Oxygen transport patterns in patients with sepsis syndrome or septic shock: Influence of treatment and relationship to outcome

Objective: To investigate the relationship between oxygen transport patterns and outcome in patients with sepsis syndrome or septic shock managed according to two different treatment regimens. Design: Retrospective study of a subgroup of patients with sepsis syndrome or septic shock taken from a randomized, prospective, controlled trial. Setting: General intensive care units in a teaching and a district general hospital. Patients: Seventy-eight patients classified according to predetermined criteria as having sepsis syndrome or septic shock were drawn retrospectively from a larger study group of 109 consecutive patients considered to be at risk for developing multiple organ failure. Interventions: Ail patients received volume expansion to an optimal pulmonary artery occlusion pressure. If the therapeutic goals (cardiac index of >4.5 L/min/m(2), oxygen delivery [Do(2)] of >600 mL/min/m(2), and oxygen consumption [Do(2)] of >170 mL/min/m(2) were not achieved with fluids alone, patients were randomized to either a control group or a treatment group, in the treatment group, dobutamine (5 to 200 mu g/kg/min) was administered to increase cardiac index and Do(2) until all three goals were simultaneously achieved. In the control group, dobutamine was administered only if the cardiac index was <2.8 L/min/m(2). In both groups, norepinephrine was infused to maintain mean arterial pressure at 80 mm Hg. Measurements and Main Results: Hemodynamic, oxygen transport, and lactate measurements were made at the time of admission to the study, at the time of optimal volume administration, at 1, 2, 4, 8, 12, 16, 20, and 24 hrs, then every 6 hrs for the next 24 hrs, and at least every 8 brs thereafter. The time at which all therapeutic goats were first achieved simultaneously or the time of maximal Do(2) was identified and termed ''tmax''. Survivors from both the control and treatment groups significantly (p < .001) increased cardiac index and Do(2) in response to maximal resuscitation, and despite an associated decrease in oxygen extraction (p < .01), there was a significant (p < .01) increase in Vo(2). In nonsurvivors from both groups, despite significant increases in cardiac index (p < .05) and Do(2) (p < .01) at tmax, oxygen extraction decreased (p < .01) and Vo(2), remained unchanged. Do(2) and Vo(2) were significantly lower (p < .05) at tmax in nonsurvivors than in survivors from both groups. Persistently high lactate concentrations were characteristic of nonsurvivors. Conclusions: Survivors of sepsis syndrome or septic shock are characterized by an ability to increase both Do(2) and Vo(2). In contrast, nonsurvivors typically have reduced cardiac reserve, they fail to increase Vo(2) following resuscitation, and when delivery is enhanced with aggressive inotropic support, oxygen extraction falls. These patterns of response were similar in both treatment and control groups, although the magnitude of the changes was exaggerated in the treatment group. These observations may help to explain the findings by some investigators that treatment aimed at achieving survivor Values of cardiac index, Do(2), and Vo(2) fails to improve outcome when instituted following admission to intensive care.