c. Hemodynamic Reaction. Hemodynamics refers to the characteristics of
blood action or flow. A hemodynamic reaction to contrast media has serious effects on
blood flow, and can result in such complications as systemic shock, myocardial
infarction, and renal shutdown.
(1) Systemic shock is caused by a drop in blood pressure occurring after the
introduction of contrast media. The characteristic course is an immediate, but short-
lived, increase in blood pressure followed by an acute drop in blood pressure. The
immediate rise is produced by increased heart action; then, trying to compensate, the
veins dilate. Because of this venous dilation, blood pressure drops and there is not an
adequate return of blood to be oxygenated. Cardiac arrest can result if enough blood is
retained by the veins.
(2) Myocardial infarction (the death of heart muscle tissue) and renal
shutdown are thought to be the product of damage to red blood cells. Some
investigators feel the contrast media damage the cell walls of erythrocytes, causing
them to clamp together to form clots. If enough of these clots block the internal blood
supply, renal shutdown occurs. Similarly, myocardial infarction is caused by the
obstruction of the coronary arteries. Either of these complications can be fatal.
(3) The symptoms of this hemodynamic response are a weak and barely
noticeable pulse, paleness, cyanosis, and possibly even unconsciousness. Like the
histamine reaction, this response may be immediate or delayed.
d. Patient Histories. Reactions to contrast media cannot be predicted, but
patient's history. The radiologist should consult the patient's medical records for a past
history of reactions to contrast media or drugs. If he has full confidence in an x-ray
specialist, he will probably delegate to him the responsibility of explaining the
examination to the patient and questioning him for clues to the possibility of a reaction.
In such a case, the specialist must use the utmost tact to avoid alarming the patient. He
Have you had this or a similar examination before?
(2) Did you have any difficulties with the previous examination? If he
answers in the affirmative, ask him:
(3) If he answers "yes" questions (1) and (2), ask: "Do you remember the
name of the drug that caused your difficulties?"
If he answers "no" to questions (1) and (2), ask:
Are you allergic to iodine?
Does seafood affect you in any special way?