Permissive hypotension in extremely low birth weight infants (≤1000 gm)

[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.

Blood pressure values and hypotension management in extremely preterm infants: a multi-center study

OBJECTIVE

To describe high/low daily blood pressures (BP) and variability in BP management with vasoactive infusions (VI) and/or hydrocortisone (HC) in extremely preterm infants.

STUDY DESIGN

Analysis of data from 24-27 weeks' gestation infants in the Preterm Erythropoietin Neuroprotection (PENUT) Trial. Daily high/low BPs, the use of VI and/or HC, and adverse outcomes were compared descriptively and using regression models.

RESULTS

936 infants were included; 64% untreated, 20% VI, 3% HC, and 13% VI + HC. BP ranges are described for the 602 untreated infants. Considerable inter- and intra-center variability was demonstrated in the rate of VI and/or HC use and the lowest BP on the day of VI or HC initiation.

CONCLUSIONS

Despite published expert opinion guidance regarding BP management in extremely preterm infants, our results suggest a continued lack of consensus result in both inter- and intra-center variability in practice. Well-designed studies in the field are urgently needed.

Risk Factors for Periventricular Leukomalacia in Preterm Infants: A Systematic Review, Meta-analysis, and GRADE-Based Assessment of Certainty of Evidence

BACKGROUND

We analyzed the certainty of evidence (CoE) for risk factors of periventricular leukomalacia (PVL) in preterm neonates, a common morbidity of prematurity.

METHODS

Medline, CENTRAL, Embase, and CINAHL were searched. Cohort and case-control studies and randomised randomized controlled trials were included. Data extraction was performed in duplicate. A random random-effects meta-analysis was utilizedused. CoE was evaluated as per Grading of Recommendations Assessment, Development and Evaluation (GRADE) guidelines.

RESULTS

One hundred eighty-six studies evaluating 95 risk factors for PVL were included. Of the 2,509,507 neonates assessed, 16,569 were diagnosed with PVL. Intraventricular hemorrhage [adjusted odds ratio: 3.22 (2.52-4.12)] had moderate CoE for its association with PVL. Other factors such as hypocarbia, chorioamnionitis, PPROM >48 hour, multifetal pregnancy reduction, antenatal indomethacin, lack of antenatal steroids, perinatal asphyxia, ventilation, shock/hypotension, patent ductus arteriosus requiring surgical ligation, late-onset circulatory collapse, sepsis, necrotizing enterocolitis, and neonatal surgery showed significant association with PVL after adjustment for confounders (CoE: very low to low). Amongst the risk factors associated with mother placental fetal (MPF) triad, there was paucity of literature related to genetic predisposition and defective placentation. Sensitivity analysis revealed that the strength of association between invasive ventilation and PVL decreased over time (P < 0.01), suggesting progress in ventilation strategies. Limited studies had evaluated diffuse PVL.

CONCLUSION

Despite decades of research, our findings indicate that the CoE is low to very low for most of the commonly attributed risk factors of PVL. Future studies should evaluate genetic predisposition and defective placentation in the MPF triad contributing to PVL. Studies evaluating exclusively diffuse PVL are warranted.

Risk factors and prognosis in very low birth weight infants treated for hypotension during the first postnatal week from the Korean Neonatal Network

Hypotension in the early stages of life appears in 20% of very low birth weight (VLBW) infants. The gestational age and birth weight are the risk factors highly related to the postnatal hypotension. Other risk factors slightly differ between different studies. So, we evaluated the risk factors and prognosis that are associated with infants treated with hypotension in the early stages of life, after excluding the influences of gestational age and small for gestational age (SGA). VLBW infants registered in the Korean Neonatal Network between 2013 and 2015 treated for hypotension within a week after their birth were selected as study subjects. The rest were used as a control group. Risk factors and the prevalence of severe complications, including mortality, were investigated and compared after matching for gestational age and SGA. The treatment rate for hypotension within the first postnatal week was inversely related to decreasing gestational ages and birth weights. In particular, 63.4% of preterm infants born at ≤ 24 weeks’ gestation and 66.9% of those with a birth weight < 500 g were treated for hypotension within a week of birth. Regression analysis after matching showed that 1-minute Apgar score, neonatal cardiac massage or epinephrine administration, symptomatic patent ductus arteriosus, early onset sepsis, and chorioamnionitis were significantly associated with hypotension. In the hypotension group, mortality, grade 3 or higher intraventricular hemorrhage, periventricular leukomalacia, and moderate to severe bronchopulmonary dysplasia rates were significantly higher after the matching for gestational age and SGA. Hypotension during the first postnatal week is very closely related to the prematurity and the condition of the infant shortly after birth. Regular prenatal care including careful monitoring and appropriate neonatal resuscitation are very crucial to decrease the risk of hypotension in the early stages of life.

Plasma Leak From the Circulation Contributes to Poor Outcomes for Preterm Infants: A Working Hypothesis

Preterm infants are at high risk of death and disability resulting from brain injury. Impaired cardiovascular function leading to poor cerebral oxygenation is a significant contributor to these adverse outcomes, but current therapeutic approaches have failed to improve outcome. We have re-examined existing evidence regarding hypovolemia and have concluded that in the preterm infant loss of plasma from the circulation results in hypovolemia; and that this is a significant driver of cardiovascular instability and thus poor cerebral oxygenation. High capillary permeability, altered hydrostatic and oncotic pressure gradients, and reduced lymphatic return all combine to increase net loss of plasma from the circulation at the capillary. Evidence is presented that early hypovolemia occurs in preterm infants, and that capillary permeability and pressure gradients all change in a way that promotes rapid plasma loss at the capillary. Impaired lymph flow, inflammation and some current treatment strategies may further exacerbate this plasma loss. A framework for testing this hypothesis is presented. Understanding these mechanisms opens the way to novel treatment strategies to support cardiovascular function and cerebral oxygenation, to replace current therapies, which have been shown not to change outcomes.

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

BACKGROUND

Cerebrovascular critical closing pressure (CrCP) is the arterial blood pressure (ABP) at which cerebral blood flow ceases. Preterm ABP is low and close to CrCP. The diastolic closing margin (diastolic ABP minus CrCP) has been associated with intraventricular hemorrhage in preterm infants. CrCP is estimated from middle cerebral artery cerebral blood flow velocity (CBFV) and ABP waveforms. However, these estimations have not been validated due to a lack of gold standard. Direct observation of the CrCP in preterm infants with hypotension is an opportunity to validate synchronously estimated CrCP.

METHODS

ABP and CBFV tracings were obtained from 24 extremely low birth weight infants. Recordings where diastolic CBFV was zero were identified. The gold standard CrCP was delineated using piecewise regression of ABP and CBFV values paired by rank ordering and then estimated using a published formula. The measured and estimated values were compared using linear regression and Bland-Altman analysis.

RESULTS

Linear regression showed a high degree of correlation between measured and calculated CrCP (r² = 0.93).

CONCLUSIONS

This is the first study to validate a calculated CrCP by comparing it to direct measurements of CrCP from preterm infants when ABP is lower than CrCP.

Postnatal blood pressure in the preterm small for gestational age neonate

OBJECTIVE

Determine how blood pressure differs in premature infants born small for gestational age (SGA).

DESIGN

A retrospective study was conducted on inborn infants 24-32 weeks gestation. Mean arterial blood pressure (MAP) was collected and averaged every 12 h for the first 96 h of life. For each time point, the difference MAP in SGA vs. AGA infants was evaluated with t-testing. Linear mixed-effects modeling was performed to model MAP over time accounting for GA, BW, gender, and SGA status.

RESULTS

356 subjects were evaluated. 52 (14.6%) were SGA. SGA infants were smaller, more likely male, exposed to maternal hypertension, born via caesarian section, and have chronic lung disease and retinopathy of prematurity. MAP in the SGA group more closely matched the MAP of AGA babies of similar GA for the first 24 h of life. Subsequently, SGA infants had lower MAPs more closely resembling their weight-matched counterparts. Mixed modeling showed GA to be significant, p < 0.0001 while BW though still marginally significant had less of an effect, p = 0.049.

CONCLUSION

SGA infants have blood pressure that is strongly associated with GA in the first 24 hours of life, but then fails to increase at the same rate as their AGA counterparts.

Hypotension in small preterms: what does it mean?

Introduction: Small preterms often have low blood pressure readings in the first few days of life. However, what is hypotension in preterms? Should there be an aggressive approach to its management? What are the immediate and long-term side effects of powerful medications? Alternatively, could a low blood pressure be accepted instead? Materials and methods: Data were collected from files of all live babies with gestational age (GA) between 23^0/7 and 31^6/7 weeks over two different periods: years 2000-2004 and 2008-2012. Results: Our data show that, despite extremely low gestational age (ELGA)/extremely low birth weight (ELBW) neonates, almost half of these tiny babies have neither low mean arterial pressure (MAP) readings nor clinical signs of impaired perfusion. Yet, many of them are, variously treated or not, depending on individual decisions, rather than on sound evidence. Discussion: We suggest, should it be required to treat persistent hypotension, rather than treating just a low MAP recording, to address the whole issue of hypotension in the overall picture of clinical settings; we to assess organ dysfunction caused by low output and use the least aggressive measures, preferably within written protocols, tailored to the given unit, but equally, sufficiently flexible to individual babies. Furthermore, allow for "permissive hypotension" especially if transient, in the absence of clinical signs of hypoperfusion, with normal superior vena cava (SVC) flow, normal cardiac output, and normal brain scanning with normal cerebral Doppler flows. Whether treating hypotension, by whichever definition, "per se", will make any difference to both, immediate and late outcomes; in the end, treating remains open to questioning and calls for careful follow-up of these very susceptible preterms.

Hypotension and Adverse Outcomes in Prematurity: Comparing Definitions

BACKGROUND

In the premature neonate, there is no consensus regarding normal blood pressure (BP). The most common definition used is a mean arterial BP (MAP) less than the gestational age (GA); however, studies indicate that the neuroprotective mechanism of autoregulation is lost below a MAP of 30 mm Hg.

OBJECTIVE

To determine whether hypotension defined as MAP <30 mm Hg or MAP less than the infant's GA better predicts adverse outcomes of intraventricular hemorrhage (IVH) and death.

STUDY DESIGN

For this retrospective study, demographic, clinical, and BP data in epochs of 12 h were collected during the first 72 h of life in 188 subjects 24-28 weeks of gestation. For each definition, outcomes of severe IVH (grade 3 or 4), death, or the composite outcome of either were evaluated using bivariate testing. Logistic regression determined independent predictors of composite outcome of death and/or grade 3 or 4 IVH.

RESULTS

Hypotension by either definition was significant for death and the composite outcome (p < 0.0001). Only the MAP <30 mm Hg definition was associated with severe IVH (p = 0.02). On logistic regression, significant predictors of the composite outcome were GA (OR 0.59, 95% CI 0.39-0.89) and vasopressor therapy (OR 5.5, 95% CI 2-17).

CONCLUSIONS

Neither definition of hypotension independently predicts adverse outcome in multivariate logistic regression. Vasopressor therapy, however, is an independent predictor of IVH and death in premature infants.

Propofol Dose-Finding to Reach Optimal Effect for (Semi-)Elective Intubation in Neonates

OBJECTIVE

To define the effective dose for 50% of patients (ED₅₀) of propofol for successful intubation and to determine the rate of successful extubation in those patients with planned intubation, surfactant administration, and immediate extubation (INSURE procedure). In addition, pharmacodynamic effects were assessed.

STUDY DESIGN

Neonates (n = 50) treated with propofol for (semi-)elective endotracheal intubation were stratified in 8 strata by postmenstrual and postnatal age. The first patient in each stratum received an intravenous bolus of 1 mg/kg propofol. Dosing for the next patient was determined using the up-and-down method. A propofol ED₅₀ dose was calculated in each stratum with an effective sample size of at least 6, via the Dixon-Masey method, with simultaneous assessment of clinical scores and continuous vital sign monitoring.

RESULTS

Propofol ED₅₀ values for preterm neonates <10 days of age varied between 0.713 and 1.350 mg/kg. Clinical recovery was not attained at the end of the 21-minute scoring period. Mean arterial blood pressure showed a median decrease between 28.5% and 39.1% from baseline with a brief decrease in peripheral and regional cerebral oxygen saturation. Variability in mean arterial blood pressure area under the curve could not be explained by weight or age.

CONCLUSIONS

Low propofol doses were sufficient to sedate neonates for intubation. Clinical recovery was accompanied by permissive hypotension (no clinical shock and no treatment). The propofol ED₅₀ doses can be administered at induction, with subsequent up-titration if needed, while monitoring blood pressure. They can be used for further dosing optimalization and validation studies.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01621373; EudraCT: 2012-002648-26.

Beyond survival; influences of blood pressure, cerebral perfusion and anesthesia on neurodevelopment

Neonates have a higher perioperative mortality risk largely due to the degree of prior illness of the infants, the complexity of their surgeries, and infant physiology. It is important to consider contributing anesthetic factors during the perioperative period that may affect cerebral perfusion and neurocognitive outcome, such as alterations in hemodynamics and ventilation. Limitations of blood pressure as a marker for cerebral perfusion are discussed, as well as the effect of hypocapnia on the brain.