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

BACKGROUND

Arterial blood gas analysis (BGA) remains a first-step diagnostic approach in patients with suspected pulmonary embolism (PE). The aim of this study was to evaluate BGA parameters in elderly patients with suspected 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 Siena, Italy. Room air arterial oxygen partial pressure (pO2), arterial carbon dioxide partial pressure (pCO2), pH, arterial oxyhemoglobin saturation (SO2), and alveolar-arterial oxygen gradient [D(A-a)O2] were performed on hospital admission of 75 patients with confirmed PE (CPE) and were compared with data from 43 patients with unconfirmed PE (UCPE). The same parameters of 54 CPE surviving patients were compared with 21 CPE nonsurviving patients.

RESULTS

Significantly lower PO2 and SO2, and higher DA-aO2 were found in CPE patients. Respiratory alkalosis was found in one third of the patients in both groups (no significant difference). In the CPE group, there was a significantly lower SO2 in nonsurviving patients, without significant differences for the other parameters. Metabolic acidosis was significantly more frequent in nonsurviving patients.

CONCLUSION

More severe hypoxemia, oxyhemoglobin hyposaturation, and higher D(A-a)O2 are associated with the diagnosis of PE in elderly patients. Respiratory alkalosis is less frequent than in younger patients, and metabolic disorders are negative prognostic indicators.