An old, mad, blind, despised, and dying king,—
Princes, the dregs of their dull race, who flow
Through public scorn,—mud from a muddy spring,—
Rulers who neither see, nor feel, nor know,
But leech-like to their fainting country cling,
Till they drop, blind in blood, without a blow,—
A people starved and stabbed in the untilled field,—
An army, which liberticide and prey
Makes as a two-edged sword to all who wield
Blood in this context holds multiple meanings: 
 
 Obviously blood can literally mean blood, in that the ruler is blindly leading England towards danger and devastation as it bleeds out and slowly withers. 
 Blood could be referenced from the leech’s perspective, in that the leech (or ruler) feeds off of the contributions of the hardworking citizens. 
 
 The  plosive  ‘b’s and  alliterative  'bl’s in 'blind’, ‘blood’ and ‘blow’ suggest spitting contempt. This line and the one that follows would be extremely effective if read aloud in performance. 

England in 1819