| Summary: | Many investigators advocate aggressive fluid therapy in sepsis, yet changes in
the microcirculation may make fluid counterproductive. Sepsis is characterized by a
generalized "leak" in capillaries which may promote interstitial edema which in
turn, may decrease diffusion of oxygen, increase the distance from capillaries to cells,
and alter capillary density. Further, fluid administration' may result in capillary
hemodilution. Therefore, the author's hypothesis was that crystalloid resuscitation
will impair the ability of tissue to extract oxygen.
Four groups (n=8) of anesthetized pigs received either normal saline infusion
(48 ml-kg-l-hr-1) or no saline, and E coli endotoxin (50 mg/kg i.v.) or no endotoxin.
Whole body and gut oxygen delivery and consumption were measured during
progressive hemorrhage. Dual line regression analysis was used to determine the
onset of ischemia (DO2C) and oxygen extraction ratio (ERc). At onset of ischemia,
gut was removed to determine degree of interstitial volume and the capillary
hematocrit. With use of radiolabelled microspheres as a marker of blood flow, the
gut blood flow transit time was determined. Endotoxin significantly decreased ERc
for the whole body (0.82+0.06 to 0.55±0.08, p < 0.05) and gut (0.77 ± 0.07 to 0.52 ± 0.06,
p < 0.05). Saline resuscitation also significantly decreased ERc in the control pigs for
the whole body (0.82 ± 0.06 to 0.62 ± 0.08, p < 0.05) and gut (0.77 ± 0.07 to 0.67 ± 0.06, p
< 0.05) but did not significantly change the already decreased ERc in the endotoxin
treated pigs. Morphometric techniques revealed that saline resuscitation increased
gut interstitial volume (p < 0.05), and lead to arterial hemodilution (p < 0.05) but not
capillary hemodilution (p > 0.05). Using radiolabeled microspheres, saline was
shown to increase the relative dispersion of blood flow transit times from 0.33 ± 0.08
to 0.72 ± 0.53 (p < 0.05). Thus, saline resuscitation impairs tissue oxygen extraction
possibly due to interstitial edema or increased heterogeneity of microvascular blood
flow. After endotoxin infusion, where ERc is already decreased, saline resuscitation
has a lesser effect. Therefore, the author questions the use of aggressive crystalloid
resuscitation for treatment of sepsis in humans. === Surgery, Department of === Medicine, Faculty of === Graduate
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