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Magnesium attenuates pulmonary hypertension due to hypoxia and group B streptococci
M E Anderson1, T M Burnette, D R Geiser
1Department of Pediatrics, University of Tennessee Medical Center at Knoxville 37920.
Abstract:
We investigated whether hypermagnesemia alleviates hypoxic or group B streptococcal (GBS) pulmonary hypertension (PH). Hypoxic PH was induced and maintained in 14 lambs by continuous ventilation with 12% oxygen. GBS PH was induced and maintained in 16 lambs by the continuous infusion of 5-10 x 10(8) colony-forming units.kg-1.h-1 of GBS. After the onset of PH, lambs were randomized to receive either magnesium sulfate (MgSO4, intermittent boluses of 0.38 mmol/kg, with a continuous infusion of 0.15 mmol.kg-1.h-1) or a similar volume of normal saline. Hypermagnesemia lowered pulmonary arterial pressure (PAP) and delayed the fall in systemic arterial pressure and stroke volume index seen in the control animals (each P < 0.05). At a serum magnesium concentration ([Mg]) of 2.75 +/- 0.25 mmol/l, PAP was 27 +/- 3 compared with 40 +/- 4 Torr in the control animals ([Mg] = 0.87 +/- 0.06 mmol/l; P < 0.05). In the GBS PH trial, hypermagnesemia prevented the continued increase in PAP seen in the control animals. At [Mg] = 2.15 +/- 0.07 mmol/l, PAP fell 2 +/- 1 Torr from prerandomization values, whereas it rose 4 +/- 2 Torr in the control animals ([Mg] = 0.59 +/- 0.07 mmol/l; P < 0.05). However, during the same time the systemic arterial pressure fell further in the magnesium-treated animals (-19 +/- 1 vs. -2 +/- 5 Torr). MgSO4 attenuates PH in both models but may cause systemic hypotension in sepsis.
Insights
Hypermagnesemia, or high blood magnesium, reduced pulmonary hypertension in lambs caused by hypoxia or Group B Streptococcus (GBS). However, magnesium sulfate may lower blood pressure in sepsis.
Area of Science:
- Cardiovascular Physiology
- Neonatal Medicine
- Pharmacology
Background:
- Pulmonary hypertension (PH) poses a significant risk in neonates, particularly when associated with hypoxia or infections like Group B Streptococcus (GBS).
- Effective therapeutic strategies for neonatal PH remain a critical area of research.
Purpose of the Study:
- To investigate the efficacy of hypermagnesemia, induced by magnesium sulfate (MgSO4), in alleviating both hypoxic and GBS-induced pulmonary hypertension in a lamb model.
- To assess the impact of hypermagnesemia on systemic hemodynamics in these PH models.
Main Methods:
- Two models of pulmonary hypertension were established in lambs: hypoxic PH (12% oxygen) and GBS-induced PH (continuous GBS infusion).
- Lambs with established PH were randomized to receive either magnesium sulfate (MgSO4) or normal saline.
- Hemodynamic parameters, including pulmonary arterial pressure (PAP) and systemic arterial pressure, were monitored.
Main Results:
- Hypermagnesemia significantly lowered pulmonary arterial pressure (PAP) in both hypoxic and GBS-induced PH models.
- MgSO4 treatment attenuated the rise in PAP in GBS-PH and reduced PAP in hypoxic-PH compared to control groups.
- While reducing PAP, hypermagnesemia was associated with a greater fall in systemic arterial pressure in the GBS-PH model.
Conclusions:
- Magnesium sulfate demonstrates a potential therapeutic benefit in attenuating pulmonary hypertension in neonatal models.
- The use of MgSO4 for PH may be limited by the risk of systemic hypotension, particularly in septic conditions.