and capillaries.

Measurement using Nuclear Medicine methods

Perfusion of various tissues can be readily measured in vivo with nuclear medicine methods, mainly positron emission tomography (PET) and single photon emission computed tomography (SPECT). Various radiopharmaceuticals targeted at specific organs are available, some of the most common being

Measurement using MRI

Two main categories of magnetic resonance imaging (MRI) techniques can be used to measure tissue perfusion in vivo.

  • The first is based on the use of injected contrast agent that changes the magnetic susceptibility of blood and thereby the MR signal which is repeatedly measured during bolus passage.
  • The other category is based on arterial spin labeling (ASL), where arterial blood is magnetically tagged before it enters into the tissue of interest and the amount of labeling is measured and compared to a control recording obtained without spin labeling.

Measurement using CT

Brain perfusion (more correctly transit times) can be estimated with contrast-enhanced computed tomography.

See also

References

External links


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