Drupal PHP Query Connection

$DB_NAME = DB_START_NAME . $clinic_id;
    dpr($DB_NAME);
    $database_info = array(
        'host' => HOST_NAME,
        'database' => $DB_NAME,
        'username' => HOSTUSER,
        'password' => HOSTPASS,
        'driver' => 'mysql',
    );

    Database::addConnectionInfo('flat_db', 'default', $database_info);
    $key = 'flat_db';
    $custom_db = Database::getConnection($DB_NAME, $key);
    $sql_query = "SELECT * FROM sc_patient_appointments LIMIT 1";  
    $result = $custom_db->query($sql_query);
       foreach ($result as $row) {
        //$reaged = (array) $row; // Standard object to array  
        dpr($row);
    }