Abstract
Magnesium relaxes constricted smooth muscle in systemic arterioles and bronchioles, and alveolar hypoxia causes pulmonary vasospasm. Since pulmonary vasoconstriction strains the right ventricle and causes shunting of blood away from the lung in the neonatal period, prevention of hypoxic pulmonary vasospasm would be beneficial; drugs used up to date to overcome this vasospasm have had undesirable side effects. We therefore determined the effect of intravenous infusions of isotonic, buffered MgCl2 in blocking hypoxic pulmonary vasospasm. Anesthetized dogs breathed 100 % O2, followed by 7 % O2, 10 % O2 or 10 % O2 6 % CO2. Systemic and pulmonary arterial pressures, heart rate, cardiac output (CO), respiration, plasma Mg and arterial pO2, pCO2 and pH were measured during high and low O2 breathing, before and following infusion of MgCl2. All dogs showed a marked rise in pulmonary vascular resistance (PVR) during hypoxia at normal blood Mg levels. As Mg-concentrations increased the rise in PVR during hypoxia lessened. At levels above 10 mEq/l hypoxic pulmonary vasoconstriction was usually absent. [Mg] of less than 13 mEq/l did not decrease resting CO or the CO response to hypoxia and did not cause hypotension or hypoventilation. [Mg] above 15 mEq/l produced hypoventilation and areflexia. It is concluded that controlled elevation of blood Mg to 10–12 mEq/l will block hypoxic pulmonary vasoconstriction without causing deleterious changes in hemodynamics or pulmonary ventilation. (Sponsored by American Heart Association) (SPR)
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Cropp, G., Battaglia, F. 5 Effect of Magnesium on Pulmonary Vasomotor Response to Hypoxia. Pediatr Res 1, 201 (1967). https://doi.org/10.1203/00006450-196705000-00012
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DOI: https://doi.org/10.1203/00006450-196705000-00012