Postobstructive pulmonary edema: A fatal complication in suicidal near-hanging

Abstract

Postobstructive pulmonary edema is a life-threatening complication that occurs after the removal of severe upper airway obstruction. Development of postobstructive pulmonary edema has been described after several cases of upper airway obstruction. However, postobstructive pulmonary edema developing after non-lethal hanging has not been reported widely in the literature. Herein, we describe a fatal case of postobstructive pulmonary edema in a 10-year-old girl, which was brought to the hospital with history of attempted suicide by hanging. At presentation, the girl was breathing laboriously. The oxygen saturation was of 82% and pulmonary auscultation revealed bilateral and diffuse crepitations. The chest computed tomographic scan showed bilateral diffuse infiltrates consistent with pulmonary edema. After 3 days of hospitalization, the respiratory state of the girl worsened leading to death despite intensive care. An autopsy was conducted and confirmed the diffuse pulmonary edema. Hence, this case confirms that delayed death in near hanging may occur. Pulmonary edema which develops subsequently in such patients is an uncommon mechanism of death that physicians should consider in emergency room.

Introduction

Fatalities from upper airway obstruction are usually due to asphyxia.¹ However, rapid re-establishment of the airway does not guarantee repair in gas exchange. In fact, it has been established that mortality could result from the delayed effects of the obstruction like secondary cerebral injury or pulmonary complications. Postobstructive pulmonary edema (POPE) is a form of “non-cardiogenic, non-neurogenic” pulmonary edema which is uncommon and occurring after acute and severe airway obstruction.² It is a potentially life-threatening condition if not diagnosed immediately and managed promptly. It develops rapidly, without warning, within seconds to minutes after the relief of severe upper airway obstruction due to tumor, strangulation or near hanging.³ The term “near hanging” refers to patients who survive a hanging injury long enough to reach the hospital. Development of POPE after non-lethal suicidal hanging has not been described widely in the literature.⁴ Its incidence is difficult to ascertain. Most reports are of single cases. A literature review and research of the topic “postobstructive pulmonary edema following near-hanging” identifies a dozen case presentations on the topic to date. Herein, we report a case of POPE in a 10-year-old girl following attempted suicidal hanging and we discuss its physiopathology.

Case presentation

A 10-year-old girl was admitted to the emergency department with alleged history of hanging. She was rescued by her father who brought her down from suspension immediately. The event was unwitnessed; thus, the duration of hanging was unknown. The girl was last seen 15 min before being found. The time to hospital presentation was about 60 min. While being transported to the hospital, the girl started breathing laboriously. At presentation, she was unconscious, with Glasgow Coma Scale (GCS)⁵ of 6, frothing from the mouth with facial congestion and peripheral cyanosis. A partial ligature mark was clearly noted around her neck. There was a sub-conjunctival hyperemia. Both pupils were dilated and reacting sluggishly to light. She was afebrile. Her respiratory rate was of 48 breaths/min with an oxygen saturation of 82%. The heart rate was of 135 beats/min and blood pressure of 80/40 mmHg. Chest auscultation revealed bilateral extensive crepitations. Resuscitative measures were undergone. Intravenous access was secured and fluids administered. His neck was stabilized using cervical collar and the airway was secured by endotracheal intubation. The girl was mechanically ventilated and volume-controlled mode was provided. The electrocardiogram showed a sinus tachycardia without ST abnormalities. A chest X-ray showed a normal cardiac silhouette but a bilateral diffuse infiltrates, consistent with pulmonary edema. The supra-aortic trunks Doppler ultrasonography was unremarkable. The brain and cervical computed tomographic (CT) scan did not reveal abnormalities. Thoracic CT scan ascertains the pulmonary edema (Figure 1). Arterial blood gases analysis (on 100% fraction inspired oxygen) revealed pO₂ 104 mmHg, pCO₂ 65 mmHg, pH 7.02 and HCO 16 mEq/L. All other biochemical and hematological parameters were reported as normal. The next day, the patient developed low-grade fever. Prophylactic parenteral antibiotics were administered. Sedation was gradually decreased, but the girl presented severe hypotension 40/20 mmHg. She received norepinephrine 4 mg/h. Few hours later, her respiratory and neurological conditions worsened. She developed a cardio-respiratory arrest leading to death despite reanimation. A medico-legal autopsy was ordered. The necropsy revealed congested and edematous lungs with an edematous brain (Figure 2). Forensic pathologist concluded to “complications following hanging” as the cause of death.

Figure 1.

Thoracic CT-scan shows diffuse pulmonary edema.

Figure 2.

Pulmonary edema at necropsy.

Discussion

Hanging is one of the most common methods of committing suicide in Tunisia. Victims of hanging usually die instantaneously due to reflex vagal inhibition or within period of few minutes because of cerebral ischemia or anoxia.⁶ However, few cases have been reported in the literature in which death happened after a surviving period of time or the patient has survived after extended period of unconsciousness. In this context, Berdai et al.⁷ reported a case of 14-year-old girl who developed POPE after accidental near hanging and then discharged home, 4 days later, after unremarkable recovery. Raj and Bhatnagar⁸ presented a case of suicidal hanging that presented with features of cerebral anoxia and developed pulmonary edema. Thereafter, he had impressive re-establishment without residual brain or lung damage.

Delayed death in near hanging occur due to hypoxic encephalopathy, infarction of brain, Duret hemorrhage, aspiration pneumonia, infections or pulmonary complications like ARDS.⁹ Aggarwal et al.⁴ reported a case of 20-year-old female who survived for 9 days in hospital after suicidal hanging attempt and then died because of cerebral ischemia. Kanchan and Atreya¹⁰ described a case of brainstem hemorrhage known as “Duret hemorrhage” in a 58-year-old victim who survived for 8 days after the attempted hanging. This complication is correlated to cerebral edema which leads to transtentorial herniation and subsequent hemorrhage. Tatiya and colleagues¹¹ reported four cases of retarded death following suicidal hanging in which development of pulmonary edema (POPE) has contributed to death despite early rescue and resuscitation.

“POPE was first described in humans in 1973.”¹² Two distinct subclasses of POPE have been recognized: type I is related to forceful inspiratory effort in the context of acute and severe airway obstruction such as epiglottitis, choking, hanging, strangulation, and near drowning, whereas type II is associated with the relief of a chronic partial airway obstruction (e.g. laryngeal mass resection, tumor, adenoidectomy, tonsillectomy).¹³ “Pulmonary edema developing after non-lethal hanging has been reported very infrequently. This is probably due to poor survival rate among victims of suicidal or accidental hangings.”⁷ “The pathophysiology of POPE is multifactorial.”¹³ The starting event is the generation of considerably negative transpulmonary pressure during a forceful inspiration against a closed upper airway and hence the synonym, “negative pressure pulmonary edema”:⁴

It has been reported that a forceful inspiration against such glottic obstruction could result in a maximum intrathoracic pressure of (−140) cm H2O from a baseline of (−4) cm H2O. This event then leads to an increase in venous return and blood flow to the right side of the heart as well as a decrease in the flow from the left side as a result of increased afterload.¹

The high pressure is also transmitted to the interstitium and alveoli and causes an increase in the hydrostatic gradient favoring transudation of fluid from the pulmonary capillary to the pulmonary interstitial space. This combination results in generation of pulmonary edema.¹⁴

Hypoxia and hyperadrenergic state are other contributors in the development of POPE. “Hypoxemia due to upper airway obstruction leads to increased pulmonary vascular resistance and pulmonary capillary pressure. The hyperadrenergic response is thought to redistribute blood from the systemic veins to the pulmonary circuit and increase pulmonary vascular resistance.” All of these events may precipitate edema formation.¹

“The etiologic factors leading to POPE type II are less clear than what has been described for type I. Type II POPE physiopathology focuses more on expiration against an obstructed airway.”¹ Expiration against a closed airway is assimilated to Valsalva which causes positive alveolar and pleural pressures, leading to a decrease in the pulmonary blood volume, a decrease in venous return to the right side of the heart and a decrease in ventricular preload.¹⁴ Thus, once the obstruction is relieved, as in the case of laryngeal mass resection or post-adenotonsillectomy, the sudden discharge induces an abrupt fall in airway pressure, an increase in the venous return, and a subsequent increase in preload. This results in an elevated hydrostatic pressure in the pulmonary circuit leading to pulmonary edema.^14,15

Nevertheless, physicians should consider other several mechanisms by which acute respiratory distress (ARDS) may develop after attempted hanging. In fact, patients presenting with a low GCS score and therefore a depressed mental status, like in the current case report, may be predisposed to aspiration, leading to pneumonia or pneumonitis with subsequent ARDS development.¹⁶ Also, serious brain injury that results in cerebral hypoxia has been associated with neurogenic pulmonary edema and acute lung injury mediated by massive sympathetic discharge. In such situation, neurogenic pulmonary edema often has poor prognostic implications, as it is associated with devastating and usually lethal brain injuries.⁷

Conclusion

Fatal period in attempted hanging is not well identified. It may vary markedly with the amount of constricting forces as well as the time of removing the compressing force around neck. Patient surviving after attempted hanging is never out of danger. Hypoxic-ischemic encephalopathy is the principal mechanism of subsequent mortality in the survivors of suicidal or accidental hanging. However, delayed ARDS due to POPE is well described but often missed complication that clinicians should keep in mind.