Membrane microdialysis: Evaluation of a new method to assess splanchnic tissue metabolism

Perioperative Fluid Accumulation Impairs Intestinal Contractility to a Similar Extent as Peritonitis and Endotoxemia

BACKGROUND

Perioperative resuscitation with large amounts of fluid may cause tissue edema, especially in the gut, and thereby impairing its functions. This is especially relevant in sepsis where capillaries become leaky and fluid rapidly escapes to the pericapillary tissue. We assessed the effects of endotoxemia and peritonitis, and the use of high and moderate volume fluid resuscitation on jejunal contractility. We hypothesized that both endotoxemia and peritonitis impair jejunum contractility and relaxation, and that this effect is aggravated in peritonitis and with high fluid administration.

METHODS

Pigs were randomized to endotoxin (n = 16), peritonitis (n = 16), or sham operation (n = 16), and either high (20 mL/kg/h) or moderate volume (10 mL/kg/h) fluid resuscitation for 24 h or until death. At the end of the experiment, jejunal contractility and relaxation were measured in vitro using acetylcholine and sodium nitroprusside reactivity, and the effect of nitric oxide synthase inhibition (NOS-I) was assessed.

RESULTS

Mortality in the respective groups was 88% (peritonitis high), 75% (endotoxemia high), 50% (peritonitis moderate), 13% (endotoxemia moderate and sham operation high), and 0% (sham operation moderate volume resuscitation). Although gut perfusion was preserved in all groups, jejunal contractility was impaired in the two peritonitis and two endotoxemia groups, and similarly also in the sham operation group treated with high but not with moderate volume fluid resuscitation (model-fluid-contraction-interaction, P = 0.036; maximal contractility 136 ± 28% [average of both peritonitis, both endotoxemia and sham operation high-volume groups) vs. 170 ± 74% of baseline [sham operation moderate-volume group]). NOS-I reduced contractility (contraction-inhibition-interaction, P = 0.011) without significant differences between groups and relaxation was affected neither by peritonitis and endotoxemia nor by the fluid regimen.

CONCLUSIONS

Intestinal contractility is similarly impaired during peritonitis and during endotoxemia. Moreover, perioperative high-volume fluid resuscitation in sham-operated animals also decreases intestinal contractility. This may have consequences for postoperative recovery.

Effect of fluid resuscitation on mortality and organ function in experimental sepsis models

INTRODUCTION

Several recent studies have shown that a positive fluid balance in critical illness is associated with worse outcome. We tested the effects of moderate vs. high-volume resuscitation strategies on mortality, systemic and regional blood flows, mitochondrial respiration, and organ function in two experimental sepsis models.

METHODS

48 pigs were randomized to continuous endotoxin infusion, fecal peritonitis, and a control group (n = 16 each), and each group further to two different basal rates of volume supply for 24 hours [moderate-volume (10 ml/kg/h, Ringer's lactate, n = 8); high-volume (15 + 5 ml/kg/h, Ringer's lactate and hydroxyethyl starch (HES), n = 8)], both supplemented by additional volume boli, as guided by urinary output, filling pressures, and responses in stroke volume. Systemic and regional hemodynamics were measured and tissue specimens taken for mitochondrial function assessment and histological analysis.

RESULTS

Mortality in high-volume groups was 87% (peritonitis), 75% (endotoxemia), and 13% (controls). In moderate-volume groups mortality was 50% (peritonitis), 13% (endotoxemia) and 0% (controls). Both septic groups became hyperdynamic. While neither sepsis nor volume resuscitation strategy was associated with altered hepatic or muscle mitochondrial complex I- and II-dependent respiration, non-survivors had lower hepatic complex II-dependent respiratory control ratios (2.6 +/- 0.7, vs. 3.3 +/- 0.9 in survivors; P = 0.01). Histology revealed moderate damage in all organs, colloid plaques in lung tissue of high-volume groups, and severe kidney damage in endotoxin high-volume animals.

CONCLUSIONS

High-volume resuscitation including HES in experimental peritonitis and endotoxemia increased mortality despite better initial hemodynamic stability. This suggests that the strategy of early fluid management influences outcome in sepsis. The high mortality was not associated with reduced mitochondrial complex I- or II-dependent muscle and hepatic respiration.