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A drowsy breathless man

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Q1: What abnormalities are seen on the chest radiograph?

There is diffuse bilateral alveolar shadowing with perihilar haziness in keeping with clinical features of pulmonary oedema.

Q2: What is the most likely diagnosis?

In the absence of any evidence of cardiac event and considering his computed tomography findings this man could have neurogenic pulmonary oedema.

Q3: What is the pathophysiology of this condition?

The exact pathophysiology of neurogenic pulmonary oedema is not clearly understood. It is thought to be due to a combination of raised pulmonary capillary pressure and increased capillary permeability.

Q4: How would you manage this patient?

The principles of treatment are reduction of intracranial pressure, diuresis, and reversing the effects of excess sympathetic activity.

Discussion

In our patient, who presented with acute pulmonary oedema, it was important to rule out a cardiac cause first, even in the absence of any significant past medical history. His ECGs and normal cardiac markers excluded a possibility of ischaemic cardiac event. As he was unconscious at presentation without any signs of type 2 respiratory failure or metabolic abnormalities on his blood tests, he underwent computed tomography of the head, which revealed a large intracerebral bleed (fig 1; see p 760). This raises the likelihood of neurogenic pulmonary oedema in the absence of a cardiac cause for pulmonary oedema in a patient who is unconscious with a primary intracranial event and is acutely breathless.

Neurogenic pulmonary oedema is a rare but dangerous complication of intracranial injury. It has been reported after subarachnoid haemorrhage, head injury, grand mal seizures, and intracranial bleeding.1–3 In the majority of cases features of pulmonary oedema may be evident within a few minutes of the cerebral insult. The incidence is hard to determine as less severe cases may be unrecognised or attributed to aspiration. It is estimated to occur, however, in fewer than 10% of patients with subarachnoid haemorrhage.1 It is related to the severity of the cerebral injury and is rarely seen in patients with normal level of consciousness. The typical clinical picture consists of unexpected dyspnoea, cyanosis, and production of pink sputum. Patients are pale, sweaty, and hypertensive and semiconscious. Absence of evidence for cardiac event is a clue.

The pathophysiology of neurogenic pulmonary oedema is not fully understood. An acute cerebral insult can lead to massive sympathetic discharge mediated by anterior hypothalamus. This leads to a large increase in systemic and pulmonary blood pressures while cardiac output falls due to increased peripheral resistance.2 Hence there is redistribution of blood volume from systemic to pulmonary circulation. This leads to pulmonary venous and left atrial engorgement. A subsequent rise in pulmonary capillary pressures also damage endothelial cells leading to increased pulmonary capillary permeability.1,4

Treatment is aimed at reduction of intracranial pressure, diuresis, and reversing peripheral effects of sympathetic stimulation.5 Controlled hyperventilation with intermittent positive pressure ventilation and surgical decompression are used to reduce intracranial pressure. Diuretics are used to control blood volume and intracranial pressure. It has been claimed that labetolol and chlorpromazine are also beneficial.1 The depression of myocardial function is shown to be reversed by dobutamine and a vasodilator.2,6 Patients are treated in intensive care unit till they are stabilised. Mortality is very high and survivors (<10%) would be left with significant disability and would need prolonged rehabilitation in appropriate cases.

The patient reported here survived the initial events including episodes of sepsis on intensive care unit. He was left with significant disability as he was aphasic, bed bound, and fed by gastrostomy. At three monthly review he had no clinical signs of heart failure.

Final diagnosis

Neurogenic pulmonary oedema secondary to intracerebral haemorrhage.

References

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