Respiratory complications in burned patients: Pathogenesis and spectrum of inhalation injury

Early single-shot intravenous steroids do not affect pulmonary complications and mortality in burned or scalded patients

BACKGROUND AND OBJECTIVES

Inhalation injury, especially in combination with cutaneous burns, is the major cause of morbidity and mortality in patients admitted to burn care centers. Either with or without the presence of a cutaneous burn, inhalation injury contributes to high risk for developing severe pulmonary complications. Steroids may reduce a prolonged and destructive inflammatory response to toxic or allergic substances. The objective of this study was to evaluate the effect of early single-shot intravenous steroids on pulmonary complications and mortality in burned or scalded patients with or without inhalation injury.

METHODS

Retrospective analysis of a prospective single center database of patients registered between 1989 and 2011 who were admitted to the intensive care unit of our burn care center after burn or scald injury. Uni-variate statistical analysis was performed comparing two groups (steroid treated vs. non steroid treated patients) with regard to clinical outcome. Main parameters were sepsis, mortality and pulmonary complications such as pneumonia, ALI and ARDS. Multi-variate analysis was used by logistic regression with mortality and pulmonary complications as the dependent variables to identify independent risk factors after burn or scald injuries.

RESULTS

A total of 1637 patients with complete data were included in the present analysis. 199 (12.2%) received single-shot intravenous steroids during the prehospital phase of care. In 133 (66.8%) of these patients, inhalation injury was diagnosed via bronchoscopy. Steroid treated patients had sustained a significantly higher severity of burn than non-steroid treated patients (Abbreviated Burn Severity Index 7.1±3 vs. 6.0±2.9; p<0.001). In a multivariate analysis using a logistic regression model early intravenous steroid treatment had no significant effect on pulmonary complications and mortality.

CONCLUSIONS

In our single center cohort of burned and scalded patients single-shot intravenous steroids during the pre-hospital phase of care was not associated with pulmonary complications or mortality.

Isolated inhalational injury: Clinical course and outcomes in a multidisciplinary intensive care unit

Background and Aims:

Although smoke inhalation is well known to cause acute lung injury, there are few reports in literature that study the evolution, clinical course and outcomes of isolated inhalational lung injury in a modern intensive care setting. A major fire disaster provided us the opportunity to study victims of isolated inhalational injury admitted to our Multidisciplinary Intensive Care Unit (MICU).

Materials and Methods:

We studied the clinical course, ICU and hospital outcomes of 13 victims of a fire disaster who required mechanical ventilation for isolated inhalational lung injury. All patients were followed up at regular intervals, and their functional status was assessed at 8 months after hospital discharge.

Results:

The Lung Injury Scores (LIS) worsened to reach a nadir on Day 3 of injury. There was a significant correlation between the LIS on Day 3 and duration of mechanical ventilation (r = 0.8; P = 0.003), ICU (r = 0.8; P = 0.002) and hospital (r = 0.6; P = 0.02) days. Late-onset airway complications were encountered in four patients. Three of them required long-term artificial airways – two with a tracheostomy while the third patient required surgical insertion of a “T” tube. Persistent problems with phonation occurred in two patients. At 8 months postdischarge, all patients were independent with activities of daily living; all were back to work, except for two who continued to need artificial airways.

Conclusions:

Inhalational lung injury progresses over the first few days and is worst after 72 h. Late-onset airway complications may manifest after several weeks and require repeated intervention.

Delayed asphyxia due to inhalation injury

We report the case of a 53-year-old man who was found dead in his apartment 2 days after a little fire during which he had suffered from second to third degree burns at 2% of the body surface, also involving the skin around the mouth and the nose. At autopsy, severe acute emphysema and mucopurulent obstructive laryngotracheobronchitis were observed. The histology showed desquamative loss of the respiratory epithelium up to the middle bronchi; the bronchial lumen was filled with clumps of mucopurulent secretions mixed with necrotic epithelial cells. The cause of death was a delayed asphyxia due to inhalation injury.

Lung injury from smoke inhalation

Significant morbidity and mortality from smoke inhalation occurs in victims of fire. Lung injury can be caused by chemical and thermal insults. A variety of noxious gases, irritants and asphyxiants are generated depending on the material burnt. Carbon monoxide is the predominant cause of death among fire victims. Treatment should be directed at reversing hypoxaemia as a result of asphyxia or carbon monoxide poisoning. There is no evidence that the routine use of corticosteroids or prophylactic antibiotics is beneficial. Through a better understanding of the pathophysiology of smoke-induced lung injury, the effects of exogenous surfactant, leukotriene inhibitors, antioxidants, nitric oxide synthase inhibitors and fibrinolytics suggest that these compounds may have a future therapeutic role in smoke-induced injury. Studies are needed to evaluate the safety and efficacy of these potential therapies before they are used clinically.

High frequency percussive ventilation and conventional ventilation after smoke inhalation: a randomised study

Inhalation injury and bacterial pneumonia represent some of the most important causes of mortality in burn patients. Thirty-five severely burned patients were randomised on admission for conventional ventilation (CV; control group) versus high frequency percussive ventilation (HFPV; study group). HFPV is a ventilatory mode, introduced 10 years ago which combines the advantages of CV with some of those of high frequency ventilation. Arterial blood gases, ventilatory and hemodynamic variables were recorded for 5 days at 2h intervals. Incident complications were classically managed. A statistical analysis (Student's t-test and Wilcoxon signed rank test) demonstrated a significant higher PaO(2)/FiO(2) from days 0 to 3 in the HFPV group. No significant differences were observed for the other parameters. Our findings suggest that HFPV can improve blood oxygenation during the acute phase following inhalation injury allowing reduction of FiO(2). No significant differences were observed between groups for mortality nor incidence of infectious complications in this study.

The usefulness of combined high-frequency percussive ventilation during acute respiratory failure after smoke inhalation

Inhalation injury and bacterial pneumonia represent some of the most important causes of mortality in burn patients. We describe 11 severely burned patients with acute respiratory failure due to inhalation injury who did not respond adequately to conventional respiratory support. High-frequency percussive ventilation (HFPV) is a recent ventilatory mode, which combines the advantages of conventional ventilation with some of those of high-frequency ventilation. Seven patients developed pulmonary infection during the acute phase; one patient died of multiple organ failure on day 25. All the other patients survived; two developed bronchiolitis obliterans symptoms before discharge. No side-effects were noted and haemodynamic tolerance of HFPV was excellent. Our findings suggest that HFPV can improve pulmonary function and gas exchange in these catastrophic pulmonary failures following inhalation injury.

Fluid resuscitation with deferoxamine hetastarch complex attenuates the lung and systemic response to smoke inhalation

BACKGROUND

We determined the effect of infusing the iron chelator deferoxamine complexed to hetastarch on the degree of lung dysfunction and systemic abnormalities produced by a severe smoke exposure.

METHODS

Adult sheep were given a smoke exposure under anesthesia that produced a peak carboxyhemoglobin between 40% and 45%. Twenty-eight sheep were studied; eight were given smoke alone and resuscitated with sufficient lactated Ringer's solution to maintain baseline hemodynamics. Seven sheep were given a bolus plus 1 ml/kg/hr of a 10% deferoxamine-hetastarch solution for resuscitation; five were given hetastarch alone. The response was compared with eight controls during a period of 24 hours.

RESULTS

Smoke alone and smoke with hetastarch resulted in a shunt fraction of greater than 25% and a 50% decrease in compliance, severe airway inflammation, mucosal slough, atelectasis, and some alveolar edema. Increased lipid peroxides measured as malondialdehyde were present in airway fluid. In addition, oxygen consumption increased by 100% early after injury, net 24-hour positive fluid balance was almost 3 L, and a significant increase occurred in liver lipid peroxidation. The group given deferoxamine had a significantly attenuated lung response, with only modest airway damage lung dysfunction, and minimal systemic changes including a net positive fluid balance of just over 1L and no liver lipid peroxidation.

CONCLUSIONS

An iron chelator deferoxamine complexed to hetastarch, given after a severe smoke exposure, significantly attenuates the airway and the systemic inflammatory (oxidant) injury, indicating free iron release and subsequent increased oxidant activity to be a major etiologic factor.

Warehouse workers' headache: emergency evaluation and management of 30 patients with carbon monoxide poisoning

BACKGROUND

Carbon monoxide (CO) is the leading cause of fatal toxic inhalation in the United States, but the medical literature contains few reports of mass exposures. Warehouse workers' headache (WWH) is an infrequently reported form of CO poisoning due to industrial exposure.

METHODS

We describe 30 persons who developed WWH after inhaling exhaust from a propane-fueled forklift, their emergency medical management at a small community hospital, and their long-term courses.

RESULTS

Workers with more direct exposures to vented exhaust had significantly higher expired CO levels (21.1 +/- 0.7% versus 8.4 +/- 4.8%, P < 0.0001) and higher acute symptom scores (9.0 +/- 2.2 versus 4.7 +/- 3.3, P = 0.01) than persons with less direct exposures. Work location, expired CO levels, and acute symptom scores did not correlate with symptom scores 2 years after exposure. Workers experiencing acute difficulty concentrating or confusion had higher expired CO levels than persons with neither of these symptoms (16.3 +/- 6.7% versus 8.4 +/- 5.2%, P = 0.005) and developed higher chronic symptom scores (3.9 +/- 3.0 versus 1.1 +/- 1.5, P = 0.04), suggesting that this subgroup may require closer follow-up for long-term complications.

CONCLUSION

With earlier recognition of ongoing CO toxicity, this disaster would likely have been averted. Since CO exposures are more common than is often recognized, general internists must be familiar with the manifestations of CO toxicity, its timely evaluation, management, and prevention.

Effect of graded increases in smoke inhalation injury on the early systemic response to a body burn

OBJECTIVE

To study the early (first 24 hrs) effect of increasing lung exposure to smoke on the hemodynamic response to a modest body burn.

DESIGN

A prospective randomized study.

SETTING

Laboratory at a university medical center.

SUBJECTS

Thirty-two adult yearling female sheep.

INTERVENTIONS

Adult sheep (n = 32) were given an 18% of body surface burn; 24 sheep were then exposed to cotton toweling smoke using 12 breaths of a tidal volume of 5, 10, or 20 mL/kg. Animals were awakened, resuscitated to baseline oxygen delivery, and then killed at 24 hrs.

MEASUREMENTS AND MAIN RESULTS

Vascular pressure, cardiac output, and oxygen consumption and delivery were measured, as well as blood gases, lung and soft tissue lymph flow, and fluid balance. We found that a 5-mL/kg tidal volume smoke exposure x 12 breaths did not produce significant airway inflammation or alter the cardiopulmonary response to a burn alone. Oxygen consumption (VO2) remained at baseline and the net 24-hr positive fluid balance of 1.5 L was comparable to a burn alone. Increasing the smoke exposure to 10 mL/kg tidal volume, which produced a moderate airway injury, resulted in a significant increase in early fluid requirements, a 40% early increase in VO2, a doubling of positive fluid balance, as well as a marked increase in burn edema. However, gas exchange was not impaired. The 20-mL/kg tidal volume exposure resulted in an early 100% increase in VO2, a three-fold increase in fluid requirements at 1 to 4 hrs, compared with burn alone, in addition to a severe airway inflammation with mucosal slough and resulting impaired gas exchange.

CONCLUSIONS

The addition of a smoke exposure which produces airway inflammation and injury significantly increases early post burn systemic metabolic demands and fluid requirements, as well as the degree of burn edema and positive fluid balance compared with a burn alone. The magnitude of the accentuated response appears to correspond with the degree of airway inflammation and not with alveolar dysfunction.

Smoke inhalation: diagnosis and treatment

Smoke inhalation, defined as airway or pulmonary parenchymal injury resulting from the inhalation of toxic combustion products, presents with a wide range of severity in patients with and without skin burns. In patients with severe injuries, the diagnosis is obvious on the basis of the history and clinical presentation; in patients with less severe injuries or those in whom the clinical consequences are delayed, diagnostic precision is difficult because diagnostic clues provide only indirect information. There is no specific treatment so diagnosis is not critical for patient management. Patients at risk include 20% to 30% of flame burn victims who should receive vigorous supportive care. The mortality rate of smoke inhalation victims without a burn is < 10%. With a burn the mortality rate is 30% to 50%, suggesting that thermal injury or its treatment is responsible for further lung damage. Endotracheal intubation provides definitive treatment for obstructed or soon-to-be obstructed patients. However the diagnosis of smoke inhalation per se is not an indication for airway intubation and respiratory support; 12% of patients without a burn require intubation versus 62% of those with a burn. A translaryngeal tube can be converted to a tracheotomy safely in burn victims; tracheotomies are easier to manage if burns of the neck are excised and grafted prior to placement. Mechanical ventilation with positive end expiratory pressure (PEEP) is the treatment for the pulmonary injury. The early lesions of smoke inhalation often progress in the context of sepsis and other complications of the burn illness to a clinical state consistent with adult respiratory distress syndrome.