A novel method for assessing cerebral autoregulation in preterm infants using transfer function analysis

Abstract

BackgroundAutoregulatory dysfunction is an important contributor to brain injury in premature infants, particularly intraventricular hemorrhage (IVH). The autoregulatory system acts as a filter that dampens the systemic blood flow to follow a normal cerebral perfusion profile.MethodsSimultaneous arterial blood pressure and cerebral near infrared spectroscopy (NIRS) data were collected from infants born before 28 weeks estimated gestational age (EGA). The resulting data were preprocessed and then divided into non-overlapping 20-minute epochs. The transfer function estimate was calculated to determine dampening ability.Results62 infants were prospectively recruited with a mean EGA of 25.4 ± 1.3 weeks and birth weight of 832 ± 199g. 67% were male, 24/62 had IVH, 17/62 received dopamine, 47/62 had antenatal steroid exposure, and 22/62 received fentanyl.Advancing EGA and birth weight z-score predicted stronger dampening while African-American race and IVH of any grade predicted weaker dampening.ConclusionThis preliminary report suggests an impairment in dampening ability associated with immaturity, decreased birth weight z-score and African-American race. Decreased dampening is also associated with IVH, although these results cannot distinguish between decreased dampening as an antecedent or sequela of IVH. These observations should be studied in a larger sample.

Cerebral Autoregulation, Brain Injury, and the Transitioning Premature Infant

“…The resulting output resembles a band pass filter (Figure 4), with dampening of low-frequency oscillations around the Mayer wave frequency (0.1 Hz). There is also a developmentally linked component to this dampening, with increased dampening found in infants of increasing gestational age (21). …”

“…Second, the white matter, particularly in the periventricular zone, is supplied by the long penetrating arteries, which first arise around 24 weeks of gestation but maintain remarkably low levels of blood flow, with minimal collateralization, until 30–32 weeks of gestation (6, 19). Finally, there is evidence of an impaired cerebrovascular autoregulatory system, suggesting that the preterm brain has limited capacity to regulate blood flow when oxygen saturation or cardiac output is reduced (20, 21). Repeated ischemic episodes associated with any of these mechanisms will generate an inflammatory response, thus increasing the metabolic demand, utilizing a greater fraction of delivered oxygen, and potentiating further injury during the next ischemic episode.…”

“…Many complicating clinical factors have been linked to causing or worsening the dysfunction of the autoregulatory system including hypotension (20), hypoxic-ischemia (57, 58), seizures (59), inotropic medications (60), and possibly even IVH itself (21). …”

“…Early in the course of hospitalization, repeated episodes of ischemia and reperfusion likely lead to weakening and then rupture of the fragile germinal matrix vessels. Indeed, impaired autoregulation has been clearly identified in infants with IVH (20, 21). This mechanism is also a likely contributing factor to WMI, where repeated episodes of ischemia, from a mismatch of perfusion and metabolic demand, accumulate in the periventricular white matter, a region with relatively limited vascular supply at this stage of development.…”

Церебральна Ауторегуляція Та Цереброваскулярні Ураження У Передчасно Народжених Дітей: Сучасні Погляди На Патогенез, Діагностику І Превентивні Стратегії

“…Існує велика кількість фізіологічних і патологічних стимулів, здатних викликати судинну відповідь мозку, однак для новонароджених дітей головними є п'ять специфічних стимулів: зміни церебрального перфузійного тиску, зміни концентрації циркулюючих кисню, вуглецю та глюкози, нейрональна активація. Клінічними факторами, що призводять до дисфункції системи церебральної ауторегуляції у постнатальному періоді, є гіпотензія, гіпоксія-ішемія, судоми, інотропні препарати та пренатальні ВШК [12][13][14][15].…”