Whole-body hypothermia: another option in smoke inhalation management?
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Biomedical subjects
Publications and source records attributed to David Herndon.
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Victims of fire accidents who sustain both thermal injury to the skin and smoke inhalation have gross evidence of oxidant injury. Therefore, we hypothesized that delivery of vitamin E, an oxygen superoxide scavenger, directly into the airway would attenuate acute lung injury postburn and smoke inhalation. Sheep (N = 17 female, 35 +/- 5 kg) were divided into 3 groups: (1) injured, then nebulized with vitamin E (B&S, Vitamin E, n = 6); (2) injured, nebulized with saline (B&S, Saline, n = 6); and (3) not injured, not treated (Sham, n = 5). While under deep anesthesia with isoflurane, the sheep were subjected to a flame burn (40% total body surface area, 3rd degree) and inhalation injury (48 breaths of cotton smoke, <40 degrees C). All groups were resuscitated with Ringer lactate solution (4 mL/kg/%burn/24 h) and placed on a ventilator [positive end-expiratory pressure (PEEP) = 5 cm H2O, tidal volume = 15 mL/kg] for 48 h. B&S injury halved the lung alpha-tocopherol concentrations (0.9 +/- 0.1 nmol/g) compared with sham-injured animals (1.5 +/- 0.3), whereas vitamin E treatment elevated the lung alpha-tocopherol concentrations (7.40 +/- 2.61) in the injured animals. B&S injury decreased pulmonary gas exchange (PaO2/FiO2 ratios) from 517 +/- 15 at baseline to 329 +/- 49 at 24 h and to 149 +/- 32 at 48 h compared with sham ratios of 477 +/- 14, 536 +/- 48, and 609 +/- 49, respectively. Vitamin E treatment resulted in a significant improvement of pulmonary gas exchange; ratios were 415 +/- 34 and 283 +/- 42 at 24 and 48 h, respectively. Vitamin E nebulization therapy improved the clinical responses to burn and smoke inhalation-induced acute lung injury.
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Health care systems constantly struggle with ways to provide higher quality care in a cost-effective manner. Outcome measures serve to evaluate what works and what does not. Whether they are used for research or for the improvement of clinical practice, they are as such, efficiency markers and the first step in determining the consequences of health care. The accomplishments of the past decade have placed us in the midst of an exciting paradigm shift from what used to be primary concern (i.e. mortality), to areas that are more likely to enhance the quality of life of burn survivors. Optimal management of severely burned persons is enormously expensive, and even after survival is ensured, may require a protracted period of surgical, medical and psychological rehabilitative measures for many years. This article aims to review the outcome measures in the acute phase of burn management (mortality and morbidity from the post-burn hypermetabolic response). We further discuss long-term outcome measures (such as, quality of life measures, exercise tolerance and evaluation of return to pre-burn activities) that are now becoming of equal importance as the numbers of burn survivors increase.
Acute respiratory distress syndrome is a major complication in patients with thermal injury. The obstruction of the airway by cast material, composed in part of fibrin, contributes to deterioration of pulmonary gas exchange. We tested the effect of aerosol administration of tissue plasminogen activator, which lyses fibrin clots, on acute lung injury in sheep that had undergone combined burn/smoke inhalation injury. Anesthetized sheep were given a 40% total body surface, third degree burn and were insufflated with cotton smoke. Tissue plasminogen activator (TPA) was nebulized every 4 h at 1 or 2 mg for each nebulization, beginning 4 h after injury. Injured but untreated control sheep developed multiple symptoms of acute respiratory distress syndrome: decreased pulmonary gas exchange, increased pulmonary edema, and extensive airway obstruction. These control animals also showed increased pulmonary transvascular fluid flux and increased airway pressures. These variables were all stable in sham animals. Nebulization of saline or 1 mg of TPA only slightly improved measures of pulmonary function. Treatment of injured sheep with 2 mg of TPA attenuated all the pulmonary abnormalities noted above. The results provide evidence that clearance of airway obstructive cast material is crucial in managing acute respiratory distress syndrome resulting from combined burn and smoke inhalation injury.
Inducible nitric oxide synthase (iNOS) is implicated in the pathogenesis of acute respiratory distress syndrome (ARDS). ARDS treatment is frequently complicated by significant extrapulmonary comorbidity. This study was designed to clarify the role of iNOS in mediating extrapulmonary comorbidity in sheep after combined burn and smoke inhalation injuries using a potent and highly selective iNOS dimerization inhibitor, BBS-2. Twenty-two female sheep were operatively prepared. After 5 days of recovery, tracheostomy was performed under ketamine-halothane anesthesia. Sheep were given a 40% total body surface third-degree burns and insufflated with cotton smoke (48 breaths, <40 degrees C). Sheep were divided into four groups: noninjured and nontreated (sham group; n = 6), noninjured but treated with BBS-2 (sham/BBS-2 group; n = 4), injured but nontreated (control group, n = 6), and injured but treated with 100 microg.kg-1.h-1 BBS-2 (BBS-2 group; n = 6). Evaluation was in a laboratory intensive care unit setting for 48 h. The sham group had stable cardiopulmonary and systemic hemodynamics. Control animals showed multiple signs of morbidity. Decreased left ventricular stroke work index and stroke volume index with elevated left atrial pressure indicated myocardial depression. Systemic vascular leak was evidenced by robust hemoconcentration, decreased plasma oncotic pressure, and increased transvascular fluid flux into the lymphatic system. Finally, severely impaired renal function (urinary output) was associated with adverse net fluid balance. Treatment with BBS-2 prevented all these morbidities without adversely effecting cardiovascular hemodynamics such as cardiac index and mean arterial pressure. The results identify a major role for iNOS in mediating extrapulmonary comorbidity in a clinically relevant and severe trauma model and support the use of highly selective iNOS inhibitors as novel treatments in critical care medicine.
Nitric oxide (NO) has been shown to play a major role in acute lung injury (ALI) after smoke inhalation. In the present study, we developed an ovine sepsis model, created by exposing sheep to smoke inhalation followed by instillation of bacteria into the airway, that mimics human sepsis and pneumonia. We hypothesized that the inhibition of neuronal NO synthase (nNOS) might be beneficial in treating ALI associated with this model. Female sheep (n = 26) were surgically prepared for the study and given a tracheostomy. This was followed by insufflation of 48 breaths of cotton smoke (40 degrees C) into the airway of each animal and subsequent instillation of live Pseudomonas aeruginosa [5 x 10(11) colony forming units (CFU)] into each sheep's lung. All sheep were mechanically ventilated using 100% O2. Continuous infusion of 7-nitroindazole (7-NI), an nNOS inhibitor, NG-monomethyl-l-arginine (l-NMMA), a nonspecific NOS inhibitor, or aminoguanidine (AG), an inducible NOS inhibitor, was started 1 h after insult. The administration of 7-NI improved pulmonary gas exchange (PaO2/FiO2; where PaO2 is arterial PO2 and FiO2 is fractional inspired oxygen concentration) and pulmonary shunt fraction and attenuated the increase in lung wet-to-dry weight ratio seen in the nontreated sheep. Histologically, 7-NI prevented airway obstruction. The increase in airway blood flow after injury in the nontreated group was significantly inhibited by 7-NI. The increase in plasma concentration of nitrate and nitrite (NOx) was inhibited by 7-NI as well. Posttreatment with l-NMMA improved the pulmonary gas exchange, but AG did not. The results of the present study show that nNOS may be involved in the pathogenesis of ALI after smoke inhalation injury followed by bacterial instillation in the airway.
In this study we examined the role of inducible nitric oxide synthase (iNOS) in acute respiratory distress syndrome (ARDS) in sheep with severe combined burn and smoke inhalation injury. BBS-2, a potent and highly selective iNOS dimerization inhibitor, was used to exclude effects on the endothelial and neuronal NOS isoforms. Seven days after surgical recovery, sheep were given a burn (40% of total body surface, 3rd degree) and insufflated with cotton smoke (48 breaths, < 40 degrees C) under anesthesia. BBS-2 was provided by constant infusion at 100 microg/kg/hour, beginning 1 hour after injury. During 48 hours, control sheep developed multiple signs of ARDS. These included decreased pulmonary gas exchange, increased pulmonary edema, abnormal lung compliance, and extensive airway obstruction. These pathologies were associated with a large increase in tracheal blood flow and elevated plasma NO2-/NO3- (NOx) levels. These variables were all stable in sham animals. Treatment of injured sheep with BBS-2 attenuated the increases in tracheal blood flow and plasma NOx levels, and significantly attenuated all the pulmonary pathologies that were noted. The results provide definitive evidence that iNOS is a key mediator of pulmonary pathology in sheep with ARDS resulting from combined burn and smoke inhalation injury.
Massive cutaneous burn combined with smoke inhalation causes high mortality in fire victims. Cyclo-oxygenase (COX) and inducible nitric oxide (NO) synthase (iNOS) have been shown to be up-regulated in burn injury. Ketorolac, a non-steroidal, anti-inflammatory agent (NSAID), inhibits prostaglandin and thromboxane synthesis through inhibition of COX. NSAIDs have been shown to down-regulate iNOS. Thus we hypothesized that treatment with ketorolac would attenuate burn/smoke-related cardiopulmonary derangements. We conducted a fully controlled long-term laboratory investigation in an Intensive Care Unit setting. Eighteen female sheep were surgically prepared for chronic study. After a recovery period of 5 days, a tracheotomy was performed under ketamine/halothane anaesthesia. Sheep were given a 40% total body surface third-degree burn and insufflated with cotton smoke (48 breaths, <40 degrees C). Sheep were divided into three groups: sham (not injured and not treated; n =6), control (injured, but not treated; n =6) and treated (injured and administered ketorolac 60 mg/day; n =6). The sham group had stable cardiopulmonary and systemic haemodynamics. Control animals showed depressed cardiopulmonary function, decreased pulmonary gas exchange, increased pulmonary microvascular leakage and decreased left ventricle stroke work index with elevated left atrial pressure. Systemic vascular leak in control animals was evidenced by robust haemoconcentration (haematocrit and fluid net balance). Treatment with ketorolac prevented all of these morbidities. Post-treatment with ketorolac also resulted in significant inhibition of elevated plasma nitrite/nitrate levels in control animals. These results suggest that ketorolac may ameliorate cardiopulmonary morbidity, at least in part, by inhibiting excessive NO.
Natural disasters have always been a threat. human-caused disasters, especially terrorist acts, are increasing in frequency. Burn centers and providers have an important contribution to make in caring for those injured in these incidents. The most effective way to make a contribution is to act in cooperation with the Federal Disaster Response, which is organized by the Department of Homeland Security and the Federal Emergency Management Agency. It appears that this can be most effectively accomplished through participation in the Burn Specialty Team Program, which has been developed to rapidly augment emergency medical teams with burn expertise.