OBJECTIVE The objective of this study is to assess carbon dioxide reactivity (CO2R) in children following traumatic brain injury (TBI). METHODS This prospective observational study enrolled children younger than 18 years old following moderate and severe TBI. Thirty-eight mechanically ventilated children had daily CO2R testing performed by measuring changes in their bilateral middle cerebral artery flow velocities using transcranial Doppler ultrasonography (TCD) after a transient increase in minute ventilation. The cohort was divided into 3 age groups: younger than 2 years (n = 12); 2 to 5 years old (n = 9); and older than 5 years (n = 17). RESULTS Children younger than 2 years old had a lower mean CO2R over time. The 2-5-year-old age group had higher mean CO2R than younger patients (p = 0.01), and the highest CO2R values compared with either of the other age groups (vs > 5 years old, p = 0.046; vs < 2 years old, p = 0.002). Having a lower minimum CO2R had a statistically significant negative effect on outcome at discharge (p = 0.0413). Impaired CO2R beyond Postinjury Day 4 trended toward having an effect on outcome at discharge (p = 0.0855). CONCLUSIONS Abnormal CO2R is prevalent in children following TBI, and the degree of impairment varies by age. No clinical or laboratory parameters were identified as risk factors for impaired CO2R. Lower minimum CO2R values are associated with worse outcome at discharge.
Keywords: AHT = abusive head trauma; CBF = cerebral blood flow; CO2R = carbon dioxide reactivity; CPP = cerebral perfusion pressure; CVR = cerebrovascular reactivity; ETCO2 = end-tidal CO2; GCS = Glasgow Coma Scale; GOS-E Peds = Glasgow Outcome Scale Extended Pediatric Version; ICH = intracranial hypertension; ICP = intracranial pressure; MOI = mechanism of injury; PID = Postinjury Day; PaCO2 = partial pressure of arterial carbon dioxide; ROC = receiver operator characteristic; TBI = traumatic brain injury; TCD = transcranial Doppler ultrasonography; VMCA = mean blood flow velocity of the right and left middle cerebral arteries; carbon dioxide reactivity; cerebrovascular reactivity; pediatric traumatic brain injury; transcranial Doppler ultrasound; trauma.