RADIOLOGY CONTRAST MEDIUM REACTIONS:MANAGEMENT,TYPES,RISK FATORS,PREVENTION,TREATMENT

Adverse reactions to contrast agents range from a mild inconvenience, such as itching 
associated with hives, to a life-threatening emergency. Renal toxicity is a well known adverse 
reaction associated with the use of intravenous contrast material. Other forms of adverse 
reactions include delayed allergic reactions, anaphylactic reactions, and local tissue damage. Previous allergic reactions to contrast material, asthma, and allergies are factors associated with an increased risk of developing an adverse reaction. Pretreatment of patients who have such risk factors with a corticosteroid and diphenhydramine decreases the chance of allergic reactions, including anaphylaxis, renal failure, or a possible life-threatening emergency. Awareness of the different types of risk factors and prescreening for their presence allows for early recognition and prompt treatment. Prophylactic treatment before administration of contrast material can prevent potential adverse reactions. If such reactions do occur, prompt recognition allows them to be treated immediately. Using the smallest amount of contrast material possible and low-molecular, nonionic agents also decreases the relative risk of reactions. Renal insufficiency induced by contrast material may be prevented by ensuring adequate hydration and discontinuing other nephrotoxic medications before the procedure. Low-osmolar, nonionic agents are helpful in patients with known conditions associated with adverse reactions.

The osmolality of a particular contrast agent is determined by the number of osmotically active particles formed when it is dissolved in solution. Ionic agents dissociate into ions when dissolved in water and contain an iodinated benzene ring. As a result, ionic agents have a higher osmolality than blood. Nonionic agents do not dissociate into separate particles when dissolved in water; their osmolality is therefore one half that of ionic agents. Contrast agents are categorized according to their chemical structure and relative osmolality. 

In this post we are discussing about:

Iv contrast induced reaction-acute reactions management

"Hives" (urticaria)

Facial or laryngeal edema

Bronchospasm

Hypotension with tachycardia

Severe hypertension 

Hypotension with bradycardia (vagal reaction)

Unconscious / unresponsive / pulseless / collapsed patient

Types of IV Contrast Agents

Responses to contrast injection

Types of Adverse Reactions

ANAPHYLACTIC

DOSE DEPENDENT

DELAYED REACTIONS

EXTRAVASATION OF CONTRAST MATERIAL

WHO IS AT RISK?RISK FACTORS

Corticosteroid prophylaxis

Contrast-induced renal toxi

Side-effects from high osmolality / viscosity (fluid shifts from different compartments)contrast media

city

Conditions Associated with Adverse Reactions to Contrast Material

Tracking contrast reactions

Future monitoring

ACR-Proposed Premedication Regimen to Reduce Contrast Reactions

Elective Premedication

Emergency Premedication

Avoiding Problems

GENERAL PRINCIPLES

Methods of Preventing Contrast Material–Induced Renal Insufficiency

HYDRATION

CORTICOSTEROIDS

OTHER DRUGS

Mannitol
Furosemide
Calcium Channel Blockers

Treating Problems

DOSE-DEPENDENT SYSTEMIC REACTIONS
RENAL FAILURE
ANAPHYLACTIC REACTIONS
DELAYED REACTIONS
EXTRAVASATION

Choosing a Contrast Agent

IV Contrast induced reactions

MANAGEMENT OF ACUTE REACTIONS:

"Hives" (urticaria)

• Discontinue injection if not completed

• No treatment needed in most cases - reassure the patient

• Consider diphenhydramine PO/IM/IV 25-50 mg

• If severe/widely disseminated: Epinephrine SC (1:1,000) 0.1-0.3 ml (= 0.1-0.3

mg) (if no cardiac contraindications)

Facial or laryngeal edema

• 0.1-0.3 ml epinephrine SC or IM (1:1,000) (= 0.1-0.3 mg) or, if hypotensive, 1  ml epinephrine IV (1:10,000) slowly (= 0.1 mg). Repeat as needed up to 1 mg.

• Give oxygen 6-10 L/min (via mask)

• If not responsive to therapy or if there is obvious acute laryngeal edema, seek

appropriate assistance (e.g., cardiopulmonary arrest response team)

Bronchospasm

• Give oxygen 6-10 L/min (via mask)

• Monitor: ECG, O2 saturation (pulse oximeter), and BP

• Give beta-agonist inhalers, such as metaproterenol, terbutaline, or albuterol

2-3 puffs; repeat as needed

• If unresponsive, epinephrine SC or IM (1:1,000) 0.1-0.3 ml (= 0.1-0.3 mg) or,

if hypotensive, epinephrine (1:10,000) slowly IV 1 ml (= 0.1 mg) - Repeat up

to 1 mg

• Alternatively, give aminophylline 6 mg/kg IV in D5W over 10-20 minutes

(loading dose), then 0.4-1 mg/kg/hr, as needed (caution: hypotension)

• Call for assistance for severe bronchospasm or if O2 saturation <88% persists

Hypotension with tachycardia

• Legs elevated 60 degrees or more (preferred) or Trendelenburg position

• Monitor: ECG, O2 saturation (pulse oximeter), and BP

• Give oxygen 6-10 L/min (via mask)

• Rapid large volumes of IV isotonic Ringer's lactate or normal saline

• If poorly responsive: Epinephrine (1:10,000) slowly IV 1 ml (=0.1 mg) (if no

cardiac contraindications). Repeat as needed up to a maximum of 1 mg

• If still poorly responsive seek appropriate assistance (e.g., arrest team)

Hypotension with bradycardia (vagal reaction)

• Monitor: ECG, O2 saturation (pulse oximeter), and BP

• Legs elevated 60 degrees or more (preferred) or Trendelenburg position

• Secure airway and give oxygen 6-10 L/min (via mask)

• Rapid large volumes of IV isotonic Ringer's lactate or normal saline

• If unresponsive, atropine 0.6-1 mg IV slowly - repeat up to 2-3 mg in adult

• Ensure complete resolution of hypotension and bradycardia prior to discharge.

Severe hypertension

• Give oxygen 6-10 L/min (via mask)

• Monitor: ECG, O2 saturation (pulse oximeter), and BP

• Give nitroglycerine 0.4-mg tablet, sublingual (may repeat x 3)

• Transfer to intensive care unit or emergency department

• For pheochromocytoma−phentolamine 5 mg IV

Unconscious / unresponsive / pulseless / collapsed patient

• CALL CODE (Know the code phone number at your hospital. A code is not the

time to look for the number in a phone book!)

• Institute Basic Life Support

1. Establish airway, head tilt, chin lift

2. Initiate ventilation and external chest compression

3. Continue uninterrupted until help arrives






The ability to see structures or fluids within the body is essential to modern medicine. For example, X-ray examinations would be much more limited without X-ray iodinated contrast media, which provides the ability to look at structures that would otherwise be indistinguishable from nearby tissue.

Types of Contrast Agents

Type		Agents
High osmolality
	Ionic	Diatrizxoate sodium (Hypaque)
		Iothalamate meglumine (Conray)
Low osmolality
	Ionic	Ioxaglate meglumine (Hexabrix)
	Nonionic	Gadodiamide (Omniscan)
		Gadoteoridol (ProHance)
		Iodixanol (Visipaque)
		Iopamidol (Isovue)
		Iopromide (Ultravist)
		Ioversol (Optiray)

Responses to contrast injection

Many people who receive contrast media injections will feel something after the injection has occurred; this is a normal physiologic response. The most common feelings are a metallic-type taste in the mouth or a feeling of warmth/flushing; responses that are rarely a cause for concern.

Unfortunately, some people suffer more substantial and adverse reactions to contrast media. According to the seminal report by Hitoshi Katayama et al, which was published in Radiology in 1990, almost 3% of all patients injected with non-ionic contrast media suffer an acute adverse reaction worthy of being recorded and monitored. Most of the reactions are mild and self-limited. However, a small number of patients can have severe or even very severe reactions, and a tiny number of reactions can even result in death.

The most common mild allergic-like contrast reaction is the development of hives, which are usually only a few in number and which usually last for only a few minutes. Moderate reactions commonly result in respiratory symptoms, including wheezing, throat tightness or hoarseness and light-headedness. Severe reactions can result in loss of consciousness, swelling of the airway to the point of closing, severe drop in blood pressure and even cardiac arrest.

GENERAL PRINCIPLES: IN CONTRAST REACTIONS

- Contrast agents with higher osmolality are more likely to cause adverse reactions of all kinds.

- Low-osmolality agents have a significantly higher cost, which prevents them from being used exclusively.

- Anaphylactic reactions are serious, potentially life-threatening reactions associated with the administration of contrast material. Acute bronchospasm, profound hypotension, and severe urticaria may occur within minutes of administration of as little as 1 mL of contrast material. These reactions are not “true” allergic reactions, because they can occur in patients who have not been exposed to contrast material previously.

- Dose-dependent, systemic adverse reactions to contrast material include nausea and vomiting, a metallic taste in the mouth, and generalized warmth or flushing. These reactions are usually nonlife-threatening, self-limited problems.

- Renal failure is another form of adverse reaction that is dependent on the dose of contrast material used. (12% of all hospital aqcuired RF)

- Contrast induced nephropathy is diagnosed by a generally accepted definition which is the elevation of serum creatinine to greater than 25 percent of baseline within three days of receiving contrast material.

- Patients with preexisting renal insufficiency and diabetes are at greatest risk of developing permanent renal failure following administration of contrast material. Patients with multiple myeloma are also at increased risk of developing renal failure, especially if they are dehydrated. The risk of renal failure in patients with myeloma is caused by an interaction of light chains and contrast material.

DELAYED REACTIONS:

- Adverse reactions that occur 30 minutes or more after the administration of contrast 
material are considered delayed reactions.

- 30% receiving ionic contrast materials develop delayed reactions.

- 10% recieving nonionic agents is associated with delayed reactions.

- Symptoms resemble a flu-like syndrome and include fever, chills, nausea, vomiting, 
abdominal pain, fatigue, and congestion.

Types of Adverse Reactions

ANAPHYLACTIC

Anaphylactic reactions are serious, potentially life-threatening reactions associated with the administration of contrast material. Acute bronchospasm, profound hypotension, and severe urticaria may occur within minutes of administration of as little as 1 mL of contrast material. These reactions are not “true” allergic reactions, because they can occur in patients who have not been exposed to contrast material previously. IgE antibodies, which are associated with allergic reactions, have not been demonstrated in most patients with anaphylactoid reactions.2 The etiology of these anaphylactic reactions is unclear.

DOSE DEPENDENT

Dose-dependent, systemic adverse reactions to contrast material include nausea and vomiting, a metallic taste in the mouth, and generalized warmth or flushing. These reactions are usually nonlife-threatening, self-limited problems.

Renal failure is another form of adverse reaction that is dependent on the dose of contrast material used. Intravenous administration of contrast material is responsible for 12 percent of cases of hospital-acquired renal failure.3 Renal failure following administration of contrast material occurs in 0.1 to 13 percent of patients who receive contrast material.4 This range results from the lack of a set definition for contrast-induced nephrotoxicity. A generally accepted definition is the elevation of serum creatinine to greater than 25 percent of baseline within three days of receiving contrast material. Proteinuria is often found on routine urinalysis but is not required for the diagnosis of contrast-induced nephropathy.

Patients with preexisting renal insufficiency and diabetes are at greatest risk of developing permanent renal failure following administration of contrast material. Patients with multiple myeloma are also at increased risk of developing renal failure, especially if they are dehydrated. The risk of renal failure in patients with myeloma is caused by an interaction of light chains and contrast material. How contrast materials cause renal failure is unclear, but direct cellular toxicity and intrarenal vasoconstriction are believed to be the primary causes of renal function changes.

DELAYED REACTIONS

Adverse reactions that occur 30 minutes or more after the administration of contrast material are considered delayed reactions. Delayed reactions are more common with the use of ionic agents.6 Up to 30 percent of patients receiving ionic contrast materials develop delayed reactions. Administration of nonionic agents is associated with delayed reactions in only 10 percent of patients. The symptoms of delayed reactions resemble a flu-like syndrome and include fever, chills, nausea, vomiting, abdominal pain, fatigue, and congestion.

EXTRAVASATION OF CONTRAST MATERIAL

Tissue damage from extravasation of contrast material is caused by the direct toxic effect of the agent. Compartment syndrome may occur if enough contrast material leaks into surrounding tissue.

WHO IS AT RISK?

- Pt. with RF are at 10X increased risk to develope RF.

- If pt. had a previous reaction, but it is not sure that the pateint will have another one.

- Pt. with asthma, drug or food allergy.

- Sea food allergy

- On nephrotoxic deugs (NSAIDS, aminoglycosides)

- Advanced age is risk for RF.

- Metformin (Glucophage), has been associated with the development of severe lactic acidosis following administration of intravenous contrast media.

- Experts recommend stopping metformin therapy at the time of the procedure, or before, and for at least 48 hours following the administration of contrast material.

Risk factors
How do radiologists ensure the risk to their patients is minimised and that the number of reactions they observe are the fewest possible? According to Cohan, the first step is to identify patients who are at increased risk of having an acute allergic-like reaction. The three commonly acknowledged risk factors for acute allergic-like reactions include patients who have had a prior adverse contrast reaction of the allergic-like type, patients with allergies to other substances, and patients with a history of asthma.

"Not surprisingly, the patients who are at the highest risk of having an allergic-like reaction are those who have had previous reactions to the same kind of contrast material," he says. "It's not a complete guarantee that someone will have the same reaction, but a subsequent allergic reaction is much more likely, compared with patients who haven't had reactions before. It has been estimated that the increased risk in these prior reactors is about five-fold. Not quite at the same level are patients who have allergies to other substances, including foods and other medications and asthmatics. Prior studies have found that the risk of an acute allergic-like reaction in these two groups is increased by a factor of about two to three."

There is also a problem with the large amount of patients who have allergies to other medications or foods. Such allergies are very common and may be present in up to 50% of people.

Cohan believes that it is important to have a number of overlapping mechanisms in place to detect patients who are at increased risk of having an allergic-like contrast reaction, so that if one component fails the others may succeed in identifying patients as having an increased risk of having a contrast reaction."Obviously, we wouldn't be doing anything very selective in such a large group by identifying them as being at increased risk," says Cohan. "So, many experts have recommended that we consider those patients who have severe allergies or have many allergies as being particularly at risk, although the data to support this behaviour is not very compelling.This is merely an assumption that many of us make."

"The clerk who schedules an imaging test usually asks the patients the relevant questions," he explains. "The patient is then interviewed by a technologist on arrival in the radiology department. In addition the medical records are reviewed."

Corticosteroid prophylaxis


If a patient who has had a prior allergic-like acute reaction contrast media is identified, then premedication is administered if they are to be re-injected or if a contrast-enhanced study is necessary. The most crucial component of this premedication is the use of high-dose corticosteroids. Premedication lowers the chance of a subsequent reaction to some extent, but does not completely eliminate the risk.

Very little has changed over recent years in terms of how high-risk patients are identified and how premedication is administered. The most significant development has resulted from the introduction and widespread adoption of non-ionic agents, which cause fewer reactions than the older ionic agents. "However, the questions that we ask our patients are still the same, the decisions about whether to use steroids are the same, and the way that we administer the steroids are the same," says Cohan.

Contrast-induced renal toxicity
Non-allergic, non-acute reactions to contrast media also occur. Another important reaction that concerns Cohan is that iodinated contrast material (used for IVPs, CTs and conventional angiography) is damaging to kidneys.

"We know that iodinated contrast material has the potential to damage kidney function," he says. "Such damage is exceedingly rare in people whose kidneys are working perfectly normally; however, it can be a problem in people who already have an element of kidney failure, such as acute renal failure or chronic kidney disease. Iodinated contrast media can make the kidneys function even more poorly in these people."

Many studies have attempted to look at this issue, but the results are conflicting.The greatest risk of contrast-media-induced renal toxicity seems to lie in patients who have renal failure and diabetes mellitus. It is less clear whether or not the presence of diabetes mellitus alone is a risk factor for contrast-induced renal toxicity.

"Some groups are believed to be at increased risk for developing renal toxicity from iodinated contrast material," says Cohan. "This includes people who have had several injections of contrast material over a short period of time – if there's more contrast material than their kidneys can handle, they may be more at risk for being damaged by that contrast material."

Also included are patients on other medications, such as some antibiotics and anti-inflammatory medication, that may damage the kidneys, and patients that have severe congestive heart failure or who are very dehydrated.

Side-effects from high osmolality / viscosity (fluid shifts from different compartments)contrast media

• • vasodilatation
  • heat
  • pain
  • osmotic diuresis
  • hemodynamic changes
• pharmacokinetics
  • distribute volume into extracellular space
  • clearance by glomerular filtration and renal excretion
• physiologic reaction
• increased plasma osmolality causes fluid shift from RBCs and pulmonary tissue leading to increased plasma volume
• then osmolar gradient reverses with passage of contrast bolus -> pulmonary capillary endothelium leaks protein into pulm interstitium --> increased pulmonary edema
• transient cardiovascular changes (magnitude increased with tonicity of medium)
  • increased PAP
  • increased CO with decreased peripheral/pulmonary vascular resistance
  • decreased systemic arterial pressure (variable)
• may activate gen receptors causing side effects

Conditions Associated with Adverse Reactions to Contrast Material

Preexisting renal insufficiency

Previous anaphylactoid reaction to contrast material

Asthma

Food or medication allergies, or hayfever

Multiple medical problems or an underlying disease (e.g., cardiac disease, preexisting  azotemia)

Treatment with nephrotoxic agents (e.g., aminoglycosides, nonsteroidal anti-inflammatory agents)

Tracking contrast reactions

Most institutions have a system in place for monitoring patients who have had contrast reactions and identifying patients who have reacted in the past, so that if they return for another contrast-enhanced study premedication can be used. Unfortunately, the tracking system relies almost entirely on the rigorous record-keeping of individual hospitals and imaging centres.

Contrast reactions are frequently reported to the contrast agent manufacturers, particularly on rare occasions when clusters of reactions are encountered. It has been speculated that there may be some unique problem to a specific batch or lot of a shipped contrast agent in these instances. Also, when contrast media is shipped at abnormal temperature or when it comes into prolonged contact with the rubber stoppers in bottles, chemicals may leach in to the contrast material, making it more allergenic. However, manufacturers can rarely identify the problem in these situations, and the reasons for occasional continued reaction clusters nearly always remain unknown."In our department, we have instructed our technologists to summon a physician to evaluate any patient who has a reaction after contrast media injection, no matter how mild the symptoms may seem at first,"  "In addition, a departmental quality assurance contrast reaction form is then completed for every patient who has a reaction. The nature of the reaction and its treatment is dictated in the official radiology report and the patient is listed as being allergic to contrast material in the patient's electronic medical record."

Future monitoring

Although reactions to contrast media are uncommon, most physicians who administer contrast agents on a routine basis can expect to see and be called to treat adverse reactions, including those that are severe.

While most reacting patients recover uneventfully, a compulsive and rigorous monitoring system should be in place to identify patients who have reacted or who have other risk factors for a contrast reaction.

All physicians should be familiar with the recommended treatment for contrast reactions. This requires a regular periodic review of the algorithms that are suggested for treating patients with the most common cutaneous, respiratory and cardiopulmonary reactions.

ACR-Proposed Premedication Regimen to Reduce Contrast Reactions

According to the version #7 (2010) ACR Manual on Contrast Media, the following regimens are recommended for premedication of patients at risk for developing contrast reaction.

Elective Premedication

1. Prednisolone: 50 mg PO at 13 hours, 7 hours and 1 hour before contrast media injection, PLUS Diphenhydramine 50 mg IV, IM or PO 1 hour before contrast medium OR
2. Methylprednisolone 32 mg PO 12 hours and 2 hours before contrast media injection. An anti-histamine (as in option 1) can be added. If unable to take oral medication, use hydrocortisone 200 mg IV instead

Emergency Premedication

1. Methylprednisolone 40 mg or hydrocortisone 200 mg IV every 4 hours until contrast study required PLUS Diphenhydramine 50 mg IV 1 hour prior to contrast injection OR
2. Dexamethasone 7.5 mg or betamethasone 6 mg IV every 4 hours until contrast study PLUS diphenhydramine 50 mg IV 1 hour prior to contrast injection OR
3. Omit steroid entirely and give diphenhydramine 50 mg IV

"IV steroids have not been shown to be effective when administered less than 4 to 6 hours prior to contrast injection."

Avoiding Problems

GENERAL PRINCIPLES

Adverse reactions can be reduced if general principles are applied to all patients. The smallest amount of contrast agent possible should be used for each procedure. Allowing at least 48 hours to elapse between procedures in which contrast material is used enables the kidneys to recover.6  Table 3 outlines methods of preventing contrast-induced renal insufficiency.

Methods of Preventing Contrast Material–Induced Renal Insufficiency

General principles	Use the smallest amount of contrast material possible.
	Discontinue other nephrotoxic medications before the procedure.
	Allow two to five days between procedures requiring contrast material.
Hydration	Oral: 500 mL before the procedure and 2,500 mL over the 24 hours after the procedure
	Intravenous: 0.9% or 0.45% saline, 100 mL per hour beginning four hours before the procedure and continuing for the 24 hours after the procedure
Calcium channel blockers	Nitrendipine (Baypress), 20 mg orally daily for three days beginning 24 hours before the procedure

HYDRATION

It has been well documented that hydration minimizes, or decreases, the incidence of renal failure induced by contrast material. Unless contraindicated, infusion of 0.45 or 0.9 percent saline at a rate of 100 mL per hour beginning four hours before the procedure and continuing for 24 hours after the procedure, is recommended.10,11

In patients able to take oral fluids, hydration can be achieved through ingestion of 500 mL of fluid before the procedure followed by 2,500 mL over the 24 hours after the procedure. There have been no prospective studies comparing different fluids for hydration.

CORTICOSTEROIDS

Nonrenal reactions to contrast material can be reduced by premedicating the patient with corticosteroids. [Reference Evidence level A, randomized controlled trial (RCT); Reference Evidence level B, uncontrolled study] This protective effect functions for ionic and nonionic contrast materials. Many physicians give corticosteroids only to patients known to have a previous history of idiosyncratic adverse reactions.

Combining corticosteroid use with a histamine H1- receptor blocker further reduces the chance that adverse reactions will develop. Adverse reactions decreased from a range of 17 to 35 percent to a range of 5 to 10 percent when corticosteroids were combined with an H1 blocker (diphenhydramine).[References  and Evidence level B, uncontrolled study]

The following premedication protocol has been recommended for use in patients with a history of idiosyncratic reactions: methylprednisolone (one 32-mg tablet at 12 hours and two hours before the study) or prednisone (one 50-mg tablet at 13 hours, seven hours, and one hour before the study).6 If the previous reaction was moderate or severe or included a respiratory component, the physician can add the following: an H1 blocker such as diphenhydramine (one 50-mg tablet one hour before the study) and an H2 blocker (optional) such as cimetidine (Tagamet), one 300-mg tablet one hour before the study, or ranitidine (Zantac), one 50-mg tablet one hour before the study. Using an H2 blocker without also using an H1 blocker is not recommended.

OTHER DRUGS

Mannitol

Mannitol (Resectisol) has been used in an attempt to increase or maintain the glomerular filtration rate (GFR) during radiographic studies using contrast media. Very little supporting evidence shows that mannitol maintains GFR during hypoperfusion. A study that compared hydration with saline alone versus saline plus mannitol showed that saline alone was more protective.5

Furosemide

Furosemide (Lasix) has not been shown to prevent contrast-induced renal failure. A significant decline in renal function occurred in patients treated with furosemide before contrast administration.16 Negative fluid balance caused a decrease in renal cortical and medullary blood flow, leading to hypoxia.

Calcium Channel Blockers

Oral administration of calcium channel blockers was shown to minimize reduction of GFR. In a prospective study,17 patients were treated with 20 mg per day of nitrendipine for three doses starting 24 hours before the procedure. Some sparing of GFR was noted in these patients compared with patients who did not receive calcium channel blockers

Treating Problems

DOSE-DEPENDENT SYSTEMIC REACTIONS

Nausea and vomiting, a metallic taste in the mouth, and generalized warmth or flushing that are associated with contrast material injection are usually nonlife-threatening, self-limited problems. Slow intravenous injection (over two minutes rather than over 10 seconds) decreases the incidence of headache and metallic taste. The rate of infusion, rapid or slow, does not make a difference in the development of nausea or vomiting.General supportive care of the patient usually suffices in the management of these reactions.

RENAL FAILURE

Monitoring patients for the development of renal failure after the administration of contrast material requires observation of the patient's renal function for at least three days. A rising serum creatinine level is usually the first sign of an impending change in renal function, but elevation of the serum creatinine level may not occur for 72 hours. However, the serum creatinine level often rises within the first 24 hours and peaks in three to five days. The patient's creatinine level usually returns to baseline by seven to 10 days after the procedure.

Electrolytes should be checked daily to ensure that hyperkalemia is not occurring. The patient's intake and output should be measured as a gross indication of renal function. Most cases of contrast-induced renal failure resolve with supportive measures such as adequate hydration and adjustment of electrolyte abnormalities. The above measures are usually adequate for renal support; rarely is dialysis or transplantation required.

ANAPHYLACTIC REACTIONS

The principles of advanced cardiac life support should be followed in the treatment of anaphylactic reactions to contrast material. Stabilization of the patient's airway, cardiac function, and blood pressure is the fundamental element of treating anaphylactic reactions. In patients who develop bronchospasm, laryngeal edema, or severe urticaria or angioedema, epinephrine should be administered immediately (0.3 to 0.5 mg subcutaneously every 10 to 20 minutes). Patients with bronchospasm should be given 50 mg of hydrocortisone or 50 mg of methylprednisolone.

Radiology personnel who have direct contact with patients should be familiar with and certified in providing emergency care. Radiology departments must be equipped and their personnel trained to respond to life-threatening reactions at any time.

DELAYED REACTIONS

Symptoms of delayed reactions (nausea, vomiting, abdominal pain, fluid overload, and fatigue) usually resolve spontaneously and require only supportive management.

EXTRAVASATION

Application of ice packs and heating pads, and elevation are used to alleviate the symptoms associated with extravasation of contrast material. Tissue damage is more likely to occur with extravasation of ionic contrast material than with nonionic contrast agents.

Choosing a Contrast Agent

Some physicians suggest that nonionic, low-osmolality agents be used universally because fewer adverse reactions are associated with them. Unfortunately, the higher cost of non-ionic agents prohibits their widespread use. Nonionic contrast agents cost up to 10 times more than high-osmolality ionic agents. Guidelines have been developed by the American College of Radiology for the use of low-osmolality, nonionic agents. According to these guidelines, nonionic agents should be used in patients who are at increased risk of adverse reactions. This group includes patients who had previous contrast reactions, or who have asthma, multiple allergies, or diseases that could be aggravated by contrast materials . Low-osmolar, nonionic agents should be used in patients known to have renal insufficiency. In addition, when a complete history is difficult to obtain and in patients who are concerned about the use of contrast material or are at risk for aspiration, low-osmolality agents should be considered.