Gamma scintigraphic analysis of albumin flux in patients with acute respiratory distress syndrome.

Computerized gamma-scintigraphy provides a new method for the analysis of albumin flux in patients with pulmonary permeability edema. In this technique, 10 mCi of 99mTc -tagged human serum albumin is administered and lung:heart radioactivity ratios are determined. This ratio remains constant unless there is a leak of albumin, when a rising ratio with time, called the "slope index" (SI), is seen. Thirty-five scintigraphic studies were obtained in 28 patients by means of a portable computerized gamma-camera. Thirteen of these patients had clinical evidence of the acute respiratory distress syndrome (ARDS) and six had or were recovering from left ventricular induced congestive heart failure (CHF). Five of the patients with CHF and pulmonary capillary wedge pressure (PCWP) below 30 mm Hg had normal scintigraphic studies. One patient in florid CHF with a PCWP of 40 mm Hg had a positive SI of 1.6 X 10(-3) U/min. The patients with ARDS were found to have significantly higher SIs than patients who did not have, or had recovered from, ARDS. The arterial:alveolar oxygen tension ratio (a/A)O2 was 0.30 +/- 0.14 in patients with positive SIs while receiving 11.0 +/- 6.8 m H2O positive end-expiratory pressure (PEEP). Both the (a/A)O2 and level of PEEP were significantly (P less than 0.01) worse in these patients than in patients with normal SIs. Positive SIs were present from 1 to 8 days following the apparent onset of ARDS in seven studies in five patients. Recovery of gas exchange was associated with a return to a normal SI in four patients. In conclusion, computerized gamma-scintigraphy was a sensitive, noninvasive tool for the detection of a pathologic increase in pulmonary protein flux. Positive scintigraphic findings were associated with significantly impaired gas exchange. The method documented that the leak of albumin in patients with ARDS may last for days but resolves with recovery.