Lab Values, Contrast Reactions, Misc

Normal eGFR

120 mL/minute

What are the drawbacks of using SeCr to estimate renal function?

• Overestimation by 10-40%

• Varies by muscle mass

• Influenced by protein in diet

What is the eGFR threshold for CIN? What should be done if a patient with this eGFR requires a contrast study?

30mL/min, consult with radiologist

At what eGFR can contrast be safely administered?

60mL/min

Normal serum creatinine levels

60-115 umol/L

Normal BUN values

7-25 mg/dL

When is PT and PTT needed?

Invasive procedures like biopsy or drainage

Normal PT

11-14 seconds

Normal PTT

20 - 35 seconds

150,000-400,000/mm3

What medications should be discontinued before invasive procedures? Why?

Anticoagulants, risk of bleeding

Rapid fluid administration protocol

• 3mL/kg/hr one hour pre-contrast

• 2L target of NaCl

• 1mL/kg/hr post-scan

Same day fluid administration protocol

• 2mL/kg/hr 3-6 hours prior

• 6 hours post contrast administration

• 2 L target

Day before fluid administration protocol

• 1mL/kg/hr 12 hours pre and post scan

• 2L target

Pediatric contrast dose calculation

2-3mL/kg

What factors affect viscosity?

• Brand

• Temperature

• Concentration

How is contrast removed from the body?

Glomerular filtration

What is the half-life of contrast in the body?

2 hours

What is a fatal dose of contrast? What is the cause of death?

250 - 300 mL of undiluted HOCM, cardiovascular and pulmonary failure

Define osmolality

Particles per unit of solution

High osmolality contrast vs low osmolality contrast vs blood

HOCM = 7X blood

LOCM = 2X blood

Osmolality of blood

290 mOsm/kg

Does osmolality of contrast media have any effect on the probability of a reaction?

Yes, higher osmolality = higher risk of reaction

Does contrast media cross the placenta?

Yes

How much of the contrast media is passed to a baby through breastfeeding?

less than 1% is in the breast milk, less than 1% of that is absorbed by the baby

What can concerned breastfeeding mothers do prior to their contrast CT?

Pump prior to scan to build up a supply, pump and discard milk for 24 hours post scan

Why might a patient have pain at the injection site? (it has not gone interstitial)

Chemotoxic reaction: contrast may cause vasodilation

CIN is the _ leading cause of ARF

3rd

How common are contrast reactions?

1/100,000

What causes a chemotoxic reaction?

Physicochemical properties

How can you tell if a patient is having a true allergic reaction to contrast media?

This was a trick question, there is no such thing as a true anaphylactic reaction to contrast as antibodies are not produced

What are normal side effects of contrast media?

• nausea

• vomiting

• metallic taste

• perspiration

• warmth, flushing

• anxiety

What are the symptoms of a mild idiosyncratic reaction?

• Cough

• Itchiness

• Hives

• Pallor

• Stuffy nose

• Mild swelling or rash of eyes and face

What are the symptoms of a moderate idiosyncratic reaction?

• Mild respiratory distress

  • bronchospasm

  • dyspnea

  • wheezing

  • laryngeal edema

• Pulse changes

• Blood pressure changes

What is the treatment for an idiosyncratic reaction?

Treat the symptoms:

• diphenhydramine for hives

• elevate legs for hypotension

• b-agonist inhaler for bronchospasm

• epinephrine for laryngeal edema

Can a moderate idiosyncratic reaction to contrast media escalate to a severe reaction?

Yes

What are the symptoms of a severe idiosyncratic contrast reaction?

• Respiratory distress

• LOC

• Convulsions

• Arrhythmias

• Cardiopulmonary arrest

What may increase the risk of idiosyncratic reaction?

• Allergies (2X)

• Asthma (7X)

• Previous reaction to contrast

• HOCM

Can a patient who had a severe idiopathic contrast reaction in the past have another CT with?

Yes, if they are premedicated

Premedication protocol

• Steroids for 6-12 hours

• prednisone, methylprednisolone, hydrocortisone steroids, H1 antihistamine

What must be documented after a patient has a reaction to contrast media?

• Amount and type of contrast

• Signs and symptoms

• Medication and interventions

• Final outcome

Does volume of contrast increase the likelihood of contrast reactions?

Chemotoxic - yes

Idiosyncratic - no

What diagnoses put patients at an increased risk of CIN?

• Diabetes

• Heart disease

• Chronic kidney disease

• Sickle cell anemia

CIN symptoms

• Tiredness

• Poor appetite

• Swelling in feet and ankles

• Puffy eyes

• Dry, itchy skin

How can CIN be prevented?

• Identify patients at risk

• LOCM

• Hydration

• Minimal volume

• 48 hours between studies

• Discontinue nephrotoxic meds prior to scan

Venous flow rate

2-3mL/s

Arterial flow rate

4-5mL/s

What controls flow rate?

• Arterial vs venous study

• Vessel of IV

• Viscosity

• Length of catheter

• Diameter of catheter

• Pressure

Why is the contrast bolus chased by saline?

• Reduced amount of contrast needed

• Better enhancement

• Reduce streak artifacts

Extravasation treatment

• Remove as much contrast as possible

• Elevate

• Warm and cold compress

• Monitor area

Is extravasation a risk to patient health?

Yes, can cause necrosis

How can risk of extravasation be reduced?

• Large gauge cannula

• Monitor site during injection

• Warm contrast

• LOCM

What are the safety devices in an automatic injecting device?

• Acceleration regulators

• Volume-limiting devices

• Function monitoring devices

• Air detection devices

• Pressure-limiting devices