Guidelines for Performing Angiography In Patients Taking Metformin Ted E. Feldman, MD, FSCAI August 2002 Catheterization and Cardiovascular Diagnosis. 43: (1998)

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Guidelines for Performing Angiography In Patients Taking Metformin  Metformin (Glucophage) associated lactic acidosis Usually in diabetics with chronic renal insufficiency Potential for contrast-induced renal failure Catheterization and Cardiovascular Diagnosis. 43: (1998)

Guidelines for Performing Angiography In Patients Taking Metformin  Old recommendation: Glucophage should be withheld for at least 48 hours prior to, and 48 hours subsequent to, the procedure and reinstituted only after renal function has been reevaluated and found to be normal  Old policy has limitations in patients in whom any such study is planned Catheterization and Cardiovascular Diagnosis. 43: (1998)

 Medical literature provides no evidence that withholding metformin for 48 hours before a contrast procedure in patients with normal renal function confers any protection Guidelines for Performing Angiography In Patients Taking Metformin Catheterization and Cardiovascular Diagnosis. 43: (1998)

 Metformin is excreted unchanged in the urine  90% of the absorbed drug is eliminated via the kidneys within 24 hours  Metformin itself does not cause renal failure  In patients with renal failure, metformin may accumulate in body tissues and produce lactic acidosis  Lactic acidosis that occurs during metformin therapy is not necessarily caused by metformin  Metformin accumulation sufficient to produce lactic acidosis can occur only in the presence of renal failure (and rarely hepatic failure), and it occurs slowly Guidelines for Performing Angiography In Patients Taking Metformin Catheterization and Cardiovascular Diagnosis. 43: (1998)

 Incidence of metformin-associated lactic acidosis is about 3 cases per 100,000 patient-years, and the mortality rate is about 1.5 cases per 100,000 patient-years  Since metformin became available in Europe in the late 1950s, there have been 13 published cases of metformin-associated lactic acidosis in patients with acute renal failure precipitated by iodinated contrast material  In 12 of the 13 cases, renal impairment existed before contrast administration, and in the remaining case, metformin therapy was continued after the onset of contrast-induced renal failure  In 10 of the 13 patients, metformin was continued after onset of contrast- induced renal failure  No cases of metformin-associated lactic acidosis have been documented in patients with normal renal function who discontinued metformin at the onset of contrast-induced renal failure Guidelines for Performing Angiography In Patients Taking Metformin Catheterization and Cardiovascular Diagnosis. 43: (1998)

Revised Guidelines for Iodinated Contrast Administration in Metformin-Treated Patients  In elective cases, renal function should be evaluated before administering iodinated contrast  Patients should discontinue metformin 2 days before the angiographic procedure  If a patient has taken metformin within 48 hr before a scheduled angiographic procedure, it is not necessary to cancel the procedure if the following policy is applied If renal function is normal, iodinated contrast material may be administered without postponing the study The patient should be adequately hydrated After the study, patient may resume metformin after renal function is shown to be normal If renal function is abnormal, the contrast study should be postponed and the patient advised to contact the referring physician regarding discontinuation of metformin A. Guidelines for Performing Angiography In Patients Taking Metformin Catheterization and Cardiovascular Diagnosis. 43: (1998)

 In emergency and urgent cases, serum creatinine level should be measured immediately and the following precautions taken: If renal function is normal, the study may proceed as with elective patients If renal function is abnormal or unknown, the physician should weigh the risks and benefits of contrast administration and take the following precautions: –Discontinue metformin –Correct hypovolemia: hydrate the patient during and after the procedure (saline 1 ml/kg/hR i.v., if hemodynamic status permits) –Correct low cardiac-output if possible –Administer minimal volume of low-osmolality iodinated contrast material –Monitor urine output and renal function after the procedure –If acute renal failure occurs after contrast administration, observe the patient for symptoms / signs of lactic acidosis (e.g., abdominal pain, obtundation, hypotension, tachypnea). The diagnosis should be confirmed by arterial blood gas analysis and measurement of plasma lactate, glucose, and ketones (including beta-hydroxy butyrate) –Consultation with a nephrologist and hemodialysis should be considered if lactic acidosis occurs B. Guidelines for Performing Angiography In Patients Taking Metformin Catheterization and Cardiovascular Diagnosis. 43: (1998)