The protective action of allopurinol in an experimental model of haemorrhagic shock and reperfusion.

Haemorrhagic shock was induced in anaesthetized, open-chest dogs by controlled arterial bleeding, sufficient to reduce and maintain mean arterial blood pressure at 40 mmHg for 30 min. The blood volume was then restored to the pre-shock level by rapid, intravenous reinfusion of the blood shed during the shock period. Haemorrhagic shock produced significant haemodynamic changes, characterized by a marked depression of myocardial function. Cardiac output (1226 +/- 57 ml min-1), peak aortic blood flow (6030 +/- 383 ml min-1) and maximum rate of rise of left ventricular pressure (2708 +/- 264 mmHg s-1) were all reduced by more than 50%. The haemodynamic profile was markedly improved by reinfusion of shed blood but this improvement was not sustained. There was a gradual decline such that 50% of the untreated animals suffered complete circulatory collapse and death between 60 and 120 min following reinfusion. Neither haemorrhagic shock, nor reinfusion of shed blood produced any consistent or significant changes in the myocardial adenine nucleotide pool. The ATP, ADP and AMP levels were, respectively, 25.9 +/- 4.2; 15.6 +/- 1.0; 4.3 +/- 1.9 nmol g-1 protein, before haemorrhagic shock; 21.6 +/- 3.4; 21.5 +/- 2.5; 10.2 +/- 2.7 nmol g-1 protein, after 30 min haemorrhagic shock; and 29.9 +/- 3.9; 16.5 +/- 1.2; 4.2 +/- 1.1 nmol g-1 protein, 60 min following reinfusion of shed blood. Pretreatment with allopurinol (50.0 mg kg-1 i.v.), 60 min before inducing haemorrhagic shock, had no significant effect upon the haemodynamic response to shock, but did prevent the gradual decline seen following reinfusion in the untreated animals. All of the allopurinol-treated animals displayed significantly better haemodynamic profiles than the untreated animals, furthermore, there was a 100% survival rate in this group. 5 Allopurinol had no significant effect upon the myocardial adenine nucleotide pool either during haemorrhagic shock or following reinfusion of shed blood.