Heat shock response: presence and effects in burn patient neutrophils.

Heat shock proteins (HSPs) are present in neutrophils (PMNs) from critically ill patients. We investigated whether HSPs were present in PMNs from burn patients and whether heat shock contributed to the functional defects observed in burn PMNs. Using both flow cytometry and Western blot techniques it was observed that inducible HSP72 (iHSP72) was present in PMNs and leukocytes from burn patients, especially in patients with inhalation injury. Similar to burn PMNs, and in contrast to normal cells, heat shocked PMNs (43 degrees C incubation) expressed iHSP72 and were unable to increase the expression of CD11b/CD18 in response to pro-inflammatory stimuli. Degranulation after pro-inflammatory stimuli was decreased for both burn- and heat-shocked PMNs when compared to normal controls. In burn PMNs these functional abnormalities were mainly due to decreased quantities of proteins (CD11b, albumin, B12 binding protein, beta-glucuronidase) present within cytoplasmic granules. However, in heat-shocked PMNs the abnormalities were primarily related to abnormal exocytosis. In conclusion, our data show that decreased quantities of cytoplasmic granule proteins and, to a smaller degree, defective exocytosis are involved in the functional abnormalities observed in burn PMNs.

Azurophilic granules of human neutrophils contain CD14.

CD14, the leukocyte receptor for lipopolysaccharide (LPS), is important in the response of human polymorphonuclear leukocytes (PMNs) to infection with gram-negative bacteria. The level of CD14 on the PMN surface increases after exposure to some inflammatory stimuli such as N-formyl-methionyl-leucyl-phenylalanine (fMLP). These newly expressed CD14 molecules probably come from an intracellular pool of preformed receptors. We sought to further characterize PMN CD14 expression, upregulation, and shedding and to define the intracellular location of CD14 molecules. Our results demonstrate that both LPS and fMLP significantly increased CD14 cell surface expression; however, neither phorbol myristate acetate (PMA) or A23187 increased receptor levels on the PMN surface. Neither fMLP, PMA, or A23187 stimulated the release of soluble CD14 from PMNs. Intracellular CD14 was observed in >90% of PMNs examined by flow cytometry and confocal microscopy. Additional analyses using CD14 enzyme-linked immunosorbent assays and electron microscopy studies, examining PMN granules separated by discontinuous sucrose or Percoll gradients, showed that CD14 was present in both the plasma membrane-secretory vesicle fractions and azurophilic granules.

Neutrophils from burn patients are unable to increase the expression of CD11b/CD18 in response to inflammatory stimuli.

Neutrophils (PMNs) from patients with thermal injury are dysfunctional for the CD11b/CD18-dependent functions of diapedesis, chemotaxis, and phagocytosis. The expression of CD11b/CD18 on normal PMNs is increased after an inflammatory stimulus. We proposed that CD11b/CD18 expression on burn patient PMNs would respond abnormally to inflammatory stimuli. PMNs were obtained from nonseptic burn patients during the second week after thermal injury. PMNs from burn patients incubated with lipopolysaccharide (LPS), N-formyl-methionyl-leucyl-phenylalanine, phorbol myristate acetate, or A23187 did not increase the expression of CD11b/CD18 to the same degree exhibited by normal PMNs. This inability to increase CD11b/CD18 was not due to differences in CD14 receptor expression, LPS binding, or factors present in the serum of burn patients. The upregulation of CD35 also was decreased on burn patient PMNs. Western blot analysis revealed decreased quantities of CD11b protein in burn patient PMNs compared with normal control PMNs. The deficiency in CD11b/CD18 expression after inflammatory stimuli may explain some of the abnormalities observed in burn PMN function.

Role of calcium during lipopolysaccharide stimulation of neutrophils.

This study investigated the role of intracellular calcium concentration ([Ca]i) as a possible intermediate in the lipopolysaccharide (LPS) second messenger pathway for the activation of neutrophils (polymorphonuclear leukocytes [PMNs]). Isolated PMNs were loaded with the calcium-sensitive fluorescent dye fura-2. The PMNs were stimulated with either LPS or the positive control formyl-Met-Leu-Phe (fMLP). As expected, PMN exposure to fMLP increased [Ca]i. However, LPS stimulation did not induce any detectable changes. Depletion of intracellular Ca stores with thapsigargin, or extracellular Ca with EGTA, significantly inhibited the upregulation of the CD11b/CD18 integrin in response to fMLP but not LPS. We conclude that [Ca]i is not an early intermediate in the second-messenger pathway for the activation of PMNs by LPS.

Nitric oxide: an overview.

Nitric oxide (NO), a paracrine-acting gas enzymatically synthesized from L-arginine, is a unique biologic mediator that has been implicated in a myriad of physiologic and pathophysiologic states. It is an important regulator of vascular tone and may be the mediator of the hemodynamic changes involved in sepsis and cirrhosis. In addition, there is increasing evidence that NO is involved in coagulation, immune function, inhibitory innervation of the gastrointestinal tract, protection of gastrointestinal mucosa, and the hepatotoxicity of cirrhosis. It has already been speculated that NO may represent a point of control or intervention in a number of disease states. The purpose of this paper is to provide the surgeon with a broad overview of the scientific and clinical aspects of this important molecule.

Use of a helium-oxygen mixture in the treatment of postextubation stridor in pediatric patients with burns.

A mixture of helium and oxygen is less dense than room air. This property allows the gas to flow with less turbulence past airway narrowings, thereby decreasing airway resistance and increasing the volume of gas exchange. Previous studies demonstrated that airway obstruction that is manifested by stridor was present in 92% of patients requiring reintubation. Eight pediatric patients with burns in whom postextubation stridor or retractions unresponsive to racemic epinephrine developed, were treated with "heliox" (helium and oxygen) for 28 +/- 5 hours with an initial helium concentration between 50% and 70%. Of the eight patients treated with heliox, only two experienced respiratory distress and required reintubation. Both patients had stridor for a longer time before the initiation of heliox therapy compared with those patients who did not require reintubation. After initiation of heliox therapy, patients experienced a significant decrease in respiratory distress scores (6.8 +/- 0.7 vs 2.0 +/- 0.7). Heliox was able to relieve persistent stridor and thereby aid in the prevention of respiratory distress and reintubation.

Improved ventilatory function in burn patients using volumetric diffusive respiration.

BACKGROUND: Volumetric diffusive respiration (VDR) offers theoretical advantages over conventional mechanical ventilation (CV) by using lower airway pressures, recruiting alveoli, and mobilizing secretions. STUDY DESIGN: Forty-eight thermally injured pediatric patients with failing respiratory status were changed from CV to VDR. Data were obtained just before transition for CV and after stabilization on VDR, within six hours of transition. RESULTS: Both ventilation and oxygenation were significantly improved with PaCO2 decreasing from 47 +/- 3 to 39 +/- 11 mm Hg and PaO2 increasing from 105 +/- 8 to 171 +/- 12 mm Hg after transition to VDR. Treatment with the VDR ventilator also resulted in a significant decrease in peak inspiratory pressures (PIP) from 52 +/- 2 to 38 +/- 2 cm H2O. The PaO2 to FiO2 ratio increased from 189 +/- 16 using CV, to 329 +/- 21 using VDR, suggesting an improvement in the ventilation and perfusion matching. Ventilatory efficiency, measured by the PaO2/FiO2/PIP ratio, greatly improved after transition from CV to VDR with fraction of inspired oxygen increasing from 3.9 +/- 0.4 to 10.3 +/- 1.0. Hemodynamic function (blood pressure and pulse rate) were not adversely affected by VDR. CONCLUSIONS: The VDR ventilator is more effective than conventional ventilation for maintaining optimal gas exchange at lower airway pressures in thermally injured pediatric patients.

Decreased pulmonary barotrauma with the use of volumetric diffusive respiration in pediatric patients with burns: the 1992 Moyer Award.

Pulmonary barotrauma is a frequent, life-threatening complication in the pediatric patient who is treated with mechanical ventilation. The volumetric diffusive respiration (VDR) ventilator, which employs a high-frequency progressive accumulation of subtidal volume breaths in a pressure-limited format with a percussive waveform, is capable of providing adequate gas exchange at lower airway pressures; this theoretically decreases the incidence of pulmonary barotrauma compared with conventional mechanical ventilation (CV). The incidence of pulmonary barotrauma since 1988 was evaluated in pediatric patients with burns who were younger than 2 years of age. Twenty-four patients who were treated with only CV were compared with 15 patients who were treated with only VDR. Pulmonary barotrauma was defined as the development of pneumothorax, pneumomediastinum, pneumopericardium, or pneumoperitoneum. There were no significant differences between CV-treated and VDR-treated groups (mean +/- SEM) in the patient characteristics of age (15.9 +/- 1.3 months vs 16.6 +/- 1.8 months), weight (11.2 +/- 0.5 kg vs 12.5 +/- 0.7 kg), percent total body surface burn (46.2% +/- 4.9% vs 55.6% +/- 6.2%), percent full-thickness burn (38.1% +/- 5.3% vs 50.0% +/- 6.6%), inhalation injury (40% vs 60%), or total number of days that mechanical ventilation was required (18.2 +/- 4.2 days vs 22.4 +/- 5.9 days); although these parameters show a slightly more severe degree of injury in the VDR-treated group. There was a reduction in the incidence of pulmonary barotrauma when VDR was used.(ABSTRACT TRUNCATED AT 250 WORDS)