Fever, leucocytosis and infection after open heart surgery. A log-linear regression analysis of 115 cases.

A prospective investigation was undertaken in adults to assess the specificity and sensitivity of fever (greater than 38 degrees C) and leucocytosis (greater than 10 000/microliters) for the diagnosis of infection after operations with cardiopulmonary bypass. A log-linear model analysis of a multiway frequency table was used for statistical evaluation. The model parameters were separately evaluated for 2 periods: the early one until the 6th day, the late period from the 7th postoperative day until discharge. Seven out of 115 patients suffered infections during their hospital stay: Bacteremia occurred in 3, pneumonia in 2, and deep sternal wound infection in 2 patients, and a superficial wound infection in one. No significant interactions between fever, leucocytosis and/or infection were found in the first period, except an inverse relation between fever and elevated WBC (p = 0.0197). After the 6th postoperative day the model parameters did show significant interactions, fever and leucocytosis being more frequent in infected patients. However, the specificity was low: only 15% of the patients with fever or elevated WBC had an infection. The risk of in-hospital infection was significantly higher after a long duration of cardiopulmonary bypass (p = 0.009), and after transfusion of more than 2500 ml of blood on the day of operation (p = 0.001).