Hemodynamic effects of combined treatment with oxygen and hypertonic saline in hemorrhagic shock

OBJECTIVE: In hemorrhagic shock, small volume resuscitation with hypertonic saline transiently increases mean arterial blood pressure (MABP) and cardiac output and augments organ perfusion. Inhalation of 100% oxygen after hemorrhage also increases MABP and redistributes blood flow to the splanchnic and renal vascular beds. We evaluated hemodynamic effects of combined resuscitation with hypertonic saline and oxygen in shock induced by controlled bleeding in rats. DESIGN: Animal study. SETTING: Research laboratory. SUBJECTS: Male Sprague-Dawley rats. INTERVENTIONS: Animals were assigned to four hemorrhage groups that received posttreatment with a) normal saline; b) normal saline + 100% oxygen; c) hypertonic saline; d) hypertonic saline + oxygen, and a fifth sham-shock group that received hypertonic saline + oxygen. MEASUREMENTS AND MAIN RESULTS: Bolus infusion of small volume hypertonic saline markedly increased MABP (p < .001), hindquarter vascular resistance (p < .05), and distal aorta blood flow (p < .01). Hypertonic saline transiently increased superior (cranial) mesenteric artery (SMA) blood flow (p < .001) and small bowel perfusion (p < .01). Inhalation of oxygen after normal saline rapidly increased MABP (p < .01) and hindquarter vascular resistance (p < .02) and decreased distal aorta blood flow (p < .02) and perfusion of the gracilis muscle (p < .05). When given after normal saline, oxygen did not change SMA resistance and increased SMA flow (p < .05). The supplementation of oxygen after hypertonic saline did not exert additional effects on vascular resistance and blood flows in the two vascular beds. However, the combined treatment prevented the oxygen-induced decrease in distal aorta blood flow and gracilis muscle perfusion and maintained MABP at slightly higher values and SMA flow at significantly higher values than hypertonic saline alone until the end of the protocol (p < .01). The two hemorrhaged groups treated with oxygen exhibited the lowest final plasma lactate concentrations (p < .05 from normal saline and hypertonic saline groups). CONCLUSIONS: We suggest that early combined use of hypertonic saline and oxygen exerts a favorable extended profile of hemodynamic effects that amends shortcomings of each treatment alone in hemorrhagic shock.