Hemodynamic and pulmonary changes after drainage of significant pleural effusions in critically ill, mechanically ventilated surgical patients.

PURPOSE: Our purpose was to study the effects of drainage of significant pleural effusions in mechanically ventilated patients in a surgical intensive care unit.
METHODS: Twenty-two ventilated patients in the surgical intensive care unit of a tertiary care center over a 12-month period who developed a pleural effusion large enough to require drainage were studied prospectively. All patients underwent serial portable chest radiography in the upright or semiupright position; the radiographs were reviewed by a radiology attending. Pleural effusions were classified as small, moderate, or large. Moderate or larger effusions were drained using an 8- to 12-Fr pigtail catheter inserted at the bedside under ultrasound guidance. Hemodynamic and pulmonary parameters were collected before and after the fluid was drained. Parameters studied included those outlined in the physiologic profile and included measured and calculated physiologic variables, arterial blood gas measurements, and Svo2 measurements. Ventilator settings before and after were also recorded.
RESULTS: Average initial pleural effusion drainage was 1,262 +/- 762 mL (range, 300-2,980 mL). Nine of the 22 patients had effusions drained from both the right and left chest. Blood pressure, systemic vascular resistance, Po2, Pco2, Svo2, Fio2, peak airway pressure, and spontaneous volume did not change significantly. Pulmonary capillary wedge pressure decreased (17.4 +/- 6.0 before, 13.6 +/- 4.4 after; p < 0.01), central venous pressure decreased (14.2 +/- 5.2 before, 11.5 +/- 4.4 after; p < 0.02), and pulmonary arteriovenous shunt decreased (26.7 +/- 15.1 before, 21.0 +/- 7.8 after; p < 0.04). Oxygen delivery increased (579.7 +/- 214.7 before, 662.8 +/- 263.3 after; p < 0.01) and oxygen consumption increased (146.3 +/- 61.6 before, 175.2 +/- 73.8 after; p < 0.01). Respiratory rate also decreased (19.4 +/- 6.5 before, 15.5 +/- 6.3 after; p < 0.05). There were no complications from the placement of the pigtail catheters.
CONCLUSION: Drainage of pleural effusions results in increased oxygen delivery and oxygen consumption coinciding with a decrease in pulmonary capillary wedge pressure. The pulmonary arteriovenous shunt decreased, implying an increase in functional residual capacity and improved oxygenation. Further study is needed to determine whether these changes lead to an improved patient outcome (i.e., reduction in length of stay, ventilator days, or mortality).