Patients are ventilated to achieve mild hypocapnia (PaCO2 = 4-4.5 kPa (30-34 mmHg), PaO2 > 13 kPa (97.5 mmHg)) using sedation and analgesia but generally without muscle paralysis unless control of ICP or blood oxygenation dictates otherwise. Continuous pulse oximetry, indwelling arterial monitoring for blood pressure and arterial blood gas determination, and capnography aid cardiorespiratory management. If there are no vertebral injuries, head elevation reduces venous engorgement, as does securing the endotracheal tube with adhesive tape rather than a circumferential bandage. Attending to the patient at 30° to the horizontal minimizes any deleterious effects due to positive end-expiratory pressure (PEEP) which may be required to correct hypoxemia. Excessive PEEP or head elevation may adversely alter both mean blood pressure and ICP, worsening cerebral perfusion pressure. Better venous drainage by excessive head elevation may improve ICP (Feldman et al. 1993). A balance must be achieved. Use of a rigid cervical collar may also raise ICP by altering the cerebrospinal fluid dynamics, but neck stability is essential. Muscle relaxation to facilitate intubation is mandatory, but prolonged use in the intensive care setting makes neurological assessment difficult although it may be necessary to ensure adequate ventilation.
An ICP below 20 mmHg with an acceptable cerebral perfusion pressure and oxygenation may allow weaning to begin. Monitoring of ICP and hemodynamics should guide weaning, with sedatives used sparingly.
Some centers perform early tracheostomy in order to facilitate weaning and reduce sedation requirements, particularly in the presence of coma and cervical paralysis. Pulmonary complications are common in the head-injured patient with multiple trauma, and scrupulous attention must be paid to all forms of respiratory physiotherapy. The presence of spontaneous bilateral extensor posturing during weaning of a head-injured patient from a ventilator is usually considered as an indication to resume artificial ventilation.
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