Extracorporeal membrane oxygenation and cerebral blood flow velocity in children

Abstract

Objective: To determine how extracorporeal membrane oxygenation affects cerebral blood flow velocity and to determine whether specific changes in cerebral blood flow velocity may be associated with neurologic injury.

Design: Prospective, observational study.

Setting: PICU in a tertiary care academic center.

Patients: Children (age less than or equal to 18 yr) requiring extracorporeal membrane oxygenation support.

Interventions: None.

Measurements and main results: Eighteen patients (age 3.8 ± 7.2 years; venovenous neck, n = 5; venoarterial neck, n = 8; venoarterial chest, n = 5) requiring extracorporeal membrane oxygenation underwent daily transcranial Doppler ultrasound measurements of cerebral blood flow velocity in bilateral middle cerebral arteries. Cerebral blood flow velocity measurements were recorded as a percentage of age and gender normal value. On extracorporeal membrane oxygenation, cerebral blood flow velocities in patients not suffering clinically evident neurologic injury were decreased with systolic flow velocity (Vs) 54% ± 3% predicted and mean flow velocity (Vm) 52% ± 4% predicted. After decannulation, Vs and Vm were higher than while on extracorporeal membrane oxygenation at 73% ± 3% predicted (p = 0.0007 vs. value on extracorporeal membrane oxygenation) and 64% ± 4% predicted (p = 0.01 vs. value on extracorporeal membrane oxygenation).Patients who developed clinically evident cerebral hemorrhage had higher Vs, diastolic flow velocity (Vd), and Vm compared with those who did not: 123% ± 8% predicted, 130% ± 18% predicted, 127% ± 9% predicted (p < compared to values in children not suffering neurological injury). Supranormal flow velocities were noted 2-6 days before clinical recognition of cerebral hemorrhage in all four patients. There were no significant differences in mean arterial blood pressure, circuit flow, or hematocrit between the children who suffered cerebral hemorrhage and those who did not. Partial pressure of carbon dioxide was lower in the group of patients who experienced cerebral hemorrhage than in those who did not (38 ± 2 vs. 44 ± 1 mm Hg, p = 0.03).

Conclusion: In children who did not suffer clinically apparent neurologic injury, cerebral blood flow velocities were lower than normal while on extracorporeal membrane oxygenation support and increased after decannulation. However, children who developed cerebral hemorrhage had higher than normal cerebral blood flow velocities noted for days prior to clinical recognition of bleeding. Cerebral blood flow velocity measurement may represent a portable, noninvasive way to predict cerebral complications of extracorporeal membrane oxygenation and deserves further study.

Figure 1

Percentage of age and gender normal value of systolic flow velocity (V_s), mean flow velocity (V_m), and diastolic flow velocity (V_d) on and following removal from extracorporeal membrane oxygenation (ECMO) support in children not suffering acute neurologic injury in each of the three patient groups (venovenous [VV] ECMO, venoarterial [VA] ECMO with neck cannulation, VA ECMO with chest cannulation). Values represent the median and interquartile range for each group. p = 0.0007 for V_s on vs. off ECMO. p = 0.01 for V_m on vs. off ECMO. p = 0.94 for V_d on vs. off VA ECMO. p = 0.01 for V_d on vs. off VV ECMO.

Figure 2

Percentage of age and gender normal value of systolic flow velocity (V_s), mean flow velocity (V_m), and diastolic flow velocity (V_d) in children suffering cerebral hemorrhage compared with those who did not suffer cerebral hemorrhage. Values represent the median and interquartile range for each group. p ≤ 0.0001 for all values.

Figure 3

Percentage of age and gender normal value of systolic flow velocity (V_s) on each extracorporeal membrane oxygenation (ECMO) day for each of the four patients ultimately experiencing cerebral hemorrhage. The arrow represents the time of clinical recognition of neurologic injury. R MCA = right middle cerebral artery; L MCA = left middle cerebral artery.

Figure 4

Transcranial Doppler ultrasound images of a patient suffering massive cerebral hemorrhage on extracorporeal membrane oxygenation (ECMO) (top) compared with an age- and gender-matched patient who did not suffer acute neurologic injury on ECMO (bottom). Note the markedly increased systolic, diastolic, and mean flow velocities in the child suffering cerebral hemorrhage. The image of the patient suffering massive cerebral hemorrhage was taken 4 days prior to any clinical recognition of bleeding. Both patients were on venoarterial ECMO (central cannulation) due to complications of congenital heart disease. Mean arterial blood pressure was 60 mm Hg, ECMO circuit flow was 100 mL/kg/minute, and Pa_CO2 was 35 mm Hg for both patients at the time these images were taken. R-MCA = right middle cerebral artery; EDV = end diastolic velocity; PI = pulsatility index; RI = resistive index; S/D = systolic/diastolic; HR = heart rate.