Few Guidelines and Current concepts for Contrast media administration in Radiology

Two major issues  always concern regarding contrast :
Teaching points by Dr MGK Murthy

(A) Allergy - Taking Meticulous history , Injecting the first inject very slowly while observing the patient , Premedicating with steroids in high risk patients , and close observation of the person for minimum of 20 minutes (most life threatening  reactions occur in 20 minutes), change of   molecule/ brand  in case of  history of previous reaction would  suffice most often

(B) Serum Creatinine --  

i) creatinine is dependent on age, gender, muscles mass , and  dynamically  variable in normal persons being  a metabolic marker . 

 Recent  literature cautions against  over dependence on  creatinine as   exclusive  renal health indicator. Unfortunately most literature regarding creatinine is created by angiocardiography (Cardiologists) and  passively  followed by Angiographers  (Radiologists)  where large quantities of contrast over short period need to be injected , apart from  short interval repeats. 

(Note--Diagnostic Radiology particularly  with the advances in  High resolution technology , uses small quantities and  repeats  if at all are far spaced and infrequent )

ii) Pre existing renal dysfunction, proteinuria, Prior kidney surgery, hypertension,and Gout , if could be reasonably excluded by history, ( 99% would have serum creatinine less than 1.7mg/dL),  serum creatinine screening is recommended to be a voided by ACR. Another  large  group recommends  a slightly  different   creatinine  Testing criterion

Age more than 60,History of renal disease ,including dialysis,kidney transplant, single kidney, renal cancer, renal surgery, history of Hypertension requiring therapy, history of Diabetes, Metformin patients need to be screened only. Metformin does not increase  chances of CIN or allergic response , but  lactic acidosis can occur in people  with renal dysfunction. 

(iii) No consensus  exists  regarding Upper limit of creatinine beyond which no contrast can be administered  , However ACR Recommends risk of  CIN  (Contrast Induced Nephropathy ) sufficiently low if creatinine is  less than 2.0mg/dL.

iv) In  all types of acute kidney injury (of course) , preferable to avoid contrast (Anuric patients however are  no longer at risk for   any further  renal injury)

v) The usual course of CIN is a transient asymptomatic elevation in serum creatinine.  Serum creatinine usually begins to rise within 24 hours of intravascular iodinated contrast medium administration, peaks within 4 days, and often returns to baseline within 7 to 10 days. It is unusual for patients to develop permanent renal dysfunction.

vi)It takes on average 24 hours to  excrete the entire contrast of diagnostic radiology (half life of LOCMs 2 hours). Hence  repeats are safe after 24 hours .

vii) Urgent dialysis is not needed (as LOCMs are not  protein bound and are of low molecular weights ) (unless  large quantities injected or severe cardiac dysfunction)

viii) No need to discontinue Metformin in normal renal function patients for iodine based contrasts or Gadolinium

ix)Radiologists commonly use contrast media for a clinical purpose not contained in the labelling referred to as "off-label use ". 

By definition, such usage is not approved by the Food and Drug Administration.  However, physicians have some latitude in using  off label as guided by clinical circumstances, as long as they can justify such usage in individual cases.  Examples include MR angiography, cardiac applications, and pediatric applications in patients younger than two years of age etc 

x) Less than 1% of injected dose is excreted in breast milk with  less than 1% of that  absorbed from infant gut making the systemic dose  to the infant less than 0.01% of the intravascular dose given to the mother.

 Hence Breast feeding women can safely receive iodinated  or Gadolinium based contrast  with no concern. (however it is preferable  to avoid during pregnancy unless benefits outweigh the risks) 

xi) Intrathecal iodinated contrast use is presently "off label" use and better used at strengths below 300mg Iodine/ml.