What are the guidelines for using high flow oxygen (oxygen delivery at rates greater than 6 liters per minute) in a 22-year-old male with traumatic brain injury (TBI) and suspected splenic injury after a road traffic accident?

High Flow Oxygen in TBI and Splenic Injury

In a 22-year-old male with traumatic brain injury and suspected splenic injury, high flow oxygen should be administered initially to achieve a PaO2 ≥ 13 kPa (approximately 97 mmHg), while avoiding extreme hyperoxia (PaO2 > 487 mmHg or >65 kPa), and once hemodynamic stability is achieved and hemoglobin levels are adequate, oxygen should be titrated to normoxia. 1

Initial Oxygen Management Strategy

The primary goal is to prevent hypoxemia while avoiding prolonged extreme hyperoxia. The European trauma guidelines strongly recommend avoiding hypoxemia in TBI patients, as hypoxia is associated with poor outcomes and increased mortality. 1 However, these same guidelines suggest avoiding hyperoxemia except in the presence of imminent exsanguination. 1

Target Oxygenation Parameters

• Maintain PaO2 ≥ 13 kPa (approximately 97 mmHg) during initial resuscitation and transfer of brain-injured trauma patients. 1
• Avoid extreme hyperoxia with PaO2 > 487 mmHg (>65 kPa), as this is associated with increased mortality and worsened neurological outcomes in TBI patients. 1
• The negative effects of extreme hyperoxia are related to altered microcirculation and increased oxygen free radical production, with severe brain injury patients at particular risk. 1

Special Considerations for Combined TBI and Splenic Injury

In the context of suspected splenic injury with potential ongoing hemorrhage and anemia, transient hyperoxia may be beneficial until hemoglobin levels are restored. 1

• High oxygen concentrations can increase oxygen content and delivery in extremely anemic trauma patients, potentially providing benefit during active hemorrhage. 1
• Once hemoglobin returns to acceptable levels, oxygen should be returned to normoxia to avoid the detrimental effects of prolonged hyperoxia. 1
• The hemoglobin transfusion threshold should be 7 g/dL in TBI polytrauma patients, though higher thresholds may be considered in elderly patients or those with cardiovascular disease. 1

Airway Management Indications

Endotracheal intubation should be performed without delay if any of the following are present: 1

• Glasgow Coma Scale ≤ 8 1
• Hemorrhagic shock 1
• Hypoxemia despite supplemental oxygen 1
• Failure to achieve PaO2 ≥ 13 kPa with non-invasive oxygen delivery 1
• Significantly deteriorating conscious level 1

Ventilation Parameters Post-Intubation

Target normoventilation with PaCO2 of 4.5-5.0 kPa (approximately 35-40 mmHg). 1

• The European guidelines strongly recommend normoventilation of trauma patients (Grade 1B). 1
• Hyperventilation should only be used as a life-saving measure in the presence of signs of cerebral herniation (unilateral or bilateral pupillary dilation, decerebrate posturing), and only for short periods until other measures are effective. 1
• Hyperventilation-induced hypocapnia can cause decreased cerebral blood flow and, in the setting of hypovolemia, may compromise venous return and produce hypotension or cardiovascular collapse. 1

Blood Pressure Management

Maintain systolic blood pressure > 110 mmHg and mean arterial pressure (MAP) > 90 mmHg in TBI patients with polytrauma. 1

• If within 6 hours of symptom onset and immediate surgery is not planned, keep systolic blood pressure < 150 mmHg. 1
• Hypotension must be corrected before transfer, as hypovolemic brain-injured patients do not tolerate transfer well and hypotension adversely affects neurological outcome. 1
• Use 0.9% saline as the isotonic crystalloid of choice for fluid resuscitation in brain injury. 1, 2

Common Pitfalls to Avoid

Do not maintain prolonged extreme hyperoxia beyond the initial resuscitation phase. While high-quality evidence shows that initial high oxygen concentrations are appropriate to prevent hypoxemia, prolonged hyperoxia (PaO2 well above normal range) is associated with increased mortality. 1

Do not hyperventilate routinely. There is a tendency for rescue personnel to hyperventilate patients during initial resuscitation, but this can worsen outcomes through decreased cerebral blood flow and impaired tissue perfusion. 1

Do not delay addressing hemorrhagic shock from splenic injury. In the setting of absolute or relative hypovolemia, positive pressure ventilation may further compromise venous return. 1 Fluid administration is usually required concurrently with intubation, as positive intrathoracic pressure can induce severe hypotension in hypovolemic patients. 1

Monitoring Requirements

• Continuous pulse oximetry targeting SpO2 to maintain PaO2 ≥ 13 kPa 1
• Arterial blood gas analysis before departure from emergency department to guide ventilation 1
• End-tidal CO2 monitoring continuously if intubated 1
• Direct arterial blood pressure monitoring with transducer at the level of the tragus 1

Evidence Nuances

Recent research suggests that the minimal PaO2 target may need to be higher than traditionally recommended. One study found that the lowest mean PaO2 observed to maintain brain tissue oxygen above the ischemic threshold was 94 mmHg. 3 Another study found that high oxygenation levels during the first 4 hours in the emergency department were not adversely associated with long-term neurologic status. 4 However, the strongest guideline evidence from the 2023 European trauma guidelines and 2020 Association of Anaesthetists guidelines provides the most reliable framework for clinical practice. 1