[Effects of different fluid resuscitation regimes on lung injury and expression of pulmonary aquaporin 1 and aquaporin 5 in uncontrolled hemorrhagic shock in rats].

OBJECTIVE: To investigate the effects of different fluid resuscitation regimes on lung injury and expression of pulmonary aquaporin 1 (AQP1) and AQP5 in rats with uncontrolled hemorrhagic shock.

METHODS: Sixty Sprague-Dawley (SD) rats were randomly assigned to the following five groups: control group (C group), no fluid resuscitation group (NF group), lactated Ringer's solution group (LRS group), 7.5%NaCl group (HS group) and hydroxyethyl starch group (hydroxyethyl starch 130/0.4, HES group). A four-phased uncontrolled hemorrhagic shock model was reproduced. Uncontrolled hemorrhagic shock phase began with blood withdrawal extended over 15 minutes, in which animals were subjected to massive hemorrhage [mean arterial pressure (MAP)=40 mm Hg (1 mm Hg=0.133 kPa)] for 60 minutes and followed by intratracheal lipopolysaccharide 2 mg/kg and continuous bleeding with amputation of the tail. Then, animals were partially resuscitated with LRS of 3 times the volume of shed blood (LRS group), followed by a bolus dose of 4 ml/kg body weight of 7.5%NaCl (HS), or hydroxyethyl starch (a volume equal to that of the shed blood), respectively, during different fluid resuscitation regimes. After that, comprehensive resuscitation phase of 60 minutes began with hemostasis, and transfusion of all the shed blood plus same amount of normal saline. Observation phase was continued for 3.5 hours. At the end the experiment, the lung tissue was sampled to measure wet-to-dry lung weight ratio (W/D), and the expression of AQP1 and AQP5 were determined with immunohistochemistry. The paraffin-embedded lungs were stained with hematoxylin and eosin for pathological analysis.

RESULTS: When compared with NF and LRS groups, the lung W/D ratio was significantly decreased, and the shock induced decreased expression of AQP1 and AQP5 in lung tissue were attenuated in HES group, but these beneficial effects were blunted in the HS group.

CONCLUSION: Uncontrolled hemorrhagic shock may induce lung injury and pulmonary edema as well as down regulation of the expression of AQP1 and AQP5 in rats. Resuscitation with hypertonic fluids, especially with HES, can reduce lung damage and pulmonary edema in this kind of shock. The cause may be due in part to maintenance of the expression of AQP1 and/or AQP5 in the lung. Pulmonary AQP1 and AQP5 play an important role in fluid transportation.