Arterial blood gas analysis and alveolar-arterial oxygen gradient in diagnosis and prognosis of elderly patients with suspected pulmonary embolism

Background. Arterial blood,aas analysis (BGA) remains a first-step diagnost ic approach in patients with suspected pulmonary embolism (PE). The aim of this study was to evaluate EGA parameters in elderly patients with suspecte d pulmonary embolism for diagnosis and 14-day prognosis. Methods. We performed a retrospective cohort observational study of 6 years (1994-1999) in a 60-bed acute geriatric ward of University Hospital in Sie na, Italy. Room air arter'al oxygen partial pressure (pO(2)), arterial carb on dioxide partial pressure (pCO(2)), pH, arterial oxyhemoglobin saturation (SO2), and alveolar-arterial oxygen gradient [D(A-a)O-2) were performed on hospital admission of 75 patients with confirmed PE (CPE) and were compare d with data from 43 patients with unconfirmed PE (UCPE). The same parameter s of 54 CPE surviving patients were compared with 21 CPE nonsurviving patie nts. Results. Significantly lower pO(2) and SO2 and higher DA-aO(2) were found i n CPE patients. Respiratory alkalosis was found in one third of the patient s in both groups (no significant difference). In the CPE group, there was a significantly lower SO2 in nonsurviving patients, without significant diff erences for the other parameters. Metabolic acidosis was significantly more frequent in nonsurviving patients. Conclusion. More severe hypoxemia, oxyhemoglobin hyposaturation, and higher D(A-a)O-2 are associated with the diagnosis of PE in elderly patients. Res piratory alkalosis is less frequent than in younger patients, and metabolic disorders are negative prognostic indicators.