Hemodynamics of the brain and perinatal brain damage

Intracranial blood flow in the acute period of perinatal encephalopathy

For newborns with hypoxic-ischemic brain damage (cerebral ischemia) of I-II severity, the same patterns in the change of cerebral hemodynamics as for healthy newborns are characteristic, however, at lower linear velocities of the blood flow (mostly diastolic). From 3 days of life, there were no significant differences in the linear rates of cerebral blood flow in healthy newborns and children with ischemia of grade II severity, which reflected the reversibility of the revealed disorders, their "functional" nature. Normal echographic characteristics of the brain in neurosonography, as well as the absence of significant differences in IR in healthy children and newborns with ischemia, indicate the preservation of autoregulation of cerebral hemodynamics.

Analysis of cerebral hemodynamics in cerebral ischaemia of the third degree, accompanied by the formation of intracranial hemorrhages, demonstrates a significant decrease in all parameters characterizing the blood flow in newborns.

The degree and rate of change of cerebral hemodynamics for various forms of hemorrhage are different. In newborns with IK-II grade II, low rates of both systolic and diastolic blood flow were noted, which was determined by high vascular resistance. This trend persists throughout the early neonatal period and is more typical for patients with grade II IV. The blood pressure remains low during the first 2 days of life and ranges mainly from 37.9 ± 1.91 to 44.2 ± 1.90 mm Hg. Art. On the 3rd day of life, a rise in blood pressure to 56.0 ± 1.80 mm Hg was noted. That is more often observed among patients with grade II PVK, which is accompanied by a rapid progression of hemorrhage to grade III-IV IV. In this case, the dopplerogram often has a fluctuating character.

Thus, PVK III-IV degrees often develop against the background of severe arterial hypotension, which persists for the first 4-6 days of life. In cases with a lethal outcome, the diastolic blood flow (after exclusion of the functioning arterial duct) in the first 6-8 hours of life is not determined. The fact of a decrease in blood flow velocities with massive III grade PVK, especially diastolic blood, high IR of the cerebral arteries, fluctuating blood flow are unfavorable prognostic signs - most such children die. Stabilization of the dopplerogram indices serves as a criterion for the effectiveness of the current therapy.

Perinatal brain lesions predominantly with ischemic focal lesions: periventricular and subcortical leukomalacia are characterized by consistently high cerebral vascular resistance throughout the early neonatal period. The maximum increase in MI occurs among patients with PVL. The drop in diastolic blood flow indicates a decrease in intracranial blood flow and an increase in cerebral ischemia. In the future, the IR decreases slightly. Children aged 3-4 weeks with increased periventricular echogenicity and small pseudocysts (stage of cystic PVL) have a high, long-lasting irrespective of the ongoing treatment of IR (0.8-0.9). Expressed intracranial hypertension and high IR in these cases are extremely unfavorable prognostic signs reflecting the severity and irreversibility of brain lesions.

Children with the phenomenon of "physiological" increased periventricular echogenicity (periventricular aureole) are noted for non-rough hypoperfusion of cerebral parenchyma and arterial hypotension in the 1-4 day of life. Beginning from 4-7 days, blood pressure in these newborns corresponds to similar indicators in healthy children and even, in some cases, exceeds their values, which does not change the level of cerebral blood flow. This is a convincing argument in favor of the preservation of the mechanisms of autoregulation of cerebral blood flow in the phenomenon of increased periventricular echogenicity and indicates the features of the periventricular blood supply in children of this gestational age.

Based on the diagnostic and prognostic values of IR in the first day of life of the newborn, algorithms for diagnosing and predicting hypoxic-ischemic brain lesions are proposed. The most unfavorable prognostic sign is the absence of diastolic blood flow (IV = 1.0) in the first 6-8 hours of life (with the exception of the hemodynamically significant functioning arterial duct), which is accompanied by the development of a heart attack or cerebral edema (less often) and 80% of cases terminate lethal. The values of IR from 0.9 and above in the first three days of life lead to the development of severe organic brain pathology in a child aged 1 year. The obtained data convincingly testify that hypoperfusion of the cerebral parenchyma in the first day of the child's life, characterized by high values of MI, is a prognostically more unfavorable sign of the outcome of perinatal encephalopathy in 1 year than hyperperfusion.

Intracranial blood flow in the recovery period of perinatal encephalopathy

In comparative analysis of intracranial hemodynamics in children older than 1 month of life and children who underwent chronic intrauterine or acute hypoxia in labor with clinical manifestations of perinatal encephalopathy (PEP) in the recovery period (children over 1 month of life), it was noted that during the year in healthy children of ID in the basin of the PMA is stable and equal to 0.66-0.7 in the first half of the year and 0.65-0.69 in the second half of the year.

In children with clinical PEP syndromes, a phase change in the IR indices in the anterior cerebral artery during the first year of life is noted:

• Phase 1 - "spasm" or stress - is characterized by an increase in MI in the basin of PMA (above 0.7) and lasts an average of 3-4 months of life. Then there is a "negative turn" of the IR from increased to lower, ie, from above 0.72 to less than 0.65.
• 2 phase - relaxation of blood vessels - lasts up to 6-7 months with acute hypoxia and 8-11 months with chronic intrauterine hypoxia. IR is reduced.
• Phase 3 - the phase of recovery occurs until the age of 12-15 months, and possibly older. In this phase, one can judge the recovery of the tone of the vascular bed. IR returns to the values of 0.65-0.69, which has a significant prognostic value. This phase suggests a persistent residual change in the regulation of the tone of the arterial vascular bed, if the IR remains lower (less than 0.65). The phases of changes in arterial blood flow during the first year of life in our work coincide with the clinical phases of perinatal encephalopathy according to Yu.A. To Barashnev.

In the study of venous blood flow, it was found that the rate of venous outflow in the Galen vein is significantly higher in children with hypertensive hydrocephalic syndrome (GHS) than in the children of the control group (p <0.01). There is a correlation between the clinic of HGS and the appearance of a pseudo-arterial nature of the venous outflow in the vein of Galen. When performing a correlation analysis of venous outflow with other basic neurological syndromes of the first year of life (syndrome of increased neural reflex excitability, muscular dystonia syndrome, vegetative-visceral dysfunction syndrome, asthenoneurotic syndrome, psychomotor development delay), there was no reliable relationship between these syndromes and outflow velocity Galen's vein or the character of the venous curve. When comparing the rates of normalization of arterial blood flow and venous outflow, it was found that venous outflow is restored significantly faster than arterial blood flow (p <0.01).

Isolation of a group of children with only vascular disorders (without structural brain lesions in neurosonography) is important for clinicians. Correct interpretation of intracranial blood flow parameters in children of the first year of life in norm and especially in conjunction with the clinic of perinatal brain injury allows more individual selection of corrective therapy aimed at eliminating vascular disorders and preventing structural changes in brain tissue. The use of dopplerography allows to answer the question, which part of the intracranial blood flow is affected - arterial or venous, which determines the choice of drugs used in rehabilitation programs for children with perinatal CNS damage.

A comprehensive ultrasound study using dopplerography of intracranial arterial and venous vessels in young children significantly expands the possibilities of early topical diagnosis of vascular pathology, which is the cause of perinatal encephalopathy.

[1], [2], [3]