Renal and systemic oxygen consumption in patients with normal and abnormal renal function

Abstract

Systemic and renal oxygen consumption and hemodynamics were studied in patients with normal renal function (NI; serum creatinine concentration (Screat), 1.0 ± 0.04 mg/dL) and those with moderate chronic renal failure with diabetes mellitus Screat, 2.7 ± 0.2 mg/dL) or without diabetes mellitus (Screat, 2.4 ± 0.1 mg/dL). Patients with chronic renal failure were anemic and had normal systemic oxygen consumption (NI, 10,564 ± 277; chronic renal failure, 9,669 ± 362 μmol of O2/min) and elevated systemic oxygen extraction (NI, 22.9 ± 1; chronic renal failure, 30.9 ± 1.2%) (P < 0.02). Cardiac output and index and arterial oxygen saturation were equivalent in normal patients and in patients with chronic renal failure. Patients with chronic renal failure had higher renal oxygen extraction (NI, 7.3 ± 0.8; chronic renal failure, 13.9 ± 1%), lower RBF (NI, 572 ± 146; chronic renal failure, 197 ± 20 mL/min/kidney), and lower renal oxygen consumption per kidney (NI, 391 ± 101; chronic renal failure, 177 ± 20 μmol of O2/min/kidney) than did normal patients (P < 0.02 ). There was a linear relationship between hemoglobin and RBF (r = 0.47, P < 0.02). Patients with chronic renal failure and diabetes had lower RBF (diabetes mellitus, 146 ± 23; without diabetes, 242 ± 28 mL/min/kidney) and renal oxygen consumption per kidney (diabetes mellitus, 131 ± 21; without diabetes, 218 ± 29 μmol of O2/min/ kidney (P < 0.03) but equivalent renal oxygen extraction when compared with patients without diabetes. Patients with chronic renal failure without diabetes mellitus had higher renal oxygen consumption when expressed per 100 mL of creatinine clearance (diabetes mellitus, 1,016 ± 150; without diabetes mellitus, 1,453 ± 175 μmol of O2/min/100 mL of creatinine clearance; P < 0.03). There was a significant linear relationship (P < 0.005, r = 0.38) between calculated creatinine clearance and renal oxygen consumption with a y intercept representing basal renal oxygen consumption (115 μmol of O2/min/kidney) and a slope of 2.3 μmol of O2/mL. Patients with moderate chronic renal failure have normal systemic oxygen consumption but reduced RBF and renal oxygen consumption. The latter parameters are even lower in patients with chronic renal failure and diabetes. Renal hypermetabolism is more likely to exist in nondiabetic than diabetic renal disease. Basic human renal physiology and pathophysiology are described by the relationships between renal oxygen consumption, blood flow, oxygen extraction, and creatinine clearance in patients with normal and abnormal renal function of varied cause.