Association between blood pressure augmentation and brain tissue oxygenation in severe pediatric traumatic brain injury: preliminary findings.

BACKGROUND

Brain tissue hypoxia has poor outcomes in pediatric traumatic brain injury (TBI). However, more data is needed on how to determine which patients benefit the most from blood pressure augmentation as a treatment for cerebral hypoxia in pediatric TBI. We examined the association between blood pressure augmentation and brain tissue oxygenation (PbtO₂) in children with severe TBI.

METHODS

We performed a retrospective review of prospectively collected data at Harborview Medical Center. We included patients < 18 years admitted from January 2014 to July 2021 with severe (admission Glasgow coma scale score [GCS] < 9) TBI who underwent static transcranial doppler cerebral autoregulatory testing using the autoregulation index (ARI), derived from transcranial doppler ultrasonography measures.

RESULTS

We evaluated 14 patients (median age 13 [IQR 6-15 years], 78.6% male, median admission GCS 3 [IQR 3-4]) between intensive care unit admission days 2-11. Starting MAP was mean 81 mmHg (SD 9.2, range 63-97) and ending MAP was mean 99.3 mmHg (SD 14.7, range 62-115), starting CPP was mean 69 mmHg (SD 8.2, range 58-84) and ending CPP was mean 91 mm, starting PbtO2 was mean 25 (SD 12, range 11-64), and ending PbtO2 was mean 29 (SD 13.1, range 10 to 62). A 22.8% MAP increase resulted in a 32.5% CPP and 23% PbtO₂ increase, respectively. Overall, percent PbtO₂ increased with percent CPP increase (R2 = 0.36, p = 0.024) but not with percent MAP change (R2 = 0.27, p = 0.057). However, PbtO₂ response to MAP augmentation was heterogeneous, resulting in four PbtO₂ response groups (Group 1, normal and maintained [n = 9, 64.3%]); Group 2, normal and deteriorated [n = 1, 7.1%]); Group 3, low and improved [n = 1, 7.1%]); and Group 4, low and not improved [n = 3, 21.4%]). Stratified by cerebral autoregulation status, percent PbtO₂ change was only associated with percent MAP change (R2 = 0.59, p = 0.045) and percent CPP change (R2 = 0.64, p = 0.032) in patients with intact cerebral autoregulation (n = 7).

CONCLUSIONS

MAP augmentation resulted in higher CPP and four distinct PbtO₂ response patterns, including PbtO₂ improvement and cerebral hypoxia. Cerebral autoregulation status and PbtO₂ response status may impact blood pressure augmentation effects. MAP and CPP augmentation may be a desirable strategy to improve PbtO₂ in severe pediatric TBI.