Results

A total of 116 patients were evaluated for inclusion in the study between February 2006 and July 2010. Eighty-eight patients were randomized, 43 to the conventional group and 45 to the restrictive group. Twenty-eight patients were excluded because of the unavailability of a trained anesthesiologist or intensivist (n = 25) or an ICU bed (n = 1), acute myocardial infarction within six months of study inclusion (n = 1) and arrhythmia (n = 1). Because of technical problems, SV and DO₂ data were not available for three patients (all in the restrictive group) in the postoperative period (arrhythmia in one patient and loss of an arterial line in two). Patients were included in the analysis on an intention-to-treat basis.

Demographic and risk-scoring data from both groups are shown in Table 2. No significant differences between groups were found. The median age of the patients was 69 years. Pre-, intra- and postoperative data, therapeutic interventions, and tissue perfusion variables are given in Table3. The conventional group received a significantly greater amount of lactated Ringer's solution (4, 335 ± 1, 546 ml) during surgery than the restrictive group (2, 301 ± 1, 064 ml) (Mea ± SD) (P < 0.001). However, the restrictive group received a significantly greater amount of colloid (1, 216 ± 814 ml) than the conventional group (915 ± 559 ml) (P < 0.05). The mean doses of dobutamine administered to the conventional and restrictive groups, respectively, were 12.3 ± 7.3 μg/kg/minute vs 10.9 ± 5.9 μg/kg/minute intraoperatively (P = 0.32) and 9.5 ± 6.2 vs 8.0 ± 4.5 μg/kg/minute postoperatively (P = 0.19). There were 26 achievers (60.4%) in the conventional group and 18 (40%) in the restrictive group during surgery (P = 0.089). After surgery, a larger number of patients in both groups achieved the therapeutic goals (31 (73.0%) vs 28 (62.2%); P = 0.39).

Temporal patterns of DO₂I were similar between the two groups. After an initial decline following anesthesia induction, DO₂I recovered similarly in both groups (Figure 2). The P value for the treatment vs time interaction was < 0.0001. DO₂I levels were maintained at levels higher than baseline most of the time in both groups. Patterns of DO₂I were also similar in patients with or without complications, regardless of group assignment (data not shown). Serum lactate and pH did not differ between groups at baseline, ICU admission or 24 hours after surgery (Table 3). S_CVO₂values were similar at baseline and ICU admission but significantly lower in the restrictive group (72 ± 9) than in the conventional group (76 ± 8) after 24 hours (P < 0.05).

All but one patient in each group received at least one fluid challenge. In the conventional group, 104 fluid challenges were performed, of which 58.6% were positive. In the restrictive group, 143 fluid challenges were performed, of which 65% were positive (Table 3).

There were no differences in pulmonary or renal function between groups at any time (Table 4). Serum levels of CRP for the conventional and restrictive groups were 2.0 ± 2.5 mg/dl and 2.1 ± 2.4 mg/dl after admission to the ICU, respectively (P = 0.97). Twenty-four hours after admission to the ICU CRP levels were 12.0 ± 5.5 mg/dl in the conventional group and 11.9 ± 6.5 mg/dl in the restrictive group (P = 0.94).

In the restrictive group, the rate of major postoperative complications was 52% less than in the conventional group (20.0% vs 41.9%, RR = 0.48, 95% CI = 0.24 to 0.94; P = 0.046) (Table 5). The 60-day mortality rates were 6.9% in the conventional group and 2.2% in the restrictive group (not significant).