Lung Recruitment Maneuvers Hazardous in Head-Injured Patients
Lung Recruitment Maneuvers Hazardous in Head-Injured Patients
Abstract & Commentary
This prospective observational study from an icu in Germany sought to determine the effects of a lung recruitment maneuver on intracranial pressure (ICP), cerebral perfusion pressure (CPP), jugular venous oxygen saturation (SJO2), and arterial-minus-jugular venous lactate content difference (AJDL), in patients with acute brain injury. Bein and colleagues studied 11 patients, aged 33-83 years, with traumatic (5) or nontraumatic (6) acute brain injury and an initial Glasgow Coma Scale score of 4-12 (mean 8). The patients also had impaired arterial oxygenation (PaO2/FIO2 244 ± 39 mm Hg); 5 had pneumonia, 3 atelectasis, and 1 "neurogenic" edema. All had ICP and SJO2 monitors, were ventilated in a pressure-controlled mode (maximum inspiratory pressure 25-30 cm H2O, with PEEP 6-12 cm H2O), and were sedated to the point of unresponsiveness to pain. The recruitment maneuver consisted of a 30-second increase in peak inflation pressure to 60 cm H2O and then a sustained inspiration at that pressure for another 30 seconds. The procedure was aborted if ICP rose above 25 mm Hg or CPP fell below 50 mm Hg.
The recruitment maneuver caused a fall in mean systemic arterial pressure from 86 ± 9 to 75 ± 10 mm Hg (P < 0.01). ICP rose from 13 ± 5 to 16 ± 5 mm Hg (P < 0.05), and CPP fell from 72 ± 8 to 60 ± 10 mm Hg (P < 0.01). As an index of cerebral metabolism, SJO2 fell from 69 ± 6 to 59 ± 7 % (P < 0.05), although AJDL did not change significantly. Ten minutes after the end of the recruitment maneuver, all measurements had returned to premaneuver levels. (Bein T, et al. Lung recruitment maneuver in patients with cerebral injury: Effects on intracranial pressure and cerebral metabolism. Intensive Care Med. 2002;28:554-558.)
Comment by David J. Pierson, MD
Acute lung injury is common in patients who are admitted to the ICU after sustaining head trauma or subarachnoid hemorrhage, and when it occurs the clinician (and the patient) are in a difficult situation. This is because current management of these two conditions according to the best available evidence includes directly conflicting strategies. The primary management approach for acute brain injury is to control ICP and maintain CPP at all times. Even very brief periods of decreased CPP, whether from a fall in arterial blood pressure or an increase in ICP, have been associated with worsened neurologic outcomes. The prevailing strategy for managing acute lung injury is to minimize lung distension and protect the lung from ventilator-induced lung injury. Allowing arterial PCO2 to rise (permissive hypercapnia) is considered an acceptable price to pay in carrying out this lung-protective ventilatory strategy. However, because it causes cerebral vasodilation, hypercapnia must be avoided in acute brain injury, making this aspect of lung-protective ventilation contraindicated in this setting.
This study suggests that we should also avoid another currently popular strategy in managing acute lung injury—the use of intermittent sustained inflations to recruit atelectatic areas as part of the "open lung" approach introduced by Lachmann et al.1,2 Lung recruitment maneuvers are becoming part of routine ventilator management in many ICUs and are currently under intensive study. Such maneuvers increase the amount of aerated lung in patients with acute lung injury, and typically improve arterial oxygenation as well. Whether their incorporation into an overall protocol for lung-protective ventilation confers any outcome advantage as compared to lung-protective ventilation without such maneuvers (as in the ARDS Network protocol3) has not yet been settled. From the findings of this study, however, it would seem wisest to avoid recruitment maneuvers in patients with both acute lung injury and acute traumatic or nontraumatic brain injury.
Dr. Pierson is Professor of Medicine, University of Washington; Medical Director, Respiratory Care, Harborview Medical Center, Seattle.
References
1. Lachmann B. Open up the lung and keep the lung open. Intensive Care Med. 1992;18(6):319-321.
2. Papadakos PJ, Lachmann B. The open lung concept of alveolar recruitment can improve outcome in respiratory failure and ARDS. Mt Sinai J Med. 2002;69(1-2): 73-77.
3. The ARDS Network: Ventilation with lower tidal volumes as compared with traditional tidal volumes for acute lung injury and the acute respiratory distress syndrome. N Engl J Med. 2000;342:1301-1308.
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