Transmural gut oxygen gradients in shocked rats resuscitated with heparan
D. D. Zabel, H. W. Hopf and T. K. Hunt
Department of Surgery, University of California-San Francisco.
OBJECTIVES: To develop a reproducible model to measure transmural gut
tissue PO2, to determine the gradient from serosa to mucosa during
normovolemia and hypovolemia, and to determine the effect of resuscitation
with heparan sulfate (danaparoid sodium) on this gradient. DESIGN:
Fluorescent tissue oxygen sensors were placed onto serosal and mucosal
surfaces of rat colon. Hemorrhagic shock was induced using a fixed pressure
(mean arterial pressure, 40 mm Hg) model and resuscitated with either
saline solution or heparan. RESULTS: Control animals had stable mean (+/-
SD) serosal and mucosal tissue oxygen tensions (PO2) of 64 +/- 4 and 10 +/-
2 mm Hg, respectively. In shocked animals, baseline serosal PO2 decreased
to 37 +/- 2 mm Hg at a mean (+/- SD) of 19 +/- 7 minutes after the
initiation of hemorrhage. Mucosal values decreased to a minimum of 4 +/- 2
mm Hg at 45 +/- 15 minutes after the initiation of hemorrhage. Serosal PO2
returned to baseline during resuscitation in both control and
heparan-resuscitated animals. Mucosal PO2 did not return to baseline in the
shock/no heparan group. In the heparan-resuscitated animals, however,
mucosal PO2 increased above baseline (13 +/- 3 mm Hg at 3 hours after
completion of hemorrhage). CONCLUSIONS: A transmural gradient of PO2 exists
across the colon with mucosal PO2 far lower than serosal PO2. Both serosal
and mucosal PO2 decrease during hypovolemia. During hypovolemia, the PO2 of
the entire gut wall is in a range in which phagocytic killing is impaired
by hypoxia. Heparan improved mucosal PO2 and it may restore and/or protect
gut function by oxygen-related mechanisms.
