Inhaled nitric oxide in burn patients with respiratory failure

Extracorporeal Membrane Oxygenation Support for Pediatric Burn Patients: Is It Worth the Risk?

OBJECTIVES

Examine the outcomes of pediatric burn patients requiring extracorporeal membrane oxygenation to determine whether extracorporeal membrane oxygenation should be considered in this special population.

DESIGN

Retrospective cohort study.

SETTING

All extracorporeal membrane oxygenation centers reporting to the Extracorporeal Life Support Organization.

SUBJECTS

Pediatric patients (birth to younger than 18 yr) who were supported with extracorporeal membrane oxygenation with a burn diagnosis between 1990 and 2016.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A total of 113 patients were identified from the registry by inclusion criteria. Patients cannulated for respiratory failure had the highest survival (55.7%, n = 97) compared to those supported for cardiac failure (33.3%, n = 6) or extracorporeal cardiopulmonary resuscitation (30%, n = 10). Patients supported on venovenous extracorporeal membrane oxygenation for respiratory failure had the best overall survival at 62.2% (n = 37). Important for the burn population, rates of surgical site bleeding were similar to other surgical patients placed on extracorporeal membrane oxygenation at 22.1%. Cardiac arrest prior to cannulation was associated with increased hospital mortality (odds ratio, 3.41; 95% CI, 0.16-1.01; p = 0.048). Following cannulation, complications including the need for inotropes (odds ratio, 2.64; 95% CI, 1.24-5.65; p = 0.011), presence of gastrointestinal hemorrhage (p = 0.049), and hyperglycemia (glucose > 240 mg/dL) (odds ratio, 3.42; 95% CI, 1.13-10.38; p = 0.024) were associated with increased mortality. Of patients with documented burn percentage of total body surface area (n = 19), survival was 70% when less than 60% total body surface area was involved.

CONCLUSIONS

Extracorporeal membrane oxygenation could be considered as an additional level of support for the pediatric burn population, especially in the setting of respiratory failure. Additional studies are necessary to determine the optimal timing of cannulation and other patient characteristics that may impact outcomes.

Ventilation strategies in paediatric inhalation injury

Inhalation injury increases morbidity and mortality in burns victims. While the diagnosis remains largely clinical, bronchoscopy is also helpful to diagnose and grade the severity of any injury. Inhalation injury results from direct thermal injury or chemical irritation of the respiratory tract, systemic toxicity from inhaled substances, or a combination of these factors. While endotracheal intubation is essential in cases where upper airway obstruction may occur, it has its own risks and should not be performed prophylactically in all cases of inhalation injury. The evidence-base informing the selection of optimal ventilation strategy in inhalation injury is sparse, and most recommendations are based on extrapolation from (largely adult) studies in acute respiratory distress syndrome (ARDS). Conventional ventilation using a lung-protective approach (i.e. low tidal volume, limited plateau pressure, and permissive hypercarbia) is recommended as the initial approach if invasive ventilation is required; various rescue strategies may become necessary if there is a poor response. The efficacy of many widely used pharmacologic adjuncts in inhalation injury remains uncertain. Further research is urgently required to address these gaps in our knowledge.

Current concepts in the pathophysiology and treatment of inhalation injury

The opinions or assertions contained herein are the private views of the author, and are not to be construed as official or as reflecting the official views of the Department of the Army or Department of Defense. Smoke inhalation injury occurs in about 10% of patients admitted to burn centres, and increases the mortality of burn patients by up to 20% over predictions based on age and burn size alone. The primary lesion in smoke inhalation injury is localized to the small airways, with alveolar injury and pulmonary oedema exercising a less prominent role during the initial phases. Injury incites a cascade of events that include ventilation-perfusion mismatch, secondary lung injury, systemic inflammation, impaired immune function, and pneumonia. The most important recent developments in the treatment of inhalation injury have included improved methods of pulmonary care targeted at the pathophysiology of the injury, such as high-frequency percussive ventilation and gentle mechanical ventilation.

Clinical review: the critical care management of the burn patient

Between 4 and 22% of burn patients presenting to the emergency department are admitted to critical care. Burn injury is characterised by a hypermetabolic response with physiologic, catabolic and immune effects. Burn care has seen renewed interest in colloid resuscitation, a change in transfusion practice and the development of anti-catabolic therapies. A literature search was conducted with priority given to review articles, meta-analyses and well-designed large trials; paediatric studies were included where adult studies were lacking with the aim to review the advances in adult intensive care burn management and place them in the general context of day-to-day practical burn management.

Prone positioning improves oxygenation in adult burn patients with severe acute respiratory distress syndrome

BACKGROUND

Prone positioning (PP) improves oxygenation and may provide a benefit in patients with acute respiratory distress syndrome (ARDS). This approach adds significant challenges to patients in intensive care by limiting access to the endotracheal or tracheostomy tube and vascular access. PP also significantly complicates burn care by making skin protection and wound care more difficult. We hypothesize that PP improves oxygenation and can be performed safely in burn patients with ARDS.

METHODS

PP was implemented in a burn intensive care unit for 18 patients with severe refractory ARDS. The characteristics of these patients were retrospectively reviewed to evaluate the impact of PP on Pao2:FiO2 ratio (PFR) during the first 48 hours of therapy. Each patient was considered his or her own control before initiation of PP, and trends in PFR were evaluated with one-way analysis of variance. Secondary measures of complications and mortality were also evaluated.

RESULTS

Mean PFR before PP was 87 (± 38) with a mean sequential organ failure assessment score of 11 (± 4). PFR improved during 48 hours in 12 of 14 survivors (p < 0.05). Mean PFR was 133 (± 77) immediately after PP, 165 (± 118) at 6 hours, 170 (± 115) at 12 hours, 214 (± 126) at 24 hours, 236 (± 137) at 36 hours, and 210 (± 97) at 48 hours. At each measured time interval except the last, PFR significantly improved. There were no unintended extubations. Facial pressure ulcers developed in four patients (22%). Overall, 14 survived 48 hours (78%), 12 survived 28 days (67%), and six survived to hospital discharge (33%).

CONCLUSIONS

PP improves oxygenation in burn patients with severe ARDS and was safely implemented in a burn intensive care unit. Mortality in this population remains high, warranting investigation into additional complementary rescue therapies.

LEVEL OF EVIDENCE

Therapeutic study, level IV.

Attenuating burn wound inflammation improves pulmonary function and survival in a burn-pneumonia model

OBJECTIVE

We previously showed that topical inhibition of inflammatory signaling in burn wounds reduced systemic inflammatory response and burn-induced pulmonary inflammation. We hypothesized that this topical intervention would attenuate burn-induced lung injury, improve pulmonary function, protect lungs from bacterial invasion, and reduce mortality.

DESIGN

Controlled, in vivo, laboratory study.

SETTING

University laboratory.

SUBJECTS

Female mice, 8-10 wks old.

INTERVENTIONS

Animals received 30% total body surface area burn followed by topical application of a specific inhibitor of p38 mitogen-activated protein kinase, a key inflammatory signaling pathway, or vehicle to the wound. Twenty-four hours after injury, pulmonary collagen deposition and pulmonary function were assessed. One day postburn, some of the animals received intratracheal instillation of Klebsiella pneumoniae and were subsequently monitored for 7 days.

MEASUREMENTS AND MAIN RESULTS

Topical inhibition of p38 mitogen-activated protein kinase significantly decreased pulmonary collagen deposition and prevented a decline in pulmonary function at 1 day after burn injury. Compared with sham controls, animals with burn injury had a significantly higher mortality in response to intratracheal bacterial challenge. Application of p38 mitogen-activated protein kinase inhibitor to the burn wound attenuated pulmonary neutrophil infiltration and reduced the mortality rate to a level experienced by sham controls.

CONCLUSIONS

Inflammatory source control in burn wounds with topical p38 mitogen-activated protein kinase inhibition attenuates acute lung injury, avoids pulmonary dysfunction, protects lungs from bacterial challenge, and improves survival.

Recent advances in burn care

The patient with severe burn injuries offers significant challenges to the anesthesiologist. Inhalation injury continues to be the most significant contributor to morbidity and mortality despite recent advances in the techniques of mechanical ventilation and respiratory therapy. Operative procedures are complicated by the presence of severe pulmonary injury, massive blood loss, significant fluid shifts, and hypermetabolism, which alter the pharmacokinetics of many anesthetic agents. Recent advances in nutrition, respiratory support, the early excision of burns, and skin substitutes are improving survival from massive burns and decreasing the resultant disability.

Advances in burn critical care

BACKGROUND

Management of burn patients requires a complex interaction of surgical, medical, critical care, and rehabilitation approaches. Severe burn patients are some of the most challenging critically ill patients who may have multiple-system organ failure with life-threatening complications.

OBJECTIVE

To review and highlight some of the recent advances in burn critical care. We focused on some of the new treatment modalities in the management of respiratory complications, advances in burn resuscitation, management of the metabolic response to burns, and recent ideas in burn immunotherapy.

DATA SOURCE

A search of the MEDLINE database and manual review of published articles and abstracts from national and international meetings. DATA SYNTHESES AND CONCLUSIONS: The respiratory management of burn patients includes strategies to minimize iatrogenic injury with low tidal volume ventilation, to improve ventilation/perfusion mismatch, and to diagnosis pneumonia. Many aspects of burn resuscitation remain controversial, and the best form of fluid resuscitation has yet to be identified. Recent research in the metabolic response to thermal injury has identified many potentially beneficial treatments. Although immunomodulation therapy is promising, currently most of these treatments are not clinically viable, and further clinical and translational research is warranted.

Lésions respiratoires et brûlures

INTRODUCTION

Smoke inhalation and respiratory complications are still the major causes of mortality in severely burned patients.

STATE OF THE ART

The diagnosis is suspected clinically on the basis of history and physical examination and can be confirmed bronchoscopically. Respiratory failure in burned patients occurs through a number of associated mechanisms. Pneumonitis and adult respiratory distress syndrome (ARDS) are common early complications. New pulmonary treatments and advances in ventilation have reduced the incidence of both barotrauma and infectious complications. Tracheal stenosis can occur as a late complication of prolonged mechanical ventilation.

PERSPECTIVES

Clinical and experimental studies have shown that damage to the mucosal barrier and the release of inflammatory mediators are the most important pathophysiological events following smoke inhalation. Manipulation of the inflammatory response following inhalation may be a treatment option in the distant future.

CONCLUSION

Inhalation injury occurring in burned patients can produce severe respiratory and systemic complications.

Lesão por inalação de fumaça

A lesão inalatória é hoje a principal causa de morte nos pacientes queimados, motivo pelo qual se justifica o grande número de estudos publicados sobre o assunto. Os mecanismos envolvidos na gênese da lesão inalatória envolvem tanto os fatores de ação local quanto os de ação sistêmica, o que acaba por aumentar muito as repercussões da lesão. Atualmente, buscam-se ferramentas que permitam o diagnóstico cada vez mais precoce da lesão inalatória e ainda estratégias de tratamento que minimizem as conseqüências da lesão já instalada. Esta revisão aborda os mecanismos fisiopatológicos, os métodos diagnósticos e as estratégias de tratamento dos pacientes vítimas de lesão inalatória. Ressalta ainda as perspectivas terapêuticas em desenvolvimento.

Is high PEEP low volume ventilation in burn patients beneficial? A retrospective study of 61 patients

In burn care lung damage by inhalation injury is a major cause of mortality in burn patients. In the field of intensive care medicine ventilation strategies to reduce lung injury caused by ventilation are under investigation. The promising results of the application of pressure controlled high PEEP low volume (HPLV) ventilation prompted us to use this ventilation strategy in our burn ICU. To establish whether this ventilation regime is beneficial the charts of 61 consecutive patients needing artificial respiration were reviewed. A scoring system for PEEP level and tidal volume was developed and treatment groups with high PEEP and low volume and low PEEP high volume regimes were compared. No statistically significant differences could be found when comparing treatment versus mortality, the number of pulmonary complications or incidence of pneumothoraces. However, the trend showed a benefit in mortality for patients with an ABSI scoring up to 9, but at the same time pulmonary complications increase. The Horovitz oxygenation index showed no advantage for the HPLV Group. In a separate analysis we found a significant correlation between absolute PEEP and mortality. The correlation between PEEP level and mortality is a dynamic factor predicting outcome, This not been described yet and can be an addition to the static ABSI score. Differences between ventilation strategies were not as evident as expected in this retrospective study, so prospective randomized studies are needed.

Burns

During the past 20 yrs, as burn care has evolved as a specialty of surgery, survival and outcome quality have soared. Public expectations for survival and long-term outcomes are at previously unprecedented levels. These changes are the result of a number of advances in aspects of burn care that have occurred in parallel and have fostered increasing regionalization of this resource-intensive activity into fewer specialized centers. These are complex hospitalizations and can be divided into four phases: initial evaluation and resuscitation, initial wound excision and biological closure, definitive wound closure, and rehabilitation and reconstruction.

[Acute respiratory insufficiency in burn patients from smoke inhalation]

Respiratory injuries by smoke inhalation are one of the most frequent reasons for acute respiratory failure in burn victims. They are most often of chemical origin and are responsible of a 20 to 70% increase of the mortality compared to the mortality of patients with similar burn injuries, but without inhalation lesions. They are often associated to a certain degree to other factors of acute respiratory failure: superior air way obstruction by oedema in face and neck burns, thoracic expansion hindrance due to thoracic burns, lung trauma lesions by blast injury. The generalized inflammatory reaction due to the extent of burns and an initial inadequate resuscitation are worsening factors. The inflammatory process may be responsible of lung injuries similar to those induced by smoke inhalation, even when there is no inhalation. The treatment remains symptomatic and based on the oxygen therapy, mechanical ventilation, prevention of infections and maintain of homeostasis by hydroelectrolytic adequate resuscitation. The nitric oxyde associated to the almitrin allows in a certain number of cases to minimize intra pulmonary shunting and to normalize the VA/O ratio. The development of treatments allowing to modulate inflammatory mediators may lead to news therapies in the future.