Clinical importance of AaDO2 and pulmonary artery pressure as predicted by pulsed Doppler echocardiography at bedside in diagnosing pulmonary embolism

Prognostic Role of Alveolar-Arterial Oxygen Pressure Difference in Acute Pulmonary Embolism

BACKGROUND

This study investigated the utility of the alveolar - arterial oxygen pressure difference (AaDO (2)) in predicting the short-term prognosis of acute pulmonary embolism (PE).

METHODS AND RESULTS

This study retrospectively enrolled 114 consecutive patients with acute PE, diagnosed by either spiral computed tomography or high probability ventilation - perfusion lung scans. During the first 24 h of admission, all patients had initial artery blood gas collected under room air. Patient exclusion criteria were chronic lung disease, septic emboli, and moderate and low probability lung scans. Patients were assigned to 2 groups based on either 30-day death or a 30-day composite event. Receiver operating characteristic analyses was used to determine the AaDO(2) cut-off value for predicting primary and composite endpoints. Statistical analysis demonstrated significant differences in AaDO(2) between the 30-day composite endpoint group and the 30-day composite event-free survival group (p=0.012). The AaDO(2) had a strong trend between the 30-day death group and the survival group (p=0.062). The best cut-off value for AaDO(2) was 53 mmHg and using this, the positive predictive value for 30-day death was 25% and the negative predictive value was 92%. For the 30-day composite endpoint, the positive predictive value for AaDO(2) was 35%, and the negative predictive value was 84%. In this study, thrombocytopenia was also an indicator of poor prognosis for patients with acute PE.

CONCLUSION

The AaDO(2) measurement is a highly useful and simple measurement for predicting short-term prognosis in patients with acute PE. It has high negative predictive value and moderate positive predictive value for 30-day death and 30-day composite event. Aggressive thrombolytic treatment strategies should be considered for patients with an initial poor prognostic parameter (ie, AaDO(2) >or=53 mmHg).

Effectiveness of end-tidal carbon dioxide tension for monitoring thrombolytic therapy in acute pulmonary embolism

OBJECTIVE

In acute massive pulmonary embolism with hemodynamic instability, monitoring of pulmonary artery pressure can be used to assess the efficacy of thrombolytic therapy. As a noninvasive alternative to pulmonary artery catheterization, we investigated the efficacy of continuous monitoring of end-tidal CO2 tension.

DESIGN

In 12 patients with massive pulmonary embolism who required mechanical ventilation, mean pulmonary arterial pressure (MPAP) and end-tidal carbon dioxide tension (ETCO2) were registered continuously during thrombolytic therapy. PaCO2, cardiac index as estimated by thermodilution catheter and respiratory ratio of arterial oxygen tension and inhaled oxygen concentration (PaO2/FIO2) were determined every 60 mins.

MEASUREMENTS AND MAIN RESULTS

Before thrombolysis, MPAP (34.5+/-9.8 mm Hg) and the difference between PaCO2 and ETCO2 (10.1+/-4.7 mm Hg) were markedly increased compared with normal values. Continuously monitored MPAP was related to ETCO2 for both all patients (r2 = .42; p < .001) and individually (mean r2 = .92; range, .79-.98; p < .001). In ten survivors, the mean cardiac index and PaO2/FIO2 increased during therapy from 1.7+/-0.4 to 2.8+/-0.6 L/min x m2 and 125+/-27 to 285+/-50 mm Hg (p < .01, respectively). In these patients, the difference between PaCO2 and ETCO2 decreased from 9.8+/-4.5 to 2.8+/-0.9 mm Hg (p < .001). Recurrent embolism was detected in two patients by sudden reduction of ETCO2.

CONCLUSIONS

Analysis of ETCO2 allows monitoring of the efficacy of thrombolysis and may reflect recurrent embolism. Thus, on the basis of this small study, analysis of ETCO2 appears to be useful for noninvasive monitoring in mechanically ventilated patients with massive pulmonary embolism.

Postoperative acute pulmonary thromboembolism in patients with acute necrotizing pancreatitis with special reference to apheresis therapy

Eight patients with pancreatic abscesses secondary to acute necrotizing pancreatitis underwent drainage of their abscesses under laparotomy. Two of them died of acute pulmonary thromboembolism (PTE) within 1 week. Autopsy revealed a large thrombus at the main trunk of the pulmonary artery and in the left common iliac vein. Femoral catheter insertion/indwelling, immobilization, surgery, increased trypsin/kinin/kallikrein, increased endotoxin, and decreased antithrombin-III (AT-III) were present following drainage of the pancreatic abscesses. With respect to the bedside diagnosis of acute PTE, alveolar-arterial oxygen gradients obtained by blood gas analysis and mean pulmonary artery pressure estimated by pulsed Doppler echocardiography are very useful. In terms of the treatment, attention should be paid to the following to prevent deep venous thrombosis: prophylactic administration of low molecular weight heparin and administration of AT-III (AT-III > or = 80%), use of the subclavian vein whenever possible as blood access for apheresis therapy, as short a compression time as possible after removing the blood access catheter (< or =6 h), and application of intermittent pneumatic compression devices or elastic compression stockings on the lower extremities.