In patients with head injury, endotracheal suctioning (ETS) is a potentially dangerous procedure, because it can increase intracranial pressure (ICP). The purpose of this prospective nonrandomized study was to evaluate the impact of ETS on intracranial dynamics in the acute phase of head injury. Seventeen patients with severe head injury (Glasgow Coma Score ≤ 8, range 4–8), sedated and mechanically ventilated, were studied during the first week after trauma. Single-pass ETS maneuver (with a 16-French catheter, negative pressure of 100 mm Hg, and duration of less than 30 seconds) was performed 60 seconds after the FiO2was increased to 100%. After ETS, FiO2was maintained at 100% for another 30 seconds. Before and after ETS, arterial blood gases and jugular oxygen saturation (SjO2), ICP, and mean arterial pressure (MAP) were measured and cerebral perfusion pressure (CPP) was calculated. A total of 131 ETS episodes, which consisted of repeated assessment of each patient, were analyzed. Six patients in 20 cases coughed and/or moved during ETS because of inadequate sedation. After ETS, ICP increased from 20 ± 12 to 22 ± 13 mm Hg in well-sedated patients and from 15 ± 9 to 28 ± 9 mm Hg in patients who coughed and/or moved (mean change, 2 ± 6 versus 13 ± 6 mm Hg,P<.0001). CPP and SjO2increased in well-sedated patients (from 78 ± 16 to 83 ± 19 mm Hg, and from 71 ± 10 to 73 ± 13%, respectively) and decreased in patients who reacted to ETS (from 79 ± 14 to 72 ± 14 mm Hg and from 69 ± 7 to 66 ± 9%, respectively), and the differences were significant (mean change, CPP: 5 ± 14 versus -7 ± 15 mm Hg,P=.003; (SjO2) 2 ± 5 vs. −3 ± 5%,P<.0001). In well-sedated patients, endotracheal suctioning caused an increase in ICP, CPP, and SjO2without evidence of ischemia. In contrast, in patients who coughed or moved in response to suctioning, there was a slight and significant decrease in CPP and SjO2. In the case of patients with head injuries who coughed or moved during endotracheal suctioning, we strongly suggest deepening the level of sedation before completing the procedure to reduce the risk of adverse effects.