Elevation of superior vena caval pressure increases extravascular lung water after endotoxemia

Abstract

In many sheep Escherichia coli endotoxin results in pulmonary hypertension, increased microvascular permeability, pulmonary edema, and increased central venous pressure. Since lung lymph drains into the systemic veins, increases in venous pressure may impair lymph flow sufficiently to enhance the accumulation of extravascular fluid. We tested the hypothesis that, following endotoxin, elevating the venous pressure would increase extravascular fluid. Thirteen sheep were chronically instrumented with catheters to monitor left atrial pressure (LAP), pulmonary arterial pressure (PAP), and superior vena caval pressure (SVCP) as well as balloons to elevate LAP and SVCP. These sheep received 4 micrograms/kg endotoxin, and following the pulmonary hypertensive spike the left atrial balloon was inflated so that (PAP + LAP)/2 = colloid osmotic pressure. It was necessary to control PAP + LAP in this way to minimize the sheep-to-sheep differences in the pulmonary hypertension. We elevated the SVCP to 10 or 17 mmHg or allowed it to stay low (3.2 mmHg). After a 3-h period, we killed the sheep and removed the right lungs for determination of the extravascular fluid-to-blood-free dry weight ratio (EVF). Sheep with SVCP elevated to 10 or 17 mmHg had significant increases in EVF (5.2 +/- 0.1 and 5.6 +/- 1.2) compared with the sheep in which we did not elevate SVCP (EVF = 4.5 +/- 0.4). These results indicate that sustained elevation in central venous pressure in patients contributes to the amount of pulmonary edema associated with endotoxemia.

Differential responses of the endothelial and epithelial barriers of the lung in sheep to Escherichia coli endotoxin.

“…Our data indicated that only interstitial edema developed with a 20% increase in extravascular lung water. These results are similar to data reported by Allen et al (22) who elevated both left atrial and cranial vena caval pressure in unanesthetized sheep that had received 4 ,ug/kg ofintravenous E. coli endotoxin. When left atrial pressure was raised to 13 mmHg and cranial vena caval pressure to 17 mmHg, extravascular lung water increased only to 5.2±0.1 g H20/g dry lung.…”

Pulmonary abnormalities after cardiac surgery are better explained by atelectasis than by increased permeability oedema

“…The fact that CVP better predicted EVLW than did PAOP, in conjunction with COP, may relate to the small numbers of EVLW or greater importance of CVP. Indeed, systemic venous pressure is the back pressure for lymphatic flow from the lungs, so that an elevated pressure contributes to pulmonary oedema, evoked by increased permeability, increased hydrostatic pressures, or both (40). The COP–PAOP gradient has been proposed as the intravascular filtration pressure linked to the development of pulmonary oedema, even though the level of the effective hydrostatic filtration pressure is somewhere between MPAP and PAOP and may be relatively independent of PAOP (6, 8, 11, 12, 26, 34, 38).…”

Pulmonary edema following scorpion envenomation: Mechanisms, clinical manifestations, diagnosis and treatment

“…Mechanical ventilation and dobutamine decrease the pulmonary capillary pressure and the central venous pressure. The decrease in the pulmonary capillary pressure prevents the pulmonary edema formation while the decrease in central venous pressure should increase the lung lymph flow and hence the removal of fluid from the interstitium into the systemic veins [88].…”