Medical Care:
" General
o Focus treatment on the underlying disorder.
o Manage NPE in a supportive and conservative fashion.
o NPE resolves within 48-72 hours in the majority of affected patients.
" General supportive care
o Supplemental oxygen is required in most patients to correct hypoxemia.
o Mechanical ventilation may be necessary, either noninvasive with a face mask or via endotracheal tube. The goals of mechanical ventilation are to assure adequate oxygenation and ventilation and to prevent iatrogenic lung injury. To avoid excessively high inflation pressures, tidal volumes between 5 and 8 mL/kg are used. With the use of low inflation volumes, positive end-expiratory pressure (PEEP) is added to prevent compression atelectasis. The peak inspiratory (plateau) pressure should be kept below 30-35 cmH2O, and eucapnia should be maintained to avoid further increases in intracranial pressure.
o In a prospective randomized clinical trial, the Acute Respiratory Distress Syndrome Network demonstrated a striking reduction in hospital mortality in patients with acute respiratory distress syndrome (ARDS) ventilated with 6 mL/kg of predicted body weight compared with 12 mL/kg. More ventilator-free and organ failure-free days occurred in patients who received the lower tidal volume strategy. In the lower tidal volume group, the target tidal volume was 6 mL/kg of predicted body weight. This strategy may lead to respiratory acidosis, which requires either high respiratory rates and/or sodium bicarbonate infusion.
o High levels of PEEP may be required to treat severe hypoxemia. Caution is advised, however, since PEEP can inhibit cerebral venous return and increase intracranial hypertension.
o Diuretic therapy may reduce lung water by decreasing capillary hydrostatic pressure and increasing colloid osmotic pressure, but the strategies to reduce lung water are not uniformly successful. The use of diuretics to minimize or reduce fluid overload seems a more reasonable approach, but adequate cardiac output and cerebral perfusion pressure must be maintained.
o The goal of management in respiratory failure is to achieve an adequate level of oxygenation in the vital organs. Swan-Ganz catheterization may be helpful in guiding fluid and hemodynamic management, particularly if diuretics are used. To maintain adequate tissue oxygenation, sufficient cardiac output (cardiac index >2.2 L/min/m2) and hemoglobin (>10 g/L) are required to ensure optimal oxygen delivery. Since cardiac output depends upon cardiac filling pressures (central venous pressure and wedge pressure), meticulous monitoring of intravascular volume is mandatory.
" Pharmacological therapy
o Pharmacological agents are not used routinely in treatment of NPE.
o Several agents such as alpha-adrenergic antagonists, beta-adrenergic blockers, dobutamine, and chlorpromazine are advocated by some authors, but assessment of their effectiveness is difficult because NPE is usually a self-limited condition that ameliorates spontaneously.
" Alpha-adrenergic antagonists
o These antagonists (eg, phentolamine) can prevent NPE or hasten its resolution in experimental models. However, no human trials have established the safety and efficacy of these agents.
o These agents may be used to treat concomitant systemic hypertension, if present, but care must be taken to avoid significant hypotension that can diminish cerebral perfusion.
Further Inpatient Care:
" The combination of NPE and a neurological insult severe enough to cause NPE always warrants admission to hospital.
" Intensive care admission may be required if patients develop increasingly severe hypoxemia or respiratory distress, or if invasive monitoring is required.
Prognosis:
" NPE usually is well tolerated by the patient, and the process usually resolves within 48-72 hours.
" Prognosis is determined by the course of underlying neurological problems.