Autologous transfusion of stored red blood cells increases pulmonary artery pressure.

RATIONALE: Transfusion of erythrocytes stored for prolonged periods is associated with increased mortality. Erythrocytes undergo hemolysis during storage and after transfusion. Plasma hemoglobin scavenges endogenous nitric oxide leading to systemic and pulmonary vasoconstriction. OBJECTIVES: We hypothesized that transfusion of autologous blood stored for 40 days would increase the pulmonary artery pressure in volunteers with endothelial dysfunction (impaired endothelial production of nitric oxide). We also tested whether breathing nitric oxide before and during transfusion could prevent the increase of pulmonary artery pressure. METHODS: Fourteen obese adults with endothelial dysfunction were enrolled in a randomized crossover study of transfusing autologous, leukoreduced blood stored for either 3 or 40 days. Volunteers were transfused with 3-day blood, 40-day blood, and 40-day blood while breathing 80 ppm nitric oxide. MEASUREMENTS AND MAIN RESULTS: The age of volunteers was 41 ± 4 years (mean ± SEM), and their body mass index was 33.4 ± 1.3 kg/m(2). Plasma hemoglobin concentrations increased after transfusion with 40-day and 40-day plus nitric oxide blood but not after transfusing 3-day blood. Mean pulmonary artery pressure, estimated by transthoracic echocardiography, increased after transfusing 40-day blood (18 ± 2 to 23 ± 2 mm Hg; P < 0.05) but did not change after transfusing 3-day blood (17 ± 2 to 18 ± 2 mm Hg; P = 0.5). Breathing nitric oxide decreased pulmonary artery pressure in volunteers transfused with 40-day blood (17 ± 2 to 12 ± 1 mm Hg; P < 0.05). CONCLUSIONS: Transfusion of autologous leukoreduced blood stored for 40 days was associated with increased plasma hemoglobin levels and increased pulmonary artery pressure. Breathing nitric oxide prevents the increase of pulmonary artery pressure produced by transfusing stored blood. Clinical trial registered with www.clinicaltrials.gov (NCT 01529502).

Transfusion of stored autologous blood does not alter reactive hyperemia index in healthy volunteers.

BACKGROUND: Transfusion of human blood stored for more than 2 weeks is associated with increased mortality and morbidity. During storage, packed erythrocytes progressively release hemoglobin, which avidly binds nitric oxide. We hypothesized that the nitric oxide mediated hyperemic response after ischemia would be reduced after transfusion of packed erythrocytes stored for 40 days. METHODS AND RESULTS: We conducted a crossover randomized interventional study, enrolling 10 healthy adults. Nine volunteers completed the study. Each volunteer received one unit of 40-day and one of 3-day stored autologous leukoreduced packed erythrocytes, on different study days according to a randomization scheme. Blood withdrawal and reactive hyperemia index measurements were performed before and 10 min, 1 h, 2 h, and 4 h after transfusion. The reactive hyperemia index during the first 4 h after transfusion of 40-day compared with 3-day stored packed erythrocytes was unchanged. Plasma hemoglobin and bilirubin concentrations were higher after transfusion of 40-day than after 3-day stored packed erythrocytes (P = 0.02, [95% CI difference 10-114 mg/l] and 0.001, [95% CI difference 0.6-1.5 mg/dl], respectively). Plasma concentrations of potassium, lactate dehydrogenase, haptoglobin, and cytokines, as well as blood pressure, did not differ between the two transfusions and remained within the normal range. Plasma nitrite concentrations increased after transfusion of 40-day stored packed erythrocytes, but not after transfusion of 3-day stored packed erythrocytes (P = 0.01, [95% CI difference 0.446-0.66 µM]). CONCLUSIONS: Transfusion of autologous packed erythrocytes stored for 40 days is associated with increased hemolysis, an unchanged reactive hyperemia index, and increased concentrations of plasma nitrite.

Pulmonary hypertension in lambs transfused with stored blood is prevented by breathing nitric oxide.

BACKGROUND: During extended storage, erythrocytes undergo functional changes. These changes reduce the viability of erythrocytes leading to release of oxyhemoglobin, a potent scavenger of nitric oxide. We hypothesized that transfusion of ovine packed erythrocytes (PRBC) stored for prolonged periods would induce pulmonary vasoconstriction in lambs, and that reduced vascular nitric oxide concentrations would increase this vasoconstrictor effect. METHODS: We developed a model of autologous stored blood transfusion in lambs (n = 36). Leukoreduced blood was stored for either 2 days (fresh PRBC) or 40 days (stored PRBC). Fresh or stored PRBC were transfused into donors instrumented for awake hemodynamic measurements. Hemodynamic effects of PRBC transfusion were also studied after infusion of N-nitro-L-arginine methyl-ester (25 mg/kg) or during inhalation of nitric oxide (80 ppm). RESULTS: Cell-free hemoglobin levels were higher in the supernatant of stored PRBC than in supernatant of fresh PRBC (Mean ± SD, 148 ± 20 vs. 41 ± 13 mg/dl, respectively, P < 0.001). Pulmonary artery pressure during transfusion of stored PRBC transiently increased from 13 ± 1 to 18 ± 1 mmHg (P < 0.001) and was associated with increased plasma hemoglobin concentrations. N-nitro-L-arginine methyl-ester potentiated the increase in pulmonary arterial pressure induced by transfusing stored PRBC, whereas inhalation of nitric oxide prevented the vasoconstrictor response. CONCLUSIONS: Our results suggest that patients with reduced vascular nitric oxide levels because of endothelial dysfunction may be more susceptible to adverse effects of transfusing blood stored for prolonged periods. These patients might benefit from transfusion of fresh PRBC, when available, or inhaled nitric oxide supplementation to prevent the pulmonary hypertension associated with transfusion of stored PRBC.

Inhaled nitric oxide improves outcomes after successful cardiopulmonary resuscitation in mice.

BACKGROUND: Sudden cardiac arrest (CA) is a leading cause of death worldwide. Breathing nitric oxide (NO) reduces ischemia/reperfusion injury in animal models and in patients. The objective of this study was to learn whether inhaled NO improves outcomes after CA and cardiopulmonary resuscitation (CPR). METHODS AND RESULTS: Adult male mice were subjected to potassium-induced CA for 7.5 minutes whereupon CPR was performed with chest compression and mechanical ventilation. One hour after CPR, mice were extubated and breathed air alone or air supplemented with 40 ppm NO for 23 hours. Mice that were subjected to CA/CPR and breathed air exhibited a poor 10-day survival rate (4 of 13), depressed neurological and left ventricular function, and increased caspase-3 activation and inflammatory cytokine induction in the brain. Magnetic resonance imaging revealed brain regions with marked water diffusion abnormality 24 hours after CA/CPR in mice that breathed air. Breathing air supplemented with NO for 23 hours starting 1 hour after CPR attenuated neurological and left ventricular dysfunction 4 days after CA/CPR and markedly improved 10-day survival rate (11 of 13; P=0.003 versus mice breathing air). The protective effects of inhaled NO on the outcome after CA/CPR were associated with reduced water diffusion abnormality, caspase-3 activation, and cytokine induction in the brain and increased serum nitrate/nitrite levels. Deficiency of the α1 subunit of soluble guanylate cyclase, a primary target of NO, abrogated the ability of inhaled NO to improve outcomes after CA/CPR. CONCLUSIONS: These results suggest that NO inhalation after CA and successful CPR improves outcome via soluble guanylate cyclase-dependent mechanisms.

Inhaled nitric oxide enables artificial blood transfusion without hypertension.

BACKGROUND: One of the major obstacles hindering the clinical development of a cell-free, hemoglobin-based oxygen carrier (HBOC) is systemic vasoconstriction. METHODS AND RESULTS: Experiments were performed in healthy mice and lambs by infusion of either murine tetrameric hemoglobin (0.48 g/kg) or glutaraldehyde-polymerized bovine hemoglobin (HBOC-201, 1.44 g/kg). We observed that intravenous infusion of either murine tetrameric hemoglobin or HBOC-201 induced prolonged systemic vasoconstriction in wild-type mice but not in mice congenitally deficient in endothelial nitric oxide (NO) synthase (NOS3). Treatment of wild-type mice by breathing NO at 80 ppm in air for 15 or 60 minutes or with 200 ppm NO for 7 minutes prevented the systemic hypertension induced by subsequent intravenous administration of murine tetrameric hemoglobin or HBOC-201 and did not result in conversion of plasma hemoglobin to methemoglobin. Intravenous administration of sodium nitrite (48 nmol) 5 minutes before infusion of murine tetrameric hemoglobin also prevented the development of systemic hypertension. In awake lambs, breathing NO at 80 ppm for 1 hour prevented the systemic hypertension caused by subsequent infusion of HBOC-201. CONCLUSIONS: These findings demonstrate that HBOC can cause systemic vasoconstriction by scavenging NO produced by NOS3. Moreover, in 2 species, inhaled NO administered before the intravenous infusion of HBOC can prevent systemic vasoconstriction without causing methemoglobinemia.

Soluble guanylate cyclase activator reverses acute pulmonary hypertension and augments the pulmonary vasodilator response to inhaled nitric oxide in awake lambs.

BACKGROUND: Inhaled nitric oxide (NO) is a potent and selective pulmonary vasodilator, which induces cGMP synthesis by activating soluble guanylate cyclase (sGC) in ventilated lung regions. Carbon monoxide (CO) has also been proposed to influence smooth muscle tone via activation of sGC. We examined whether direct stimulation of sGC by BAY 41-2272 would produce pulmonary vasodilation and augment the pulmonary responses to inhaled NO or CO. METHODS AND RESULTS: In awake, instrumented lambs, the thromboxane analogue U-46619 was intravenously administered to increase mean pulmonary arterial pressure to 35 mm Hg. Intravenous infusion of BAY 41-2272 (0.03, 0.1, and 0.3 mg x kg(-1) x h(-1)) reduced mean pulmonary arterial pressure and pulmonary vascular resistance and increased transpulmonary cGMP release in a dose-dependent manner. Larger doses of BAY 41-2272 also produced systemic vasodilation and elevated the cardiac index. N(omega)-nitro-l-arginine methyl ester abolished the systemic but not the pulmonary vasodilator effects of BAY 41-2272. Furthermore, infusing BAY 41-2272 at 0.1 mg x kg(-1) x h(-1) potentiated and prolonged the pulmonary vasodilation induced by inhaled NO (2, 10, and 20 ppm). In contrast, inhaled CO (50, 250, and 500 ppm) had no effect on U-46619-induced pulmonary vasoconstriction before or during administration of BAY 41-2272. CONCLUSIONS: In lambs with acute pulmonary hypertension, BAY 41-2272 is a potent pulmonary vasodilator that augments and prolongs the pulmonary vasodilator response to inhaled NO. Direct pharmacological stimulation of sGC, either alone or in combination with inhaled NO, may provide a novel approach for the treatment of pulmonary hypertension.