Reverse ventilation/perfusion mismatch

Acute paraquat intoxication: using nuclear pulmonary studies to predict patient outcome

STUDY OBJECTIVES

Paraquat, a widely used herbicide, has been shown to cause severe and often fatal pulmonary fibrosis in humans and laboratory animals. Although paraquat is known to be directly cytotoxic to lung parenchyma, changes in routine lung scintigraphy results after acute paraquat intoxication have not been reported. The objective of this project was to investigate changes in lung ventilation (LV) and alveolar permeability (AP) in patients with paraquat intoxication, using 99mTc diethylenetriamine pentaacetate (DTPA) radioaerosol lung scintigraphy.

DESIGN

Prospective, blinded study.

SETTING

Nuclear medicine and toxicology departments in two university-affiliated teaching hospitals.

PATIENTS OR PARTICIPANTS

Thirteen patients with acute paraquat intoxication were included in this study. Ten volunteers without acute paraquat intoxication were studied for comparison.

MEASUREMENTS AND RESULTS

99mTc DTPA aerosol inhalation and 99mTc macroaggregated albumin (MAA) perfusion lung scintigraphies were performed to determine LV, AP, and lung perfusion (LP). Five of the 13 patients (38%) had significant LV abnormalities; 3 of these 5 patients also showed abnormal LP. Of the 13 patients, 4 patients (31%) showed normal AP and survived. The remaining 9 patients (69%) showed abnormal AP and died. The mean values for AP were statistically different (p < 0.01) between survivor (0.72 +/- 0.16%) and nonsurvivor (1.52 +/- 0.40%) groups. Data from the normal volunteers and survival patients showed a 99mTc clearance slope < 1.00%. Data from patients who died showed a clearance slope > 1.00%.

CONCLUSION

These results indicate that AP, measured by 99mTc DTPA aerosol inhalation lung scintigraphy, may help predict outcome in patients with paraquat intoxication.