Oxygen free radical generation in healthy blood donors and cardiac patients: the protective effect of allopurinol

Cardiopulmonary bypass (CPB) activates the complement system, which leads to granulocyte activation and free radical production. Free radical activity during CPB has been associated with myocardial dysfunction. However, the relationship between cardiac enzymes and granulocytes to lipid peroxidation in cardiac surgery patients is unknown. Moreover, the effect of allopurinol on lipid peroxidation during mechanical trauma has to be explored. Thirty-four patients undergoing coronary bypass surgery and 26 healthy blood donors participated in this prospective study where granulocyte counts, cardiac enzymes and malondialdehyde (MDA) were measured and related. Allopurinol was used ex vivo, as scavenger, to explore its effect on lipid peroxidation. In the patient group, the mean preoperative MDA level (2.2 +/- 0.7, nmol/ml) significantly increased after 30 min of bypass (3.3 +/- 0.9 nmol/ml; p < 0.0001), and showed a second peak at aortic declamping (4.1 +/- 0.9 nmol/ml). There were significant correlations between MDA and granulocyte counts (r = 0.59, p < 0.0001) and cardiac enzymes (r = 0.55, p < 0.0001). In an ex vivo setting, further mechanical trauma to blood significantly increased the MDA levels, both in the control (p < 0.0001) and in the patient group (p < 0.0001) and this effect could be reduced by allopurinol (p < 0.0001). CPB and mechanical trauma generate oxygen free radicals. Allopurinol was found to reduce lipid peroxidation of red cells following mechanical trauma and this has to be further investigated regarding its ability to reduce morbidity in patients undergoing open heart surgery.

The importance of the measurement of ATP depletion and subsequent cell damage with an estimate of size and nature of the market for a practicable method: a review designed for technology transfer

ATP is the energy currency of cells. ATP depletion is a central process in pathogenesis, in particular ischaemia, hypoxia and hypoglycaemia. ATP depletion in cells can be indirectly measured from the increased concentrations of extracellular hypoxanthine, a central intermediate in the metabolism of ATP. Cell damage secondary to ATP depletion can also be measured from extracellular hypoxanthine. The relevant biochemistry and physiology is briefly reviewed. Since market size is needed for investment decisions that would allow technology transfer, the numbers of hypoxanthine analyses that are clinically justified from the extensive published evidence are calculated per million population from UK, Norwegian and other evidence. The concentration of oxygen in blood is measured to estimate whether mitochondrial oxidative phosphorylation is adequate. Measurements of bicarbonate are used to estimate anaerobic glycolysis. Since the indirect estimation of ATP depletion is a major objective of blood gas and acid-base analyses, the number of such analyses per million population provides a good estimate of potential market size for a more direct method of estimating ATP depletion. A method is required for the rapid, dispersed emergency analyses needed clinically. Routes for method development are indicated. Competition, risks, acceptability, consumer motivation and timetables are indicated for the development phase. There are medicolegal pressures, especially in the USA, for the proposed advances to be widely used.

Prolonged granulocyte activation, as well as hypoxanthine and free radical production after open heart surgery in children

OBJECTIVE

To investigate granulocyte activation, as well as hypoxanthine and free radical production in children during the first day after cardiopulmonary bypass.

DESIGN

A prospective study of pediatric patients undergoing either cardiac surgery with a cardiopulmonary bypass or thoracotomy and extracardiac vascular surgery not requiring a cardiopulmonary bypass.

SETTING

Operative and intensive care units, Children's Hospital, University of Helsinki, Finland.

PATIENTS

Seven consecutive patients undergoing elective correction of a ventricular septal defect and six patients undergoing extracardiac surgery for ligation of a patent ductus arteriosus or repair a coarctation of the aorta.

MEASUREMENTS AND MAIN RESULTS

Plasma concentrations of myeloperoxidase (140-334 micrograms/l preoperatively, 460-1692 micrograms/l at 0.2 h after declamping, 471-1386 micrograms/l at 0.5 h after declamping) and lactoferrin (77-258 micrograms/l preoperatively, 533-1783 at 0.2 h, 404-1482 micrograms/l at 0.5 h) as markers of granulocyte activation, and hypoxanthine (0-5.7 mumol/l preoperatively, 4.3-17.0 mumol/l at 0.2 h, 6.5-17.9 mumol/l at 0.5 h) increased in a biphasic manner at 0.2-0.5 h and 6-10 h postoperatively (all p < 0.05). Expired ethane, as an index of free radical activity, increased at 10 h postoperatively (36-119 pmol/kg per min preoperatively, 72-152 pmol/kg per min, p < 0.005).

CONCLUSION

Granulocyte activation, and hypoxanthine and free radical production occur at least 10 h after cardiopulmonary bypass. In children undergoing open heart surgery, attempts to reduce free radical activity should be extended to the postoperative period.

Regional generation of free oxygen radicals during cardiopulmonary bypass in children

Studies on free radical generation during cardiopulmonary bypass have focused mainly on the heart and the lungs. However, low pumping pressure, nonpulsatile perfusion, and hypothermia affect the entire circulation, resulting in decreased splanchnic blood flow, increased intestinal permeability, and endotoxemia. To evaluate regional phenomena, we studied 16 children undergoing cardiopulmonary bypass. Free radical production, granulocyte activation, and hypoxanthine metabolism were assessed separately in the circulations drained by the inferior and superior venae cavae, as well as in the oxygenator. Three minutes after the onset of cardiopulmonary bypass, significant gradients between the inferior vena cava and the arterial line of the oxygenator existed in malondialdehyde (+0.60 +/- 0.12 mumol/L, lactoferrin (+18.21 +/- 7.65 micrograms/L), myeloperoxidase (+53.75 +/- 16.50 micrograms/L), hypoxanthine (-0.62 +/- 0.15 mumol/L), and urate (+8.87 +/- 4.03 mumol/L). These gradients decreased in parallel with decreasing body temperature. Except for a transient gradient in malondialdehyde at 3 minutes after the onset of cardiopulmonary bypass (+0.23 +/- 0.08 mumol/L), no changes were detected between the superior vena cava and the arterial line. In the oxygenator, granulocyte activation was observed only after aortic declamping. We conclude that during cardiopulmonary bypass, significant free radical generation, granulocyte activation, hypoxanthine elimination, and urate production take place in the region drained by the inferior vena cava. In the oxygenator, granulocyte activation occurs only after aortic declamping.

Plasma adenosine changes during cardiac surgery

Changes in plasma adenosine and inosine were measured during high-dose narcotic anesthesia and surgery for coronary artery bypass grafting (CABG), and mitral or aortic valve replacement (V). Arterial and mixed venous blood samples were obtained for measurement of adenosine and inosine at eight sampling intervals ranging from preanesthesia induction to discontinuation of cardiopulmonary bypass (CPB). Arterial but not mixed venous adenosine was markedly elevated in blood samples 10 minutes after intubation, but the fourfold elevation was significant only in the CABG patient group. Mixed venous inosine and adenosine were most consistently elevated in post-CPB samples. In a separate study of arterial adenosine changes during induction, a uniform drug administration protocol was used, and again adenosine was significantly increased immediately after intubation. It is possible that adenosine and perhaps inosine may contribute to cardiovascular responses following induction-intubation and also after discontinuing CPB.