Solution:
Your parameters are string values, so they should be enclosed in quotes:
echo "<td><a id='".$row['Patient_Id']."' onclick=changename( '".$row['Patient_Id']."' , '".$row['age']."' , '".$row['Notes']."' ) >".$row["Patient_Name"]."</a></td></tr>";
// ^----------------------^ etc
As it stands, JavaScript perceives your strings as identifiers. If you had checked your console you’d have seen corresponding errors (assuming these identifiers aren’t defined).