Reduction of hypoxia-induced pulmonary hypertension (HIPH) by mgso4 in sheep

Several drugs have been used to reduce HIPH. We investigated the effect of MgSO4 on HIPH in 7 sheep anesthetized and paralyzed, ventilated with 0.85 or 0.1 FİO2 and nitrogen. We monitored heart rate (HR), systemic and pulmonary arterial pressures, cardiac output (CO), end tidal CO2, arterial blood gases and serum Mg++ during hyperoxia and hypoxia before and after infusion of 0.9 saline (placebo) or MgSO4 (200 mg/kg) into the right atrium during the steady state of hypoxia. The table shows the results for all animals (X+SD). PaCO2 and pH were similar during hyperoxia & hypoxia. Serum Mg++ were similar in all the states before infusion and increased from 0.88+0.21 to 2.88 mmol/L after infusion. SPAP, DPAP and MPAP increased significantly during hypoxia compared to hyperoxia (p<0.001) with no change during placebo. Post MgSO4 infusion; a significant decrease in SPAP and MPAP occurred ( p <0.01,<0.001 respectively), DPAP showed a trend to decrease p<0.1 while systemic MBP and SBP did not change and DBP decreased (p<0.1, <0.1 and <0.01 respectively). CO did not change post Mg (p<0.6) and HR decreased transiently (p<0.001). We conclude that MgSO4 decreases pulmonary artery pressure significantly during HIPH without affecting significantly the BP and CO. Clinical applications in patients with hypoxia induced pulmonary hypertension require further studies.