title: The combined effects of hypoxemia and mechanical ventilation on renal function.
abstract: The combined effects of hypoxemia and mechanical ventilation on renal function were investigated in anesthetized dogs. Spontaneously breathing dogs (S) and dogs mechanically ventilated with a volume-ventilator (V) were made hypoxemic by breathing hypoxic gas to achieve PaO2 values of 35 and 22 mm Hg. At a PaO2 of 35 mm Hg, urine output and sodium excretion were increased in both groups. These responses closely followed the blood pressure response, which was greater in the V group. Renal blood flow (RBF), glomerular filtration rate (GFR), and fractional sodium excretion (FNA) were unchanged. At a PaO2 of 22 mm Hg, both groups demonstrated a reduction in urine flow, sodium excretion, FNA, RBF, and GFR. However, the mechanism involved was different and ventilator-dependent. At this low PaO2, arterial blood pressure was reduced in the S group with no change in renal resistance, while blood pressure increased in the V group with a marked increase in renal resistance as a result of the modification of the cardiovascular effects of lung inflation reflexes by mechanical ventilation. These results indicate that renal function is well-maintained at low PaO2 values (35 mm Hg) and reduced at more severe hypoxemia, mainly in response to systemic hemodynamics.
mesh_terms: D000818:Animals; D001794:Blood Pressure; D004285:Dogs; D005919:Glomerular Filtration Rate; D006339:Heart Rate; D000860:Hypoxia / Q000503:physiopathology* / Q000652:urine; D007668:Kidney / Q000098:blood supply / Q000503:physiopathology*; D012039:Regional Blood Flow; D012121:Respiration, Artificial / Q000009:adverse effects; D012964:Sodium / Q000652:urine
chemical_list: D012964:Sodium