LATE COMPLICATION OF RESPIRATORY THERMAL INJURIES

INTRODUCTION

Burns represent a serious type of trauma, and if combined with inhalation injury they also incur high morbidity and mortality. Respiratory complications rank as the major cause of death in burns patients. Injury in smoke inhalation is the result of three separate assaults: exposure to heat (thermal injury), exposure to asphyxiants, and pulmonary irritation (toxin-induced lung injury). Potentially fatal injury is from direct heat-steam coagulation, from hypoxic gas inhalation because of oxygen consumption, from local toxins such as nitrogen monoxide, and from systemic toxins such as carbon monoxide and cyanide (1). Diagnosis of inhalation injury depends on adequate accident history, clinical examination, blood gas tests/level of carboxyhaemoglobin/bronchoscopy and chest X-rays. Despite the frequency of pulmonary complications and abnormal lung function, most studies evaluate the immediate post-burn period (2). There are only a few which are concerned with long-term follow-up. Results of a 1-year follow-up of lung function changes in individuals who survived the London Underground fire at Kings Cross Station in 1987 have been reported. Nine survivors had 6 months persistent symptoms of hoarseness, cough, and shortness of breath (3).Most of the lung function studies following thermal injury indicate that patients may not regain normal lung function, and that they may have also tracheal deformation, laryngeal and phonetic problems. We report our clinical experience with large-burn patients with inhalation injury and late complication in the 51 patients studied.

PATIENTS AND METHODS

This study was carried out during the period January 2006 to December 2007 in Košice Burn Center. During this two-year period 147 patients were admitted to ICU with serious burns. 51 of them had bronchoscopy-proven different types of inhalation injury, and all patients with acute inhalation injury had ventilatory support. All 51 patients of varying age from 6 to 79 years were evaluated on late complications of the thermal lung injuries. None of the patients had pre-existing lung disease prior to injury. All patients were treated with standard fluid resuscitation (3ml/kg/%TBSA), intubation (from 1 hour to 24 hours post burn) and mechanical ventilation from 12 to 37 days. Most of the large surgical procedures and skin transplatation were performed within the first 30 days. Each patient was subjected to regular chest radiographs and CT scans during the hospital stay; ENT specialist and lung consultant cooperated during the treatment. The results were analyzed and compared with clinical examination. In 11 patients tracheostomy was performed between the 5^th and 21^st post-burn day. Late tracheostomy in one patient was performed two months after discharge, because of acute stridor and dyspnoe.

RESULTS

Patient demographic data of 51 patients were as follows: 48 male, 3 female patients; mean TBSB: 57±27%; mean third degree: 42±18%; 11 patients had severe inhalation injury diagnosed by bronchoscopy,and in all 11 patients tracheostomy was performed between the 5^th and 21^st post-burn day. Bronchopneumonia was the most frequent complication diagnosed in 46 patients (90.2%). Fluidothorax was diagnosed in 11 patients (21.6%). Thirteen patients had ARDS (25.5 %) diagnosed. Tracheal constriction in 4 patients (7.8%). Three patients had tracheoesophageal fistula (5.8%) (Fig.1). One patient presented 2 months after injury with progressive stridor and dyspnoe necessitating tracheostomy because of tracheal stenosis. Three patients were endotracheally intubated for 21 days, and the tracheostomy was performed thereafter, because of tracheoesophageal fistula. A subglottic granuloma, du to prolonged intubation, was found as a late complication (6 months post burn) in one patient. Repair was carried out with multiple surgical procedures. The mortality rate was 45.1% (23 patients). Twenty-two patients died, of septic complications and ARDS. One patient died 6 months post discharge after septic mediastinitis followed by reconstructive surgery for tracheal stricture. Fifteen survivors were followed 6 months at the ONT clinic. Six patients of this group had persistent hoarseness, cough, and shortness of breath. Evidence of small airway obstruction was found in 5 of the survivors and persisted for more then 6 months. Two patients showed spirometry and lung volumes with an obstructive disease process.

DISCUSSION

Inhalation injury with large cutaneous burns is a complex syndrome, and many factors determine its severity. Direct-inhalation injuries, which can lead to other respiratory complications such as aspiration of fluids by unconscious patients, bacterial pneumonia, pulmonary edema, obstruction of pulmonary arteries, and post-injury respiratory failure, are especially common. Late complications include fluidothorax, tracheal stenosis, tracheoesophageal fistula, atelectasis and phoniatric problems, while restrictive and obstructive disease are very common (2). Inhalation injury, despite effective management of fluid resuscitation, improved ventilation techniques, still have high mortality. The etiology of acute respiratory failure, acute lung injury and ARDS are multifactorial, and the incidence is high according to diagnostic criteria and patients’ condition. Appropriate fluid resuscitation combined with aggressive pulmonary care and early burn excision may reduce the mortality rate. Mortality varies from 30% to 70%. In our study the mortality rate was 45.1% (23 patients). Twenty-two patients died, of septic complications and ARDS. One patient died 6 months post discharge after septic mediastinitis followed by reconstructive surgery for tracheal stricture. Development of ARDS depends also on actual volume of fluid resuscitation in our study it was over 25%, with standard fluid resuscitation (3ml/kg/%TBSA) (Fig. 2). Intravenous resuscitation should be practiced with extreme caution, because a smoke-injured lung is vulnerable to fluid accumulation when crystalloids are infused rapidly (5). Smoke-inhalation and burn injuries show an increase in extravascular lung water, which returns to normal by 28 hours after injury and which remains normal until 5 days after injury – and then increases again. Lung edema formation is attributed to the toxic effect of smoke inhalation (4). An important decision must be made early: whether the patient requires endotracheally intubation. Because the most urgent concern in patients relates to the patency of the upper airway and adequacy of ventilation, whenever there is a doubt it is safer to intubate with the largest endotracheal tube possible, because of amounts of thick secretions. Care should be taken to prolong cuff ischemia. Ischemic injury begins within the first few hours of intubation, and healing of the damaged region can result in web-like fibrosis within 3 to 6 weeks (7). Longer intubation, such as 14 days, needs tracheostomy to avoid mucosal granulation and tracheal rings malatia and tracheal stenosis or tracheoesophageal fistula. (Fig. 3.) Among all intubated patients, the reported incidence of post-intubation and post-tracheal stenosis ranges from 10% to 22% as well as delayed tracheal stenosis caused by inhalation injury (4 patients in our study). Early tracheostomy reduces these complications. In contrast, tracheal stenosis following tracheostomy most commonly results from abnormal wound healing with granulation tissue around the tracheal stoma. In a recent review paper by Sarper et al. wound sepsis was also found as a causative factor in 42% of the stoma stenosis cases following open tracheostomy (7). CT scan, X-ray, spirometry and lung volume examination should be performed to evaluate late post-burn complications. Spirometry and lung volume follow-up is important for those patients with obstructive and restrictive disease process. (Fig. 4–6.)

CONCLUSION

On the basis of this study it may be concluded that large burns with inhalation injury have late and long-term complications. The data indicate that patients who survive severe thermal injury may not regain normal lung function. Complications such as atelectasis, tracheal strictures, stenosis, hoarseness, phoniatric problems and obstructive disease may last for months and years after inhalation injury. Early diagnosis and aggressive treatment may prevent severe complications and improve morbidity and mortality.

Address for correspondence:

Jan Babík, M.D.

Clinic for Burns and Reconstructive Surgery

Košice-Šaca

Lúčna 57

040 15 Košice-Šaca, Slovakia

E-mail: jbabik@nemocnicasaca.sk