Comparison of Melatonin, Hypertonic Saline, and Hydroxyethyl Starch for Resuscitation of Secondary Intra-Abdominal Hypertension in an Animal Model

A variety of agents may have a beneficial effect in reducing injury-induced intestinal edema of fluid, but studies confirming the efficacy and mechanisms of these agents in secondary intra-abdominal hypertension (IAH) are lacking. This study was to compare the effectiveness of melatonin, 7.5% hypertonic saline (HS), and hydroxyethyl starch 130/0.4 (HES) on the resuscitation of secondary IAH in a rat model. Female SD rats were divided into: sham group, shock group, lactated Ringer solution (LR) group, melatonin group, HS group, and HES group. Except for the sham group, all rats underwent a combination of inducing portal hypertension, hemorrhaging to a MAP of 40 mmHg for 2 hr, and using an abdominal restraint device. The collected blood was reinfused and the rats were treated with LR (30ml/h), melatonin (50 mg/kg) + LR, HS (6 ml/kg) + LR, and HES (30 ml/kg) + LR, respectively. The shock group received no fluids. LR was continuously infused for 6hr. The intestinal permeability, immunofluorescence of tight junction proteins, transmission electron microscopy, level of inflammatory mediators (TNF-a, IL-1β, IL-6) and of biochemical markers of oxidative stress (malondialdehyde, myeloperoxidase activity, and glutathione peroxidase) were assessed. Expressions of the protein kinase B (Akt) and of tight junction proteins were detected by Western blot. Compared with LR, HS, and HES, melatonin was associated with less inflammatory and oxidative injury, less intestinal permeability and injury, and lower incidence of secondary IAH in this model. The salutary effect of melatonin in this model was associated with the upregulation of intestinal Akt phosphorylation.