FACTORS PREDICTING PROLONGED MECHANICAL VENTILATION IN CRITICALLY INJURED PATIENTS - INTRODUCING A SIMPLIFIED QUANTITATIVE RISK SCORE

Our objective was to identify a set of readily available and easily ob tainable parameters that would predict prolonged mechanical ventilatio n in the critically injured patient. A surgical intensive care unit of an academic Level 1 trauma center. Prospectively collected data were retrospectively analyzed on all critically injured patients receiving mechanical ventilation for more than 2 days between January and Decemb er 1994. Prolonged mechanical ventilation (PMV) was defined as the nee d for mechanical ventilatory support for more than 7 days. One hundred and nineteen patients entered the final analysis. Of these, 63 remain ed on the ventilator for 7 days or less and 56 for more than 7 days. T he Injury Severity Score (ISS), partial arterial oxygen tension (PaO2) /inspired fraction of oxygen (FiO(2)), net fluid balance, and use of S wan-Ganz were significantly different between the two groups when calc ulated 48 hours after surgical intensive care unit admission. Furtherm ore, we dichotomized these four variables across cutpoints that were d etermined by statistical analysis (ISS more or less than 20, PaO2/FiO( 2) more or less than 250, fluid retention more or less than 2000 cc, a nd presence or absence of Swan-Ganz). Again, significantly more patien ts required PMV if they had any one of the following: Swan-Ganz, ISS m ore than 20, PaO2/FiO(2) less than 250, or fluid retention more than 2 000 cc at 48 hours. An easily calculated five-point risk score (0-4 po ints) for predicting PMV based on these four variables was developed. Among the 35 patients at the extremes of the risk score (0 or 4 points ), 33 (94.3%) were correctly prognosticated as to their needs for PMV. The need for an easily calculated score, which is derived from readil y available parameters and can reliably identify patients with prolong ed needs for ventilatory support, is obvious in the trauma setting. We describe a five-point risk score by which we can predict the need for PMV early in the course of the disease. Resource utilization and pers onnel allocation issues, as well as important therapeutic procedures, can be planned based on this score.