Liposomal prostaglandin E1 in acute respiratory distress syndrome: a placebo-controlled, randomized, double-blind, multicenter clinical trial

OBJECTIVE

To evaluate the safety and efficacy of liposomal prostaglandin E1 (TLC C-53) in the treatment of patients with the acute respiratory distress syndrome (ARDS).

DESIGN

Randomized, prospective, multicenter, double-blind, placebo-controlled, phase II clinical trial.

SETTING

Eight community and university-affiliated hospitals in the United States.

PATIENTS

Twenty-five patients with ARDS.

INTERVENTIONS

Patients were prospectively randomized in an unbalanced ratio within each site to receive either TLC C-53 (n = 17) or placebo (n = 8). Study drug was infused intravenously over 60 mins every 6 hrs for a 7-day period, starting at a dose of 0.15 micrograms/kg/hr. The dose was increased every 12 hrs until the maximal dose (3.6 micrograms/kg/hr) was attained, intolerance to further increases developed, or invasive monitoring was discontinued. Patients received standard, aggressive, medical/surgical care throughout the trial.

MEASUREMENTS AND MAIN RESULTS

Outcome measurements were Pao2/FI0(2), dynamic pulmonary compliance, ventilator dependence on day 8, and 28-day all-cause mortality rate. At baseline, the distribution of variables describing Lung Injury Scores, Acute Physiology and Chronic Health Evaluation II scores, Pao2/FI0(2), pulmonary compliance, and time from onset of ARDS to first dose of study drug was similar between patients in the TLC C-53 and placebo treatment groups. On day 8, all eight patients given placebo required mechanical ventilation, while eight of 17 patients given TLC C-53 were healthy enough to be removed from the ventilator (p = .03). Improvement in PaO2/FIO2 during the initial 8-day study period was greater in patients receiving TLC C-53. This trend achieved statistical significance on day 3, when the increase in PaO2/FIO2 from baseline was 82.5 +/- 14.6 in the TLC C-53 group compared with 28.3 +/- 22.1 in the placebo group (p = .05). By day 8, lung compliance also increased from baseline significantly more in TLC C-53 patients than in placebo patients (5.7 +/- 1.7 vs -1.5 +/- 1.8 mL/cm H2O; p = .01). The 28-day mortality rate was 6% (1/17 patients) in the TLC C-53 group and 25% (2/8 patients) in the placebo group (p = .23). Drug-related adverse events were reported in 82% of the patients receiving TLC C-53 compared with 38% of the placebo group, with half of the adverse events in the TLC C-53 group being localized infusion site irritation. TLC C-53 was hemodynamically well tolerated, with transient hypotension occurring in three patients.

CONCLUSIONS

In patients with ARDS, TLC C-53 was associated with improved oxygenation, increased lung compliance, and decreased ventilator dependency.

Contribution of tumor necrosis factor-alpha to pulmonary cytokine expression and lung injury after hemorrhage and resuscitation

OBJECTIVE

To examine the role of tumor necrosis factor-alpha (TNF-alpha) in producing acute inflammatory lung injury after hemorrhage and resuscitation.

DESIGN

Prospective, controlled animal study.

SETTING

Research laboratory.

SUBJECTS

Male BALB/c mice.

INTERVENTIONS

Treatment with rat antimouse monoclonal anti-TNF-alpha antibodies or control rat immunoglobulin G 1 hr after 30% blood volume hemorrhage and resuscitation.

MEASUREMENTS AND MAIN RESULTS

Therapy with monoclonal anti-TNF-alpha antibodies prevented the posthemorrhage increases in pulmonary TNF-alpha and interferon-gamma protein levels that normally occur after blood loss. Administration of monoclonal anti-TNF-alpha antibodies also diminished the increases in interleukin-1 beta, interleukin-6, and interleukin-10 mRNA, but not the increases in TNF-alpha and interferon-gamma mRNA, which are found in the lungs following hemorrhage. In addition, therapy with monoclonal anti-TNF-alpha antibodies was associated with significant improvement in the histologic parameters of posthemorrhage lung injury, particularly intra-alveolar hemorrhage and pulmonary vascular congestion.

CONCLUSIONS

These results indicate that TNF-alpha has an important role in the development of acute inflammatory lung injury after blood loss. Blockade of TNF-alpha with monoclonal antibodies significantly reduces hemorrhage-induced lung injury.

Human papillomaviruses in 91 oral cancers from Indian betel quid chewers--high prevalence and multiplicity of infections

India has one of the world's highest incidences of oral cancer. The habit of chewing betel quid is widespread and is suspected to play a role in the etiology of this disease. Studies in many other countries have also pointed to a role for human papilloma-viruses (HPVs) in the etiology of some oral cancers. In this study we analyzed biopsies from 91 Indian oral cancer patients, most of whom were betel quid chewers, by PCR amplification and direct DNA sequencing. HPV DNA was detected in 74% of these lesions, of which 41% had multiple HPV infections. Among the lesions from different oral sites, lesions of the tongue had the highest rate (9 of 11) of HPV infection. These HPV prevalences are among the highest ever reported in oral cancers. As to individual HPV types, prevalences of HPV-6, HPV-11, HPV-16 and HPV-18 were 13%, 20%, 42% and 47%, respectively. No additional known or novel HPV types were detected. To understand the unexpectedly high prevalences of the "low-risk" types HPV-6 and HPV-11, we compared the subtypes and variants that were found in oral cancers against those from benign genital warts from the same patient population but found no differences. The high prevalence of HPV in the oral cancers of these Indian patients suggests that viral infection is an important etiological component, with betel quid probably causing additional mutagenic steps in the carcinogenic process.

Xanthine oxidase-derived oxygen radicals increase lung cytokine expression in mice subjected to hemorrhagic shock

Acute inflammatory lung injury often complicates hemorrhagic shock, a systemic ischemia-reperfusion syndrome. Because oxygen radicals are generated during ischemia-reperfusion, and oxygen radicals can activate nuclear regulatory factors that affect transcription of proinflammatory cytokines, we examined the premise that oxygen radicals increase interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) expression in lung mononuclear cells after hemorrhage. Intraparenchymal pulmonary mononuclear cells isolated 1 h after hemorrhage from control mice had increased levels of mRNA for IL-1 beta (P < 0.001) and TNF-alpha (P < 0.05) compared with cells from sham-hemorrhaged mice. Hemorrhaged mice treated with the oxygen radical scavenger dimethylthiourea (DMTU) had decreased levels of mRNA for IL-1 beta in pulmonary mononuclear cells, compared with hemorrhaged controls (P < 0.05). In hemorrhaged mice depleted of xanthine oxidase (XO) by a tungsten-enriched diet, pulmonary mononuclear cell mRNA levels for IL-1 beta and TNF-alpha were significantly decreased (P < 0.01 and 0.05, respectively), compared with cells from hemorrhaged control mice fed a normal diet. Similarly, mRNA transcripts for IL-1 beta and TNF-alpha among pulmonary mononuclear cells from hemorrhaged mice treated with allopurinol, an inhibitor of XO, were also significantly reduced (P < 0.05 and 0.001, respectively), compared with hemorrhaged control mice not treated with allopurinol. Our results indicate that XO-derived oxygen radicals contribute to the increased expression of mRNA for IL-1 beta and TNF-alpha, which occurs among pulmonary mononuclear cell populations immediately after hemorrhage.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphatidic acid signaling mediates lung cytokine expression and lung inflammatory injury after hemorrhage in mice

Because phosphatidic acid (PA) pathway signaling may mediate many basic reactions involving cytokine-dependent responses, we investigated the effects of CT1501R, a functional inhibitor of the enzyme lysophosphatidic acid acyltransferase (LPAAT) which converts lysophosphatidic acid (Lyso-PA) to PA. We found that CT1501R treatment not only prevented hypoxia-induced PA increases and lyso-PA consumption in human neutrophils, but also prevented neutrophil chemotaxis and adherence in vitro, and lung injury and lung neutrophil accumulation in mice subjected to hemorrhage and resuscitation. In addition, CT1501R treatment prevented increases in mRNA levels and protein production of a variety of proinflammatory cytokines in multiple lung cell populations after blood loss and resuscitation. Our results indicate the fundamental role of PA metabolism in the development of acute inflammatory lung injury after blood loss.

Effects of treatment with the 21-aminosteroid, U7438F, on pulmonary cytokine expression following hemorrhage and resuscitation

OBJECTIVE

To determine the effects of therapy with the antioxidant 21-aminosteroid, U74389F, on cytokine mRNA levels following hemorrhage and resuscitation.

DESIGN

Prospective, controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Male bronchoalveolar lavage B/c (BALB/c) mice.

INTERVENTIONS

U74389F (10 mg/kg) in CS4 vehicle or CS4 vehicle alone, was administered intravenously to bronchoalveolar lavage B/c mice 15 mins before 30% blood volume hemorrhage, with resuscitation 60 mins later.

MEASUREMENTS AND MAIN RESULTS

Semiquantitative polymerase chain reactions were used to determine the effects of therapy with U74389F on cytokine mRNA levels among intraparenchymal pulmonary mononuclear cells, alveolar macrophages, and peripheral blood mononuclear cells obtained 2 hrs and 3 days after hemorrhage. In mice treated with U74389F, mRNA levels for interleukin (IL)-1 beta, IL-6, IL-10, tumor necrosis factor-alpha, and interferon-gamma were significantly decreased among intraparenchymal pulmonary mononuclear cells obtained 3 days, but not 2 hrs, after hemorrhage. No effects of therapy with U74389F were found in modulating posthemorrhage cytokine expression among alveolar macrophages or peripheral blood mononuclear cells.

CONCLUSIONS

These studies demonstrate that treatment with U74389F, a 21-aminosteroid whose major activity is inhibition of lipid peroxidation due to the generation of reactive oxygen intermediates, significantly decreases hemorrhage-induced activation of proinflammatory cytokine expression among pulmonary cell populations. In addition, the present results, showing decreased expression of proinflammatory and immunoregulatory cytokines among intraparenchymal pulmonary mononuclear cells following treatment with U74389F, suggest that 21-aminosteroids may have clinical utility in preventing and/or modulating acute lung injury in the postinjury period.

Effects of therapy with interleukin-1 receptor antagonist on pulmonary cytokine expression following hemorrhage and resuscitation

Acute lung injury frequently develops following hemorrhage and is characterized by increased proinflammatory cytokine levels and massive neutrophil accumulation in the lung. Blood loss produces rapid increases in IL-1 alpha and IL-1 beta mRNA expression among pulmonary cell populations. To examine the role of IL-1 in producing acute inflammatory lung injury after hemorrhage, we treated mice following hemorrhage and resuscitation with recombinant interleukin-1 receptor antagonist (IL-1Ra), a competitive inhibitor of the actions of IL-1. Therapy with IL-1Ra prevented the posthemorrhage increases in pulmonary TNF-alpha levels normally found after blood loss. Administration of IL-1Ra also diminished the increases in IL-1 beta and IL-6 mRNA levels that occur in the lungs following hemorrhage. However, the amounts of TNF-alpha and IFN-gamma mRNA among intraparenchymal pulmonary mononuclear cells remained elevated after hemorrhage despite therapy with IL-1Ra. These results indicate that therapy with IL-1Ra in the posthemorrhage period is capable of normalizing the expression of some, but not all, of the proinflammatory cytokines whose production among pulmonary cellular populations is increased by blood loss.

Effects of therapy with soluble tumour necrosis factor receptor fusion protein on pulmonary cytokine expression and lung injury following haemorrhage and resuscitation

Acute lung injury frequently develops following haemorrhage, and is characterized by increased proinflammatory cytokine levels and massive neutrophil accumulation in the lung. Blood loss produces rapid increases in tumour necrosis factor-alpha (TNF-alpha) mRNA expression among pulmonary cell populations which precede the development of lung injury. In order to examine the role of TNF-alpha in producing acute inflammatory lung injury, we treated mice following haemorrhage and resuscitation with a TNF antagonist, composed of soluble dimeric human p80 TNF receptor linked to the Fc region of human IgG1 (sTNFR:Fc). Therapy with sTNFR:Fc prevented the post-haemorrhage increases in circulating and pulmonary TNF-alpha levels normally found following blood loss. Administration of sTNFR:Fc also diminished the increase in IL-1 beta, IL-6, TNF-alpha and interferon-gamma (IFN-gamma) mRNA normally found in the lungs following haemorrhage. However, therapy with sTNFR:Fc was not associated with improvement in the histologic parameters of post-haemorrhage lung injury, such as neutrophil infiltration and interstitial oedema. In contrast to the effects of sTNFR:Fc on cytokine mRNA levels among intraparenchymal pulmonary mononuclear cells, such therapy following haemorrhage was associated with increased amounts of mRNA for TNF-alpha among peripheral blood mononuclear cells, as well as increased IFN-gamma titres in serum and bronchoalveolar lavage (BAL) specimens. These results indicate that therapy with sTNFR:Fc in the post-haemorrhage period, although capable of decreasing proinflammatory cytokine expression in the lungs, does not prevent the development of acute lung injury in this setting.

Anti-transforming growth factor-beta monoclonal antibodies prevent lung injury in hemorrhaged mice

Acute lung injury, characterized as the adult respiratory distress syndrome (ARDS), is a common clinical occurrence following blood loss and injury. We previously found increased levels of transforming growth factor (TGF)-beta 1 mRNA in murine intraparenchymal mononuclear cells and in alveolar macrophages within 1 h after hemorrhage. Because TGF-beta has potent proinflammatory and immunoregulatory properties, we investigated the effect of blocking TGF-beta with mAb on hemorrhage-induced pathology, cytokine mRNA levels in lungs, as well as survival from pneumonia. Mice treated with anti-TGF-beta mAb showed normal pulmonary histology 3 days after hemorrhage and resuscitation in contrast to the mononuclear and neutrophil infiltrates, intraalveolar hemorrhage, and interstitial edema found in hemorrhaged mice either treated with control antibody or not treated with any antibody. Decreased mRNA levels for IL-1 beta, TNF-alpha, IL-6, IL-10, and IFN-gamma as compared with untreated, hemorrhaged controls were present in intraparenchymal pulmonary mononuclear cells following therapy with anti-TGF-beta. In contrast, therapy with anti-TGF-beta increased mRNA levels for IL-1 beta and TNF-alpha in alveolar macrophages and for TGF-beta in peripheral blood mononuclear cells collected 3 days after hemorrhage. Administration of anti-TGF-beta to hemorrhaged mice did not correct the enhanced susceptibility to Pseudomonas aeruginosa pneumonia that exists after hemorrhage. These results suggest that TGF-beta has an important role in hemorrhage-induced acute lung injury, but does not contribute to the post-hemorrhage depression in pulmonary antibacterial response.

Intrathecal injection of cell-permeable analogs of cyclic 3',5'-guanosine monophosphate produces hyperalgesia in mice

Several recent studies suggest that spinal cord levels of cyclic 3',5'-guanosine monophosphate (cGMP) may participate in the development of hyperalgesia. The purpose of this study was to directly evaluate whether cell permeable analogues of cGMP evoke a thermal hyperalgesia (using a hot-plate assay) when administered intrathecally in mice. Our results indicate that two cell permeable forms of cGMP evoke a dose dependent hyperalgesia when administered intrathecally in mice. Additionally, this hyperalgesia was selective since neither non-cell permeant cGMP nor guanosine had any effect on the latency of paw withdrawal when compared to the vehicle injected controls. These data indicate that cGMP is involved in the facilitation of thermal hyperalgesia at the level of the spinal cord.

Elevated levels of soluble ICAM-1 correlate with the development of multiple organ failure in severely injured trauma patients

Serum levels of interleukin-6, interleukin-8, the soluble receptor for tumor necrosis factor (sTNFr), and the soluble receptor for intercellular adhesion molecule-1 (sICAM-1) were measured serially in a series of 13 severely injured trauma patients to determine if any of these elements of the inflammatory response are predictive of multiple organ failure (MOF). Six of the 13 patients developed MOF as determined by a MOF scoring system. At the completion of resuscitation (when oxygen delivery and consumption were maximized) sICAM-1 levels were significantly higher in MOF patients before the development of clinical evidence of organ failure (700 +/- 67 ng/mL) compared with non-MOF patients (302 +/- 18 ng/mL). There was a significant correlation between the absolute level of sICAM-1 at the time of resuscitation and the severity of subsequent MOF. This finding suggests that leukocyte-endothelial cell interactions are upregulated immediately after injury and may be implicated in the end-organ injury that leads to MOF.

Temporal patterns of hemodynamics, oxygen transport, cytokine activity, and complement activity in the development of adult respiratory distress syndrome after severe injury

The aim of this study was to search for early inflammatory mediators in severely traumatized patients that could predict the occurrence of adult respiratory distress syndrome (ARDS). We measured sequential plasma levels of tumor necrosis factor (TNF), interleukin 1 (IL-1), interleukin 6 (IL-6), interleukin 8 (IL-8), complement fragment C3a, and endotoxin. In addition, we measured sequentially the values of hemodynamics, oxygen transport, and pulmonary function. The temporal patterns seen in the patients who developed ARDS were compared with those who did not. In the patients who developed ARDS, the first observed findings were low cardiac index (CI) and oxygen delivery (DO2) followed by progressive increases in IL-6, IL-8 and C3a levels, worsening of pulmonary function, and increases in hemodynamic values. The maximum values of IL-6, IL-8, and C3a occurred after the onset of ARDS. In the patients who did not develop ARDS, initial oxygen transport values were not low, the levels of IL-6, IL-8, and C3a decreased rapidly from their initial peaks, and there were no further increases in hemodynamic values. In both ARDS and nonARDS patients, no measurable quantities of TNF, IL-1, or endotoxin were found. We concluded that none of the mediators we measured reached their peaks before the onset of ARDS and none were found to be predictive of posttraumatic ARDS. However, these and other mediators may augment or intensify the development of ARDS.

Cytokine, complement, and endotoxin profiles associated with the development of the adult respiratory distress syndrome after severe injury

OBJECTIVE

The adult respiratory distress syndrome (ARDS) is a frequent complication after severe accidental trauma. This study examines the hypothesis that increased systemic concentrations of proinflammatory cytokines, endotoxin, or complement fragments may predict the development of ARDS.

DESIGN

Prospective, observational study.

SETTING

Two Level I university trauma centers.

PATIENTS

Fifteen severely injured patients (Injury Severity Score of > or = 25).

INTERVENTIONS

Standard emergency department, operating room, and intensive care unit management.

MEASUREMENTS AND MAIN RESULTS

Plasma samples were obtained at 4-hr intervals from the time of injury and were assayed for concentrations of endotoxin, tumor necrosis factor-alpha, interleukin (IL)-1 beta, IL-6, IL-8, and complement fragments C3a and C4a. Hemodynamic and oxygen metabolism variables also were measured at 4-hr intervals after injury. Seven patients developed ARDS and eight patients did not. The PaO2/FIO2 ratio was significantly decreased in the patients with ARDS compared with non-ARDS patients as early as 4 hrs postinjury, and remained significantly decreased throughout the initial 24 hrs after severe accidental injury. Plasma IL-8, IL-6, C3a, and C4a concentrations were markedly increased starting in the immediate postinjury period in both ARDS and non-ARDS patients, but no significant differences were found between the two groups until 16 hrs after injury when plasma IL-8, C3a, and C4a concentrations became significantly higher in the ARDS group. Neither the ARDS nor non-ARDS patients showed the presence of circulating IL-1 beta, TNF-alpha, or endotoxin at any postinjury time point.

CONCLUSIONS

These results demonstrate that measurements of plasma concentrations of proinflammatory cytokines, endotoxin, or complement fragments are not helpful in predicting the development of ARDS after severe accidental injury.

Hemorrhage and resuscitation induce alterations in cytokine expression and the development of acute lung injury

Acute pulmonary injury occurs frequently following hemorrhage and injury. In order to better examine the sequence of events leading to lung injury in this setting, we investigated lung histology as well as in vivo mRNA levels for cytokines with proinflammatory and immunoregulatory properties (IL-1 beta, IL-6, IL-10, TNF-alpha, TGF-beta, IFN-gamma) over the 3 days following hemorrhage and resuscitation. Significant increases in mRNA levels for IL-1 beta, IL-6, IL-10, and IFN-gamma, but not TNF-alpha, were present among intraparenchymal pulmonary mononuclear cells obtained 1 and 3 days after hemorrhage. Among alveolar macrophages, TNF-alpha and IL-1 beta mRNA levels were increased 3 days after hemorrhage. Few changes in cytokine mRNA levels, with the exception of TNF-alpha at 3 days after hemorrhage, were present among peripheral blood mononuclear cells. Histologic examination of lungs from hemorrhaged animals showed no alterations 1 day after hemorrhage, but neutrophil and mononuclear cell infiltrates, edema, intra-alveolar hemorrhage, and fibrin generation were present 3 days after hemorrhage. These results suggest that hemorrhage-induced enhancement of proinflammatory cytokine gene transcription may be an important mechanism contributing to the frequent development of acute lung injury following blood loss and injury.

Cytokine expression in Peyer's patches following hemorrhage and resuscitation

Intestinal dysfunction commonly occurs following hemorrhage and injury and appears to contribute to the development of multiple organ system failure in this setting. In order to examine possible mechanisms leading to intestinal dysfunction following blood loss, we investigated mRNA levels for cytokines with proinflammatory and immunoregulatory properties (interleukin 1 beta (IL-1 beta), IL-6, IL-10, TNF-alpha, TGF-beta, IFN-gamma) as well as mRNA expression for inducible nitric oxide synthase (NOS) over the 3 days following hemorrhage and resuscitation. Significantly increased levels of mRNA for IL-1 beta, IL-10, and IFN-gamma were found among cells isolated from Peyer's patches 3 days following hemorrhage. Amounts of mRNA for inducible NOS were not significantly altered 24 or 72 h after blood loss. In addition to being increased 72 h following hemorrhage, levels of mRNA for IL-10 also were increased 1 and 4 h posthemorrhage. No alterations in cytokine or NOS expression were found 24 h following blood loss. These results demonstrate that significant increases in proinflammatory and immunoregulatory cytokine mRNA levels among cellular populations in Peyer's patches are present at late posthemorrhage time points. These alterations in cytokine expression may contribute to the morphologic, immunologic, and functional changes in the intestines which are present following blood loss and injury.

Randomized, prospective trial of pressure-limited versus volume-controlled ventilation in severe respiratory failure

OBJECTIVE

Volume-controlled ventilation is frequently chosen as the initial mode of ventilatory support in patients with hypoxic respiratory failure. Recent data, however, suggest that pressure-limited ventilation, using a rapidly decelerating flow delivery pattern, may produce a more desirable clinical effect through reduced peak airway pressures and increased static compliance, tissue oxygen delivery, and consumption. This study was performed to assess the feasibility and utility of early and sustained use of pressure-limited ventilation in patients with this clinical syndrome.

DESIGN

Randomized, prospective trial.

SETTING

Medical intensive care unit (ICU) of a university hospital.

PATIENTS

The study encompassed all patients (n = 27) receiving care in a medical ICU for acute, severe hypoxic respiratory failure (PaO2/FIO2 ratio of < 150) during a 6-month period.

INTERVENTIONS

Ventilatory support via either pressure-limited or volume-controlled ventilation, initiated within 24 hrs of endotracheal intubation.

MEASUREMENTS

On-line monitoring of the following ten ventilatory variables at 1-min intervals for 72 hrs or until extubation or death (maximum of 43,200 data points per patient): peak airway pressure, mean airway pressure, end-tidal CO2 concentration, CO2 minute excretion, inspiratory tidal volume, expiratory tidal volume, pause pressure, end-expiratory pressure, static thoracic compliance, and inspiratory resistance. Additionally, PaO2/FIO2 values and Acute Physiology and Chronic Health Evaluation (APACHE) II scores were recorded on a daily basis, as were significant clinical events and changes in ventilator settings.

RESULTS

Although the severity of illness at study entry as determined by APACHE II score and PaO2/FIO2 was similar in patients treated with pressure-limited or volume-controlled ventilation, peak airway pressure was consistently lower in patients randomized to pressure-limited ventilation (p = .05 at 12 hrs postintubation). The use of pressure-limited ventilation also was associated with a more rapid increase in static compliance (p = .05) than that found with volume-controlled ventilation. There was a trend toward more rapid normalization of CO2 minute excretion in patients treated with pressure-limited ventilation. Pressure-limited treated patients who survived their illness and were extubated, required fewer days of mechanical ventilation than did patients randomized to volume-controlled treated ventilation (p = .05). No pneumothoraces occurred in any study patients. One volume-controlled patient developed subcutaneous emphysema. Pressure-limited ventilation was well tolerated, and sedation requirements were equivalent in the two groups.

CONCLUSIONS

Pressure-limited ventilation can be used safely and is well tolerated as an initial mode of ventilatory support in patients with acute hypoxic respiratory failure. Because the early initiation of pressure-limited ventilation is associated with lower peak airway pressure and more rapid improvement in static thoracic compliance than volume-controlled ventilation, pressure-limited ventilation may have a beneficial role when used as the primary ventilatory modality in patients with this clinical condition.

Sequence of physiologic patterns in surgical septic shock

OBJECTIVES

Gradual, almost imperceptible transitions occur between localized infection, generalized infection, systemic manifestations of the sepsis syndrome, septic shock, and death. The aim of this study was to describe the sequential pattern of hemodynamic and oxygen transport patterns of survivors and nonsurvivors of septic shock, so as to differentiate primary from secondary and tertiary events, to evaluate possible physiologic mechanisms, and to provide a template to relate the appearance of biochemical mediators to the sequence of physiologic events.

DESIGN

Prospective, cohort study.

SETTING

University-run county hospital.

PATIENTS

A series of 300 consecutive surgical patients with septic shock; 85 survived and 215 died.

INTERVENTIONS

We used specific criteria to define stages as: a) early period, the first recorded increase in cardiac output; b) middle period, time of maximal metabolic activity defined as the highest recorded oxygen consumption (VO2); and c) late period, the time of death or recovery.

MEASUREMENTS AND MAIN RESULTS

Hemodynamic and oxygen transport variables were measured at frequent intervals throughout the course of septic shock. Beginning with increased cardiac index and oxygen delivery (Do2), which were the earliest observed hemodynamic changes, there were progressive increases in cardiac index, DO2, and VO2. The values of these variables in the survivors were both greater than normal and greater than those values of the nonsurvivors at comparable time periods. These values decreased in the late stage in nonsurvivors. There were early transient reductions in VO2 that preceded the increase in temperature and the decrease in blood pressure in both survivors and nonsurvivors. Although 86% of the septic patients were hyperdynamic, there were transient hypodynamic episodes (defined as cardiac index < 2.5 L/min/m2) in < 10% of the measurements. Transient preterminal hypermetabolic periods occurred in 9% of the nonsurvivors.

CONCLUSIONS

Increased cardiac index and DO2 represent compensations for circulatory deficiencies that limit body metabolism, as reflected by inadequate VO2. Survivors have higher cardiac index, DO2, and VO2 values than those values of both the nonsurvivors and normal values. These data suggest that therapy should be directed toward increasing cardiac index to > 5.5 L/min/m2, DO2 to > 1000 mL/min/m2, and VO2 to > 190 mL/min/m2 as therapeutic goals; these supranormal values were empirically determined by the patterns of the survivors. Further studies to describe temporal relationships of biochemical mediators of these physiologic patterns are needed.

Temporal hemodynamic and oxygen transport patterns in medical patients. Septic shock

STUDY DESIGN

Because of the gradual insidious transitions between localized infection, generalized infection, and septic shock, it is difficult to compare data of patients in various stages and to differentiate primary from secondary and tertiary events. The aim of the present study was to describe the sequential pattern of hemodynamic and oxygen transport patterns of survivors and nonsurvivors of septic shock in order to evaluate possible physiologic mechanisms and to provide a template to relate the sequence of physiologic events to biochemical mediators.

PROCEDURE

A previously described defined protocol was used prospectively to study the sequence of physiologic events using specific criteria to define stages as: (a) early period, the first recorded change in cardiac output; (b) middle period, time of maximal metabolic activity defined as the highest recorded oxygen consumption (VO2); and (c) late period, the time of death or recovery. In addition, three time lines were defined as the first time mean arterial pressure fell below 70 mm Hg, the first time temperature rose above 38 degrees C, and the earliest fall in VO2. Physiologic data were aligned in actual time before or after the time these criteria were met. Invasive hemodynamic and oxygen transport variables were measured with systemic and pulmonary artery catheters; intravascular pressures, arterial and mixed venous gas levels, cardiac output, and derived calculations were made at frequent intervals and keyed to the time of the cardiac output; each set of measurements in turn was keyed to the aforementioned time periods to describe the early, middle, and late periods.

RESULTS

Beginning with increased cardiac index and oxygen delivery (DO2) as the early physiologic changes, there were progressive increases in cardiac index, DO2, and VO2 throughout the early and middle periods. They were maintained above the normal range in the late stage of survivors, but fell in the last 16 h in nonsurvivors. These values were greater in survivors than in nonsurvivors throughout. There were early transient reductions in VO2 that preceded the rise in temperature and the fall in mean arterial pressure (MAP). Although 84 percent of the septic patients were hyperdynamic, there were transient hypodynamic episodes defined as cardiac index of less than 2.5 L/min.m2 in approximately 10 percent of the measurements. There were also transient preterminal hypermetabolic periods in about 8 percent of the nonsurvivors.

CONCLUSION

We conclude that increased cardiac index and DO2 represent compensations for circulatory inadequacies that limit body metabolism as reflected by VO2. Cardiac index, DO2, and VO2 values of survivors were higher than those of nonsurvivors and normal values. Therapy directed toward increasing cardiac index to supranormal values empirically determined by survivors has been reported to improve outcome. Additional studies to describe temporal relationships of biochemical mediators of these physiologic patterns are needed.