Observed and calculated cerebral critical closing pressure are highly correlated in preterm infants

Determinants of the dynamic cerebral critical closing pressure response to changes in mean arterial pressure

Objective. Cerebral critical closing pressure (CrCP) represents the value of arterial blood pressure (BP) where cerebral blood flow (CBF) becomes zero. Its dynamic response to a step change in mean BP (MAP) has been shown to reflect CBF autoregulation, but robust methods for its estimation are lacking. We aim to improve the quality of estimates of the CrCP dynamic response.Approach. Retrospective analysis of 437 healthy subjects (aged 18-87 years, 218 males) baseline recordings with measurements of cerebral blood velocity in the middle cerebral artery (MCAv, transcranial Doppler), non-invasive arterial BP (Finometer) and end-tidal CO2(EtCO2, capnography). For each cardiac cycle CrCP was estimated from the instantaneous MCAv-BP relationship. Transfer function analysis of the MAP and MCAv (MAP-MCAv) and CrCP (MAP-CrCP) allowed estimation of the corresponding step responses (SR) to changes in MAP, with the output in MCAv (SRVMCAv) representing the autoregulation index (ARI), ranging from 0 to 9. Four main parameters were considered as potential determinants of the SRVCrCPtemporal pattern, including the coherence function, MAP spectral power and the reconstruction error for SRVMAP, from the other three separate SRs.Main results. The reconstruction error for SRVMAPwas the main determinant of SRVCrCPsignal quality, by removing the largest number of outliers (Grubbs test) compared to the other three parameters. SRVCrCPshowed highly significant (p< 0.001) changes with time, but its amplitude or temporal pattern was not influenced by sex or age. The main physiological determinants of SRVCrCPwere the ARI and the mean CrCP for the entire 5 min baseline period. The early phase (2-3 s) of SRVCrCPresponse was influenced by heart rate whereas the late phase (10-14 s) was influenced by diastolic BP.Significance. These results should allow better planning and quality of future research and clinical trials of novel metrics of CBF regulation.

Consequences of Preterm Birth: Knowns, Unknowns, and Barriers to Advancing Cardiopulmonary Health

Preterm birth occurs in 10% of all live births and creates challenges to neonatal life, which persist into adulthood. Significant previous work has been undertaken to characterize and understand the respiratory and cardiovascular sequelae of preterm birth, which are present in adulthood, i.e., "late" outcomes. However, many gaps in knowledge are still present and there are several challenges that will make filling these gaps difficult. In this perspective we discuss the obstacles of studying adults born preterm, including (1) the need for invasive (direct) measures of physiologic function; (2) the need for multistate, multinational, and diverse cohorts; (3) lack of socialized medicine in the United States; (4) need for detailed and better-organized birth records; and (5) transfer of neonatal and pediatric knowledge to adult care physicians. We conclude with a discussion on the "future" of studying preterm birth in regards to what may happen to these individuals as they approach middle and older age and how the improvements in perinatal and postnatal care may be changing the phenotypes observed in adults born preterm on or after the year 2000.

[Influence of hypotension on the short-term prognosis of preterm infants with a gestational age of <32 weeks]

OBJECTIVES

To investigate the influence of early-stage hypotension defined as mean arterial pressure (MAP)<gestational age (weeks) or MAP<30 mmHg on the short-term prognosis of preterm infants with a gestational age of <32 weeks.

METHODS

A total of 320 preterm infants who were admitted to Maternal and Child Health Hospital of Hubei Province, Tongji Medical College, Huazhong University of Science and Technology from April 2020 to August 2021 and met the inclusion criteria were enrolled in this prospective study. Blood pressure within 72 hours was monitored. The definition of hypotension and grouping were as follows: (1) Of the 320 preterm infants, those with MAP<gestational age in 2 consecutive measurements served as the hypotension group (n=104), and the others (n=216) served as the control group; (2) Of the 320 preterm infants, those with MAP<30 mmHg in 2 consecutive measurements served as the hypotension group (n=114), and the others served as the control group (n=206). Perinatal data and clinical data during hospitalization were collected.Poor short-term prognosis was defined as death during hospitalization and/or grade Ⅲ-Ⅳ periventricular-intraventricular hemorrhage identified within 1 week after birth. The multivariate logistic regression analysis was used to investigate the influence of hypotension based on the above two definitions on the short-term prognosis of preterm infants.

RESULTS

Compared with the control group, the hypotension group based on the above two definitions had higher incidence rates of the clinical manifestations of hypoperfusion, poor prognosis, hemodynamically significant patent ductus arteriosus, and pulmonary hemorrhage (P<0.05). In addition, compared with the control group, the hypotension group defined by MAP<30 mmHg had higher incidence rates of periventricular-intraventricular hemorrhage and bronchopulmonary dysplasia and mortality rate during hospitalization (P<0.05). The incidence of poor short-term prognosis in the hypotension group defined by MAP<30 mmHg was higher than that in the hypotension group defined by MAP<gestational age (18.4% vs 12.5%), but the difference was not statistically significant (P>0.05).The univariate analysis showed that the poor short-term prognosis was related to birth of cesarean section, gestational age, an Apgar score of ≤ 5 at 5 minutes, use of vasoactive drugs within 72 hours, mechanical ventilation within 72 hours, and hypotension under the two definitions (P<0.05).The multivariate logistic regression showed that hypotension based on either definition was not an independent risk factor for poor prognosis (P>0.05).

CONCLUSIONS

Hypotension based on either definition is not an independent risk factor for short-term poor prognosis in preterm infants with a gestational age of <32 weeks. Hypotension defined by MAP<30 mmHg might be more sensitive than that defined by MAP<gestational age in predicting short-term adverse outcomes, which needs further analysis by large sample studies.

Cerebral Critical Closing Pressure in Concomitant Traumatic Brain Injury and Intracranial Hematomas

The critical closing pressure (CrCP) is the pressure below which the local pial blood pressure is inadequate to prevent blood flow cessation. The cerebral CrCP in concomitant traumatic brain injury (TBI) and intracranial hematomas (TBI + ICH) remains understudied. The aim was to determine the status of the CrCP at сTBI with and without the ICH development.

MATERIAL AND METHODS

The results of the treatment of 90 patients with severe to moderate сTBI were studied (male/female - 49:41). The average age was 34.2 ± 14.4 years. Depending on the presence of ICH, patients were divided into two groups. All patients were subjected to transcranial Doppler of the both middle cerebral arteries, and evaluation of mean arterial pressure (MAP). Based on data obtained, the CrCPs were calculated. Significance was preset to p < 0.05.

RESULTS

The mean CrCP values in each group appeared to be significantly higher than a referral value (р < 0.05). The mean CrCP values in the perifocal zone of removed hematoma were significantly higher than in TBI patients without ICH (р = 0.015 and р = 0.048, respectively). Analysis of CrCP values in various types of ICH showed no statistically significant differences (р > 0.05).

DISCUSSION

The CrCP significantly differs in the groups of TBI patients with and without ICH. The comparability of the groups in respect to the concomitant injury structure proves that the revealed CrCP changes result from the traumatic compression of the brain.

Management of Neonatal Hypotension and Shock

The current standard approach to manage circulatory insufficiency is inappropriately simple and clear: respond to low blood pressure to achieve higher values. However, the evidence for this is limited affecting all steps within the process: assessment, decision making, therapeutic options, and treatment effects. We have to overcome the 'one size fits all' approach and respect the dynamic physiologic transition from fetal to neonatal life in the context of complex underlying conditions. Caregivers need to individualize their approaches to individual circumstances. This paper will review various clinical scenarios, including managing transitional low blood pressure, to circulatory impairment involving different pathologies such as hypoxia-ischemia and sepsis. We will highlight the current evidence and set potential goals for future development in these areas. We hope to encourage caregivers to question the current standards and to support urgently needed research in this overlooked but crucial field of neonatal intensive care.