Final answer:
The age-related change that may have contributed to the presenting signs and symptoms of dig toxicity in the older adult client is decreased renal blood flow.
Step-by-step explanation:
The age-related change that may have contributed to the presenting signs and symptoms of dig toxicity in the older adult client is decreased renal blood flow. As individuals age, there is a natural decline in renal function, including a decrease in renal blood flow. This can lead to impaired clearance of medications, like digoxin, and an increased risk of toxicity.