Effect of vasoactive treatment on the relationship between mixed venous and regional oxygen saturation

Abstract

Objective To evaluate the relationship between the mixed venous (So2), hepatic, and femoral venous oxygen saturations before and during sympathomimetic drug infusions. Design Case series. Setting Tertiary care center. Patients Twenty-four ICU patients: postoperative open-heart surgery patients (n = 12), patients with septic shock (n = 8), and patients with acute respiratory failure (n = 4). Interventions In postoperative open-heart surgery patients and patients with respiratory failure, cardiac output was increased by at least 25% following therapy with either dobutamine or dopamine. Patients with septic shock were treated with either dopamine or norepinephrine to correct hypotension. Measurements and Main Results Vasoactive drug infusions increased cardiac index and oxygen delivery by 34% and oxygen consumption by 8%. So2 increased (62.6 ± 6.7% vs. 69.5 ± 6.0%, p < .001). Although cardiac index was the most important determinant of So2, the correlation between cardiac index and So2 was weak (r2 = .32). The hepatic and femoral venous saturations also increased (49.0 ± 12.1% vs. 59.4 ± 9.8%, p < .01, and 51.9 ± 16.6% vs. 63.4 ± 9.8%, p < .001, respectively) in response to vasoactive treatment. The mean gradient between So2 and hepatic venous saturation was 11.9 ± 8.7% and was independent of the clinical condition and baseline So2. The hepatic venous oxygen saturation increased in parallel with So2 regardless of the initial So2 value. Conclusions The individual values of So2 have no predictive value concerning regional oxygen transport. The parallel increase in So2 and hepatic venous oxygen saturation suggests that the vasoactive treatment did not compromise splanchnic oxygenation.