The postischemic gut serves as a priming bed for circulating neutrophils that provoke multiple organ failure

Effects of abdominal decompression on cardiopulmonary function and visceral perfusion in patients with intra-abdominal hypertension

OBJECTIVE

Increased intra-abdominal pressure (IAP) compromises cardiopulmonary function and visceral perfusion. Our goal was to characterize acute changes in these subsystems associated with operative abdominal decompression.

PATIENT POPULATION

A series of 11 consecutive injured patients monitored with a pulmonary artery catheter and nasogastric tonometer in whom operative decompression was performed. Indications for decompression included oliguria or progressive acidosis despite aggressive resuscitation in the presence of elevated IAP (>25 mm Hg).

MAIN OUTCOME MEASURES

Studied hemodynamic variables included pulmonary artery occlusion pressure (PAOP), right ventricular end-diastolic volume index (RVEDVI), and cardiac index (CI). Pulmonary variables included shunt fraction (Qs/Qt) and dynamic compliance (Cdyn). Visceral perfusion was assessed using hourly urine output 4 hours before and after decompression (UOP) and gastric intramucosal pH (pHi). Mean values before and after decompression were compared using the paired t test. Linear regression and Fisher's z transformation were used to evaluate the relationships between RVEDVI, PAOP, CI, and IAP. IAP was transduced via bladder pressures. Significance was defined as p < 0.05. Data are expressed as means+/-SD.

RESULTS

IAP decreased with decompression (49+/-11 to 19+/-6.8 mm Hg; p < 0.0001). RVEDVI improved independent of CI and correlated better (p < 0.01) with CI (r =0.49, p=0.04) than PAOP did (r=-0.36, p=0.09). PAOP correlated significantly with IAP (r=0.45, p=0.04). Decompression resulted in significant improvements in Qs/Qt, Cdyn, UOP, and pHi.

CONCLUSION

Abdominal decompression in patients with increased IAP improves preload, pulmonary function, and visceral perfusion. Elevated IAP has important effects on PAOP, which makes the PAOP an unreliable index of preload in these patients.

The impact of antioxidant and splanchnic-directed therapy on persistent uncorrected gastric mucosal pH in the critically injured trauma patient

BACKGROUND

Critically ill trauma patients with gastric intramucosal acidosis, as measured by gastric tonometry, have an increased incidence of multiple organ dysfunction syndrome despite supranormal O2 delivery. We altered our resuscitation protocol to maximize splanchnic blood flow and decrease oxygen-derived free radical damage.

DESIGN

Prospective clinical trial with historical controls.

METHODS

The protocol differed from control by including administration of folate, mannitol, and low-dose isoproterenol. All patients had gastric tonometers and pulmonary artery catheters. If the intramucosal pH (pHi) was less than 7.25, splanchnic-sparing inotropic and vasodilatory agents were used to optimize systemic cardiac output. Two groups of trauma patients with persistent intramucosal acidosis at 24 hours (pHi < 7.25) were compared: a control group (n = 7), and patients who received the splanchnic/antioxidant protocol (n = 13).

RESULTS

The two groups were similar based on Acute Physiology and Chronic Health Evaluation II score, Injury Severity Score, age, cardiac index, oxygen delivery, and oxygen consumption. The "splanchnic therapy" group had fewer organ system failures as well as shortened length of intensive care unit and hospital stay. Three of 7 patients in the control group and 2 of 13 patients in the splanchnic therapy group had a final pHi < 7.25.

CONCLUSION

Gastric tonometry-guided resuscitation and antioxidant/splanchnic therapy in critically ill trauma patients with persistent gastric mucosal acidosis may decrease multiple organ dysfunction syndrome.

Influence of arginine, omega-3 fatty acids and nucleotide-supplemented enteral support on systemic inflammatory response syndrome and multiple organ failure in patients after severe trauma

This study investigated the influence of an enteral diet supplemented with arginine, omega-3 fatty acids, and nucleotides (Impact, Sandoz Nutrition, Berne, Switzerland) on the incidence of systemic inflammatory response syndrome (SIRS) and multiple organ failure (MOF) in patients after severe trauma. Thirty-two patients with an injury-severity score > 20 were included in this prospective, randomized, double-blind, controlled study. Primary endpoints were the incidence of SIRS and MOF. Secondary endpoints were parameters of acute phase and immune response as well as infection rate, mortality, and hospital stay. For statistical analysis 29 patients (test group n = 16, control n = 13) were eligible. In the test group, significantly fewer SIRS days per patient were found during 28 d. The difference was highly significant between d 8-14 (P < 0.001). MOF score was significantly lower in the test group on d 3 and d 8-11 (P < 0.05). Acute phase parameters showed lower C-reactive protein serum levels (significant on D day 4) and fibrinogen plasma levels (significant on d 12 and 14; P < 0.05). HLA-DR expression on monocytes showed significantly higher fluorescence activity on d 7. No significant difference was found for T-lymphocyte CD4/CD8 ratio, interleukin-2 receptor expression, infection rate, mortality (2/16 vs. 4/13), and hospital stay. The results of the study provide further support for beneficial effects of arginine, omega-3-fatty acids and nucleotide-supplemented enteral diet in critically ill patients.

Randomized, prospective comparison of increased preload versus inotropes in the resuscitation of trauma patients: effects on cardiopulmonary function and visceral perfusion

OBJECTIVE

To evaluate the effects of maintaining increased levels of preload on cardiopulmonary function and visceral perfusion during resuscitation.

METHODS

Randomized, prospective study of 39 consecutive trauma patients with a low right ventricular ejection fraction (<40%) admitted to a university Level I trauma center during a 10-month period. Patients were randomized to one of two groups: increased preload (PL), or normal preload with inotropes (INO). The PL group received fluid administration to maintain a target right ventricular end-diastolic volume index (RVEDVI) > or = 120 mL/m2 during resuscitation. The INO group had inotropes added according to a prospectively determined protocol and was maintained at a RVEDVI of 90 to 100 mL/m2. Systemic perfusion was assessed using oxygen transport and acid-base parameters, and pulmonary function was evaluated with PaO2/FiO2 ratio, dynamic compliance, ventilator days, and incidence of adult respiratory distress syndrome. Gut perfusion was assessed by measuring gastric intramucosal pH (pHi). Data are expressed as means +/- SD.

RESULTS

The mean RVEDVI was significantly higher in the PL group (n = 19) than in the INO group (n = 20) during resuscitation (119+/-18 vs. 103+/-22 mL/m2, p = 0.01). There was no difference in oxygen delivery, mixed venous oxygen saturation, lactate, PaO2/FiO2 ratio, dynamic compliance, or ventilator days between the groups. The incidence of adult respiratory distress syndrome was not significantly different (PL 31% vs. INO 50%, p > 0.1). In the patients who had pHi measured sequentially during resuscitation (PL = 13, INO = 17), the final pHi was significantly higher in the PL group (7.31+/-0.1 vs. 7.16+/-0.2, p = 0.03).

CONCLUSION

Patients resuscitated at higher levels of preload have significantly better visceral perfusion than those resuscitated at normal preload with addition of inotropes. This higher preload does not adversely affect pulmonary function.

Early onset of acute pulmonary dysfunction after cardiovascular surgery: risk factors and clinical outcome

OBJECTIVE

To define the incidence, risk factors, and clinical outcome of early pulmonary dysfunction after cardiovascular surgery for adults.

STUDY

Inception cohort.

SETTING

Adult cardiovascular intensive care unit (ICU).

PATIENTS

All adult admissions after cardiovascular surgery without preoperative pulmonary parenchyma or vascular disease over a period of 12 consecutive months.

INTERVENTION

Collection of data on demographics, preoperative organ insufficiency, emergency surgery, type of surgical procedure, cardiopulmonary bypass time, transfusion of blood products, postoperative arterial blood gases, and systemic hemodynamics on admission to the cardiovascular ICU.

MEASUREMENTS AND MAIN RESULTS

Early postoperative pulmonary dysfunction was defined by mechanical ventilation with a PaO2/FIO2 ratio of < or = 150 torr (< or = 20 kPa) and chest radiography on admission to the cardiovascular ICU. Secondary outcome included postoperative renal and neurologic dysfunction, nosocomial infections, length of mechanical ventilation, hospitalization, and death. A total of 3,122 patients were evaluated and 1,461 patients satisfied the entry criteria of the study. Early postoperative pulmonary dysfunction was present in 180 (12%) patients on admission to the cardiovascular ICU. Preoperative variables: age of > or = 75 yrs (odds ratio 1.69, 95% confidence interval [CI] 1.06 to 2.65), body mass index of > or = 30 kg/m2 (odds ratio 1.60, 95% CI 1.09 to 2.32), mean pulmonary arterial pressure of > or = 20 mm Hg (odds ratio 1.60, 95% CI 1.13 to 2.28), stroke volume index of < or = 30 mL/m2 (odds ratio 1.57, 95% CI 1.08 to 2.26), serum albumin (odds ratio 0.71, 95% CI 0.49 to 0.97), history of cerebral vascular disease (odds ratio 1.81; 95% CI 1.08 to 2.96); operative variables: emergency surgery (odds ratio 2.12, 95% CI 1.01 to 4.51), total cardiopulmonary bypass time of > or = 140 mins (odds ratio 1.54, 95% CI 1.0 to 2.34); and postoperative variables (on admission to cardiovascular ICU): hematocrit of > or = 30% (odds ratio 2.46, 95% CI 1.71 to 3.56), systemic mean arterial pressure of > or = 90 mm Hg (odds ratio 1.67, 95% CI 1.13 to 2.42), and cardiac index of > or = 3.0 L/min/m2 (odds ratio 2.09, 95% CI 1.44 to 3.01) were predictors of early postoperative pulmonary dysfunction. Pulmonary dysfunction was associated with a postoperative increase of serum creatinine (1.36 +/- 0.4 vs. 1.24 +/- 0.4 mg/dL, p < .02), neurologic complications (3% vs. 1.6%, p < .001), nosocomial infections (3% vs. 1.6%, p < .001), prolonged mechanical ventilation (2.2 +/- 5.9 vs. 1.7 +/- 5.6 days, p < .001), length of stay in the cardiovascular ICU (4.4 +/- 12.2 vs. 2.6 +/- 6.2 days, p < .001) and hospital (14.8 +/- 13.1 vs. 10.5 +/- 8.0 days, p < .001), and death (4.4% vs. 1.6%, p < .001).

CONCLUSIONS

The incidence of early postoperative pulmonary dysfunction is uncommon; however, once developed, it is associated with increased morbidity and mortality after cardiovascular surgery. Advanced age, large body mass index, preoperative increased pulmonary arterial pressure, low stroke volume index, hypoalbuminemia, history of cerebral vascular disease, emergency surgery, and prolonged cardiopulmonary bypass time are risk factors for early onset of severe pulmonary dysfunction after surgery. Postoperative hematocrit and systemic hemodynamics suggest that early postoperative pulmonary dysfunction can be a component of a generalized inflammatory reaction to cardiovascular surgery.

Lipid mediators up-regulate CD11b and prime for concordant superoxide and elastase release in human neutrophils

BACKGROUND

The pathogenesis of multiple organ failure after injury is believed to involve priming and activation of the inflammatory cascade, and the polymorphonuclear neutrophil (PMN) appears to be an integral effector. Characterization of the primed PMN is evolving. Because much research has focused on the respiratory burst, the synergistic role of cytotoxic proteases, especially elastase, has been largely ignored. In addition, CD11b has been identified as pivotal in PMN-mediated tissue injury. Our hypothesis is that the well-recognized postinjury mediators platelet-activating factor (PAF) and leukotriene B4 (LTB4) prime PMNs for the concordant release of elastase and superoxide (O2-) as well as for CD11b up-regulation.

METHODS

Human PMNs were isolated and then incubated with PAF or LTB4 before N-formyl-methionyl-leucyl-phenylalanine activation. O2- generation was measured by reduction of cytochrome c. Elastase was measured by cleavage of Ala-Ala-Pro-Val p-nitroanilide. CD11b expression was quantified by incubation with R-phycoerythrin-labeled monoclonal antibodies followed by flow cytometry.

RESULTS

PAF and LTB4 primed PMNs maximally within 5 minutes for the production of O2-, elastase release, and simultaneous up-regulation of CD11b expression on the PMN surface.

CONCLUSION

PAF and LTB4 prime human PMNs for the concordant release of elastase, generation of O2-, and CD11b up-regulation. Understanding the physiologic characteristics of PMN priming may offer new therapeutic targets to avoid the development of multiple organ failure after injury.

Interleukin-10 reduces the systemic inflammatory response in a murine model of intestinal ischemia/reperfusion

BACKGROUND

Intestinal ischemia/reperfusion (I/R) is known to increase systemic cytokine levels, as well as to activate neutrophils in distant organs. This study was designed to investigate the effect of interleukin-10 (IL-10) on cytokine release, pulmonary neutrophil accumulation, and histologic changes in a murine model of I/R.

METHODS

Forty female Swiss-Webster mice were divided into four groups. Group 1 underwent 45 minutes of superior mesenteric artery occlusion followed by 3-hour reperfusion (I/R). Group 2 underwent laparotomy alone (Sham). Group 3 underwent I/R, but was treated with IL-10, 10,000 units IP every 2 hours, starting 1 hour before reperfusion (Pretreatment). Group 4 was treated with an equal dose of IL-10, starting 1 hour after reperfusion (Posttreatment). All animals were killed at 3 hours, standard assays were performed for serum cytokine levels, and lung myeloperoxidase activity and intestinal histology were scored.

RESULTS

Serum cytokines (TNF-alpha and IL-6), lung myeloperoxidase levels, and histologic score were significantly reduced when IL-10 was administered either before or after reperfusion.

CONCLUSIONS

IL-10 reduced the severity of local and systemic inflammation in a murine model of intestinal I/R when given before or after reperfusion injury. These observations suggest that IL-10 may exert its effect by blocking cytokine production and distant organ neutrophil accumulation.

Poor outcome from peritonitis is caused by disease acuity and organ failure, not recurrent peritoneal infection

OBJECTIVE

The purpose of the study is to determine whether organ failure develops in patients despite control of peritoneal infection and whether the process is, in part, neutrophil (polymorphonuclear leukocyte [PMN]) mediated.

SUMMARY BACKGROUND DATA

Peritonitis generally responds to prompt surgical intervention and systemic antibiotics; however, some patients continue a septic course and progress to organ failure and death.

METHODS

One hundred five consecutive patients with peritonitis between 1988 and 1996 who required operation and a postoperative hospital stay greater than 10 days were studied. Mice were injected with a monoclonal anti-PMN antibody 24 hours before cecal ligation and puncture (CLP) to deplete PMNs.

RESULTS

Thirty-eight patients died, and all but 1 had identified organ failure. Seventy-seven patients had either pulmonary failure alone (25 patients) or as a component of multisystem organ failure (52 patients). All but one of these patients showed resolution of their intraperitoneal infection as evident by clinical course, abdominal computed tomographic scan, second-look laparotomy, or autopsy. Recurrent intra-abdominal infection developed in 15 patients, but only 1 had organ failure, and 2 died. At 18 hours after CLP, lung injury, PMN content, interleukin-1 mRNA expression, and liver injury were significantly reduced by anti-PMN treatment, whereas serum endotoxin levels actually increased.

CONCLUSIONS

Disease acuity and organ failure, and not recurrent peritoneal infection, are the major causes of adverse outcome in patients with peritonitis. The authors' experimental data indicate that such organ injury is, in part, PMN mediated but not endotoxin mediated. Attraction of PMNs toward the site of primary infection, and thereby away from remote organs, is a logical future therapeutic approach in such patients who are critically ill with peritonitis.

Prediction of posttraumatic adult respiratory distress syndrome by albumin excretion rate eight hours after admission

BACKGROUND

Adult respiratory distress syndrome (ARDS) in trauma victims carries a mortality on the order of 50%. An early feature is an increased capillary permeability causing an extravasation of plasma proteins and water, leading to interstitial edema. In the kidney, the increase in microvascular permeability is manifested as increased albumin excretion detectable by sensitive immunoassay.

METHODS

Forty seven trauma victims were studied for 5 days; 32 of them had Injury Severity Scores > 18. A diagnosis of ARDS was made on the recommendations of the American-European Consensus Conference on ARDS (1994). Eight patients developed ARDS, five developed pulmonary dysfunction, and the remainder showed no significant pulmonary abnormality.

RESULTS

Using the near patient urine albumin immunoassay, albumin excretion rate (AER) was measured after admission. For patients with Injury Severity Score > 18, the median (95% confidence interval) AER 8 hours after admission was 63 (range, 40-99) microg per minute for those without impaired lung function and 339 (range, 162-454) microg per minute for those in the combined ARDS and pulmonary dysfunction group (Mann-Whitney test, p = 0.0004). The median AER was 51 (range, 27-98) microg per minute for patients with Injury Severity Score < 18. The positive predictive value for the development of ARDS or pulmonary dysfunction of AER > 130 microg per minute was 85%, with a negative predictive value of 95%.

CONCLUSIONS

These data indicate that the capillary leak associated with the subsequent development of pulmonary dysfunction and ARDS can be detected within 8 hours of admission at the patient's bedside, thus providing a means of early identification of patients at greatest risk and allowing for early intervention.

Cardiac preload, splanchnic perfusion, and their relationship during resuscitation in trauma patients

INTRODUCTION

Low gastric intramucosal pH (pHi) after shock resuscitation is associated with organ dysfunction and death in trauma patients. However, the relationship between hemodynamic performance, global oxygen transport, and pHi is unclear. Our purpose was to evaluate the relationship between intravascular volume status, splanchnic hypoperfusion, and outcome after shock resuscitation in trauma patients.

DESIGN/SETTING

Cohort study of 79 consecutive critically ill patients at a Level I trauma center stratified by normal (NORM, > or = 7.32) or low (LOW, < 7.32) pHi when lactate normalized (< 2.2 mmol/L).

MAIN OUTCOME MEASURES

Differences during resuscitation in mean values of right ventricular end-diastolic volume index (RVEDVI), pulmonary artery occlusion pressure, cardiac index, oxygen delivery index, and oxygen consumption index. The incidence of multiple organ failure and death in the NORM and LOW groups were analyzed via odds ratio and chi 2.

RESULTS

Patients in the NORM group (n = 45) had a lower incidence of multiple organ failure (4 of 45 vs. 11 of 34, odds ratio 5.0, p < 0.01) and death (5 of 45 vs. 11 of 34, odds ratio 3.8, p < 0.05) than patients in the LOW group (n = 34). NORM patients had a higher initial RVEDVI (116 +/- 31 vs. 95 +/- 25 mL/m2, p < 0.001) and maintained a significantly higher RVEDVI (114 +/- 27 vs. 97 +/- 17 mL/m2, p = 0.003) throughout resuscitation than the LOW group did. There were no differences in the other studied variables.

CONCLUSIONS

Supranormal levels of preload during shock resuscitation are associated with better outcome. Maintaining a RVEDVI higher than 100 mL/m2 during shock resuscitation may be of benefit in critically injured patients.

Use of tissue oxygen tension measurements during resuscitation from hemorrhagic shock

BACKGROUND

Tissue oxygen tension can be measured directly in selected organ beds, and these measurements may be more sensitive in assessing the adequacy of resuscitation than global physiologic parameters. We hypothesized that heart tissue oxygen tension would be an important marker for the severity of ischemic insult to the heart during hemorrhagic shock. We further hypothesized that gut oxygen tension measured in the jejunum would prove to be a better measure of splanchnic hypoperfusion than intramucosal pH (pHi).

METHODS

Tissue oxygen probes were inserted directly into the myocardium of the left ventricle and into the lumen of the proximal jejunum in 10 anesthetized swine. A pHi catheter was introduced into the stomach. The animals were subjected to a controlled hemorrhage of 50% of estimated blood volume. Gut and cardiac oxygen were monitored continuously during hemorrhage and resuscitation, which was performed with shed blood and crystalloid.

RESULTS

While gut O2 and pHi trended together, we were unable to establish a correlation between changes in these two variables during hemorrhage and resuscitation. Heart PO2 decreased significantly during hemorrhage, but surpassed baseline values after resuscitation, a finding not seen in gut PO2. No standard physiologic variables reliably predicted changes in heart PO2 during these experiments.

CONCLUSIONS

Tissue oxygen tensions measurements are highly responsive to changes induced during graded hemorrhagic shock and resuscitation. Gut PO2 and pHi appear to be measuring different physiologic processes in the gastrointestinal tract. The compensatory ability of the heart far exceeds that of the gut after ischemic insult. This hemorrhagic shock model appears feasible for the study of various methods of resuscitation.

The effect of LPS on cytokine synthesis and lung neutrophil influx after hepatic ischemia/reperfusion injury in the rat

OBJECTIVE

To determine if cytokine responses and lung injury induced by intravenous (i.v.) lipopolysaccharide (LPS) at 4 hr were enhanced in rats that had been previously subjected to 30 min of total liver ischemia (Pringle's maneuver) followed by 24 hr or 3 days of reperfusion.

BACKGROUND

Many patients with liver trauma require occlusion of hepatic blood flow to control hemorrhage and facilitate repair. A significant number of these patients subsequently develop the systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction (MOD) characterized by the release of cytokines and tissue neutrophil influx. Macrophages, including Kupffer cells, may be activated by ischemic injury and dysregulation of their response to LPS may contribute to the development of SIRS and acute respiratory distress syndrome.

METHODS

Adult male Sprague-Dawley rats were randomly divided into six groups: three groups received total hepatic ischemia for 30 min and three groups had a sham procedure. Twenty-four hours or 3 days after hepatic ischemia/reperfusion injury, rats were treated with LPS (5 mg/kg) or saline and monitored for 4 hr. We collected serum, bronchoalveolar lavage (BAL) fluid, and lung tissue.

RESULTS

Serum and BAL cytokine concentrations were significantly increased by i.v. LPS; however, hepatic ischemia/reperfusion injury 24 hr or 3 days before iv LPS ameliorated this cytokine response. The LPS-induced pulmonary neutrophil influx and histopathological changes were similar in sham and hepatic ischemia/reperfusion-injured groups.

CONCLUSIONS

Hepatic ischemia/reperfusion injury significantly attenuated the serum and BAL cytokine concentrations, but did not change pulmonary neutrophil influx or histopathological alterations in response to i.v. LPS.

Interleukin-6 in the injured patient. Marker of injury or mediator of inflammation?

OBJECTIVE

The effects of interleukin (IL)-6 in the injured patient are examined in an attempt to clarify the potential pathophysiologic role of IL-6 in the response to injury.

SUMMARY BACKGROUND DATA

Interleukin-6 is an integral cytokine mediator of the acute phase response to injury and infection. However, prolonged and excessive elevations of circulating IL-6 levels in patients after trauma, burns, and elective surgery have been associated with complications and mortality. The mechanistic role of IL-6 in mediating these effects is unclear.

METHODS

A review of current literature is performed to summarize the origins, mechanisms of action, and biologic effects of IL-6 and to characterize the IL-6 response to injury.

RESULTS

Interleukin-6 is a multifunctional cytokine expressed by a variety of cells after a multitude of stimuli, under complex regulatory control mechanisms. The IL-6 response to injury is uniquely consistent and related to the magnitude of the insult. Moreover, the early postinjury IL-6 response correlates with complications as well as mortality.

CONCLUSIONS

Interleukin-6 appears to play an active role in the postinjury immune response, making it an attractive therapeutic target in attempts to control hyperinflammatory provoked organ injury.

Jack A. Barney Resident Research Award winner. The inflammatory profile of interleukin-6, interleukin-8, and soluble intercellular adhesion molecule-1 in postinjury multiple organ failure

BACKGROUND

Interleukin-6 (IL-6), interleukin-8 (IL-8), and adhesion molecules have been implicated as mediators in neutrophil (PMN) and endothelial cell (EC) interactions leading to postinjury multiple organ failure (MOF). Our hypothesis was that circulating levels of IL-6, IL-8, and soluble intercellular adhesion molecule-1 (sICAM-1) would discriminate patients at risk for postinjury MOF.

METHODS

Serial plasma levels of IL-6, IL-8, and sICAM-1 were measured in 27 high-risk trauma patients.

RESULTS

The IL-6 and IL-8 levels were significantly elevated in MOF patients compared with non-MOF patients at 12 and 36 hours postinjury. The IL-6 level was also elevated at 84 and 132 hours, and IL-8 at 84 hours. The sICAM-1 level did not become elevated in MOF patients until 132 hours postinjury.

CONCLUSION

Interleukin-6 and IL-8 are elevated early after trauma and discriminate patients who will develop MOF. Late elevation of sICAM-1 likely results from PMN cytotoxicity leading to EC injury or inflammation.

Effects of E-selectin and P-selectin blockade on neutrophil sequestration in tissues and neutrophil oxidative burst in burned rats

OBJECTIVE

Neutrophil deposition in tissues (leukosequestration) after shock may produce local tissue injury from proteases and high-energy oxygen species released from sequestered neutrophils. The initial step in the binding of neutrophils to capillary endothelium is the interaction of adhesion molecule (selectin) receptors between neutrophils and endothelial cells. We quantified leukosequestration in the tissues of burned rats using two methods of analysis: a) measurement of lung myeloperoxidase; and b) measurement of radiolabeled neutrophils and erythrocytes deposited in multiple tissues. We then determined the ability of a selectin receptor blocking agent to affect neutrophil deposition in tissues after burn injury.

DESIGN

Prospective, controlled, laboratory study.

SETTING

University research laboratory.

SUBJECTS

Male Wistar rats (200 to 300 g).

INTERVENTIONS

After tracheostomy and venous cannulation, rats received 17% total body surface area full-thickness contact burns and were resuscitated with saline (20 mL i.p.). Experimental animals received 2 mg/kg body weight i.v. administration of a P- and E-selectin blocking monoclonal antibody, CY-1747, immediately after burn. Lung tissue neutrophils were estimated by measuring myeloperoxidase in lung tissue. Neutrophil retention in lung, liver, spleen, gut, skin, muscle, kidney, and brain tissues was determined by removing (preburn) and differentially radiolabeling neutrophils (111In) and erythrocytes (51Cr), reinfusing cells 4.5 hrs after burn, and measuring tissue radioactivity 30 mins later. Edema was estimated by measuring extravasated 125 I-labeled albumin in the various tissues. Peripheral blood neutrophils were analyzed for intracellular hydrogen peroxide content, utilizing a fluorescent dye that reacts with hydrogen peroxide, coupled with analysis of cell fluorescence by flow cytometry.

MEASUREMENTS AND MAIN RESULTS

Myeloperoxidase concentration was increased in lungs 5 hrs after burn (p < .05), indicating neutrophil deposition. Radioisotope studies demonstrated significant (p < .05) leukosequestration into the lung, gut, kidney, skin, and brain tissues at 5 hrs after burn. Flow cytometry showed increased intracellular hydrogen peroxide content in peripheral blood neutrophils 5 hrs after burn. Tissue edema, manifested by radiolabeled albumin retention, was not seen in any tissues. Postburn neutrophil deposition in lungs and liver was blocked (p < .05) by administration of CY-1747 after burn, but maximal neutrophil hydrogen peroxide content was unaffected.

CONCLUSION

Burn injury in rats results in accumulation of neutrophils in multiple tissues. Neutrophil deposition in the lungs and liver is blocked by administration of the E/P-selectin blocking antibody, CY-1747. Since sequestration of metabolically active neutrophils may induce tissue injury, therapies that block postburn leukosequestration may improve clinical outcomes by limiting remote tissue injury.

The relationship of oxygen consumption measured by indirect calorimetry to oxygen delivery in critically ill patients

OBJECTIVE

The existence of oxygen supply dependency, defined as oxygen consumption (VO2) limited by oxygen delivery (DO2), is still questioned. This study examined the relationship between VO2 and DO2 in two groups of critically ill surgical patients 50 years and older in the first 24 hours of resuscitation after pulmonary artery catheter insertion. Group 1 patients had systemic inflammatory response syndrome (SIRS), sepsis, severe sepsis, septic shock, and adult respiratory distress syndrome (ARDS). Group 2 patients had hemorrhagic shock.

METHODOLOGY

Study methodology included (1) augmenting DO2 with fluids, blood, and vasopressors, (2) measuring VO2 by indirect calorimetry to avoid the problem of mathematical coupling with DO2 calculation, and (3) analyzing data during steady states of temperature, sedation, paralyzing agents, and vasopressors.

RESULTS

Six to 18 measurements collected on all study patients during a period within the first 24 hours were analyzed using a linear regression analysis. Statistical significance was set at p < or = 0.05. Seven of nine patients in group 1 demonstrated positive, statistically significant relationships between VO2 and DO2. Of six patients in group 2, one patient demonstrated a positive, significant relationship of VO2 and DO2, three demonstrated inverse relationships, and two patients did not show a DO2/VO2 relationship. Supply dependency did not exist in all patients but was present in seven out of nine patients with systemic inflammatory response syndrome, sepsis, severe sepsis, septic shock, and adult respiratory distress syndrome in the first 24 hours of treatment.

Effects of recombinant bactericidal/permeability-increasing protein (rBPI23) on neutrophil activity in burned rats

Bactericidal/permeability-increasing protein (BPI) is a neutrophil granule protein with potent bactericidal and lipopolysaccharide (LPS)-neutralizing activities. The purpose of this study was to determine if a human recombinant BPI product, rBPI23, would influence neutrophil (PMN) sequestration into various tissues in a rat burn injury model. Leukosequestration may produce local tissue injury from proteases and high-energy oxygen species released from PMNs. Rats received tracheostomy and venous cannulation, then received 17 to 20% total body surface area full-thickness contact burns and resuscitation with 20 ml, of intraperitoneal saline. Ten mg/kg body weight rBPI23 in saline was given by intravenous injection immediately after burn injury, followed by intravenous doses of 2 mg/kg at 2 and 4 hours. Control animals received intravenous saline only. PMN retention in lung, liver, spleen, gut, skin, muscle, kidney, and brain tissues was determined by removing (before burn injury) and differentially radiolabeling PMNs (111In) and erythrocytes (51Cr), reinfusing cells 4.5 hours after burn injury, and measuring tissue radioactivity 30 minutes later. Edema was estimated by measuring extravasated 125I-labeled albumin in the various tissues, 30 minutes after injection. Peripheral blood PMNS were analyzed for intracellular H2O2 content by flow cytometry using a fluorescent dye that reacts with H2O2. Radioisotope studies demonstrated significant (p < 0.05) leukosequestration into lung, liver, gut, kidney, and skin tissues at 5 hours after burn injury. Tissue edema, manifested by radiolabeled albumin retention, was not observed in any tissues. Postburn PMN deposition in lungs and skin was decreased (p < 0.05) by the immediate administration of rBPI23 after burn injury. Flow cytometry showed increased intracellular H2O2 content in peripheral blood PMNs 5 hours after burn injury (p < 0.05), which was unaffected by administration of rBPI23. Since sequestration of metabolically active PMNs may induce tissue injury, therapies that block leukosequestration after burn injury may improve clinical outcomes by limiting remote tissue injury.

Postinjury multiple organ failure: a bimodal phenomenon

To better define the epidemiology of postinjury multiple organ failure (MOF), we prospectively evaluated 457 high-risk trauma patients who survived more than 48 hours. Overall, 70 (15%) developed MOF. In 27 (39%) patients, the occurrence was early, while in 43 (61%) patients the presentation was delayed. At presentation, early MOF had more cardiac dysfunction, while late MOF had greater hepatic failure. Indices of shock were more critical risk factors for early MOF, while advanced age was more important for late MOF. While early and late MOF had a similar high incidence of major infections, these appeared to be more important in precipitating late MOF. Finally, while mortality is similar, early MOF patients appear to succumb faster. In conclusion, postinjury MOF remains a significant challenge and appears to present in at least two patterns (i.e., early versus late). Better understanding of the relative roles of the dysfunctional inflammation and infections in early MOF versus late MOF may facilitate the development of new strategies for the prevention and treatment of morbid syndrome.

Cost effectiveness in the intensive care unit

Effective policies to reduce true costs will require integrated information systems and demand behavioral changes from providers. A congenial environment must be created among medical educators, providers, vendors, and consumers if cost reduction is to be accomplished without compromising quality or access to critical care services. Physicians should do everything they believe may be of benefit for their patients, but we have an obligation to educate the public about the limitations of our art and the fact that "doing everything" is not always best for the patient or the grieving family. A significant method of controlling ICU costs is closely monitoring which patients are admitted and when they are discharged. Laboratory tests represent a source of cost reduction, and physicians must learn to order specific tests and not simply a battery of tests which includes the actual test desired. Limits should be placed on the tests that are ordered in terms of number and frequency. Improved efficiency of the utilization of resources should improve the care of our patients. The largest budget item of any or most critical care units is nursing; it is paramount that this essential and invaluable resource be utilized in a cost-effective manner. Diminishing unnecessary activity will both decrease complications and have salutary effects. Having more time to be with patients and their families will decrease our sense of failure and fulfill the important goal of caring. Physicians and nurses can return to thinking, assessing, and decision making instead of frenetically ordering, reacting, and intervening, which, we believe, accurately describes informational overload created by undue emphasis on high technology. In this way, we can respond to Fuch's exhortation that "physicians consider the possibility of contributing more by doing less." In responding, however, we must never forget that the societal, not merely the economic impact of medical care, is our principal consideration. We must first contribute more by achieving a greater understanding of the medical care process. Only then can we know how to do less at the bedside. We can and must distinguish between costly and high-quality care--they are not necessarily synonymous.

Hemorrhagic shock

A great deal has been learned about the pathophysiologic condition of hemorrhagic shock. The response of the hormonal and inflammatory mediator systems in patients in hemorrhagic shock appears to represent a distinct set of responses different from those of other forms of shock. The classic neuroendocrine response to hemorrhage attempts to maintain perfusion to the heart and brain, often at the expense of other organ systems. This intense vasoconstriction occurs via central mechanisms. The response of the peripheral microcirculation is driven by local tissue hypoperfusion that results in vasodilation in the ischemic tissue bed. Activation of the systemic inflammatory response by hemorrhage and tissue injury is an important component of the pathophysiologic condition of hemorrhagic shock. Activators of this systemic inflammatory response include ischemia/reperfusion injury and neutrophil activation. Capillary "no-flow" with prolonged ischemia and "no-reflow" with reperfusion may initiate neutrophil activation in patients in hemorrhagic shock. The mechanisms that lead to decompensated and irreversible hemorrhagic shock include (1) "arteriolar hyposensitivity" as manifested by progressive arteriolar vasodilation and decreased responsiveness of the microcirculation to alpha-agonists, and (2) cellular injury and activation of both proinflammatory and counterinflammatory mechanisms. These changes represent a failure of the microcirculation. Redistribution of cardiac output and persistent gut ischemia after adequate resuscitation may also contribute to the development of irreversible hemorrhagic shock. Treatment of hemorrhagic shock includes rapid operative resuscitation to limit activation of the mediator systems and abort the microcirculatory changes that result from hemorrhagic shock. Volume resuscitation and control of hemorrhage, should occur simultaneously. The end point in volume resuscitation of hemorrhagic shock must be maintenance of organ system and cellular function. Whether we use adequate urine output, correction of lactic acidemia, optimization of oxygen delivery, or oxygen consumption as our specific goal, the general objective is to provide adequate crystalloid solution and packed red blood cells to achieve and maintain normal organ and cellular perfusion and function.

CD11b blockade prevents lung injury despite neutrophil priming after gut ischemia/reperfusion

Gut ischemia/reperfusion (I/R) provokes lung injury via a mechanism that involves neutrophils [polymorphonuclear neutrophils (PMNs)]. CD11b/CD18 (alpha mB2) is the integrin receptor on PMNs critical for adhesion-dependent oxidative burst. The purpose of this study was to investigate the mechanistic role of CD11b in the process of gut I/R-induced lung injury. Sprague-Dawley rats underwent 45 minutes of superior mesenteric artery (SMA) occlusion with and without CD11b monoclonal antibody treatment (IB6) (1 mg/kg, i.v.), before SMA clamping. At 2-hour reperfusion, PMN presence in tissue was quantitated by myeloperoxidase activity and circulating PMN priming determined by the difference in superoxide production with and without N-formyl-methionyl-leucyl-phenylalanine, whereas lung leak was assessed by 125I-albumin lung/blood ratio. In sum, CD11b blockade prevented gut I/R-induced lung leak, but did not attenuate gut I/R-induced PMN priming or tissue PMN accumulation. In conclusion, gut I/R promotes PMN priming and PMN adhesion in both local and distant beds via receptors other than CD11b, but this B2 integrin receptor is critical for PMN-mediated endothelial injury.