Incidence of hypertension in infants on extracorporeal membrane oxygenation

Neonatal Hypertension

Neonatal hypertension is uncommon but is becoming increasingly recognized. Normative blood pressure data are limited, as is research regarding the risks, treatment, and long-term outcomes. Therefore, there are no clinical practice guidelines and management is based on clinical judgment and expert opinion. Recognition of neonatal hypertension requires proper blood pressure measurement technique. When hypertension is present there should be a thorough clinical, laboratory, and imaging evaluation to promptly diagnose causes needing medical or surgical management. This review provides a practical overview for the practicing clinician regarding the identification, evaluation, and management of neonatal hypertension.

Systemic Hypertension in Pediatric Veno-Venous Extracorporeal Membrane Oxygenation

Systemic hypertension (HTN) is a recognized complication of veno-venous (VV) extracorporeal membrane oxygenation (ECMO) in children. We sought to determine the prevalence and associated features of HTN in a retrospective cohort of children (>1 year old) supported with VV ECMO from January 2015 to July 2019 at our institution. Patient and ECMO-related characteristics were reviewed, including intensive care unit (ICU) length of stay (LOS), ECMO duration, corticosteroids and nephrotoxic medication exposure, acute kidney injury (AKI), overall fluid balance, and transfusion data. We analyzed 23 children (43% female) with a median age of 8.5 years (interquartile range [IQR] = 4-14.5). Median ICU LOS was 26 days (IQR = 15-47) with a median ECMO duration of 288 hours (IQR = 106-378) and a mortality rate of 35%. HTN was diagnosed in 87% subjects at a median of 25 ECMO hours (IQR = 9-54) of whom 55% were hypertensive >50% of their ECMO duration. AKI and fluid overload were documented in >50% of cohort. All but two subjects received at least one nephrotoxic medication, and nearly all received corticosteroids. Our data demonstrate that HTN is present in a preponderance of children supported with VV ECMO and appears within the first 3 days of cannulation. Underlying etiology is likely multifactorial.

The hypertensive neonate

Hypertension in neonates is increasingly recognized because of improvements in neonatal intensive care that have led to improved survival of premature infants. Although normative data on neonatal blood pressure remain limited, several factors appear to be important in determining blood pressure levels in neonates, especially gestational age, birth weight and maternal factors. Incidence is around 1% in most studies and identification depends on careful blood pressure measurement. Common causes of neonatal hypertension include umbilical catheter associated thrombosis, renal parenchymal disease, and chronic lung disease, and can usually be identified with careful diagnostic evaluation. Given limited data on long-term outcomes and use of antihypertensive medications in these infants, clinical expertise may need to be relied upon to decide the best approach to treatment. This review will discuss these concepts and identify evidence gaps that should be addressed.

Extracorporeal Membrane Oxygenation for Hemodynamic Support

Extracorporeal membrane oxygenation was first successfully achieved in 1975 in a neonate with meconium aspiration. Neonatal extracorporeal membrane oxygenation has expanded to include hemodynamic support in cardiovascular collapse before and after cardiac surgery, medical heart disease, and rescue therapy for cardiac arrest. Advances in pump technology, circuit biocompatibility, and oxygenators efficiency have allowed extracorporeal membrane oxygenation to support neonates with increasingly complex pathophysiology. Contraindications include extreme prematurity, extremely low birth weight, lethal chromosomal abnormalities, uncontrollable hemorrhage, uncontrollable disseminated intravascular coagulopathy, and severe irreversible brain injury. The future will involve collaboration to guide and evolve evidence-based practices for this life-sustaining therapy.

Nicardipine for the Treatment of Neonatal Hypertension During Extracorporeal Membrane Oxygenation

Extracorporeal membrane oxygenation (ECMO) is one of the primary reasons systemic hypertension is experienced in hospitalized neonates. Commonly used antihypertensive agents have resulted in significant adverse effects in neonatal and pediatric populations. Nicardipine is a desirable option because of its rapid and titratable antihypertensive properties and low incidence of adverse effects. However, data for use in neonatal ECMO are limited. We conducted a retrospective review of patients less than 44 weeks post-menstrual age who received a nicardipine infusion for first-line treatment of systemic hypertension while on ECMO at our institution between 2010 and 2016. Systolic (SBP), diastolic (DBP), and mean arterial (MAP) blood pressures were evaluated for 48-h after nicardipine initiation. Eight neonates received a nicardipine infusion while on ECMO during the study period. Nicardipine was initiated at a mean dose of 0.52 ( ± 0.22) mcg/kg/min and titrated to a maximum dose of 1.1 ( ± 0.85) mcg/kg/min. The median duration of nicardipine use was 51 (range 4-227) hours. Significant decreases in SBP, DBP, and MAP occurred within one hour of initiation of nicardipine and were sustained through the majority of the 48-h evaluation period. No patients experienced hypotension. Prospective studies are warranted to evaluate the optimal dose, safety, and efficacy of nicardipine in neonates who require ECMO.

Neonatal hypertension: cases, causes, and clinical approach

Neonatal hypertension is increasingly recognized as dramatic improvements in neonatal intensive care, advancements in our understanding of neonatal physiology, and implementation of new therapies have led to improved survival of premature infants. A variety of factors appear to be important in determining blood pressure in neonates, including gestational age, birth weight, and postmenstrual age. Normative data on neonatal blood pressure values remain limited. The cause of hypertension in an affected neonate is often identified with careful diagnostic evaluation, with the most common causes being umbilical catheter-associated thrombosis, renal parenchymal disease, and chronic lung disease. Clinical expertise may need to be relied upon to decide the best approach to treatment in such patients, as data on the use of antihypertensive medications in this age group are extremely limited. Available data suggest that long-term outcomes are usually good, with resolution of hypertension in most infants. In this review, we will take a case-based approach to illustrate these concepts and to point out important evidence gaps that need to be addressed so that management of neonatal hypertension may be improved.

An overview of medical ECMO for neonates

Extracorporeal membrane oxygenation (ECMO), a life-saving therapy for respiratory and cardiac failure, was first used in neonates in the 1970s. The indications and criteria for ECMO have changed over the years, but it continues to be an important option for those who have failed other medical therapies. Since the Extracorporeal Life Support Organization (ELSO) Registry was established in 1989, more than 29,900 neonates have been placed on ECMO for respiratory failure, with 84% surviving their ECMO course, and 73% surviving to discharge or transfer. In this chapter, we will review the basics of ECMO, patient characteristics and criteria, patient management, ECMO complications, special uses of neonatal ECMO, and patient outcomes.

Systemic hypertension requiring treatment in the neonatal intensive care unit

OBJECTIVES

To determine the difference in the risk factors for systemic hypertension in preterm and term infants in the neonatal intensive care unit (NICU).

STUDY DESIGN

Data were collected from an existing database of NICU children and confirmed by chart review. Systemic hypertension was defined when 3 separate measurements of systolic and/or diastolic blood pressure were >95th percentile and an antihypertensive medication was administered for >2 weeks in the NICU.

RESULTS

Of 4203 infants, we identified 53 (1.3%) with treated hypertension, of whom 74% were preterm, 11% required surgical intervention, and 85% required medications on discharge. The presence of a patent ductus arteriosus, umbilical catheterization, left ventricular hypertrophy, hypertensive medication at discharge, and mortality was similar between the term and preterm infants. The major risk factors for preterm infants, especially those <28 weeks' gestation, were bronchopulmonary dysplasia and iatrogenic factors, but, in term infants, they were systemic diseases. Term infants were diagnosed with hypertension earlier during hospitalization, had a shorter duration of stay in the NICU, and had a higher incidence of hypertension needing >3 medications than preterm infants.

CONCLUSIONS

Perinatal risk factors are significant contributors to infantile hypertension. Term infants were diagnosed with hypertension earlier, had a shorter duration of stay, and had a higher incidence of resistant hypertension than preterm infants.

Medical and nursing care of the child on mechanical circulatory support

OBJECTIVES

To review the medical and nursing care of children receiving mechanical circulatory support as part of the Pediatric Cardiac Intensive Care Society/Extracorporeal Life Support Organization Joint Statement on Mechanical Circulatory Support. DATA SOURCES/STUDY SELECTION/DATA EXTRACTION/DATA SYNTHESIS: This is a general review of current issues of medical and nursing care of children on mechanical circulatory support. It consists of knowledge gained from practical experience combined with supporting evidence and/or discussion of controversies for which evidence exists or is inconclusive. The scope of this review includes assessment and monitoring, cardiovascular, pulmonary, and renal and fluid management, as well as infection prevention and treatment, neurological, and nutritional considerations. Physical and psychological care is discussed, as well as ethical and practical issues regarding termination of support.

CONCLUSIONS

There are unique aspects to the medical and nursing care of a patient requiring mechanical circulatory support. Preserving the possibility for cardiac recovery when possible and preventing damage to noncardiac organs are essential to maximizing the probability that patients will have quality survival following support with a mechanical circulatory support device.

Hypertension in infancy: diagnosis, management and outcome

Advances in the ability to identify, evaluate, and care for infants with hypertension, coupled with advances in the practice of Neonatology, have led to an increased awareness of hypertension in modern neonatal intensive care units. This review will present updated data on blood pressure values in neonates, with a focus on the changes that occur over the first days and weeks of life in both term and preterm infants. Optimal blood pressure measurement techniques as well as the differential diagnosis of hypertension in the neonate and older infants will be discussed. Recommendations for the optimal immediate and long-term evaluation and treatment, including potential treatment parameters, will be presented. We will also review additional information on outcome that has become available over the past decade.

A tale of two bridges: effect of the bloodless bridge on renal function and blood pressure in neonates managed with venoarterial extracorporeal membrane oxygenation

OBJECTIVE

To investigate if a change in bridge design of the extracorporeal membrane oxygenation (ECMO) circuit had an impact on renal function and blood pressure in neonates requiring venoarterial ECMO support.

DESIGN

: Retrospective chart review.

SETTING

A tertiary care neonatal intensive care unit and ECMO center.

PATIENTS

The medical records of neonates admitted to the neonatal intensive care unit and treated with venoarterial ECMO were reviewed. Data were collected on 50 consecutive neonates treated previous to (prebridge group) and following (postbridge group) transition to a new bridge design on the ECMO circuit.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Gestational age, gender, racial distribution, and use of hypertensive therapy were similar between the two groups. Daily blood urea nitrogen, serum creatinine, urine output, fluid balance, and average and maximum systolic and mean arterial blood pressures were recorded for the first 3 days on bypass. The postbridge group had lower maximum mean arterial blood pressure and systolic blood pressure on day 2 of ECMO and lower average mean arterial blood pressure and systolic blood pressure on days 2 and 3 of ECMO. These differences remained significant after controlling for covariates in a multiple regression model. A higher percentage of patients were hypertensive (mean arterial blood pressure >60) in the prebridge group compared with the postbridge group. There were no differences in blood urea nitrogen, serum creatinine, fluid balance, and urine output between the two groups.

CONCLUSIONS

Patients managed on venoarterial ECMO after the transition to the "bloodless" bridge had less hypertension compared with those managed before the bridge change. This may reflect improved maintenance of renal perfusion associated with transition to an ECMO bridge design that does not require intermittent circulation with associated arterial-venous shunting.

Comparison of the effect of venovenous versus venoarterial extracorporeal membrane oxygenation on renal blood flow in newborn lambs

Venovenous extracorporeal membrane oxygenation (VV ECMO) using double lumen catheters is an alternative to venoarterial (VA) ECMO and allows for total blood flow using the patient's cardiac output in comparison to partial blood flow provided during VA ECMO.

OBJECTIVE

To compare the effects of VV versus VA ECMO on renal blood flow.

DESIGN

Prospective study.

SETTING

Research laboratory in a hospital.

SUBJECT

Newborn lambs 1-7 days of age (n = 15).

INTERVENTIONS

In anesthetized, ventilated lambs, femoral artery and vein were cannulated for monitoring and renal venous blood sampling. An ultrasonic flow probe was placed on the left renal artery for continuous renal blood flow measurements. Animals were randomly assigned to control (non-ECMO), VV ECMO and VA ECMO groups. After systemic heparinization, the animals were cannulated and studied at bypass flows of 120 mL/kg/min (partial bypass) for two hours in both ECMO groups and 200 mL/kg/min (full bypass) for an additional 30 min in the VA group. Changes in blood pressure and renal flow on ECMO and during ECMO bridge unclamping were recorded continuously. Plasma renin activity (PRA) levels were sequentially sampled.

RESULTS

Systemic blood pressure was not different in VV or VA ECMO at partial bypass flow. However, systemic blood pressure increased significantly at maximal bypass flow in the VA ECMO group. There was no change in renal flow in either VV or VA ECMO groups. PRA levels did not correlate with bypass flow change. During unclamping of the ECMO bridge, blood pressure and renal flow drop significantly in the VA group, but not in the VV group.

CONCLUSION

VV and VA ECMO at partial bypass flows had comparable effect on blood pressure, renal blood flow and PRA level in this short-term study. However, unclamping of the ECMO bridges did differentially affect blood pressure and renal blood flow between VV and VA groups. We speculate that this repeated acute change in long-run VA ECMO support may play a role in the persistent hypertension seen in some patients.

Systemic hypertension associated with venovenous extracorporeal membrane oxygenation for pediatric respiratory failure

BACKGROUND/PURPOSE

Arterial hypertension (HTN) is common in neonates on venoarterial (VA) extracorporeal membrane oxygenation (ECMO), but HTN in pediatric venovenous (VV) ECMO has not been well described. The authors noted HTN in their VV ECMO experience and hypothesized that HTN was associated with fluid status, steroid use, and renal insufficiency.

METHODS

Records of 50 patients receiving VV ECMO for respiratory failure were reviewed. HTN was defined as systolic blood pressure greater than 95th percentile for age for > or =1 hour, unresponsive to sedation/analgesia. Hypertensive index (HI) is defined as total hypertensive hours per total ECMO hours. Fluid status was estimated by a fluid index (FI = total fluid balance during ECMO per ECMO hours per weight).

RESULTS

Forty-seven of 50 patients (94%) had HTN. Median HI was 0.21 (range, 0.01 to 1.0). Thirteen patients had renal insufficiency, 39 received steroids, and 23 received continuous venovenous hemofiltration (CVVH). There was no association between HI and FI, steroid use, or renal insufficiency. Thirty-three patients were treated for HTN, often requiring multiple agents. Bleeding complicated the course of 18 patients, and HI was significantly higher in those patients (P = .03). HI was not different between survivors (37 of 39 with HTN) and nonsurvivors (10 of 11 with HTN).

CONCLUSIONS

Hypertension is a common complication associated with VV ECMO with unclear etiology. HTN was frequently difficult to control. This study emphasizes the need for the development of treatment protocols to decrease the incidence, severity, and associated morbidity. Improved insight into the etiology of HTN associated with pediatric VV ECMO, including evaluation of the renin-angiotensin system, would help guide therapy.

Venoarterial extracorporeal membrane oxygenation impairs basal nitric oxide production in cerebral arteries of newborn lambs

OBJECTIVE

Based on previous studies in our laboratory showing that exposure of newborn lambs to venoarterial extracorporeal membrane oxygenation (ECMO) alters cerebral blood flow autoregulation, we postulated that this altered vascular reactivity is mediated through changes in endothelial function caused by the pumping systems used in venoarterial ECMO. We tested that hypothesis in this study.

DESIGN

Prospective, controlled, laboratory trial.

SETTING

Animal research laboratory.

SUBJECTS

Two groups of newborn lambs.

INTERVENTIONS

One group of animals was exposed to venoarterial ECMO (n = 6) and another group of control animals (n = 5) was maintained under similar conditions for 2 hrs on the ventilator without ECMO.

MEASUREMENTS AND MAIN RESULTS

Third-order branches of the middle cerebral arteries (140-300 microm diameter) were isolated from animals at the end of the experiment, mounted on glass cannulae in an arteriograph, and superfused with Krebs-Ringer buffer. Decrease in the diameter of the arteries induced by exposure of the vessels to nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (200 micromol/L) for 30 mins was significantly less (p <.05) in arteries from lambs exposed to ECMO compared with control animals. There were no significant differences between the two groups in myogenic response or in the contractile activity of the arteries to increasing concentrations of serotonin.

CONCLUSIONS

These results demonstrate that 2 hrs of exposure of newborn lambs to venoarterial ECMO leads to a decrease in basal production of nitric oxide in cerebral arteries, and suggest that venoarterial ECMO selectively impairs cerebral arterial endothelial function.

Variability in systemic arterial pressure during closed- and open-bridge extracorporeal life support: an in vitro evaluation

OBJECTIVE

To compare fluctuations in systemic arterial pressure (SAP) resulting from changes in systemic vascular resistance (SVR) during closed- and open-bridge extracorporeal life support (ECLS).

DESIGN

In vitro laboratory study.

SETTING

Physiology laboratory of a tertiary care pediatric hospital.

METHODS

A standard neonatal ECLS circuit with simulated SAP was established using normal saline as circulating fluid. Our reference setting included an extracorporeal flow rate of 300 mL/min, a simulated SAP of 60 mm Hg, and a postoxygenator pressure of 150 mm Hg. The simulated SVR was modified by changing the degree of occlusion of the arterial catheter distal to the bridge. For this purpose, we used a graduated clamping device. Subsequently, the pressure changes were measured at four ports in the circuit. They were located as follows: a) on the venous tubing of the circuit between the bridge and the reservoir; b) on the arterial tubing of the circuit between the heat exchanger and the bridge; c) between the first and the second resistance clamps on the arterial tubing of the circuit for monitoring the simulated systemic arterial pressure; and d) at the reservoir. The experiment was repeated with various extracorporeal flow rates to the reservoir (100-300 mL/min) and through the bridge (100-300 mL/min using a custom-made clamp). Variations in the simulated SAP created by varying degrees of occlusion and flow rates were compared with repeated measures analysis of variance followed by the Tukey-Kramer test.

MEASUREMENTS AND MAIN RESULTS

The open-bridge ECLS significantly reduced the variations in the simulated SAP by 15% to 45% (p < .001) compared with the closed-bridge. During closed-bridge ECLS, flashing of the bridge resulted in a decrease in the SAP and transient reversal of flows through the arterial and venous cannulae.

CONCLUSIONS

Open-bridge ECLS decreases the fluctuations in the SAP that occur because of changes in the SVR. Open-bridge ECLS prevents transient iatrogenic changes in blood flow and blood pressure, caused by flashing of the bridge. Other potential advantages and disadvantages of the open-bridge ECLS are discussed. The application of prolonged open-bridge ECLS to the patients needs to be evaluated in animal models.

Bacterial and fungal infection in neonates undergoing venoarterial extracorporeal membrane oxygenation: an analysis of the registry data of the extracorporeal life support organization

A review and analysis of 5,001 neonatal venoarterial (VA) extracorporeal membrane oxygenation (ECMO) cases showed that bacterial and fungal infection occurred in 147 (2.9%) and 26 (0.6%) patients, respectively, with an overall incidence of 3.5%. Bivariate analysis was used to compare infected infants with controls, bacterial versus fungal groups, and bacterial subgroups with respect to patient demographics, primary diagnosis, mechanical complications, patient complications, duration of the ECMO course, and hospital mortality. Logistic regression models were constructed using variables that were statistically significant from the bivariate comparisons. Variables that remained significant after multivariate analysis included primary diagnosis of pneumonia/sepsis, mechanical complications of oxygenator failure, rupture of raceway or tubing, clots, and patient complications of hypertension and hyperbilirubinemia. The infection group had significantly longer mean total hours on bypass and higher hospital mortality. Infants with fungal infection had a significantly higher hospital mortality rate compared with those with bacterial infection. We conclude that infection during ECMO, especially fungal infection, carries an increased risk of hospital mortality and that mechanical complications are associated with an increased risk of infection, Key Words: Extracorporeal membrane oxygenation-Nosocomial-Bacterial infection-Fungal infection-Extracorporeal membrane oxygenation outcome.

Extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation has now evolved into standard therapy for patients unresponsive to conventional ventilatory and pharmacological support. This article presents a clinical review of extracorporeal life support and its application to neonatal and pediatric patients as well as children requiring circulatory support after open heart surgery.

Hypertension in infancy

Hypertension in infants is rare and requires a thorough evaluation. The incidence of hypertension in infancy has risen in recent years, reflecting both better monitoring methods and increasingly successful salvage of smaller and smaller newborns. Overall mortality and morbidity rates for uncontrolled hypertension in infants are unknown. With appropriate treatment, the prognosis for resolution of hypertension is good. In most cases, hypertension is short-lived and blood pressures return to normal even when medication is discontinued. Recent experience with improved antihypertensive agents in infancy has meant that nephrectomy for renovascular hypertension is rarely required. There is still much to learn about the indications for treatment of elevated blood pressures in infancy and the potential adverse effects of therapy. Infants with a history of neonatal hypertension should be followed closely because the long-term prognosis is not known and recurrence of hypertension remains a possibility. Because hypertension can develop in high-risk newborns following discharge from the nursery, these infants deserve routine blood pressure measurements as part of their outpatient follow-up.

Hidden mortality rate associated with extracorporeal membrane oxygenation

We reviewed the outcome of all infants referred to, and accepted in, our extracorporeal membrane oxygenation (ECMO) program during a 52-month period. One hundred sixty-seven referrals, representing 158 infants and nine mothers who had not yet delivered their infants, were accepted. Eighteen infants (11.3% of all neonates transported) died before leaving the referring hospital, during transport, or shortly after admission to our unit. Contraindications to ECMO excluded 17 (10.1%) of the 167 referrals. Sixty-two infants (37.1%) initially did not meet ECMO criteria. Two died before ECMO could be started. Sixty-eight infants (40.7%) were given ECMO therapy, and 11 died (16.1%). Nine mothers were referred because of fetal conditions that might require ECMO; of these infants, two died during delivery and three had contraindications to the use of ECMO. The four remaining infants were given ECMO therapy; three survived. The overall mortality rate was 27.5% (46/167); 18 (39.1%) of the 46 deaths were associated with transfer. The mortality rate associated with congenital diaphragmatic hernia was 63.6%. We recommend early transport of infants with this type of hernia during the postoperative "honeymoon" or during in utero transport with delivery at an ECMO center. We also recommend that infants with meconium aspiration syndrome be transported to an ECMO center when an oxygenation index of 25 is reached. The mortality rate associated with transport needs to be considered in evaluating ECMO programs. Earlier, expedited transfers may increase the survival rate.