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Extravascular lung water measurement in septic sheep
The Journal of Surgical Research
|February 1, 1986
Summary
The thermal-dye technique overestimated extravascular lung water (EVTV) in septic sheep, likely due to altered blood flow. Gravimetric measurement (EVWV) is more reliable in sepsis.
Area of Science:
- Pulmonary Physiology
- Critical Care Medicine
- Medical Imaging
Background:
- Accurate measurement of extravascular lung water (EVTV) is crucial for diagnosing and managing pulmonary edema.
- The thermal-dye technique is a common method for estimating EVTV, but its accuracy in sepsis is questionable.
- Sepsis can significantly alter lung hemodynamics and microcirculation, potentially affecting measurement accuracy.
Purpose of the Study:
- To evaluate the accuracy of the thermal-dye technique for measuring extravascular lung water (EVTV) in unanesthetized sheep during sepsis.
- To compare EVTV measurements with gravimetric lung water (EVWV) in control, oleic acid-induced edema, and Escherichia coli-induced septic models.
- To investigate the correlation between EVTV and EVWV under different physiological conditions.
Main Methods:
- Sheep were instrumented with chronic lung lymph fistulas and studied unanesthetized.
- Sepsis was induced via intravenous infusion of live Escherichia coli, or lung edema via oleic acid injection.
- Extravascular lung water was measured using the thermal-dye technique (EVTV) and compared to gravimetric measurements (EVWV).
Main Results:
- Septic sheep exhibited increased pulmonary artery pressure, decreased mean arterial blood pressure, and reduced cardiac output.
- A strong correlation between EVTV and EVWV was observed in control (r=0.70) and oleic acid (r=0.93) groups.
- In septic sheep, no significant correlation was found between EVTV and EVWV (r=-0.25), with the thermal-dye technique yielding erroneously high values.
Conclusions:
- The thermal-dye technique for measuring extravascular lung water (EVTV) is unreliable in septic sheep.
- Erroneously high EVTV values in sepsis may result from erythrostasis, leukocyte plugging, uneven perfusion, and prolonged transit times.
- Gravimetric measurement (EVWV) provides a more accurate assessment of lung water in the context of sepsis-induced circulatory changes.