Hypertonic colloid solutions reportedly exert protective effects on the microcirculation. The present study investigated the effects of a hypertonic saline hydroxyethyl starch (HES) solution on the oxygen extraction capabilities in an endotoxic shock model in the dog. Fourteen anesthetized and mechanically ventilated dogs received 2 mg/kg of Escherichia coli endotoxin before being randomly divided into two groups to receive a 4 mL/kg infusion in 10 min of either hypertonic (7.5%, n = 7), or isotonic (.9%, n = 7) HES solution. Thereafter, each animal received isotonic HES titrated to restore cardiac index to baseline levels, followed by a constant infusion of normal saline at 20 mL/kg throughout the study. The amount of fluid required to restore cardiac index to baseline levels was approximately one-half in the hypertonic saline HES group as compared with the isotonic group (123 ± 12 vs. 291 ± 62 mL/kg, p < .05). The two groups of dogs had similar mean arterial pressure and cardiac index values. Hypertonic saline HES-treated animals had a higher sodium concentration than the control group (144.4 ± 4.0 vs. 138.7 ± 3.1 mM/L, p < .05). There were no significant differences in blood gases or lactate concentrations between the groups. When cardiac tamponade was induced to study the tissue oxygen extraction capabilities, hypertonic saline HES-treated dogs had a slightly lower critical oxygen delivery (11.1 ± 1.6 vs. 14.2 ± 3.3 mL/kg·min, p = NS), and a significantly higher critical oxygen extraction ratio (61.9 ± 17.1 vs. 44.0 ± 11.5%, p < .05) than the isotonic group. We conclude that during endotoxic shock in dogs, hypertonic saline HES solution can increase whole body oxygen extraction capabilities, probably by an improvement in microvascular perfusion in septic conditions.