A client who has diabetes mellitus is scheduled for a colonoscopy. The nurse instructs the client to stop taking metformin 48 hours before and after the procedure.

What is the rationale for this instruction?

To prevent lactic acidosis due to contrast dye

Rationale: Metformin is an oral antidiabetic agent that lowers blood glucose levels by decreasing hepatic glucose production and increasing peripheral glucose uptake. However, metformin can cause lactic acidosis, a rare but serious condition that occurs when lactate accumulates in the blood faster than it can be metabolized. Lactic acidosis can be triggered by contrast dye used for radiographic procedures, such as colonoscopy, especially in clients who have renal impairment or dehydration. Therefore, metformin should be discontinued 48 hours before and after any procedure that involves contrast dye.

Incorrect options:

A) To prevent hypoglycemia during fasting - This is not the rationale for discontinuing metformin, as metformin does not cause hypoglycemia by itself. However, the client may need to adjust the dose of other antidiabetic medications or insulin to prevent hypoglycemia during fasting.

C) To prevent hyperglycemia due to stress response - This is not the rationale for discontinuing metformin, as metformin does not cause hyperglycemia by itself. However, the client may need to monitor blood glucose levels more frequently and report any signs of hyperglycemia to the provider.

D) To prevent nephrotoxicity due to dehydration - This is not the rationale for discontinuing metformin, as metformin does not cause nephrotoxicity by itself. However, the client should be advised to maintain adequate hydration before and after the procedure to prevent dehydration and renal impairment.

Cyanosis of the lips and nail beds

Rationale: Cyanosis of the lips and nail beds indicates severe hypoxia and requires immediate intervention. The nurse should report this finding to the provider and administer oxygen as prescribed.

Incorrect options:

A) Barrel-shaped chest - This is a common finding in clients with COPD, due to the increased anteroposterior diameter of the chest caused by air trapping and hyperinflation of the lungs. It does not require immediate intervention.

B) Clubbing of the fingers - This is a sign of chronic hypoxia and is often seen in clients with COPD. It results from the proliferation of connective tissue at the base of the nails due to chronic low oxygen levels. It does not require immediate intervention.

D) Wheezes on auscultation - This is an expected finding in clients with COPD, due to the narrowing of the airways caused by inflammation, mucus production, and bronchospasm. It does not require immediate intervention.