Airway/VentilationAlveolar recruitment maneuver in patients with subarachnoid hemorrhage and acute respiratory distress syndrome: A comparison of 2 approaches☆
Introduction
Acute traumatic or nontraumatic brain injury and acute respiratory distress syndrome (ARDS) or acute lung injury (ALI) are dangerous conditions with high mortality risk. Several ARDS patients present hypercapnia and as a consequence, the cerebral blood flow and intracranial pressure (ICP) become higher [1]. Acute lung injury may be caused by neurologic pulmonary edema in patients with traumatic and nontraumatic neurologic injury [2]. Acute lung injury is a frequent and potentially lethal complication of severe traumatic brain injury [2]. The observed incidence of ALI in aneurysmal subarachnoid hemorrhage (SAH) in 620 patients analyzed was around 27% [3].
Hypotension, defined as systolic blood pressure less than 90 mm Hg, and hypoxemia, defined as a PaO2 less than 60 mm Hg, are important factors as secondary brain injury [4]. Once hypoxemia increases ICP [1] and consequently decreases the cerebral perfusion pressure (CPP), one of the main objectives of mechanical ventilation in brain injury patients with ARDS/ALI is to avoid hypoxemia. As hypotension can get worse with high positive end-expiratory pressure (PEEP) levels, CPP can deteriorate, too. Strategies to improve oxygenation and to decrease mortality such as recruitment maneuvers, high PEEP levels, permissive hypercapnia, prone position, and inverse ratio ventilation can be used in severe ARDS/ALI patients [2], although these should not always be used in the presence of acute brain injury. Ventilation with low tidal volumes with permissive hypercapnia, deeply investigated by Amato et al [5], is the main strategy to decrease the mortality in ARDS and ALI patients, but should not be used in some acute brain injury patients, at least in the presence of intracranial hypertension [4], [6]. Another essential aim of mechanical ventilation in ARDS/ALI patients with intracranial hypertension is to avoid hypercapnia to avoid increases in cerebral blood flow. The use of high PEEP levels and alveolar recruitment maneuvers (ARMs) is controversial because both of them can increase ICP and decrease CPP [4], [7]; but on the other hand, it can avoid hypoxemia, and this one can increase ICP and decrease CPP, too.
Therefore, ventilating ARDS or ALI patients with brain injury is more difficult than ventilating ARDS/ALI patients alone. Our hypothesis with the present study is that ARM and high PEEP levels can be used in acute brain injury patients with ARDS/ALI, according to the proposed approach.
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Material and methods
Sixteen patients with SAH and ARDS were evaluated. The study was conducted from July 2004 to September 2007 in 3 general intensive care units (ICUs) of the Hospital de Clínicas de Niterói (Rio de Janeiro, Brazil), with a total of 27 beds. The study was approved by the ethics committees of our institution; and informed consent was obtained from each patient, whenever possible, or from the patient's next of kin. The criteria for admission were the evidence of SAH on computed tomography, ICP
Results
In the beginning of the study, no patient presented intracranial hypertension (defined as ICP ≥20 mm Hg), hypotension (defined as systolic blood pressure <90 mm Hg), and cerebral hypoperfusion (defined as CPP <60 mm Hg). The baseline characteristics among the groups were not statistically different and are shown in Table 1. The incidence of pulmonary and extrapulmonary ARDS was exactly the same in the 2 groups (5 patients with pulmonary ARDS and 3 patients with extrapulmonary ARDS in each
Discussion
In the ICU, neurologic disorder is responsible for 20% of indication for mechanical ventilation [10], [11]. Patients with Glasgow Coma Scale less than 8 have abnormal lung elasticity and resistance as early as day 1 postinjury [10], [12]. In acute brain injury patients, complications like ARDS and ALI can worsen the neurologic function and, as a consequence of hypercapnia and hypoxemia, can increase the risk of death. Hypercapnia and hypoxemia increase the cerebral blood flow and ICP, so one of
Acknowledgment
The authors are indebted to the other physiotherapists (Cláudia Savedra, Cláudia Cadilhe, Cláudia Geraldo, Léa Ferreira, Lara Tabajaras, Lílian Parízo, Luciene Caldeira, Március Rocha, Lívia Osório, Eduardo Faria, Jordan Brust, Juliana Dias, Luis Silva, Luis Almeida, Michelle Cabral, Rafael Maia, Rodrigo Ávila, Paulo Reis, Monclar Ramalho, Vladimir Nery, Vinícus Nery, Victor Carvalho, Elaine Ávila, Marcelo Andrade, Thiago Clipes, Maíra Daumas, Michele Vannie, and Thiago Loureiro) and physicians
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There is no conflict of interest in the study.