Lactate generation is not related to tissue partial pressure of oxygen levels in sepsis

Objective

To analyze behavior of tissue partial pressure of oxygen (pO₂) measured in the liver during sepsis and to correlate its reduction with lactate levels.

Methods

Eleven large white pigs, weight 35 kg, in general anesthesia (isofluorane, fentanyl, pancuronium), fully monitored (electrocardiography, etCO₂, invasive pressure, pulmonary artery catheter, portal vein Doppler ultrasound flow, small bowel tonometry), were submitted to fecal peritonitis sepsis (1 g/kg feces plus 150 ml warm saline) after pO₂ and laser Doppler fluxometry probes were placed inside liver parenchyma. Laboratory and hemodynamic data were registered hourly. After the experiments, pigs were sacrificed with sedative overdose and KCl 19.1% injection.

Results

The model is well studied and very consistent. Hypotension occurs only in late phases (8th hour). Lactate generation seems to occur earlier (1st hour) than tissue pO₂ level reduction (4th hour), in septic pigs. (See Figures 1 and 2.)

Figure 1

(abstract P5)

Figure 2

(abstract P5)

Conclusion

Lactate generation not only seems to be related to tissue hypoxia in septic pigs. Inflammation and mitochondrial dysfunction may probably play a role in this pathological process. Further studies are needed to clarify these mechanisms. Perhaps other interventions, not only oxygen uptake optimization, ought to be necessary for early reversal of septic cascade.