Br. Soller et al., Application of fiberoptic sensors for the study of hepatic dysoxia in swine hemorrhagic shock, CRIT CARE M, 29(7), 2001, pp. 1438-1444
Objectives: To determine whether the simultaneous measurement of tissue pH,
Pco(2), and Po-2 with a multiple-parameter fiberoptic sensor can be used t
o indicate the onset of hepatic dysoxia, to determine critical values, and
to assess their use in predicting negative outcomes.
Design: Prospective animal study.
Setting: University research laboratory.
Subjects: Fourteen Yorkshire swine.
Interventions: Hemorrhagic shock (n = 11) was induced over 15 mins to lower
systolic blood pressure to 40 mm Hg and was maintained for 30, 60, or 90 m
ins. Resuscitation was achieved with shed blood and warm saline to maintain
mean pressure > 60 mm Hg for 120 mins. Sham animals (n = 3) were subjected
to 90 mins of sham shock, followed by a 120-min recovery period,
Measurements and Main Results: The multiple-parameter sensor continuously m
easured tissue pH, Pco(2), and Po-2 pH and Pco(2), indicators of anaerobic
metabolism, were plotted against tissue Po-2. All shocked animals, but no s
ham animals, showed a biphasic relationship between Po-2 and both pH and Pc
o(2). Curves were fit to both an exponential and a dual-line linear functio
n to determine critical values for Po-2, pH, and Pco(2). The length of time
the animal was dysoxic was evaluated as a predictor of negative outcome. C
ritical values determined from the exponential models were more sensitive i
ndicators of negative outcome than values determined from the linear model
and more sensitive than arterial lactate and tonometric intramucosal pH and
Pco(2),
Conclusions: The multiple-parameter sensor offers the unique opportunity to
study solid as well as hollow organ dysoxia through the simultaneous measu
rement of interstitial pH, Pco(2), and Po-2 in a small tissue region. The g
radual transition from sufficient oxygen availability to dysoxia as a resul
t of hemorrhage was better described by an exponential equation. The length
of time that ph was below or Pco(2) was above the critical value determine
d from the exponential model was predictive of a negative outcome.