The effect of hypoxemic resuscitation from hemorrhagic shock on blood pressure restoration and on oxidative and inflammatory responses

Objective: We whether hypoxemic resuscitation from hemorrhagic shock prevents the late circulatory instability and attenuates the oxidative and inflammatory responses associated with the standard strategy. Design and setting: Prospective, randomized, controlled animal study in an experimental laboratory of a university intensive care unit. Subjects: Thirty-one New Zealand white rabbits weighting 3.1-3.4 kg Interventions: Anesthetized animals were subjected to hemorrhagic shock by exsanguinations to a mean arterial pressure of 40 mmHg for 60 min. Resuscitation was performed by reinfusing the shed blood for 30min under normoxemia ( PaO2 95-105 mmHg, control group, n = 10) or hypoxemia ( PaO2 35-40 mmHg, hypox-res group, n = 10); Ringer's lactate was given from 30 to 60min to restore arterial pressure within baseline values. A sham group was assigned ( n = 11). Animals were recorded for 120 min postresuscitation and for further 360 min to assess the early mortality rate. Measurements and results: Hypoxemic resuscitation compared with normoxemic resuscitation from hemorrhagic shock was associated with ( a) a better hemodynamic condition assessed by the gradual restoration of blood pressure, higher urinary output associated with less fluid infusion; (b) lower reactive oxygen species production assessed by the reduced blood geometric mean fluorescence intensity, lower malondialdehyde, and higher ratio of reduced to total glutathione levels; ( c) attenuation in the plasma concentrations of IL-1 beta, TNF-alpha, and IL-6; and (d) no difference in mortality rate. Conclusions: Hypoxemic resuscitation from hemorrhagic shock is more efficient than normoxemic in restoring the blood pressure and in attenuating the excessive oxidative and inflammatory responses observed during normoxemic resuscitation.