Pulmonary microembolization in experimental aortic surgery.

Abstract

Pulmonary dysfunction frequently follows major surgery and has many features identical to "shock lung'. A porcine model of aortic surgery is described in which 111In-labelled platelet kinetics were related to subsequent pulmonary function. In 14 pigs, standardized aortic surgery resulted in reproducible shock and a 50 per cent mortality at 3 days. Cardiac output fell from 2.3 +/- 0.2 to 1.0 +/- 0.1 litres min-1 following removal of the aortic clamp and mean platelet and leucocyte counts fell from 437 +/- 48 to 252 +/- 39 x 10(9) litres-1 and 21.7 +/- 1.5 to 12.9 +/- 1.2 x 10(9) litres-1 respectively (P less than 0.01). Aggregate levels in inferior vena caval blood were maximal at this time and radiolabelled platelets accumulated in the lung with a rise in pulmonary vascular resistance. Alveolar-arterial oxygen difference subsequently increased from initial values of 13.7 +/- 2.0 to 23.4 +/- 3.5 mmHg (P less than 0.01) following resuscitation and to 32.5 +/- 3.4 mmHg at 3 days following surgery (P less than 0.01). This clear sequence suggests that pulmonary platelet microembolization occurs during surgical shock and may be responsible for subsequent pulmonary dysfunction.