Effects of inhaled nitric oxide on gas exchange and acute lung injury in premature lambs with moderate hyaline membrane disease✩

We previously demonstrated that 48 h of 100 ppm inhaled nitric oxide (NO) and 90% O2 causes surfactant dysfunction and pulmonary inflammation in mechanically ventilated newborn piglets. Because peroxynitrite (the product of NO and superoxide) is thought to play a major role in the injury process, recombinant human superoxide dismutase (rhSOD, a scavenger of superoxide) might minimize this insult. Four groups of newborn piglets (1-3 days of age) were ventilated with 100 ppm NO and 90% O2 for 48 h. Piglets received no drug, 5 mg/kg rhSOD intratracheally at time 0, 5 mg/kg rhSOD intratracheally at 0 and 24 h, or 10 mg/kg rhSOD by nebulization at time 0. At 48 h, bronchoalveolar lavage (BAL) was performed, and lung tissue was analyzed for markers of inflammation, oxidative injury, acute lung injury, and surfactant function. There were significant differences between rhSOD-treated piglets and untreated controls with respect to BAL neutrophil chemotactic activity, cell counts, and protein concentration as well as lung tissue malondialdehyde concentrations. Minimum surface tension of BAL surfactant from all groups studied was increased, with no differences found among groups. These data suggest that rhSOD, at the doses used, mitigated the inflammatory changes, oxidative damage, and acute lung injury from exposure to 100 ppm NO and 90% O2 but did not appear to improve surfactant function. This has important clinical implications for infants treated with hyperoxia and NO for neonatal lung disorders.

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Effect of inhaled nitric oxide on pulmonary hemodynamics after acute lung injury in dogs

Journal of Applied Physiology ◽

10.1152/jappl.1994.76.3.1356 ◽

1994 ◽

Vol 76 (3) ◽

pp. 1356-1362 ◽

Cited By ~ 19

Author(s):

J. A. Romand ◽

M. R. Pinsky ◽

L. Firestone ◽

H. A. Zar ◽

J. R. Lancaster

Keyword(s):

Nitric Oxide ◽

Acute Lung Injury ◽

Gas Exchange ◽

Lung Injury ◽

Dead Space ◽

Left Ventricular ◽

Right Atrial ◽

Adrenergic Blockade ◽

Pulmonary Hemodynamics ◽

Beta Adrenergic

Increased pulmonary vascular resistance (PVR) and mismatch in ventilation-to-perfusion ratio characterize acute lung injury (ALI). Pulmonary arterial pressure (Ppa) decreases when nitric oxide (NO) is inhaled during hypoxic pulmonary vasoconstriction (HPV); thus NO inhalation may reduce PVR and improve gas exchange in ALI. We studied the hemodynamic and gas exchange effects of NO inhalation during HPV and then ALI in eight anesthetized open-chest mechanically ventilated dogs. Right atrial pressure, Ppa, and left ventricular and arterial pressures were measured, and cardiac output was estimated by an aortic flow probe. Shunt and dead space were also estimated. The effect of 5-min exposures to 0, 17, 28, 47, and 0 ppm inhaled NO was recorded during hyperoxia, hypoxia, and oleic acid-induced ALI. During ALI, partial beta-adrenergic blockade (propranolol, 0.15 mg/kg i.v.) was induced and 74 ppm NO was inhaled. Nitrosylhemoglobin (NO-Hb) and methemoglobin (MetHb) levels were measured. During hyperoxia, NO inhalation had no measurable effects. Hypoxia increased Ppa (from 19.8 +/- 6.1 to 28.3 +/- 8.7 mmHg, P < 0.01) and calculated PVR (from 437 +/- 139 to 720 +/- 264 dyn.s.cm-5, P < 0.01), both of which decreased with 17 ppm NO. ALI decreased arterial PO2 and increased airway pressure, shunt, and dead space ventilation. Ppa (19.8 +/- 6.1 vs. 23.4 +/- 7.7 mmHg) and PVR (437 +/- 139 vs. 695 +/- 359 dyn.s.cm-5, P < 0.05) were greater during ALI than during hyperoxia. No inhalation had no measureable effect during ALI before or after beta-adrenergic blockade. MetHb remained low, and NO-Hb was unmeasurable. Bolus infusion of nitroglycerin (15 micrograms) induced an immediate decrease in Ppa and PVR during ALI.(ABSTRACT TRUNCATED AT 250 WORDS)

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