Multiple organ failure syndrome

A pilot study to explore the safety of perioperative postpyloric enteral nutrition

BACKGROUND

The practice of holding enteral nutrition (EN) 8 hours prior to surgery is common. We hypothesized that it was safe to continue postpyloric EN, and we developed an institutional practice pattern to investigate our hypothesis.

METHODS

Our pilot study included intubated patients in the surgical intensive care unit at Froedtert Memorial Lutheran Hospital who received EN via a nasojejunal (NJ) feeding tube and underwent 1 or more surgical procedures. Demographic, illness, and injury information were collected as well as length of time to NJ placement, time to initiation of EN, EN interruptions, and complications. Additional hours of EN were calculated by totaling the number of hours a patient received EN past midnight on the day of surgery.

RESULTS

A total of 14 patients with mean (SD) age 44.3 (19.9) were included. Patients had a mean (SD) Injury Severity Score (ISS) of 26.1 (9.2) on admission and underwent a total of 38 operations following placement of a feeding tube. The most frequent operation performed was an orthopedic procedure (n = 17; 46.1%). The mean (SD) length of EN interruptions for a single procedure was 222.4 (206.9) minutes. Patients received an additional 11.9 (4.7) hours of EN over the course of their hospitalization and an additional 1064.9 (490) kcal/d per operation. There were no adverse events.

CONCLUSION

Perioperative continuation of postpyloric EN is feasible in some critically ill surgical patients and can result in additional calories provided. A multidisciplinary approach and an institutional policy can increase the likelihood of meeting nutrition goals in these patients.

Severe acute pancreatitis: case-oriented discussion of interdisciplinary management

The clinical course of an episode of acute pancreatitis varies from a mild, transitory illness to a severe often necrotizing form with distant organ failure and a mortality rate of 20-40%. Patients with severe pancreatitis, representing about 15-20% of all patients with acute pancreatitis, need to be identified as early as possible after onset of symptoms allowing starting intensive care treatment early in the disease process. An episode of severe acute pancreatitis progresses in two phases. The first 10-14 days are characterized by a systemic inflammatory response syndrome maintained by the release of various inflammatory mediators. The second phase, beginning about 10-14 days after the onset of the disease is dominated by sepsis-related morbidity due to infected peripancreatic and pancreatic necrosis. This state is associated with septic multiple organ systemic failure. The importance of infection on the outcome of necrotizing pancreatitis has been clearly delineated and the pre-emptive use of broad-spectrum antibiotics that achieve effective tissue concentrations is considered standard management of patients with severe necrotizing pancreatitis, especially if associated with organ failure or extended necrosis. Patients with infected necrosis should undergo a surgical intervention. The standard open technique consisting of an organ preserving necrosectomy followed by a postoperative concept of lavage and/or drainage to evacuate necrotic debris occurring during the further course has recently been challenged by various minimally invasive approaches.

Bladder Mucosa pH and Pco2 as a Minimally Invasive Monitor of Hemorrhagic Shock and Resuscitation

BACKGROUND

Continuous monitoring of pH, Pco2, and Po2 using fiberoptic sensor technology has been proposed recently as a clinical monitor of the severity of shock and impaired tissue perfusion. Surrogates of gut tissue perfusion such as gastric tonometry, although cumbersome, have been used to indirectly quantify the degree of gut ischemia. The purpose of this study was to demonstrate the feasibility of monitoring bladder mucosa (BM) and to compare urinary bladder mucosa and proximal jejunum mucosa interstitial pH and Pco2 during hemorrhagic shock and resuscitation.

METHODS

Eleven male miniature swine (25-35 kg) (control, n = 4; shock, n = 7) underwent jejunal tonometry and cystostomy. A multisensor probe was placed adjacent to the BM. Urine was diverted. Normocarbia was maintained. Animals were hemorrhaged and kept at a mean arterial pressure of 40 mm Hg. When a constant infusion was required to maintain the mean arterial pressure at 40 mm Hg (decompensation), animals were resuscitated with shed blood plus two times the shed volume in lactated Ringer's solution (20 minutes) and observed for 2 hours.

RESULTS

During decompensation, BM pH values decreased significantly from 7.33 +/- 0.08 to 7.01 +/- 0.2 (p < 0.01) and recovered to 7.11 +/- 0.19 at 120 minutes after completion of resuscitation. During decompensation, BM Pco2 values increased significantly compared with baseline (from 49 +/- 6 mm Hg to 71 +/- 19 mm Hg, p < 0.05) and returned to baseline with resuscitation. Jejunum mucosa and BM interstitial Pco2 correlated throughout shock and resuscitation (r = 0.49). Bland-Altman analysis demonstrated significant differences between jejunum mucosa (intramucosal pH) and BM interstitial pH.

CONCLUSION

Shock-induced changes in the Pco2 of the BM are comparable to tonometric changes in the gut. These data suggest that continuous fiberoptic multisensor probe monitoring of the BM could potentially provide a minimally invasive method for the assessment of impaired tissue perfusion of the splanchnic circulation during shock and resuscitation.

Induction of a hypermetabolic state in cultured hepatocytes by glucagon and H2O2

Stress hormones and pro-inflammatory cytokines are putative signals triggering increased energy expenditure or "hypermetabolism" commonly observed in inflammatory states. Cytokines also cause the release of reactive oxidants by immune cells resident in tissues in vivo. Therefore, we hypothesized that oxidative stress plays a role in the induction of hypermetabolism. We examined the effect of glucagon (1.0 nM), a catabolic stress hormone, and the oxidant H(2)O(2) (1.0 mM) on the metabolism of stable hepatocyte cultures for 4 days. Combined H(2)O(2) and glucagon treatment, but not H(2)O(2) or glucagon used alone, increased the hepatocyte oxygen uptake rate 25% above control untreated cells after a lag-time of 72 h. The same treatment also increased the expression of mitochondrial uncoupling protein-2 (UCP2). These effects were significantly inhibited by the antioxidant N-acetylcysteine (5mM) and the pentose phosphate pathway (PPP) inhibitor dehydroepianderosterone (200 microM). Glucagon alone induced urea synthesis and H(2)O(2) alone induced the PPP. These findings show, for the first time, that oxidative stress, in combination with glucagon, increases metabolic energy expenditure in cultured cells, and that this effect may be mediated by UCP-2. Furthermore, the results implicate the PPP in the induction of the hypermetabolic response.

Profiling of dynamic changes in hypermetabolic livers

The liver plays an important role in the overall negative nitrogen balance leading to muscle wasting commonly observed in patients following many conditions, including severe injury, cancer, and diabetes. In order to study changes in liver metabolism during the establishment of such catabolic states, we used a rat skin burn injury model that induces hypermetabolism and muscle wasting. At various times during the first week following the injury, livers were isolated and perfused in a recirculating system under well-defined conditions. We applied a steady-state metabolic flux analysis model of liver metabolism and then used k-means clustering to objectively group together reaction flux time profiles. We identified six distinct groups of reactions that were differentially responsive: (1) pentose phosphate pathway (PPP); (2) amino acid oxidation reactions leading to the formation of tricarboxylic acid (TCA) cycle intermediates; (3) gluconeogenesis; (4) TCA-cycle and mitochondrial oxidation; (5) lipolysis, beta-oxidation, and ketone body formation; and (6) urea-cycle. Burn injury sequentially upregulated the urea-cycle, the PPP, and the TCA-cycle, in order, while beta-oxidation and gluconeogenesis remained unchanged. The upregulation of the PPP was transient, whereas the rise in urea- and TCA-cycle fluxes was sustained. An ATP balance predicted an increased production of ATP and energy expenditure starting on day 3 post-burn, which correlated with the induction of the oxidative phosphorylation uncoupler uncoupling protein-2. We conclude that metabolic profiling using flux analysis and clustering analysis is a useful methodology to characterize the differential activation of metabolic pathways in perfused organs and to identify specific key pathways that are sensitive to a stimulus or insult without making a priori assumptions.

Metabolic flux analysis of postburn hepatic hypermetabolism

The hepatic response to severe injury is characterized by a marked upregulation of glucose, fatty acid, and amino acid turnover, which, if persistent, predisposes the patient to progressive organ dysfunction. To study the effect of injury on liver intermediary metabolism, metabolic flux analysis was applied to isolated perfused livers of burned and sham-burned rats. Intracellular fluxes were calculated using metabolite measurements and a stoichiometric balance model. Significant flux increases were found for multiple pathways, including mitochondrial electron transport, the TCA and urea cycles, gluconeogenesis, and pentose phosphate pathway (PPP). The burn-induced increase in gluconeogenesis did not significantly increase glucose output. Instead, glucose-6-phosphate was diverted into the PPP. These changes were paralleled by increases in glucose-6-phosphate dehydrogenase (G6PDH) and glutathione reductase (GR) activities. Given that G6PDH and GR are the most significant NADPH producers and consumers in the liver, respectively, and that GR is responsible for recycling the free radical scavenger glutathione, these data are consistent with the notion that hepatic metabolic changes are in part due to the induction of liver antioxidant defenses.

Increased intestinal permeability is associated with the development of multiple organ dysfunction syndrome in critically ill ICU patients

We conducted a prospective, observational cohort study designed to compare intestinal permeability (IP) and development of multiple organ dysfunction syndrome (MODS) in a subset of critically ill patients in an intensive care unit (ICU). All patients with an expected ICU stay of 72 h or more were entered into the study, and IP was determined on a daily basis whenever possible from the urinary fractional excretion of orally administered lactulose and mannitol (LMR). Forty-seven consecutive patients were studied, and 28 developed MODS either at the time of admission or during their ICU course. These patients, as a group, had significantly worse IP at admission than did a non-MODS cohort (LnLMR: -2.10 +/- 1.10 versus -3.26 +/- 0.83). Those patients who developed MODS following admission also had a significantly greater admission IP than did the non-MODS group (-2.51 +/- 0.85). Differences in IP between cohorts could not be explained by differences in the incidence of systemic inflammatory response syndrome (SIRS)/sepsis or shock. With multivariate regression analysis, the only parameter present on admission that was predictive of subsequent MODS was IP. Differences in IP and the severity of organ dysfunction were also present (MODS severity mild: -3.01 +/- 0.72; moderate: -1.97 +/- 0.69; and severe: -1.12 +/- 0.96). Patients who developed MODS had a persistently abnormal IP during their ICU stay, and a significantly delayed improvement in their IP compared with the non-MODS cohort. We conclude that the development of MODS is associated with an abnormal and severe derangement of IP that is detectable prior to the onset of the syndrome. This observation lends credence to the premise that gastrointestinal (GI) dysfunction may be causally associated with the development of MODS in the critically ill patient.