Background: The rate and magnitude of pH changes in the bowel during hemorr
hagic shock are greater than those in the stomach, implying that gastric in
tramucosal pH may not be a reliable indicator of gut perfusion. Here, we ev
aluate near-infrared spectroscopy (NIRS) to assess bowel pH in a swine shoc
k model.
Methods: Laparotomy was performed to place flow probes, pH microelectrodes,
and NIRS probes. Shock was maintained for 45 minutes at a blood pressure o
f 45 mm Hg, and resuscitation was achieved with shed blood and lactated Rin
ger's solution to baseline over 60 minutes.
Results: Hemodynamic measurements were significantly reduced during shock.
Lactic acid peaked during resuscitation and remained elevated. NIRS-measure
d pH was correlated to electrode-measured pH (R-2 = 0.903 [ischemia] and R-
2 = 0.889 [reperfusion]). Estimated measurement accuracy after subject-spec
ific offset correction was 0.083 pH units during ischemia and 0.076 pH unit
s during reperfusion.
Conclusion: NIRS determination of small-bowel pH may be a good tool to moni
tor the adequacy of resuscitation.