Evaluation of tissue perfusion by microdialysis technique with 3H₂O indicator in the rat model of haemorrhagic shock

Overview

Objective:
To evaluate the indicator microdialysis technique with 3H₂O as a method of estimation of local blood flow in skeletal muscle and liver in the rat model of haemorrhagic shock.

Methods:
Microdialysis probes were inserted in the hind limb muscle and liver of 9 rats and perfused with perfusate containing 3H₂O. Haemorrhagic shock was induced in 6 rats by repeated exsanguinations and 3 rats were used as the control group.The outflow-to-inflow ratio of water activity, lactate and pyruvate in the dialysate were repeatedly measured and the lactate to pyruvate ratio (L/P) was calculated. Spearman correlation coefficient and T-test were used for statistical analysis, *P = 0.05.

Results:
There was no correlation between the blood loss and the outflow-inflow ratio in either the muscle (r = 0.49) or the liver (r = 0.23). Similarly there was no correlation between the lactate concentration in the dialysate and the outflow-inflow ratio in both the muscle (r = 0.29) and the liver (r = –0.15). Significant difference in both the lactate concentration (P < 0.05) and L/P ratio (P < 0.05) between the rats with haemorrhagic shock and the control animals was found in more severe grades of blood loss.

Conclusions:
Microdialysis with 3H₂O cannot be used as a sensitive method for estimation of the regional blood flow changes during haemorrhagic shock in rats. Measuring the lactate, pyruvate and L/P ratio in the microdialysate seems to be a better method for estimation of tissue hypoperfusion due to haemorrhagic shock.

Key words:
microdialysis technique with 3H₂O – ratio of water activity, lactate and pyruvate in the dialysate – lactate to pyruvate ratio – severe grades of blood loss