What symptom would indicate a toxic effect of daunorubicin in a patient?

The symptom indicating a toxic effect of daunorubicin in a patient is the presence of crackles on auscultation of the lungs. Daunorubicin, which is an anthracycline chemotherapy agent, is known to have cardiotoxic effects. This toxicity can manifest as heart failure, which may exhibit symptoms such as pulmonary congestion. When fluid accumulates in the lungs due to heart failure, crackles may be heard during auscultation, signaling a potential severe adverse reaction to the medication.

Recognizing crackles is important because they indicate that the lungs are not functioning optimally and that the patient may be experiencing fluid overload or pulmonary edema, both of which would require prompt medical intervention. Other symptoms associated with daunorubicin toxicity, such as fever, diarrhea, or nausea and vomiting, may be seen but are not specific indicators of its toxic effects on the lungs or cardiovascular system. Hence, monitoring for respiratory symptoms, particularly crackles upon lung auscultation, is crucial in recognizing daunorubicin toxicity.