The Process Of Contrast Media Biology Essay

Contrast media are agents used to better the image contrast of anatomical constructions which are non usually easy visualized. Contrast techniques provide item of organ size, form, place and internal item.Technique:The patient ‘s full cooperation shoul be obtained. Communication with patient before scrutiny and during injection is required to cut down the hazard of contrast medium extravasation. Intravenous contrast media should be administered by power injector through a flexible plastic cannula.

Use of metal acerate leaf in power injection should be avoided.22 gage catheters able to digest flow rates up to 5ml/sec. Before injection, place of catheter tip should be checked for venous backflow. Monitoring of the site during injection is required.

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Contrast media should non be administered by power injector through little bone, peripheral entree cardinal venous catheters because of the hazard of catheter breakage.Principles of contrastContrast on the radiogram is the difference in optical denseness ( OD ) between country of the radiogram. The denseness produced on a radiogram at 50-70kV is proportion to the atomic figure squared of the tissue under scrutiny.

Contrast media can be divided into positive contrast media and negative contrast media.In general, positive contrast media are those which have an increased soaking up of x beams and demo up as white/grey. Positive contrast media – iodinated compounds.

Advantages – Insoluble, inert, and gives good mucosal inside informations.Disadvantages – Aspiration pneumonia if aspirated, can do granulomatous reaction if leaks into organic structure pit.Negative contrast media is which have less soaking up and demo up as dark/grey.

Negative contrast media gaseous – air or C dioxide.Advantages – Readily available and inexpensiveDisadvantages – Do non give as much mucosal item, fatal air embolus reported following pneumocystography and urethrography, O is a fire hazard.Although contrast media can do inauspicious reaction, the existent ground for the inauspicious cause is still unknown. There are TWO common theories that used to depict inauspicious reaction to endovenous iodinated contrast media. Adverse reaction can be classified into physiochemotoxic and idiosynchratic in nature. Physiochemotoxic is related to inauspicious reaction to the chemotoxicity of the contrast media. Physiochemotoxic reaction are believed to ensue from contrast media ‘s ability to upset the homeostasis of the organic structure particularly the blood and blood circulation.

The term hemodynamics is used to depict blood and the factors that effects the blood circulation within the organic structure. Injected contrast media ever have the possible to change blood cells and the circulation of the blood every bit good as the other organ system in the organic structure. The organic structure system most normally effected by physiological alterations that can be produced by contrast media are the cardiovascular, respiratory, urinary, GI, neurologic and the integumental system. The integumental system include the tegument and its fond regard including the manus and nails which are cuticular derived functions. Integumentary system is sometimes referred to as the cutaneal system. Under certain fortunes, the system of the organic structure may non be able to counterbalance for the physiological alterations brought on by the debut of contrast media.Physiochemotoxic reaction are normally related to the followers: -Physical belongingss of contrast mediaIodine concentration of contrast mediaEntire dosage or volume of contrast mediaRate or velocity of injection


The Physical belongingss

The physical belongingss of contrast media include the ions or atoms associated to the chemical dislocation of the contrast media when it enters a solution, the figure and size of the I molecules and the figure and size of the molecules of any chemical additives. The chemical composing of ionic and non-ionic contrast media contains I. One of the primary differences between ionic and non-ionic contrast media is that an ionic compound dissociates or dissolves into charged atoms when it enters a solution such as blood.Non-ionic contrast media do non fade out into charged atoms when it enters a solution. The osmolality of a solution is the measuring of the figure of molecules and atoms in a solution per kg of H2O.

Osmolality can be described as a measuring of the figure of the molecules that can herd out or displace H2O molecules in a kg of H2O. The radiographic significance of the osmolality value of contrast media is that it is higher than the osmolality value of blood plasma. Any solutions that has an osmolality value greater than the blood plasma is said to be a hyperosmolar solution. Therefore, ionic and non-ionic contrast media are hyperosmolar solutions when compared to blood plasma. The following are illustrations of approximative mean osmolality values of blood plasma, cerebrospinal fluid, ionic and non-ionic contrast media.Blood plasma and cerebrospinal fluid – 300Ionic – CM 1400-1800Non Ionic – CM 400-750Contrast media is chiefly divided into TWO classs, high osmolar contrast media ( HOCM ) and low osmolar contrast media ( LOCM ) . Most non-ionic agents are placed into the LOCM class while all ionic agents are in the HOCM class. An injection of contrast media, particularly ionic HOCM, consequences in a large addition in the figure of atoms contained in the vascular system.

The injection of contrast media in the vascular system cause H2O from organic structure tissue to travel into the vascular system an effort to equalise concentrations.The contrast media atoms draw plasma H2O towards them hence, H2O from organic structure tissue ( cells ) quickly moves into the vascular system via the capillary membranes to equilibrate or equalise the state of affairs. This procedure is known as osmosis. The blood vass dilate in an effort to counterbalance from the increased fluid volume. Sometimes the unstable displacement may be excessively dramatic for the vass to manage hence, fluid really extravasates into the environing tissues.

Hypervolemia is the term that is used to depict an unnatural addition in the volume of go arounding fluids or bloods. The rapid fluid motion, particularly H2O, throughout the vascular system is believed to lend to trouble associated with vessel dilation, flushing, harm to the vascular endothelium, ruddy cell alterations, sickness, purging and desiccation. The osmotic effets can do arterias of the kidneys to spread out. When the arterias expand vasoconstrictives are released to counterbalance for the artery enlargement.

The vasoconstrictives constrict the arterias result in a rapid gap and shutting actions of the arterias. The consequence of this action is a lessened blood supply to kidneys which can take to entire close down of the kidneys. There is besides a opportunity that the arterias may be constricted adequate and wholly closed.

The organic structure must try to modulate the fluid overload in the vascular system. If the kidneys are non functional, the fluid is forced to seek other avenues of flight doing fluid overload to happen in other organic structure systems. One of the major consequences of the event is pneumonic hydrops.

2.The iodine concentration.

The iodine concentration is determined by the figure of iodine molecules in milligrams nowadays in a mililitre of a solution ( mg/ml ) . The iodine concentration of an single contrast agents determines how radio-opaque an agent will be. The higher the iodine concentration, the better the opportunity that more ten beam photon will be absorbed hence, that peculiar contrast agents may be more radiopaque than a comparative low I concentrated agent.

The iodine concentration have an consequence on the badness of an inauspicious reaction. The higher te I concentration, the greater the hazard of an inauspicious reaction.


The Entire Volume

The entire volume or dosage is dependent upon several factors. Iodine concentration of the contrast media, type of contrast media being injected, organic structure weight, anatomical constructions of parts and velocity of the injection and age or disease procedure that could increase the hazard of an inauspicious reaction. The acute lethal dosage ( LD50 ) is the dosage of a contrast medium required to do a mortality rate of 50 % following an endovenous injection of 1 infinitesimal continuance. Increasing the injected volume increases the possibility of an inauspicious reaction happening. An injection of a big sum of contrast media normally is accompanied by the usage of a low I concentrated agent.

4.The rate or Speed of Injection.

It is an of import factor associated with physiochemotoxic reaction. Increasing the velocity or rate of injection may increase hazard of inauspicious reactions. Viscosity is the term that associated with the thickness of contrast agent. It describes about the thickness or opposition to flux of a contrast agents. The thickness of contrast agent is related to concentration, the size of the molecules in a specific contrast agents and the temperature of contrast agent. The thickness or viscousness effects the rate that the contrast media can be injected.

Contrast media with higher viscousness values will hold to be injected at a slower rate. Heating the contrast media to personify temperature reduces viscousness. All power injection devices are equipped with a “ heating tablet ” covering a part of the syringe. The warming devices heats the filled syringe to a temperature about to human organic structure temperature.The heating of the contrast media reduces the viscousness whichdecreases the hazard of hindering the flow.

Iodine concentration, viscousness, temperature of the contrast media, catheter inner diameter, catheter length and the figure of catheter holes are all factors that influence contrast media flow.The 2nd theory classifies inauspicious reaction to contrast media as idiosynchratic reactions. Idiosynchratic reactions may non be influenced by the iodine concentration, chemical belongingss and rate or volume of the injected contrast media.Idiosynchratic reactions resemble allergic reactions or a hypersensitivity to a peculiar substance, in this instance the substance is iodinated contrast media.

The ground for this type of reaction remains unknown. A comparing has been made to allergic reaction that occurIn hypersensitivity to grains and pollen. The common term for allergy type reaction is “ anaphylactoid reaction ” .

Antibodies are formed in response to antigens which produces the symptoms of an allergic reaction. The antibody-antigen response stimulates the release of histamine. Histamine is a of course happening chemical in the organic structure and its release in the organic structure is the most of import go-between in allergy reactions. Histamines is found in most tissues and in specific cells of the lungs, GI mucous membrane, GI piece of land, liner of blood vass and portion of cardinal nervous system. Histamine chiefly effects the cardiovascular, GI, respiratory and cardinal nervous systems. Histamine constrict smooth musculus, dilates arteriolas, constrict venulas, produces localize hydrops, accelerates bosom rate, lowers blood force per unit area, increase stomachic secernment and increase mucose secernment.

When an inordinate sum of histamine is released in the organic structure and vascular system become overloaded, histamine extravasates outside the vas in the environing tissue. The extravasation can do redness, swelling and reddening of the environing tissue which is urticaria or urtications. “ Watery eyes ” , “ runny nose ” , migraine concerns, sickness, purging, laryngospasm and bronchospasm are all effects that related to an inordinate sum of histamine release in the organic structure. Idiosynchratic and anaphylactoid reactions to contrast media are categorized either mild, moderate or terrible.Contrast media reactions are classified in proportion to the type of intervention that is utilised to handle the reactions. Anytime contrast media is introduced into the organic structure, there exists a possibility that an inauspicious reaction can happen.

The radiologic engineer ‘s immediate acknowledgment and response to an inauspicious reaction is really of import because it can safe a patient ‘s life. Technologists must go familiar with radiology section protocols sing inauspicious reactions to contrast media every bit good as all exigency state of affairss that may originate.


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