The effect of different volumes of fluid resuscitation on traumatic-hemorrhagic shock at high altitude in the unacclimated rat.

The effects of different volumes of fluid resuscitation on traumatic hemorrhagic shock in unacclimated rats to high altitude were investigated. Seventy-eight Wistar rats were transported to LaSa, Tibet, 3760 meters above sea level, and traumatic hemorrhagic shock was induced by right-femur fracture plus bleeding to 45 mmHg of mean arterial pressure (MAP) for 1 h under the anesthesia of sodium pentobarbital (40 mg/kg, i.p.). Experiments were conducted in two series. In series I, 36 rats were equally divided into six groups: sham-operated, untreated (traumatic shock without fluid infusion), and with lactated Ringer's resuscitation (LR) of 1.0, 1.5, 2.0 or 3.0 times the shed blood (1, 1.5, 2, 3 vol LR group). MAP, left intraventricular systolic pressure, the maximal change rate of intraventricular pressure rise or decline (+/-dp/dtmax), the maximal physiological velocity of contractile element shortening, and the area of left intraventricular pressure-dp/dt vector loop (Lo) were observed at 30, 60, 90, and 120 min and the blood gases were determined at 30 and 120 min after resuscitation. Meanwhile the survival time was observed after the observation period. In series II, 42 rats were used to observe the effects of different volumes of fluid resuscitation on water content of lung and brain and hematocrit. One and 1.5 vol LR resuscitation significantly lifted MAP, left intraventricular systolic pressure, +dp/dtmax, and Lo, partially improved the blood gases and significantly prolonged the survival time. Although 2 and 3 vol of LR resuscitation caused apparent hemodilution and lung edema, they only partially improved hemodynamic parameters. Meanwhile 2 and 3 vol of LR resuscitation decreased the survival time. These results suggest that 1 and 1.5 vol of LR resuscitation can effectively resuscitate traumatic hemorrhagic shock at high altitude. More than two volumes of LR resuscitation would deteriorate the resuscitation outcome.