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

Abstract

Objective: To evaluate the relationship between the mixed venous (SvO2), 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%. SvO2 increased (62.6 +/- 6.7% vs. 69.5 +/- 6.0%, p less than .001). Although cardiac index was the most important determinant of SvO2, the correlation between cardiac index and SvO2 was weak (r2 = .32). The hepatic and femoral venous saturations also increased (49.0 +/- 12.1% vs. 59.4 +/- 9.8%, p less than .01, and 51.9 +/- 16.6% vs. 63.4 +/- 9.8%, p less than .001, respectively) in response to vasoactive treatment. The mean gradient between SvO2 and hepatic venous saturation was 11.9 +/- 8.7% and was independent of the clinical condition and baseline SvO2. The hepatic venous oxygen saturation increased in parallel with SvO2 regardless of the initial SvO2 value.

Conclusions: The individual values of SvO2 have no predictive value concerning regional oxygen transport. The parallel increase in SvO2 and hepatic venous oxygen saturation suggests that the vasoactive treatment did not compromise splanchnic oxygenation.