Pleiotropic effects of intravascular haemolysis on vascular homeostasis

The breakdown of senescent or defective red blood cells releases red cell contents, especially haemoglobin, which scavenges nitric oxide (NO) and decomposes to haem and free iron. These are potent oxidants, all of which have promoted the evolution of inducible and vasculoprotective compensatory pathways to rapidly clear and detoxify haemoglobin, haem and iron. Chronic haemolytic red cell disorders as diverse as sickle cell disease, thalassaemia, unstable haemoglobinopathy, cytoskeletal defects and enzymopathies have been linked to a clinical constellation of pulmonary hypertension, priapism, leg ulceration and possibly cerebrovascular disease and thrombosis. Besides free haemoglobin, haemolysis has been associated with extracellular arginase that limits substrate availability to NO synthase, endogenous inhibitors of NO synthase activity, and inappropriate activation of haemostatic pathways. This article reviews the haemolytic disorders that have been reported to manifest vascular complications, and explores the speculative possibility that haemolysis mediates some of the vascular complications of inflammation and diabetes.     

Traction injury during minimally invasive harvesting of the saphenous vein is associated with impaired endothelial function

OBJECTIVE: Many methods of minimally invasive surgical harvesting of the great saphenous vein have been developed because of the morbidity related to the long skin incision after traditional (open) great saphenous vein harvesting. One such method involves the use of multiple small incisions separated by 10- to 15-cm skin bridges through which the saphenous vein is harvested. We hypothesized that this method of saphenous vein harvesting might subject the saphenous vein to considerable traction forces, resulting in impaired endothelial cell function. METHODS: Four-millimeter great saphenous vein segments were obtained from patients undergoing elective coronary artery bypass graft surgery. Group A (minimally invasive surgery) consisted of 23 rings from 20 patients (age, 65.8 +/- 11.1 years, mean +/- SD). Group B (open harvesting) consisted of 33 rings from 8 patients (age, 69.8 +/- 8.6 years). All great saphenous vein segments were undistended and were used within 24 hours of harvesting. Isometric tension experiments were performed on each ring of the great saphenous vein by using a force-displacement transducer to measure the force of contraction in grams. Measurements included developed force after exposure to high-potassium depolarizing solution and 50 micromol/L phenylephrine and decrease in force of contraction (relaxation) after exposure to 1 and 10 micromol/L acetylcholine. RESULTS: There were no differences between the minimally invasive surgery and open harvesting groups in their responses to high-potassium depolarizing solution or phenylephrine: high-potassium depolarizing solution, contractions of 4.26 +/- 0.72 g (mean +/- SEM) and 3.95 +/- 0.38 g, respectively (P =.70); phenylephrine, contractions of 3.49 +/- 0.63 g and 2.73 +/- 0.39 g, respectively (P =.41). There was no net relaxation in segments from the minimally invasive surgery group after exposure to 1.0 or 10 micromol/L acetylcholine. In contrast, rings from the open harvesting group demonstrated relaxation of -0.41 +/- 0.07 g and -0.32 +/- 0.09 g after exposure to 1.0 and 10 micromol/L acetylcholine, respectively. CONCLUSIONS: In undistended saphenous vein segments isolated from patients undergoing minimally invasive surgical and open techniques of harvesting, there was no acetylcholine-mediated endothelium-dependent relaxation in the minimally invasive surgery group. Therefore harvesting of the great saphenous vein through multiple small incisions might result in endothelial dysfunction, possibly caused by traction injury.     

Benzene exposure assessment for use of a mineral spirits-based degreaser

This study examines benzene emissions from the use of a metal parts washer ("degreaser") supplied with a mineral spirits solvent containing either 9 or 58 ppm benzene. Air samples were obtained during a one-hour session of relatively vigorous parts cleaning activity using a degreaser station equipped with wet brush and sprayer attachments and a compressed air hose. Two methods were utilized to assess airborne benzene levels: U.S. EPA TO-14 (summa stainless steel canister) and NIOSH 1501 (charcoal tube). Overall, both methods provided similar results, excepting detection limit differences. The first simulation was performed with recycled solvent (9 ppm benzene in solvent) showing average one-hour airborne benzene levels < or =33 ppbv in the worker's breathing zone and directly above the parts cleaning tank. Average airborne benzene concentrations 18 inches away from the tank were below 2 ppbv during the 60-minute cleaning protocol. The second simulation with benzene-spiked recycled solvent (58 ppm benzene) showed airborne benzene levels averaging 500 ppbv measured over the 60-minute cleaning period in the worker's breathing zone and directly above the tank, while average concentrations 18 inches from the tank perimeter were 63 ppbv. The data indicate that average and peak exposures to airborne benzene were roughly proportional to the solvent benzene content, although the brief peak exposures exhibited greater variance probably related to aerosol generation associated with the use of the brush and/or spraying attachment. Under this selected upper bound exposure simulation, we found that cleaning parts using a recycled mineral spirits-based solvent in an open warehouse setting did not result in exposures in excess of the current occupational exposure limit of 0.5 ppm averaged over 8 hours for solvent benzene content between 9 and 58 ppm.