Microvascular oxygen pressure in the pig intestine during haemorrhagic shock and resuscitation

1 The aim of this study was to investigate the relation between microvascular and venous oxygen pressures during haemorrhagic shock and resuscitation in the pig intestine. To this end microvascular P${}_{\text{O}{}_{\text{2}}}$ (μP${}_{\text{O}{}_{\text{2}}}$) was measured by quenching of Pd-porphyrin phosphorescence by oxygen and validated for the intestines. In addition, mesenteric venous blood gasses, blood flow, ilial CO₂ production and global haemodynamics were also measured. 2 In one group (n= 11), moderate shock was induced by withdrawal of 40% of the circulating blood volume. Seven of these animals were resuscitated with a crystalloid solution and four with the withdrawn blood. In a second group of three animals, a more severe shock was induced by withdrawal of 50% of the circulating blood volume; these animals were not resuscitated. 3 Baseline mesenteric venous P${}_{\text{O}{}_{\text{2}}}$ and μP${}_{\text{O}{}_{\text{2}}}$ values were similar (60 ± 9 and 60 ± 11 mmHg, respectively). During moderate shock, μP${}_{\text{O}{}_{\text{2}}}$ dropped significantly below mesenteric venous P${}_{\text{O}{}_{\text{2}}}$ (26 ± 10 versus 35 ± 8 mmHg). After resuscitation with crystalloid solution, μP${}_{\text{O}{}_{\text{2}}}$ and mesenteric venous P${}_{\text{O}{}_{\text{2}}}$ rose to 44 ± 9 and 44 ± 6 mmHg, respectively. In the group that received the withdrawn blood, values were 41 ± 9 and 53 ± 12 mmHg, respectively. Severe shock resulted in a drop in the mesenteric venous P${}_{\text{O}{}_{\text{2}}}$ (n= 3) to a value similar to that seen in the moderate shock group, but the gut μP${}_{\text{O}{}_{\text{2}}}$ dropped to a much lower value than that of the moderate shock group (15 ± 5 versus 26 ± 10 mmHg). 4 The results indicate that the oxygenation of the microcirculation of the gut can become lower than the venous P${}_{\text{O}{}_{\text{2}}}$ under conditions of haemorrhagic shock.