Utility of an artificial oxygen carrier in a rat haemorrhagic shock model

Introduction

Hemorrhagic shock is a frequent encountered entity in a critical situation. The initial treatment for hemorrhagic shock is rapid replacement of massive extracellular fluid (ECF); however, sufficient oxygen transportation to peripheral tissue cannot be obtained only by ECF replacement. Lately, using state-of-the-art nanotechnology, an artificial oxygen transporter with the ribosome inclusion body (hemoglobin endoplasmic reticulum (HbV)) has been developed. In this study, measuring the serum lactate level and tissue lactate level, we investigated the effect of HbV on the peripheral oxygen metabolism by the microdialysis method in a fatal rat (Wister rat) model with hemorrhagic shock.

Methods

Cannulation was placed in the femoral vein of a rat and probes for measurement of the tissue oxygen partial pressure and microdialysis method were inserted into subcutaneous tissue of the abdominal wall. A shock model was made by exsanguinations from the femoral vein by 60% of the total body blood volume until the mean arterial pressure decreased to 25 ± 5 mmHg. We classified this shock model into two arms at random; ECF replacement arm (n = 10) and HbV arm (n = 8). The mean arterial pressure, plasma oxygen pressure, plasma lactate (p-lac), tissue partial oxygen pressure and tissue lactate (t-lac) of this shock model were measured every 50 minutes after exsanguinations until 250 minutes elapsed.

Results

Elevation of p-lac and t-lac was observed in each arm after exsanguinations. In both arms, p-lac elevated rapidly and then decreased after exsanguinations. While p-lac in the ECF arm re-elevated, that in the HbV arm decreased steadily. The p-lac in the HbV arm showed a significantly lower value than that in the ECF arm at each measured point (P < 0.05). After exsanguinations, t-lac elevated rapidly and then steadily elevated thereafter in the ECF arm, while t-lac in the HbV arm decreased. Similarly, t-lac in the HbV arm showed a significantly lower value than that in the ECF arm at each measured point (P < 0.05). In conclusion, the HbV arm significantly decreased p-lac and t-lac compared with the ECF arm in a fatal rat model with hemorrhagic shock.

Conclusion

Our study showed that HbV had better outcomes than ECF in terms of oxygen metabolism in peripheral tissue.