Reperfusion of Ischemic Lower Limbs Increases Pulmonary Microvascular Permeability

Abstract

Lower torso ischemia and reperfusion has been shown to stimulate the generation of thromboxane (Tx)A₂, leading to transient pulmonary hypertension and later to polymorphonuclear leukocyte accumulations in the lungs. This study investigated whether hind limb ischemia leads to increased pulmonary microvascular permeability. Anesthetized sheep (n=6) previously prepared with a lung lymph fistula underwent 2 hr of tourniquet ischemia of both lower limbs. One minute following tourniquet release mean pulmonary arterial pressure (MPAP) rose from 14 ± 1 to 36 ± 4 mm Hg (p < 0.05) and returned to baseline within 30 min. The pulmonary arterial wedge pressure of 4 ± 1 mm Hg was unchanged. Plasma TxB₂ levels rose from 211 ± 2 1 to 304 ± 52 pg/ml (p < 0.05) 10 min after tourniquet release and were back to baseline at 30 min. Lymph flow (QL) rose from 4.3 ± 0.6 ml/30 min to 8.3 ± 1.8 ml/30 min (p < 0.05); the lymph/plasma (L/P) protein ratio rose slightly but not significantly. In three sheep, inflation of a left atrial balloon increased left atrial pressure from 3 to 16 mm Hg. MPAP rose from 14 to 24 mm Hg. There was an increase in QL from 3.6 to 17 ml/30 min; the L/P protein ratio declined from 0.63 to 0.41. These results indicate that reperfusion following 2 hr of bilateral hind limb ischemia results in increased pulmonary microvascular permeability.