Effect of naloxone on microcirculatory behavior during irreversible hemorrhagic shock

Thirty-six male Sprague-Dawley rats were divided into three groups (n = 12): simple hemorrhagic shock group, saline-treated group, and naloxone-treated group. Synchronous videotape recording with two cameras was used to observe the relationship between the change of blood pressure and that of microcirculation of cremaster muscle. It has been suggested that the temporary plugging of capillaries by WBC may be the explanation for no reflow in microvessels after transfusion and infusion during the irreversible stage of shock. Administration of naloxone (2 mg/kg iv) followed by reinfusion of the shed blood is associated with an increase in blood pressure and pulse pressure. Coincidentally, a pulsatile movement of the blood, impacted on the stationary blood cells in capillaries, eventually dislodges them and leads to reperfusion of capillaries. Thereafter systemic blood pressure and carotid artery red blood cell velocity were increased and remained stable. The 24-hr survival rate was significantly increased in the naloxone-treated group (10/12), as compared with that in the saline-treated group (1/12). The mechanism of naloxone treatment is discussed. The suggestion is advanced that the effects on cardiac and microcirculatory performance may influence each other, and that both contribute to the pathogenesis of irreversible hemorrhagic shock.