Optimal Partial Pressure of Oxygen Affects Outcomes in Patients With Severe Traumatic Brain Injury

Abstract

Introduction Severe traumatic brain injury (TBI) is a leading cause of death and disability. Not all neuronal damage occurs at the time of primary injury, but rather TBI initiates a cascade of events that leads to secondary brain injury. Oxygenation is one crucial factor in maintaining brain tissue homeostasis post-injury. We performed a retrospective review of patients admitted to a single trauma center after TBI. Statistical analysis was performed to ascertain if the measured partial pressure of oxygen (PaO₂) affected overall outcome at the time of discharge from the hospital. Materials and Methods Statistical analysis was performed retrospectively on patients admitted with a Glasgow Coma Scale (GCS) < 8 and a diagnosis of TBI. GCS and Glasgow Outcome Scale (GOS) were calculated from physical examination findings at the time of hospital discharge or death. Patient data were separated into two groups: those with consistently higher average PaO₂ scores (≥ 150 mmHg; n = 7) and those with lower average PaO₂ scores (< 150 mmHg; n = 8). The minimum requirement to be categorized in the consistently higher group was to have an average hospital day 1 through 5 PaO₂ value of ≥ 150 mmHg. Results Patients with consistent hospital Day 1 through 5 PaO₂ scores of ≥ 150 mmHg had statistically significant higher GCS scores at the end of intensive care unit (ICU)-level care or hospital discharge (mean = 12, p = 0.01), compared to those in group 2 with lower PaO₂ levels (mean = 7.9). There was no statistically significant difference in GOS when comparing the two groups (p = 0.055); however, the data did show a trend toward significance. Discussion and Conclusion In our study we analyzed patients diagnosed with TBI and stratified them into groups based on PaO₂ ≥ or < 150 mmHg. We demonstrate overall outcome improvement based on GCS with a trend toward improved GOS. The GCS showed statistical significance in patients with PaO₂ consistently ≥ 150 mmHg versus those in group 2 over the first five days of hospitalization.

Keywords: brain trauma; neurosurgery; pao2; partial pressure of oxygen; tbi; traumatic brain injury.

Figure 1. Average GOS at discharge/end of care for patients stratified into the two groups

Figure 2. Average GCS at DC/end of care for patients stratified into the two groups

GCS = Glasgow Coma Scale DC = discharge

Figure 3. Graph for Patient A, demonstrating maximum and minimum PaO₂ levels above the predefined 150 mmHg threshold (dotted line)

GCS during the first day of monitoring and at the hospital discharge or the end of ICU-level care are demonstrated by yellow diamonds. Partial pressure of oxygen (PaO₂); Glasgow Coma Scale (GCS); intensive care unit (ICU).

Figure 4. Graph for Patient B, demonstrating maximum and minimum PaO₂ levels above the predefined 150 mmHg threshold (dotted line)

GCS during the first day of monitoring and at the hospital discharge or the end of ICU-level care are demonstrated by yellow diamonds. Partial pressure of oxygen (PaO₂); Glasgow Coma Scale (GCS); intensive care unit (ICU).

Figure 5. Graph for Patient C, demonstrating maximum and minimum PaO₂ levels above the predefined 150 mmHg threshold (dotted line)

GCS during the first day of monitoring and at the hospital discharge or the end of ICU-level care are demonstrated by yellow diamonds. Partial pressure of oxygen (PaO₂); Glasgow Coma Scale (GCS); intensive care unit (ICU).

Figure 6. Graph for Patient D, demonstrating maximum and minimum PaO₂ levels above the predefined 150 mmHg threshold (dotted line)

GCS during the first day of monitoring and at the hospital discharge or the end of ICU-level care are demonstrated by yellow diamonds. Partial pressure of oxygen (PaO₂); Glasgow Coma Scale (GCS); intensive care unit (ICU).

Figure 7. Graph for Patient E, demonstrating maximum and minimum PaO₂ levels above the predefined 150 mmHg threshold (dotted line)

GCS during the first day of monitoring and at the hospital discharge or the end of ICU-level care are demonstrated by yellow diamonds. Partial pressure of oxygen (PaO₂); Glasgow Coma Scale (GCS); intensive care unit (ICU).

Figure 8. Graph for Patient F, demonstrating maximum and minimum PaO₂ levels above the predefined 150 mmHg threshold (dotted line)

GCS during the first day of monitoring and at the hospital discharge or the end of ICU-level care are demonstrated by yellow diamonds. Partial pressure of oxygen (PaO₂); Glasgow Coma Scale (GCS); intensive care unit (ICU).

Figure 9. Graph for Patient G, demonstrating maximum and minimum PaO₂ levels above the predefined 150 mmHg threshold (dotted line)

GCS during the first day of monitoring and at the hospital discharge or the end of ICU-level care are demonstrated by yellow diamonds. Partial pressure of oxygen (PaO₂); Glasgow Coma Scale (GCS); intensive care unit (ICU).

Figure 10. Graph for Patient H, demonstrating maximum and minimum PaO₂ levels above the predefined 150 mmHg threshold (dotted line)

GCS during the first day of monitoring and at the hospital discharge or the end of ICU-level care are demonstrated by yellow diamonds. Partial pressure of oxygen (PaO₂); Glasgow Coma Scale (GCS); intensive care unit (ICU).

Figure 11. Graph for Patient I, demonstrating maximum and minimum PaO₂ levels above the predefined 150 mmHg threshold (dotted line)

GCS during the first day of monitoring and at the hospital discharge or the end of ICU-level care are demonstrated by yellow diamonds. Partial pressure of oxygen (PaO₂); Glasgow Coma Scale (GCS); intensive care unit (ICU).

Figure 12. Graph for Patient J, demonstrating maximum and minimum PaO₂ levels above the predefined 150 mmHg threshold (dotted line)

GCS during the first day of monitoring and at the hospital discharge or the end of ICU-level care are demonstrated by yellow diamonds. Partial pressure of oxygen (PaO₂); Glasgow Coma Scale (GCS); intensive care unit (ICU).

Figure 13. Graph for Patient K, demonstrating maximum and minimum PaO₂ levels above the predefined 150 mmHg threshold (dotted line)

GCS during the first day of monitoring and at the hospital discharge or the end of ICU-level care are demonstrated by yellow diamonds. Partial pressure of oxygen (PaO₂); Glasgow Coma Scale (GCS); intensive care unit (ICU).

Figure 14. Graph for Patient L, demonstrating maximum and minimum PaO₂ levels above the predefined 150 mmHg threshold (dotted line)

GCS during the first day of monitoring and at the hospital discharge or the end of ICU-level care are demonstrated by yellow diamonds. Partial pressure of oxygen (PaO₂); Glasgow Coma Scale (GCS); intensive care unit (ICU).

Figure 15. Graph for Patient M, demonstrating maximum and minimum PaO₂ levels above the predefined 150 mmHg threshold (dotted line)

GCS during the first day of monitoring and at the hospital discharge or the end of ICU-level care are demonstrated by yellow diamonds. Partial pressure of oxygen (PaO₂); Glasgow Coma Scale (GCS); intensive care unit (ICU).

Figure 16. Graph for Patient N, demonstrating maximum and minimum PaO₂ levels above the predefined 150 mmHg threshold (dotted line)

GCS during the first day of monitoring and at the hospital discharge or the end of ICU-level care are demonstrated by yellow diamonds. Partial pressure of oxygen (PaO₂); Glasgow Coma Scale (GCS); intensive care unit (ICU).

Figure 17. Graph for Patient O, demonstrating maximum and minimum PaO₂ levels above the predefined 150 mmHg threshold (dotted line)

GCS during the first day of monitoring and at the hospital discharge or the end of ICU-level care are demonstrated by yellow diamonds. Partial pressure of oxygen (PaO₂); Glasgow Coma Scale (GCS); intensive care unit (ICU).