Fentanyl is excreted by the kidneys. Therefore, the patient with acute kidney failure following a severe myocardial infarction is at the greatest risk for respiratory depression due to the inability to excrete the drug. The patient with end-stage renal disease (ESRD) excretes the fentanyl via dialysis and is therefore at less of a risk for respiratory depression. The patient with severe cirrhosis of the liver and hepatic encephalopathy is at risk for respiratory depression due to an inability to metabolize the drug, not excrete it. The patient with COPD requiring oxygen is at risk for respiratory depression related to an underlying respiratory disorder, not an inability to excrete the medication.