Abstract
Simultaneous hemodynamic, ventilatory, and blood gas studies were performed in 16 men with congestive heart failure before and during infusion of sodium nitroferricyanide (nitroprusside). The cardiac index increased from 2.00 ± 0.16 L/min/sq m (SE) to 2.38 ± 0.14 L/min/sq m, and the total pulmonary and systemic peripheral resistances fell from 928 ± 123 to 494 ± 57 dynes sec cm -5 and from 2,208 ± 210 to 1,558 ± 121 dynes sec cm -5 , respectively. Both systemic and pulmonary arterial pressures decreased during infusion of sodium nitroferricyanide, and the mixed venous oxygen pressure increased. There was no change in total or alveolar ventilation, arterial carbon dioxide tension, pH, or base excess; however, the mean arterial oxygen pressure (PaO 2 ) decreased from 74 ± 3 mm Hg to 68 ± 3 mm Hg and the venous admixture effect increased from 8 ± 1 percent to 13 ± 2 percent We conclude that the decrease in PaO 2 during infusion of sodium nitroferricyanide resulted from a worsening of the ventilation-perfusion relationships due to increased perfusion of underventilated pulmonary units.
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