This prospective study was carried out to develop a model for the prediction of cardiac risk in non-cardiac surgery. Detailed data were collected concerning the preoperative status of 2609 consecutive patients, who were followed closely during the postoperative course. Fatal or life-threatening cardiac complications occurred in 68 patients (2.6%). By utilizing logistic regression, a model for prediction of cardiac risk was developed. The model contained six significant preoperative predictor variables: Congestive heart failure (with 3 degrees of severity); ischaemic heart disease (with 2 degrees of severity); diabetes mellitus; serum creatinine above 0.13 mmol l-1; emergency operation; and the type of operation (two categories). With this model it seems possible to discriminate between patients with very different levels of cardiac risk.

In pigs subjected to pulsatile or nonpulsatile cardiopulmonary bypass (CPB) at normothermia for 3 hours, evaluation was made of water content in brain tissue (specific gravity measurements), blood-brain permeability to serum proteins (immunocytochemical demonstration of extravasated proteins, using peroxidase-antiperoxidase technique) and histopathology (paraffin sections). The specific gravity in parietal cortex was higher after pulsatile than after nonpulsatile CPB or in control pigs, the change corresponding to a 6.3% water increase. The tissue water content was unchanged in the internal capsule, basal ganglia and nucleus accumbens after CPB. The vascular permeability to serum proteins was unchanged after nonpulsatile CPB, but after pulsatile CPB minute foci of extravasated serum proteins appeared. All the animals showed dark neurons in cortical and subcortical regions, but these could have been artefacts in immersion-fixed tissue. There were no other signs of ischaemic tissue damage. The study indicated that cortical oedema may follow pulsatile CPB, the cause being altered permeability of the blood-brain barrier to serum proteins.

The effect of hypothermia during cardiopulmonary bypass (CPB) on cerebral histopathology, blood-brain barrier permeability to serum proteins and water content was evaluated. Pigs were subjected to non-pulsatile CPB for 2 h at either normothermia or hypothermia, and a group of anaesthetised pigs served as normothermic controls. The histopathology was assessed on paraffin embedded sections. The permeability of the cerebral vessels was studied by immunocytochemical demonstration of extravasated serum proteins. The cerebral water content was assessed by specific gravity measurements. The histological studies demonstrated hydropic degeneration of the brain parenchyma and perivascular swelling of the astrocytic endfeet throughout both white and gray matter in the normothermic CPB group. Similar changes were not encountered during hypothermic CPB, which suggests a beneficial effect of decreased temperatures on brain tissue during CPB. Neither normothermic nor hypothermic CPB induced significant changes in the cerebrovascular permeability or in the specific gravities.

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