Prehospital triage for mass casualty incidents using the META method for early surgical assessment: retrospective validation of a hospital trauma registry

BACKGROUND

In mass casualty incidents (MCI), death usually occurs within the first few hours and thus early transfer to a trauma centre can be crucial in selected cases. However, most triage systems designed to prioritize the transfer to hospital of these patients do not assess the need for surgery, in part due to inconclusive evidence regarding the value of such an assessment. Therefore, the aim of the present study was to evaluate the capacity of a new triage system-the Prehospital Advanced Triage Method (META)-to identify victims who could benefit from urgent surgical assessment in case of MCI.

METHODS

Retrospective, descriptive, observational study of a multipurpose cohort of patients included in the severe trauma registry of the Gregorio Marañón University General Hospital (Spain) between June 1993 and December 2011. All data were prospectively evaluated. All patients were evaluated with the META system to determine whether they met the criteria for urgent transfer. The META defines patients in need of urgent surgical assessment: (a) All penetrating injuries to head, neck, torso and extremities proximal to elbow or knee, (b) Open pelvic fracture, (c) Closed pelvic fracture with mechanical or haemodynamic instability and (d) Blunt torso trauma with haemodynamic instability. Patients who fulfilled these criteria were designated as "Urgent Evacuation for Surgical Assessment" (UESA) cases; all other cases were designated as non-UESA. The following variables were assessed: patient status at the scene; severity scales [RTS, Shock index, MGAP (Mechanism, Glasgow coma scale, Age, pressure), GCS]; need for surgery and/or interventional procedure to control bleeding (UESA); and mortality. The two groups (UESA vs. non-UESA) were then compared.

RESULTS

A total of 1882 cases from the database were included in the study. Mean age was 39.2 years and most (77%) patients were male. UESA patients presented significantly worse on-scene hemodynamic parameters (systolic blood pressure and heart rate) and greater injury severity (RTS, shock index, and MGAP scales). No differences were observed for respiratory rate, need for orotracheal intubation, or GCS scores. The anatomical injuries of patients in the UESA group were less severe but these patients had a greater need for urgent surgery and higher mortality rates.

CONCLUSION

These findings suggest that the META triage classification system could be beneficial to help identify patients with severe trauma and/or in need of urgent surgical assessment at the scene of injury in case of MCI. These findings demonstrate that, in this cohort, the META fulfils the purpose for which it was designed.

[Not Available]

Zusammenfassung. Die Versorgung von schwerverletzten Patienten stellt eine Hauptaufgabe der Unfallchirurgie dar. Aufgrund einer hohen Mortalität, insbesondere in den ersten 24 h nach Unfall, und Morbidität dieser Patienten ist initial ein gezieltes Vorgehen nach dem ABCDE-Algorithmus (ATLS®) notwendig. Nachdem lebensbedrohliche Verletzungen behandelt oder ausgeschlossen wurden, können weitere Verletzungen gesucht und therapiert werden. Das Timing und Ausmass dieser Therapien richtet sich nach pathophysiologischen Kriterien, den Verletzungen und den geplanten Eingriffen. Beim Vorliegen von negativen Prädiktoren sollte lediglich ein verkürztes operatives Vorgehen, sogenannte «damage control surgery», angewendet werden. Die definitive Versorgung erfolgt nach einer Phase der intensivmedizinischen Stabilisierung und Normalisierung der pathophysiologischen Werte (Körpertemperatur, pH, Gerinnung). Es folgt eine Anschlussbehandlung mit dem Ziel, den Patienten wieder möglichst gut in sein Leben zu integrieren.

Understanding traumatic shock: out-of-hospital hypotension with and without other physiologic compromise

BACKGROUND

Among trauma patients with out-of-hospital hypotension, we evaluated the predictive value of systolic blood pressure (SBP) with and without other physiologic compromise for identifying trauma patients requiring early critical resources.

METHODS

This was a secondary analysis of a prospective cohort of injured patients 13 years or older with out-of-hospital hypotension (SBP ≤ 90 mm Hg) who were transported by 114 emergency medical service agencies to 56 Level I and II trauma centers in 11 regions of the United States and Canada from January 1, 2010, through June 30, 2011. The primary outcome was early critical resource use, defined as blood transfusion of 6 U or greater, major nonorthopedic surgery, interventional radiology, or death within 24 hours.

RESULTS

Of 3,337 injured patients with out-of-hospital hypotension, 1,094 (33%) required early critical resources and 1,334 (40%) had serious injury (Injury Severity Score [ISS] ≥ 16). Patients with isolated hypotension required less early critical resources (14% vs. 52%), had less serious injury (20% vs. 61%), and had lower mortality (24 hours, 1% vs. 26%; in-hospital, 3% vs. 34%). The standardized probability of requiring early critical resources was lowest among patients with blunt injury and isolated moderate hypotension (0.12; 95% confidence interval, 0.09-0.15) and steadily increased with additional physiologic compromise, more severe hypotension, and penetrating injury (0.94; 95% confidence interval, 0.90-0.98).

CONCLUSION

A minority of trauma patients with isolated out-of-hospital hypotension require early critical resuscitation resources. However, hypotension accompanied by additional physiologic compromise or penetrating injury markedly increases the probability of requiring time-sensitive interventions.

LEVEL OF EVIDENCE

Prognostic study, level II.

[Surgical strategy in bullet wound of the thorax accompanied by shock]

The article analyzes the experience of treatment of bullet penetrating wounds of the thorax accompanied by shock in 131 armed forces personnel of internal army and officers of the Ministry of Home Affairs of Russia during contra-terrorist operations on the North Caucasus at the period from 2000 to 2011. The postoperative lethality was reduced from 22.7% to 10.8% due to usage of the strategy which was directed to decrease of surgical aggression in 65 patients.

Corticotropin-releasing factor is present in intestinal tissue of patients with gastrointestinal dysfunction following shock and abdominal surgery

OBJECTIVE

Corticotropin-releasing factor (CRF) is implicated in stress-related gastrointestinal dysfunction, possibly causing gut dysfunction following trauma and surgery. We investigated plasma and intestinal tissue CRF levels and gut function in patients with traumatic shock or those undergoing elective abdominal surgery.

RESEARCH METHODS AND PROCEDURES

In a prospective, parallel, observational study in a university hospital surgical intensive care unit (ICU), 8 shocked patients (systolic blood pressure <90 mmHg and/or acidosis and/or urine output <1 mL/kg/hr and/or requiring >2 L of intravenous fluid resuscitation) undergoing small bowel resection during emergency laparotomy following abdominal injury and 17 stable patients undergoing elective hepatobiliary surgery were included if they required postoperative ICU management. Serial plasma and intestinal CRF was measured and postoperative gastric emptying and intestinal permeability were evaluated.

RESULTS

Plasma CRF was significantly increased in the shocked patients compared with the elective surgery patients at all times. CRF peptide was quantified in intestinal tissue at similar levels in both groups. Intestinal permeability was increased and associated with shock and resuscitation fluid volume. Gastric emptying was retarded and correlated significantly with shock but not with plasma CRF. Delayed gastric emptying in shocked patients was associated with longer ICU stay.

CONCLUSIONS

The novel finding is the presence of CRF in the small bowel of both elective and emergency gastrointestinal surgery patients with concomitant gastrointestinal dysfunction. Circulating CRF is associated with poor gastric emptying, which prolongs ICU stay, whereas shock significantly impairs gastric emptying and gut permeability.

Differentiating disseminated intravascular coagulation (DIC) with the fibrinolytic phenotype from coagulopathy of trauma and acute coagulopathy of trauma-shock (COT/ACOTS)

Two concepts have been proposed for the hemostatic changes occurring early after trauma. Disseminated intravascular coagulation (DIC) with the fibrinolytic phenotype is characterized by activation of the coagulation pathways, insufficient anticoagulant mechanisms and increased fibrinolysis. Coagulopathy of trauma and acute coagulopathy of trauma-shock (COT/ACOTS) occurs as a result of increased activation of the thrombomodulin and protein C pathways, leading to the suppression of coagulation and activation of fibrinolysis. Despite the differences between these two conditions, independent consideration of COT/ACOTS from DIC with the fibrinolytic phenotype is probably incorrect. Robust diagnostic criteria based on its pathophysiology are required to establish COT/ACOTS as a new independent disease concept. In addition, the independency of its characteristics, laboratory data, time courses and prognosis from DIC should be confirmed. Confusion between two concepts may be based on studies of trauma lacking the following: (i) a clear distinction of the properties of blood between the inside and outside of vessels, (ii) a clear distinction between physiologic and pathologic hemostatic changes, (iii) attention to the time courses of the changes in hemostatic parameters, (iv) unification of the study population, and (v) recognition that massive bleeding is not synonymous with coagulation disorders. More information is needed to elucidate the pathogenesis of these two entities, DIC with the fibrinolytic phenotype and COT/ACOTS after trauma. However, available data suggest that COT/ACOTS is not a new concept but a disease entity similar to or the same as DIC with the fibrinolytic phenotype.

[Pharmacological prophylaxis of reperfusion syndrome in patients with severe polytrauma accompanied by shock]

A comparative assessment of buffer activity of reamberin and polyoxyfumaren was made. Their influence on systemic consumption of oxygen, content of lactate in blood, parameters of central hemodynamics were followed. The research includes 44 victims (aged 25-70 years) with severe shockogenic injuries. Reamberin was included in composition of fluid therapy of I group (n=30)and polyoxyfumaren was used in 11 group (n=14). Parameters of acid-base balance of arterial blood, VO2, VCO,, contents of lactate in mixed venous blood, parameters of central hemodynamics were measured in monitor regimen before the infusion. It was proved, that the intravenous infusion of reamberin and polyoxyfumaren accompanied by reliable rise of minute consumption of oxygen (27 and 18% respectively). The drugs decrease the lactate level in blood, reliably increase buffer capacity of blood, correct the metabolic acidosis. Both antihy-poxanthines allow the increase of minute volume of circulation: reamberin on 15%, polyoxyfumaren on 34,9%. The volemic effect of polyoxyfumaren resulted in the increase of circular plasma volume after finishing the infusion on 49,5%, in the case of reamberin - on 16%.

[Risk factors of gastroduodenal bleeding in patients with severe burns]

An experience of treatment of 133 patients with severe bums was analyzed. Bleedings from the upper parts of the gastrointestinal tract were diagnosed in 16 patients in different terms since their admission to the hospital. At the moment of carrying out of the endoscopic research all bleedings were considered as taking place. Statistically significant risk factors of the development of gastroduodenal bleedings were considered to be an alcoholic intoxication at the moment of injury and insufficient fluid therapy during the pre-admission stage and young age of the patients. The antisecretory therapy showed that the detection of risk factors in question should be regarded as an indication to the reinforced regime of preventive measures for gastroduodenal injuries.

[Test for the reaction of blood circulation to a shockogenic trauma during pre-hospital stage]

Was proposed a method of determination of type of reaction of blood circulation on pre-hospital stage by patients with shock-producing trauma on the base of signs of saturation of hemoglobin by oxygen and on the base of endurance of period of isolation, without using difficult apparatuses and devices. It permits to individualize contra-shock therapy at early stages of traumatic disease on pre-hospital period.

[Plasma membrane depolarization and activation of receptors for endogenous vasoconstrictors as possible mechanisms of potentiation of vasoconstrictive response to serotonin in traumatic shock in rats]

The goal of this work was to study possible mechanisms underlying the potentiation of vasopressor response to serotonin observed in traumatic shock. Experiments with isolated aorta and mesenteric artery of the rat showed that vasoconstriction is caused by the activation of 5HT2A receptors. Agonists of 5HT1B, 5HT1D, 5HT2B, and 5HT4 receptors induced vasodilation. Agonists of 5HT1A receptors had a dual effect determined by interaction with alpha1-adrenergic receptors and 5HT1A receptors. Plasma membrane depolarization with 15 mM KCl increased the vasoconstrictive force in response to serotonin. This effect was determined by the ability of KCl to activate voltage-gated calcium channels, as a result of which the intracellular calcium stores are replenished. Inhibition of serotonin response by ketanserin, a 5HT2A receptor blocker, did not depend on the presence of 15 mM KCl. Constriction in response to serotonin was potentiated after its addition to vessels preconstricted with noradrenaline or endothelin-1. The constriction response partially retained in the presence of 2 x 10(-7) M ketanserin, which completely suppressed the serotonin-induced constriction of dilated vessels both at normal membrane potential and after plasma membrane depolarization. It can be assumed that noradrenalin and endothelin-1 alter the characteristics of 5HT2A receptors and possibly 5HT1A receptors as a result of their heterodimerization with the receptors for these vasoconstrictive hormones or interreceptor interaction at the level of signaling systems. Along with the potentiating effect of KCl, this mechanism may underlie the enhancement of vasopressor response to serotonin in shock.

[Application of Rheosorbilactum in the therapy of traumatic shock: comparative study]

The authors have studied influence of infusion of 800 ml RHEOSORBILACTUM, 500 ml VENOFUNDIN and 800 ml of 0,9% isotonic solution of sodium chloride with speed of 50-55 ml/mines on hemostasis, the maintenance of a liquid in the thorax, hemodynamic parameters in 60 patients with traumatic shock. It was revealed that the use of investigated volume of RHEOSORBILACTUM increases reliably (P<0,05) oxygen delivery for the account of the expressed haemodynamic effect which duration is less than during the use of VENOFUNDIN. It was revealed also that RHEOSORBILACTUM increases reliably (P<0,05) quantity of liquid in the thorax without an considerable difference with other investigated medications. There was no influence of RHEOSORBILACTUM on time of trombus formation tests--prothrombin time, the international normalized index, activated partial thromboplastin time.

[Study of homeostasis in children with traumatic shock]

The time course of changes in oxygen and acid-base homeostatic parameters was studied in children with grades 1, 2, 3, and 4 traumatic shock. The directionality of changes was ascertained in oxygen and acid-base balance and the influence of hemodynamic, hemocoagulation, hemorheological, and energy-generating functions in the destabilization of oxygen and acid-base homeostatic parameters were established. A package of medical measures that promote improved oxygen and acid-base balance in children with traumatic shock is stated.

The link between childhood trauma and depression: insights from HPA axis studies in humans

Childhood trauma is a potent risk factor for developing depression in adulthood, particularly in response to additional stress. We here summarize results from a series of clinical studies suggesting that childhood trauma in humans is associated with sensitization of the neuroendocrine stress response, glucocorticoid resistance, increased central corticotropin-releasing factor (CRF) activity, immune activation, and reduced hippocampal volume, closely paralleling several of the neuroendocrine features of depression. Neuroendocrine changes secondary to early-life stress likely reflect risk to develop depression in response to stress, potentially due to failure of a connected neural circuitry implicated in emotional, neuroendocrine and autonomic control to compensate in response to challenge. However, not all of depression is related to childhood trauma and our results suggest the existence of biologically distinguishable subtypes of depression as a function of childhood trauma that are also responsive to differential treatment. Other risk factors, such as female gender and genetic dispositions, interfere with components of the stress response and further increase vulnerability for depression. Similar associations apply to a spectrum of other psychiatric and medical disorders that frequently coincide with depression and are aggravated by stress. Taken together, this line of evidence demonstrates that psychoneuroendocrine research may ultimately promote optimized clinical care and help prevent the adverse outcomes of childhood trauma.

[Traumatic shock--physiopathologic aspects]

Traumatic shock is a complex phenomenon that represents the culminating element of a series of events. It is, in fact, the outcome of an imbalance-decompensation of the organism's defence mechanisms, in which the oxygen supply to the mitochondria is hampered by a macro and/or microcirculation failure. Basically, it is a form of hypovolemic shock in which further factors have a role, including the activation of inflammation mediators. It should also be stressed that part of the cellular damage is caused by tissue reperfusion. Good hemodynamic compensation is maintained with loss of up to 30% of the circulation mass but, beyond this amount, a fall of the cardiac index, peripheral pO2, and an increase of blood lactates will ensue. Hypoxia causes capillary injury and increased permeability, resulting in the formation of edema and finally in loss of the self-regulating power of the microcirculation. Moreover, it strongly stimulates pro-inflammatory activation of the macrophages and the release of vasoactive substances, such as prostaglandins and thromboxanes. The inflammatory response is triggered by cascade systems (such as the complement, coagulation, kinins, fibrinolysis), cell elements (endothelium, leukocytes, macrophages, monocytes, mast cells) and the release of mediators (cytokines, proteolytic enzymes, histamine, etc.) and others interacting factors. In severe trauma, the inflammatory process extends beyond the local limits, maintaining and aggravating the state of shock and causing a Systemic Inflammatory Response Syndrome (SIRS), with involvement and injury of healthy organs and tissues even at a distance from the site of trauma, raising a risk of onset of ARDS (Acute Respiratory Distress Syndrome), sepsis, MODS (Multiple Organ Dysfunction Syndrome). Tissue reperfusion (reoxygenation) also induces the production of toxic metabolites, such as hydroxylated anions, superoxide, hydrogen peroxide: peroxidation of the phospholipid cell membranes alters the barrier functions, permitting entry of substances such as calcium, which interfere with the intracellular enzymatic systems.

Intestinal and gastric tonometry during experimental burn shock

INTRODUCTION

The occurrence of organ failure following thermal injury, despite restoration of hemodynamic parameters and urine output during resuscitation, has led to efforts to measure end-organ perfusion. The purpose of this 24-h study was to evaluate the utility of gastrointestinal (GI) tonometry during burn shock and resuscitation.

METHODS

Male swine (n=11, 23.3+/-0.9 kg) were anesthetized with ketamine and propofol. A 70% full thickness burn was caused by immersion in 97 degrees C water for 30 s. Resuscitation with lactated Ringer's, 4 ml/kg/% burn, was begun at hour 6 and titrated to urine output (UO). Arterial blood gases and pulmonary artery catheter data were measured every 6 h. Gastric and ileal regional PCO(2) (PrCO(2)) were measured continuously by air tonometry, and the gastric and ileal intramucosal pH (pHi) and PCO(2) gap (PrCO(2)-PaCO(2)) were calculated every 6 h.

RESULTS

Gastric pHi, ileal PrCO(2), ileal pHi, and ileal PCO(2) gap (but not gastric PrCO(2) or PCO(2) gap) all decreased with shock and were restored to baseline levels by resuscitation. Changes in ileal PrCO(2) were of greater magnitude and demonstrated decreased variability than those in gastric PrCO(2).

CONCLUSIONS

In this model, ileal tonometry outperformed gastric tonometry during burn shock and resuscitation.

CT evaluation of shock viscera: a pictorial review

The purpose of this article is to review both the pathophysiology and the computed tomography features of the hypoperfusion complex and shock viscera. The main findings include dilated fluid-filled loops of bowel with hyperenhancing mucosa, intensely enhancing kidneys and mesenteric vasculature, and small caliber, dense aorta and collapsed, slit-like inferior vena cava. Variable features include increased enhancement of the adrenals, decreased enhancement of the spleen, and altered enhancement of the pancreas with both hypo- and hyperenhancement described. This complex of findings indicates a tenuous hemodynamic status and has been associated with a poor prognosis. In addition, it is important to discern this collection of findings from direct injury to the viscera to aid in appropriate triage and management of the patients' injuries.

Gelatin colloids in the resuscitation of trauma

To date, the specific role of gelatins in trauma resuscitation remains under-investigated. Their adverse affects are well described and relate principally to the provocation of allergic responses whilst their influence upon haemostasis is relatively benign in comparison to the other colloids. However, their benefits are only sparsely documented and the evidence to choose one gelatin over another virtually non-existent. As knowledge of the microcirculatory dysfunction inherent in the shocked state increases, the role of the gelatins in trauma resuscitation is being increasing sidelined by other colloids--notably the starches. Their role beyond a basic resuscitation tool is now uncertain.

SEX DIFFERENCES IN THE LONG-TERM OUTCOME AFTER A SEVERE THERMAL INJURY

We have recently shown that during the acute phase, postburn female pediatric burn patients had significantly increased levels of anabolic hormones with an associated decreased hypermetabolism leading to a significant shorter intensive care unit stay compared with male patients. The aim of the present study was to determine possible differences between girls and boys in body composition, hypermetabolism, and hormone pattern in the long term. Sixty-two children (1-16 years old) who sustained a severe thermal injury (>or=40% total body surface area) were included into the study. Patients were further divided into girls (n = 22) and boys (n = 40). Patient demographics, nutritional support, and mortality were noted. Resting energy expenditure (REE) was measured by indirect calorimetry, body composition by dual-energy x-ray absorptiometry (Hologic Inc, Waltham, Mass) at discharge, 3, 6, 9, 12, 18, and 24 months after burn. In addition, blood was drawn at the same time points, and serum hormones were measured. There were no significant differences between girls and boys for demographics, nutritional intake, or concomitant injuries. Predicted REE was significantly decreased in girls at discharge, 6, 12, and 18 months postburn (P < 0.05). Dual-energy x-ray absorptiometry scan showed that girls had improved change in bone mineral content and percent fat compared with boys (P < 0.05). There were no differences in changes in height, body weight, lean body mass, and total fat between groups. Girls had significantly higher levels of insulinlike growth factor 1, insulinlike growth factor binding protein 3, free thyroxine index, T4, and insulin when compared with boys (P < 0.05). No differences were found for T3 uptake, osteocalcin, cortisol, growth hormone, and parathyroid hormone (PTH) between groups. Data indicate that girls have a reduced REE associated with changes in bone content and endogenous anabolic hormones.

Tissue oxygen saturation predicts the development of organ dysfunction during traumatic shock resuscitation

BACKGROUND

Near-infrared spectroscopy (NIRS) can continuously and noninvasively monitor tissue oxygen saturation (StO2) in muscle and may be an indicator of shock severity. Our purpose was to evaluate how well StO2 predicted outcome in high-risk torso trauma patients presenting in shock.

METHODS

The primary outcome in this prospective study was multiple organ dysfunction syndrome (MODS). StO2 data were obtained upon hospital arrival and for 24 hours along with other known predictors of hypoperfusion and clinical outcomes. Clinicians were blinded to StO2 measurements.

RESULTS

Seven Level I trauma centers enrolled 383 patients, 50 of whom developed MODS. Minimum StO2 performed similarly to maximum base deficit (BD) in discrimination of MODS patients. The sensitivity for both measures (StO2 cutoff = 75%; BD cutoff = 6 mEq/L) was 78%, the specificity was 34% to 39%, the positive predictive value was 18% to 20% and the negative predictive value was 88% to 91%. StO2 and BD were also comparable in predicting death.

CONCLUSIONS

NIRS-derived muscle StO2 measurements perform similarly to BD in identifying poor perfusion and predicting the development of MODS or death after severe torso trauma, yet have the additional advantages of being continuous and noninvasive.

Relationship between disruption of the unstirred mucus layer and intestinal restitution in loss of gut barrier function after trauma hemorrhagic shock

BACKGROUND

The factors involved in shock-induced loss of gut barrier function remain to be defined fully and studies investigating gut injury have focused primarily on the systemic side of the intestine.

METHODS

Male Sprague-Dawley rats were subjected to a laparotomy (trauma) and 90 minutes of trauma sham shock (T/SS) or actual trauma (laparotomy) hemorrhagic shock (T/HS) (30 mm Hg). At 0, 30, 60, or 180 minutes after the end of shock and volume resuscitation (reperfusion), the animals were killed and samples of the ileum were collected for intestinal morphologic analysis, analysis of the unstirred mucus layer, and for barrier function by measuring permeability to flourescein dextran.

RESULTS

T/HS-induced morphologic evidence of mucosal injury as well as epithelial apoptosis was present at the end of the shock period and maximal after 60 minutes of reperfusion. At 3 hours after reperfusion, the degree of villous injury and enterocyte apoptosis had decreased. In contrast to the morphologic appearance of the villi, disruption of the mucus layer became progressively more severe over time and was manifest as a decrease in mucus thickness, progressive loss of coverage of the luminal surface by the mucus layer, and a change in mucus appearance from a dense to a loose structure. Studies of intestinal permeability documented that T/HS-induced loss of gut barrier function persisted throughout the 3-hour reperfusion period and were associated with injury to the mucus layer as well as the villi.

CONCLUSIONS

T/HS leads to changes in the intestinal mucus layer as well as increased villous injury, apoptosis, and gut permeability. Additionally, increased gut permeability was associated with loss of the intestinal mucus layer suggesting that T/HS-induced injury to the mucus layer may contribute to the loss of gut barrier function.

[Shock as a universal pathogenetical process at critical states of organism]

Based on his clinical experience and analysis of literature the author considers shock as a monopathogenetical process which is universal in different critical states. The basis of its development is impaired microcirculation caused by disseminated intravascular coagulation of blood and development of polyorganic insufficiency.

[The role of desensitization of glucocorticoid receptors in the development of vascular resistance to endogenous vasoconstrictors in traumatic shock]

The fact that the activity of cytosol glucocorticoid receptors decreases in shock have been shown before [Golikov P. P. et al., 2001]. The connection between the development of vascular hyporeactivity to endogenous vasoconstrictors and desensitization of glucocorticoid receptors was studied in this investigation. On Kenton traumatic model in a rat experiment, it was shown that the strength of the isometric constriction of the isolated aorta in response to angiotensin II, endothelin-1, phenylephrine, noradrenaline, and vasopressin falls on the second day after a severe mechanical injury (3.3, 2.1, 1.7, 1.6, and 1.5 times, respectively; p < 0.01). On the contrary, the strength of the constriction in response to serotonin increases more then twice. Artificial desensitization of glucocorticoid receptors by long-term administration of dexamethasone (3 mg per kg during five days) results in similar changes of vascular reactivity i.e. a 2.5, 2, 7, and 1.4-fold decrease in the strength of aortal constriction in response to angiotensin II, vasopressin, and endothelin-1, respectively. The strength of the constriction in response to serotonin tended to increase as well. Carbahol-induced relaxation of the aorta pre-constricted with noradrenaline did not change compared with control, being 70 to 80%, both in shock and after desensitization of glucocorticoid receptors with dexamethasone. Presumably, the pathogenetic mechanism of pressor reaction suppression, connected with a decrease in cytosol glucocorticoid receptor activity and thus with inhibition of glucocorticoid-induced expression of the membrane receptors of endogenous vasoconstrictors, is realized in traumatic shock together with other mechanisms.

Supplemental l-arginine enhances wound healing following trauma/hemorrhagic shock

To determine whether parenteral L-arginine supplementation enhances the impaired wound healing of rats subjected to trauma/hemorrhagic shock. Impaired wound healing after trauma and shock has been documented experimentally and clinically. L-arginine has been shown to enhance wound strength and collagen synthesis in rodents and humans. Its efficacy under conditions of impaired wound healing is less well defined. Forty-eight male Lewis rats were used in this study. Using a well-defined model, 24 rats underwent trauma/hemorrhagic shock before wounding. Twenty-four untreated rats served as controls. All animals underwent a dorsal skin incision with implantation of polyvinyl-alcohol sponges. Half of the animals in each group were assigned to receive 1 g/kg/day of L-arginine by intraperitoneal injection in three divided doses, while the other half received saline injections only. Animals were sacrificed 10 days postwounding, and wound-breaking strength (WBS) and wound sponge total hydroxyproline (OHP) and nitrite/nitrate (NO(x)) content were determined. Wound sponge RNA was collected and subjected to Northern blot analysis for procollagens I and III. Trauma/hemorrhage greatly decreased WBS with a concomitant diminution in collagen (OHP) deposition. L-arginine significantly enhanced WBS (19%) and increased OHP (21%) levels in control animals as well as in rats subjected to trauma/hemorrhage (WBS +29%, OHP 40%) compared with their saline-treated counterparts. Procollagen I and III mRNA levels were elevated by L-arginine treatment in both trauma/hemorrhage and control rats. Arginine treatment had no effect on wound fluid and plasma NO(x). The data demonstrate that the impaired healing subsequent to trauma/hemorrhage can be greatly alleviated by L-arginine supplementation.

Hemodynamic Patterns of Blunt and Penetrating Injuries

BACKGROUND

The aims of this prospective observational study were to describe early hemodynamic patterns of blunt and penetrating truncal injury and to evaluate outcomes prediction using noninvasive hemodynamic monitoring with a mathematical model tested against actual in-hospital outcomes. The hypothesis was that traumatic shock is a circulatory disorder that can be monitored by noninvasive hemodynamic parameters that reflect cardiac, pulmonary, and tissue perfusion functions.

STUDY DESIGN

The cardiac index (CI), heart rate (HR), mean arterial pressure (MAP), pulse oximetry (SapO(2)), transcutaneous oxygen tension indexed to FiO(2) (PtcO(2)/FiO(2)), and carbon dioxide (PtcCO(2)) tensions were monitored beginning shortly after emergency department admission in 657 emergency patients with severe blunt and penetrating chest, abdominal, and extremity trauma. Of these, 113 patients had associated head injury, and these patients also were analyzed separately. A search and display mathematical model, with a decision support program, was based on continuous online, real-time, noninvasive hemodynamic monitoring.

RESULTS

There were similar patterns in the blunt and penetrating injuries; the cardiac index, mean arterial pressure, pulse oximetry, transcutaneous oxygen tension indexed to FiO(2), and survival probability values of the survivors were significantly higher (p < 0.01) than the corresponding values of those who died, although heart rate and carbon dioxide tension were higher in the nonsurvivors during the first 24 hours after their emergency department admission. These patterns occurred more rapidly in patients with penetrating injuries. After initial resuscitation in the emergency department, results were correlated with actual outcomes at hospital discharge and found to be 88% correct.

CONCLUSIONS

Early noninvasive hemodynamic monitoring with a computerized information system provided a feasible pattern recognition program for outcomes prediction and therapeutic decision support.

Androstenetriol improves survival in a rodent model of traumatic shock

Trauma results in activation of the hypothalamic-pituitary-adrenal axis to mediate a cascade of neurohormonal changes as a defensive mechanism. Its prolongation, however, leads to a hypermetabolic, hypoperfused, and immunosuppressed state, setting the stage for subsequent sepsis and organ failure. Androstenetriol (5-androstene-3beta, 7beta, 17betatriol - AET), a metabolite of dehydroepiandrosterone, up-regulates the host immune response markedly, prevents immune suppression and controls inflammation, leading to improved survival after lethal infections by several diverse pathogens and lethal radiation. Such actions may be useful in improving survival from traumatic shock.

HYPOTHESIS

The neurosteroid AET will increase survival following traumatic shock.

METHODS

A combat relevant model of traumatic shock was used. Male Sprague-Dawley rats were anesthetized, catheterized and subjected to soft tissue injury (laparotomy). Animals were allowed to regain consciousness over the next 0.5 h and then bled 40% of their blood volume over 15 min. Forty-five minutes after the onset of hemorrhage animals were randomized to receive either a single subcutaneous dose of AET (40 mg/kg, sc) or vehicle (methylcellulose). Volume resuscitation consisted of l-lactated Ringer's (three times the shed blood volume), followed by packed red blood cells (one-third shed red cell volume). Animals were observed for three days.

RESULTS

A total of 24 animals were studied. Of the 12 animals randomized to receive AET, all (100%) survived compared to 9 of 12 animals (75%) randomized to receive the vehicle (p < 0.05).

CONCLUSION

AET significantly improved survival when administered subcutaneously in a single dose in this rodent model of traumatic shock. Further survival and mechanism studies are warranted.

Resuscitation of traumatic shock: a hemodynamic review

Shock, or tissue hypoperfusion, is a frequent complication from traumatic injury. Despite the etiology of the shock state, there is always some component of hypovolemia. The body's innate ability to compensate for impaired perfusion may mask clinical signs, leading to delays in treatment. This article presents an overview of these compensatory mechanisms and resuscitation strategies from the vantage point of routine hemodynamic monitoring.

[The influence of changes in the levels of calcitonin gene-related peptide and neuropeptide Y on cardiac function of severe burn patients during shock stage]

OBJECTIVE

To investigate the influence of the changes in the levels of calcitonin gene-related peptide (CGRP) and neuropeptide Y (NPY) on cardiac function of severe burn patients during shock stage.

METHODS

Sixty severe burn patients with total burn surface area larger than 30% were enrolled as experiment group (E group) , and they received fluid resuscitation and debridement during shock stage. Sixty healthy volunteers were enrolled as control group (C group). The changes in the plasma level of CGRP, NPY and cTnT in E and C groups were observed at 1, 3, 6, 12, 24, 48 post-burn hours (PBH). The correlation among the CGRP, NPY and cTnT in the C group were analyzed.

RESULTS

At 3 PBH, the plasma level of CGRP in E group (28 +/- 6) ng/L was lower than that in C group (55 +/- 7) ng/L , and it reached the lowest level at 12 PBH (15 +/- 4)ng/L . It was still lower than that in C group at 48 PBH (P < 0.05). The levels of NPY and cTnT in E group were significantly increased at 1PBH [(136 +/- 20) ng/L, (0.41 +/- 0.08) microg/L] compared with that in C group[ (86 +/- 13) ng/L, (0.16 +/- 0.06) microg/L], peaking at 12PBH [(189 +/- 31) ng/L, (1.78 +/- 0. 47) microg/L], and remaining higher than those in C group at 48PBH. There exhibited obvious negative correlation between the changes in the level of CGRP and cTnT ( r = -0.76, P < 0.01), while obvious positive correlation was found between the changes in level of NPY and cTnT ( r = 0.79, P < 0.01).

CONCLUSION

The decrease in CGRP level and the increase in NPY level might play important roles in myocardial injury during shock stage of severe burn patients.

Noninvasive Hemodynamic Monitoring for Combat Casualties

The aims of this study were to develop and to test a noninvasive hemodynamic monitoring system that could be applied to combat casualties to supplement conventional vital signs, to use an advanced information system to predict outcomes, and to evaluate the relative effectiveness of various therapies with instant feedback information during acute emergency conditions. In a university-run inner city public hospital, we evaluated 1,000 consecutively monitored trauma patients in the initial resuscitation period, beginning shortly after admission to the emergency department. In addition to conventional vital signs, we used noninvasive monitoring devices (cardiac index by bioimpedance with blood pressure and heart rate to measure cardiac function, arterial hemoglobin oxygen saturation by pulse oximetry to reflect changes in pulmonary function, and tissue oxygenation by transcutaneous oxygen tension indexed to fractional inspired oxygen concentration and carbon dioxide tension to evaluate tissue perfusion). The cardiac index, mean arterial pressure, pulse oximetry (arterial hemoglobin oxygen saturation), and transcutaneous oxygen tension/fractional inspired oxygen concentration were significantly higher in survivors, whereas the heart rate and carbon dioxide tension were higher in nonsurvivors. The calculated survival probability was a useful outcome predictor that also served as a measure of severity of illness. The rate of misclassification of survival probability was 13.5% in the series as a whole but only 6% for patients without severe head injuries and brain death. Application of noninvasive hemodynamic monitoring to acute emergency trauma patients in the emergency department is feasible, safe, and inexpensive and provides accurate hemodynamic patterns in continuous, on-line, real-time, graphical displays of the status of cardiac, pulmonary, and tissue perfusion functions. Combined with an information system, this approach provided an early outcome predictor and evaluated, with an objective individualized method, the relative efficacy of alternative therapies for specific patients.

Amiloride moderates increased gut permeability and diminishes mesenteric lymph-mediated priming of neutrophils in trauma/hemorrhagic shock

BACKGROUND

Amiloride, an inhibitor of Na+/H+ exchangers and Na+ channels has been shown recently to ameliorate both gut and lung injury in rats subjected to a combined insult of trauma and hemorrhagic shock (T/HS). We have shown previously that mesenteric lymph duct ligation prevents T/HS-induced lung endothelial injury and neutrophil activation, suggesting that toxic inflammatory factors originating from the gut and carried in the lymph are responsible for the lung injury observed after T/HS. This study investigates whether the protective effect of amiloride against T/HS-induced lung injury was associated with decreased lymph toxicity and gut permeability.

METHODS

Male rats subjected to trauma (laparotomy) plus hemorrhagic shock (mean arterial pressure, 30 mm Hgx90 min) (T/HS) or trauma plus sham shock (T/SS) and treated with amiloride or its vehicle had their mesenteric lymph duct catheterized. Mesenteric lymph collected before and after shock was assayed for biologic activity on endothelial cells (cytotoxicity and permeability) and neutrophils (respiratory burst activity). Gut permeability was assessed by monitoring plasma concentrations of the fluorescent dye FITC-dextran after its injection into the ileum.

RESULTS

Amiloride administration reduced the capacity of post-shock mesenteric lymph to prime neutrophils for an increased respiratory burst. Amiloride failed to decrease the ability of mesenteric lymph to kill endothelial cells or increase their permeability. Amiloride decreased gut permeability.

CONCLUSIONS

The mechanisms of the lung protective effect of amiloride in rats undergoing T/HS may be secondary to decreased neutrophil activation, diminished gut permeability, or an effect on the end organ.

Use of power Doppler ultrasound to monitor renal perfusion during burn shock

BACKGROUND

Renal cortical blood flow can be quantified by means of power Doppler ultrasound (PDUS) image analysis. We hypothesized that renal cortical perfusion, estimated by PDUS image intensity (PDUSII), would decrease during burn shock and improve during resuscitation in a porcine model.

METHODS

Eight anesthetized swine sustained a 75% scald injury. Resuscitation began 6h postburn. Renal cortical blood flow was measured directly using fluorescent microspheres (CORFLO), and was estimated noninvasively by PDUSII. PDUSII, CORFLO, and cardiopulmonary data were recorded every 2h.

RESULTS

PDUSII decreased significantly from preburn to postburn hour 6, and increased with resuscitation by hour 8. CORFLO correlated well with PDUS image intensity (n=48, r(2)=0.696) but poorly with urine output (n=48, r(2)=0.252).

CONCLUSION

PDUS in this study was superior to the urine output in assessing renal cortical microvascular blood flow during shock and resuscitation, and may be useful in the care of injured patients.

Traumatic shock

The association of shock with trauma has long been recognized. There are three types of shock, i.e., (1) hypovolemic or hemorrhagic shock, (2) traumatic shock, and (3) septic shock. The conditions and their treatments are described.

[Myocardial depression in the burn patient]

Myocardial depression and heart failure are frequent complications in critically ill burn patients. The physiopathology is complex and involves the activation of inflammatory pathways, ischemia-reperfusion, oxidative stress and endothelial lesion. Diagnosis should be made early by means of hemodynamic monitoring. Treatment is accomplished by inotropics that act on different pathways of the contractile function and immune response associated with antioxidants and allopurinol.

Comparison of blood rheological changes in the microcirculation during experimental hemorrhagic and traumatic shock

OBJECTIVE

The aim of the present study was the analysis of the specific hemorheological disorders during the middle stages of experimental traumatic and hemorrhagic shock.

METHODS

The following hemorheological properties were investigated: Red Blood Cell (RBC) aggregability, their deformability, and systemic hematocrit. The RBC aggregability was assessed by using the "Georgian technique". The RBC deformability was determined with the nuclepore membrane filter method of Reid. The hematocrit was measured by blood centrifugation. The results obtained were treated statistically by using the "Two sample T-test".

RESULTS

We found that in the animals with traumatic shock the erythrocyte aggregability index increased by mean 181%, while in the hemorrhagic group this index on contrary decreased by mean 68% as compared to control group; The RBC deformability underwent a significant decrease during both traumatic and hemorrhagic shock: by a mean of 52% during the first and 62% during the second one. The systemic hematocrit decreased by a mean of 45% during the traumatic shock and by a mean of 50% during the hemorrhagic shock.

CONCLUSION

The data obtained provide evidence that the hemorheological disorders are among the most significant microcirculatory disturbances in the pathogenesis of both the traumatic and the hemorrhagic shock.

[Perfusion disturbances and their correction in the acute period of traumatic disease in patients with concomitant shockogenic lesions]

The topicality of a study is determined by high mortality rates in victims with concomitant shockogenic injuries. A large proportion of victims die in the acute period of traumatic disease (TD). At this time, major changes are observed in the circulatory system. For optimization of intensive care, the authors have changed a clinical classification of the acute period of TD, by applying the principles of general pathology, the data on altered hemodynamics and microcirculation. The stages of infusing-transfusion therapy considering the specific features of changes during each period, which are characteristic for victims with reversible and irreversible shock, are described. Implementation of the infusion-transfusion therapy program proposed by the authors could reduce mortality in victims with concomitant mechanical shockogenic trauma.

Store-Operated Calcium Channel Inhibition Attenuates Neutrophil Function and Postshock Acute Lung Injury

BACKGROUND

A wide variety of neutrophil (PMN) functions are regulated by cytosolic calcium concentration. Calcium channel blockade might therefore decrease postshock inflammation but could also limit important cardiovascular compensations. PMN Ca2+ entry occurs, however, through store-operated calcium entry (SOCE) channels rather than the voltage operated (L-type) channels that regulate cardiovascular tone. We hypothesized that SOCE inhibition might suppress postshock PMN activation, lessening lung injury without compromising cardiovascular performance.

METHODS

Human PMNs were treated in vitro with N-propargyl-nitrendipine (MRS1845 [MRS]) a dihydropyridine Ca2+ channel blocker with relative specificity for SOCE channels. Calcium flux was measured by fura fluorescence. Chemotaxis was studied in modified Boyden chambers. Respiratory burst was studied by dihydrorhodamine fluorescence. Exploratory studies were then performed where rats were subjected to trauma and hemorrhagic shock (T/HS) (laparotomy, then hemorrhage to a mean arterial pressure of 30-40 mm Hg for 90 minutes) after pretreatment with MRS or vehicle given intraperitoneally at laparotomy. In vivo PMN CD11b expression was then assayed by flow cytometry and lung injury was assessed as percentage Evans blue dye leak 3 hours after resuscitation. The shed blood volume required to achieve standardized hypotension was measured.

RESULTS

In vitro, MRS suppressed human PMN SOCE without affecting calcium store release; it suppressed chemotaxis (60 +/- 6 vs. 150 +/- 15 x 10(3) PMNs/well, p = 0.002) and suppressed respiratory burst (62 +/- 11% vs. 100%, p < 0.05) at IC50 concentrations similar to those needed to suppress SOCE. In subsequent in vivo rat studies, MRS decreased postshock PMN CD11b expression from 397 +/- 93 to 268 +/- 39 MFU mean flourescent units (p < 0.05) and decreased lung Evans blue dye permeability from 8.1 +/- 1.9% to 3.4 +/- 0.1% (p < 0.05). MRS had no noticeable effect on the relationship between blood pressure and blood loss, with shed blood volume remaining almost identical (26 +/- 2 mL/kg vs. 27 +/- 3 mL/kg, p = not significant).

CONCLUSION

Modulation of PMN Ca2+ entry by means of selective SOCE channel inhibition attenuates PMN inflammatory responses in vitro. In vivo, SOCE channel blockade attenuates trauma and hemorrhagic shock-induced PMN priming and lung injury without gross evidence of hemodynamic side effects. The relative specificity of SOCE channel blockade for "nonexcitable" cells such as PMNs may make it a valuable form of chemoprophylaxis for the inflammatory consequences of hemorrhagic shock in trauma patients.

Corticosterone binding globulin regulation and thymus changes after thermal injury in mice

Thermal injury is extremely stressful, and data characterizing the systemic endocrine stress response to this injury are sparse. The objective of this study was to measure the effects of thermal injury on mice on corticosterone (Cort) levels in relation with corticosteroid-binding globulin (CBG) and thymus cell populations. The endocrine stress response was determined by measuring total Cort, free Cort, CBG binding capacity, liver CBG mRNA, and circulating CBG levels at 1, 2, 5, and 10 days postburn. Thymus cell populations were also analyzed. After thermal injury, a rapid increase of total Cort was observed in the first 48 h. This was associated with a decrease of hepatic CBG mRNA, protein levels, and binding capacity. Percentage of free Cort in the burn group peaked at day 2 postburn with a dramatic (+500%) increase. This correlated with a significant decrease of thymus cellularity (50% less). Phenotypic analyses showed that corticosensitive cells were significantly altered. After treatment (5 days), both endocrine and immune parameters returned to control levels. Our results demonstrate that, after a thermal injury, CBG is mainly responsible for Cort's action on corticosensitive immune cells.

CD14- and toll-like receptor 4-dependent regulation of c-Fos, c-Jun and c-Jun phosphorylation in the adrenal gland after burn injury

OBJECTIVES

Although the pathophysiology of the adrenocortical response after injury has been described, alterations in the molecular profile (e.g. transcription factors) of the adrenal gland itself are not well understood. The regulation of c-Fos, c-Jun, and c-Jun phosphorylation in the adrenal gland after burn injury was investigated in this study. In addition, since burn injury is often associated with lipopolysaccharide (LPS)-mediated sepsis, we examined the involvement of the LPS signaling pathway in the regulation of these transcription factors utilizing CD14 knockout and C3H/HeJ (encoding defective toll-like receptor 4) mice.

METHODS

Adrenal glands harvested after an 18% total body surface area burn were subjected to RT-PCR and Western blot analyses of c-Jun and c-Fos.

RESULTS

There was a rapid induction of c-Jun and c-Fos expression (mRNA and protein), and c-Jun serine phosphorylation. The induction of c-Jun and its phosphorylation after injury was greater in CD14 knockout and C3H/HeJ mice compared to their respective controls. A similar pattern was observed in the c-Fos regulation.

CONCLUSIONS

These data suggest that c-Fos and c-Jun are activated in the adrenal gland in response to burn injury. In addition, an LPS-mediated signaling pathway may influence the regulation of these transcription factors after injury.

[The diagnosis and correction of impairments of microcirculation, central hemodynamics, and oxygen status in children with traumatic shock]

The paper presents the results of studies of microcirculation, central hemodynamics, and oxygen status in 120 children aged 2-14 years who had traumatic shock of various etiology (40 with burn injury, 50 with mixed injury, and 30 with brain injury). The following studies were used: biomicroscopy of conjunctival microvessels with photo recording and processing on a computer; central hemodynamic monitoring; studies of a thromboelastogram, acid-alkali balance, and blood gases. The authors found the previously unknown parallels of the impairments of microcirculation, the severity of traumatic injury, and the parameters of central hemodynamics, and oxygen status in the patient. Traumatic shock was characterized by spastic impairments of all the components (perivascular, vascular, and intravascular) of microcirculation progressing to spastic-and-atonic ones. The degree of microcirculatory disorders depended on the severity of shock and the nature of injury. The criteria for compensation and decompensation in the microcirculatory module were defined. The routine infusion therapy initiated in the compensation period promotes to a significant alleviation of microcirculatory disorders; however, the mentioned shifts long persist. In this connection, a package of additional measures (infucol GEC solutions, disaggregatory, antihypoxic, and antioxidant agents, and coenzymes of vitamins) has been developed.

Attenuation of Shock-Induced Acute Lung Injury by Sphingosine Kinase Inhibition

BACKGROUND

Prolonged elevations of cytosolic calcium concentrations ([Ca2+]i) are required for optimal neutrophil (PMN) activation responses to G-Protein coupled chemoattractants. We recently showed that the coupling of endosomal Ca2+ store depletion to more prolonged entry of external Ca2+ depends on cellular conversion of sphingosine to sphingosine 1-phosphate (S1P) by sphingosine kinase (SK). We therefore hypothesized that inhibition of SK might inhibit PMN activation and thus ameliorate lung injury after trauma and hemorrhagic shock (T/HS).

METHODS

Chemotaxis (CTX) of human PMN was studied using modified Boyden chambers in the presence or absence of the selective SK inhibitor, SKI-2. After determining the concentration of SKI-2 that inhibited human PMN CTX by 50% (IC50) we subjected rats to T/HS (laparotomy, hemorrhage to 30-40 mm Hg x 90 minutes, 3 hours resuscitation). We then studied rat PMN CD11b expression using flow cytometry and lung injury using the Evans Blue dye technique in the presence of IC50 doses of SKI-2 or vehicle given in pretreatment at laparotomy.

RESULTS

Human PMN CTX was suppressed slightly more than 50% by 40 micromol/L SKI-2 (233 +/- 20 vs 103 +/- 12 x 10(3) cells/well, p < 0.001). Rat PMN expression of CD11b after T/HS was decreased from 352 +/- 30 to 232 +/- 7 MFU (p < 0.001) in the presence 30 micromol/L SKI-2. Lung permeability to Evans Blue was decreased from 9.5 +/- 2 to 4.1 +/- 0.7% (p = 0.036.). SKI-2 did not cause hemodynamic instability or alter resuscitation requirements.

CONCLUSION

Modulation of PMN Ca entry via SK inhibition inhibits PMN CTX in vitro, and inhibits CD11b expression in vivo without major effects on hemodynamics. These cellular changes were associated with amelioration of lung injury in vivo in a rat model of T/HS. These findings suggest that SK inhibition allows modulation of inflammation via control of [Ca2+]i without the cardiovascular compromise expected with Ca2+ channel blockade. SK inhibition therefore appears to be an important novel candidate therapy for inflammatory organ injury after shock.

Systemic Neutrophil Priming by Lipid Mediators in Post-Shock Mesenteric Lymph Exists Across Species

BACKGROUND

Post-hemorrhagic shock mesenteric lymph (PHSML) has been linked with neutrophil (PMN) priming, endothelial cell (EC) activation, and acute lung injury (ALI) in rodent models. We have previously identified the lipid fraction of PHSML as containing the causative agent(s). Due to the lesson learned from the rodent gut bacterial translocation experience, we sought to confirm this phenomenon using a large animal model; hypothesizing that lymph collected from the porcine gut following ischemia/reperfusion (I/R) would cause PMN priming.

METHODS

Mesenteric lymph was collected from adult pigs before, during, and for 2 hours after non-lethal hemorrhagic shock (mean arterial pressure = 30 mm Hg x 45 minutes). Whole lymph and the extracted lipid fractions of the lymph were then added to isolated human and porcine PMNs and superoxide production was measured by cytochrome C reduction.

RESULTS

Hemorrhagic shock profoundly affected mesenteric lymph flow from baseline (pre-shock) flow rates of 75.63 +/- 8.86 mL/hr to 49.38 +/- 5.76 mL/hr during shock and increasing to 253.38 +/- 27.62 mL/hr after 2 hours of resuscitation. Human PMNs exposed to both whole lymph (PHSML) and its extracted lipids (PHSML Lipid) collected 2 hours after shock exhibited more than a two-fold increase in superoxide release upon activation compared with pre-shock samples: PHSML- 6.27 +/- 0.83 versus 2.56 +/- 0.60 nmolO2(-)/ 3.75 cells/mL/min, respectively (p = 0.007), PHSML Lipid- 4.93 +/- 0.34 versus 2.49 +/- 0.11 nmolO2(-)/ 3.75 cells/mL/min (p < 0.001). Similarly, porcine PMNs exhibited close to a two-fold activation when exposed to the lymph and lipid fraction: PHSML- 4.51 +/- 0.42 versus 1.06 +/- 0.28 nmolO2(-)/ 3.75 cells/mL/min (p = 0.008), PHSML Lipid-4.80 +/- 0.81 versus 1.55 +/- 0.23 nmolO2(-)/ 3.75 cells/mL/min (p = 0.002).

CONCLUSION

Mesenteric lymphatics serve as the conduit for inflammatory mediators elaborated by the post-ischemic gut in both small and large animal models. Further, the causal agent(s) exist in the lipid fraction of the lymph and are active on both human and animal PMNs.

Uncompensated Metabolic Acidosis: An Underrecognized Risk Factor for Subsequent Intubation Requirement

BACKGROUND

There are no published reports identifying an inadequate ventilatory response to metabolic acidosis as a predictor of impending respiratory failure. Metabolic acidosis should induce a respiratory alkalosis in which the partial pressure of carbon dioxide (Paco2) is (1.5 [HCO3-] + 8) +/- 2. This study examined the relation between inadequate ventilatory compensation and intubation among trauma patients.

METHODS

A retrospective chart review was performed for trauma patients admitted between January 1999 and December 2000. Age, gender, Injury Severity Score and combined Trauma and Injury Severity Score, chest injury, history of cardiac or pulmonary disease, partial pressure of oxygen (Pao2), Paco2, Glasgow Coma Score, respiratory rate, systolic blood pressure, base deficit, and ability to compensate were analyzed with respect to intubation and need for ventilator support.

RESULTS

Of 140 patients with metabolic acidosis, 45 ultimately were intubated. The mean Paco2 for the unintubated patients was 34 +/- 7 mm Hg, as compared with 41 +/- 11 mm Hg for the intubated patients (p < 0.001). Only injury severity and ability to compensate for metabolic acidosis were independent predictors of intubation. Patients with inadequate compensation were 4.2 times more likely to require intubation when control was used for the Injury Severity Score (95% confidence interval, 1.8-9.7; p < 0.001).

CONCLUSIONS

Inability to mount an adequate hyperventilatory response to metabolic acidosis is associated with an increased likelihood of respiratory failure and a need for ventilatory support. Recognition of this relation should lead to closer monitoring of patients with this condition, and could help to avert unforeseen crisis intubations. This observation needs to be validated in a prospective study.