Ambulatory Blood Pressure and Number of Subclinical Target Organ Injury Markers in Youth: The SHIP AHOY Study

Background

Hypertension in adolescence is associated with subclinical target organ injury (TOI). We aimed to determine whether different blood pressure (BP) thresholds were associated with increasing number of TOI markers in healthy adolescents.

Methods

244 participants (mean age 15.5±1.8 years, 60.1% male) were studied. Participants were divided based on both systolic clinic and ambulatory BP (ABP), into low- (<75 th percentile), mid- (75 th -90 th percentile) and high-risk (>90 th percentile) groups. TOI assessments included left ventricular mass, systolic and diastolic function, and vascular stiffness. The number of TOI markers for each participant was calculated. A multivariable general linear model was constructed to evaluate the association of different participant characteristics with higher numbers of TOI markers.

Results

47.5% of participants had at least one TOI marker: 31.2% had one, 11.9% two, 3.7% three, and 0.8% four. The number of TOI markers increased according to the BP risk groups: the percentage of participants with more than one TOI in the low-, mid-, and high groups based on clinic BP was 6.7%, 19.1%, and 21.8% (p=0.02), and based on ABP was 9.6%, 15.8%, and 32.2% (p<0.001). In a multivariable regression analysis, both clinic BP percentile and ambulatory SBP index were independently associated with the number of TOI markers. When both clinic and ABP were included in the model, only the ambulatory SBP index was significantly associated with the number of markers.

Conclusion

High SBP, especially when assessed by ABPM, was associated with an increasing number of subclinical cardiovascular injury markers in adolescents.

Screening and Management of Pediatric High Blood Pressure-Challenges to Implementing the Clinical Practice Guideline

PURPOSE OF REVIEW

Elevated blood pressure (BP) and hypertension in childhood convey risk for hypertension and cardiovascular events in adulthood. Early recognition of abnormal BPs is key to preventing or lessening this risk. However, the process for making the diagnosis of hypertension is complex, and overall adherence to the 2017 American Academy of Pediatrics Clinical Practice Guidelines (CPG) is poor. We will review obstacles to adherence to the CPG and approaches designed to improve the diagnosis and management of hypertension in children.

RECENT FINDINGS

Baseline data from the multi-center quality improvement intervention, "Boosting Primary Care Awareness and Treatment of Hypertension" (BP-CATCH), demonstrate that childhood hypertension remains underdiagnosed. Other studies confirm a lack of compliance with the process outlined in the CPG. The provision of electronic prompts, coaching, and education results in modest improvements. The combination of embedded medical record tools and education seems to offer the most hope for improvement.

Association of Blood Pressure-Related Increase in Vascular Stiffness on Other Measures of Target Organ Damage in Youth

BACKGROUND

Hypertension-related increased arterial stiffness predicts development of target organ damage (TOD) and cardiovascular disease. We hypothesized that blood pressure (BP)-related increased arterial stiffness is present in youth with elevated BP and is associated with TOD.

METHODS

Participants were stratified by systolic BP into low- (systolic BP <75th percentile, n=155), mid- (systolic BP ≥80th and <90th percentile, n=88), and high-risk BP categories (≥90th percentile, n=139), based on age-, sex- and height-specific pediatric BP cut points. Clinic BP, 24-hour ambulatory BP monitoring, anthropometrics, and laboratory data were obtained. Arterial stiffness measures included carotid-femoral pulse wave velocity and aortic stiffness. Left ventricular mass index, left ventricular systolic and diastolic function, and urine albumin/creatinine were collected. ANOVA with Bonferroni correction was used to evaluate differences in cardiovascular risk factors, pulse wave velocity, and cardiac function across groups. General linear models were used to examine factors associated with arterial stiffness and to determine whether arterial stiffness is associated with TOD after accounting for BP.

RESULTS

Pulse wave velocity increased across groups. Aortic distensibility, distensibility coefficient, and compliance were greater in low than in the mid or high group. Significant determinants of arterial stiffness were sex, age, adiposity, BP, and LDL (low-density lipoprotein) cholesterol. Pulse wave velocity and aortic compliance were significantly associated with TOD (systolic and diastolic cardiac function and urine albumin/creatinine ratio) after controlling for BP.

CONCLUSIONS

Higher arterial stiffness is associated with elevated BP and TOD in youth emphasizing the need for primary prevention of cardiovascular disease.

Pediatric and Adult Ambulatory Blood Pressure Thresholds and Blood Pressure Load as Predictors of Left Ventricular Hypertrophy in Adolescents

[Figure: see text].

Use of Automated Office Blood Pressure Measurement in the Evaluation of Elevated Blood Pressures in Children and Adolescents

OBJECTIVES

To determine the level of agreement between automated office blood pressures (AOBP), auscultated or manual office BP (manual office blood pressure), and 24-hour ABPM, and to explore the ability of AOBP and manual office blood pressure to correctly identify daytime ambulatory hypertension in children.

STUDY DESIGN

We retrospectively compared BPs obtained by AOBP and manual office blood pressure to predict daytime hypertension on ABPM. Six BPs were taken by AOBP followed by manual office blood pressure. Office hypertension was defined by BPs ≥95th percentile for sex and height percentiles for those <13 years of age and a BP of ≥130/80 mm Hg for ages ≥13 years. Daytime ambulatory hypertension was diagnosed if mean wake BPs were ≥95th percentile and BP loads were ≥25%. Application of adult ABPM thresholds for daytime hypertension (130/80 mm Hg) was assessed in ages ≥13 years. Sensitivity and specificity were calculated considering ABPM as the reference.

RESULTS

Complete data were available for 187 patient encounters. Overall, the best agreement was found if both AOBP and manual office blood pressure showed hypertension, but owing to low sensitivity up to 49% of children with hypertension would be misclassified. The use of adult thresholds for ABPM did not improve agreement.

CONCLUSIONS

Neither AOBP nor manual office blood pressure confirm or exclude daytime ambulatory hypertension with confidence. These results suggest an ongoing role for ABPM in evaluation of hypertension in children.

Subclinical Systolic and Diastolic Dysfunction Is Evident in Youth With Elevated Blood Pressure

Hypertension is associated with cardiovascular events in adults. Subclinical changes to left ventricular strain and diastolic function have been found before development of decreased left ventricular ejection fraction and cardiovascular events. Our objective was to study effects of blood pressure (BP) on ventricular function in youth across the BP spectrum. Vital signs and labs were obtained in 346 participants aged 11 to 19 years who had BP categorized as low-risk (N=144; systolic BP <75th percentile), mid-risk (N=83; systolic BP ≥80th and <90th percentile), and high-risk (N=119; systolic BP ≥90th percentile). Echocardiography was performed to assess left ventricular strain and diastolic function. Differences between groups were analyzed by ANOVA. General linear models were constructed to determine independent predictors of systolic and diastolic function. Mid-risk and high-risk participants had greater adiposity and more adverse metabolic labs (lower HDL [high-density lipoprotein], higher glucose, and higher insulin) than the low-risk group. Mid-risk and high-risk participants had significantly lower left ventricular ejection fraction and peak global longitudinal strain than the low-risk group (both P≤0.05). The E/e' ratio was higher in the high-risk group versus the low-risk and mid-risk groups, and the e'/a' ratio was lower in the high-risk versus the low-risk group (both P≤0.05). BP and adiposity were statistically significant determinants of left ventricular systolic and diastolic function. Subclinical changes in left ventricular systolic and diastolic function can be detected even at BP levels below the hypertensive range as currently defined.

Changes in Ambulatory Blood Pressure Phenotype over Time in Children and Adolescents with Elevated Blood Pressures

OBJECTIVE

To determine the stability of ambulatory blood pressure monitoring (ABPM) over time in children referred for evaluation of elevated BPs and assess for factors predicting change.

STUDY DESIGN

This retrospective chart review conducted at Seattle Children's Hospital and University of Pittsburgh Medical Center Children's Hospital of Pittsburgh identified 124 children referred for elevated BPs with 2 ABPM studies at least 6 months apart. All subjects received lifestyle counseling. Subjects with secondary hypertension (HTN) or on antihypertensive medication were excluded. ABPM phenotype was classified using American Heart Association guidelines as showing normal BP, prehypertension, and HTN. Generalized linear mixed effect regression models were used to regress stable, improving, or worsening HTN outcomes at study follow-up on baseline BP index and load variables.

RESULTS

The median age of patients was 14.1 years (73% males) and the median interval between studies was 18 months. ABPM phenotype changed in 58 of 124 children, with 16% worsening and 31% improving. Older age was associated with persistence of HTN. Although not significant, decrease in body mass index z-score tracked with sustained normal ambulatory BPs.

CONCLUSIONS

Although the sample size is small, our study suggests ABPM phenotype shows variability over time. Further study is required to identify factors supporting risk for progression of ABPM phenotype over time.

Prediction of Ambulatory Hypertension Based on Clinic Blood Pressure Percentile in Adolescents

Ambulatory blood pressure (BP) monitoring provides a more precise measure of BP status than clinic BP and is currently recommended in the evaluation of high BP in children and adolescents. However, ambulatory BP monitoring may not always be available. Our aim was to determine the clinic BP percentile most likely to predict ambulatory hypertension. We evaluated clinic and ambulatory BP in 247 adolescents (median age, 15.7 years; 63% white; 54% male). Clinic BP percentile (based on the fourth report and the 2017 American Academy of Pediatrics clinical practice guidelines) and ambulatory BP status (normal versus hypertension) were determined by age-, sex-, and height-specific cut points. Sensitivity and specificity of different clinic BP percentiles and cutoffs to predict ambulatory hypertension were calculated. Forty (16%) and 67 (27%) patients had systolic hypertension based on the fourth report and the 2017 guidelines, respectively, whereas 38 (15%) had wake ambulatory systolic hypertension. The prevalence of ambulatory wake systolic hypertension increased across clinic systolic BP percentiles, from 3% when clinic systolic BP was <50th percentile to 41% when ≥95th percentile. The 2017 guidelines' 85th systolic percentile had similar sensitivity (86.8%) and better specificity (57.4% versus 48.1%) than elevated BP (≥90th percentile or ≥120 mm Hg) to diagnose ambulatory hypertension. When evaluating adolescents for hypertension, 2017 guidelines' clinic systolic 85th percentile may be the optimal threshold at which to perform ambulatory BP monitoring.

SHIP-AHOY (Study of High Blood Pressure in Pediatrics: Adult Hypertension Onset in Youth)

Although hypertension is identifiable in children and adolescents, there are many knowledge gaps on how to best define and manage high blood pressure in the young. SHIP-AHOY (Study of High Blood Pressure in Pediatrics: Adult Hypertension Onset in Youth) is being conducted to address these knowledge gaps. Five hundred adolescents will be recruited and will undergo ambulatory blood pressure monitoring, echocardiographic, vascular, and cognitive assessments, as well as epigenetic studies to identify mechanisms that underlie the development of hypertensive target organ damage. Details of the design and methods that will be utilized in SHIP-AHOY are presented here, as well as baseline characteristics of the first 264 study participants. The primary aim of the study is to develop a risk-based definition of hypertension in the young that will result in better understanding of the transition from blood pressure in youth to adult cardiovascular disease.

Angiotensin II and the Natriuretic and Blood Pressure Response to Mental Stress in African Americans

Objective

To test the hypothesis that Angiotensin II (Ang II) is a contributing factor to the response pattern in African Americans (AAs) who retain rather than excrete sodium during mental stress.

Design/Study Participants

Double-blind, randomized, cross-over trial of 87 healthy AAs aged 18 to 50 years.

Interventions

The study participants received either a placebo or irbesartan, (150 mg PO), an Ang II receptor antagonist, for seven days prior to stress testing. Urinary sodium excretion (UNaV) and systolic blood pressure (SBP) were collected prior to and throughout a mental stress protocol (rest and stress period).

Setting

A southeastern university.

Main Outcome Measures

Ang II, SBP, and sodium retention.

Results

During the placebo condition, 62 participants showed the expected increase in UNaV (excreters) while 25 participants reduced UNaV during stress (retainers). Irbesartan retainers demonstrated a reversal in the direction of their natriuretic response, now increasing UNaV in response to stress (∆ UNaV of -.094 mmol/min with placebo vs .052 mmol/min on irbesartan; P<.001). In excreters, irbesartan reduced SBP levels during both rest (-2.36 mm Hg; P=.03) and stress (-4.59;P<.0001), and an even more pronounced reduction in SBP was demonstrated by retainers on treatment during both rest (-4.29 mm Hg; P=.03) and stress (-6.12; P<.001).

Conclusions

Ang II contributes to sodium retention in retainers. Furthermore, our findings indicate that suppression of Ang II has a beneficial effect on SBP during rest and stress in this population.

Ambulatory Blood Pressure Control in Children and Young Adults After Kidney Transplantation

BACKGROUND

Ambulatory blood pressure (BP) monitoring (ABPM) is the preferred method to characterize BP status, and its use in kidney transplant recipients is increasing. Data on longitudinal ambulatory BP (ABP) trends in pediatric and young adult kidney transplant recipients are limited.

METHODS

Retrospective review of a large cohort of children and young adults following kidney transplantation and evaluation of their ABP status over time and its associations with any patient and clinical characteristics.

RESULTS

Two hundred and two patients had baseline ABPM available for analysis, and 123 of them had a follow up (median time 2.3 years) ABPM. At the time of follow up, more patients were treated for hypertension (80% vs. 72%, P = 0.02), and less patients had ambulatory hypertension (36% vs. 54%, P = 0.005), uncontrolled or untreated, compared with baseline, with 45% of all patients classified as having controlled hypertension (compared to 26% at baseline, P = 0.002). Prevalence of ambulatory hypertension decreased only in patients who were less than 18 years old at baseline. High baseline mean 24-hour systolic BP was independently associated with persistent hypertension.

CONCLUSIONS

In young kidney transplant recipients followed by ABPM, the prevalence of ambulatory hypertension decreases over time, mainly due to the increased number of patients with controlled hypertension.

Abstract P479: Stability of Ambulatory Blood Pressure Patterns Over Time in Children and Adolescents

Little is known about the stability of ambulatory blood pressure (ABP) patterns in children and adolescents undergoing evaluation for high blood pressure (HBP). It is possible that children with initially normal ABP may progress to hypertension (HT) or pre-hypertension (PHT), or that those with initial PHT or HT may be normal on repeat. Our objective was to assess stability of ABP patterns over time in children with HBP.

We analyzed changes in ABP classification in patients undergoing a minimum of 2 ABP monitoring (ABPM) studies at least 0.5 years (yrs) apart. Exclusion criteria included known secondary HT, therapy with antihypertensive medication and inadequate recordings. ABPM were interpreted according to the 2014 AHA guidelines using BP thresholds of 95 th % for sex and height for children ≤17 yrs. For those > 18 yrs awake and sleep thresholds were 140/85 and 120/70, respectively. Dipping was considered normal if > 10%, blunted if <10% and reversed if < 0%. For those with > 2 ABPM the difference between the 1 st and last were analyzed.

Two hundred ABPM on 100 patients (76 males; median age 14.6 yrs at 1st ABPM) were analyzed. Median interval between ABPM was 1.5 yrs. ABP classification was stable in 53% (53/100). As shown in the table 50% (9/18) of those with normal ABPM showed progression to PHT or HT on follow up. PreHT progressed in 31% (8/26) and improved in 38% (10/26). HT improved in 43% (20/46). Dipping designation was stable in 70% (70/100); but blunted dipping normalized in 48% (10/21).

In our population ABP patterns were not stable over time, supporting the need for follow up studies even with normal initial ABPM. If confirmed in larger studies, these findings support greater use of repeat ABPM.

The Association of Pediatric Obesity With Nocturnal Non-Dipping on 24-Hour Ambulatory Blood Pressure Monitoring

BACKGROUND

Obesity has been linked with abnormal nocturnal dipping of blood pressure (BP) in adults, which in turn is associated with poor cardiovascular outcomes. There are few data regarding abnormal dipping status in the obese pediatric population. The goal of this study was to further describe the relationship between obesity and non-dipping status on ambulatory blood pressure monitor (ABPM) in children.

METHODS

We conducted a cross-sectional study using a database of patients aged 5-21 years who had undergone 24-hour ABPM at Seattle Children's Hospital from January 2008 through May 2014. Subjects were grouped by body mass index (BMI) into lean (BMI 15th-85th percentile) and obese (BMI >95th percentile) groups.

RESULTS

Compared to lean subjects (n = 161), obese subjects (n = 247) had a prevalence ratio (PR) for non-dipping of 2.15, adjusted for race (95% confidence interval (CI) = 1.25-3.42). Increasing severity of obesity was not further associated with nocturnal non-dipping. Nocturnal non-dipping was not associated with left ventricular hypertrophy (PR = 1.01, 95% CI = 0.71-1.44).

CONCLUSIONS

These results suggest that in children, just as in adults, obesity is related to a relatively decreased dipping in nocturnal BP.

Sodium intake and blood pressure in children

Elevation of blood pressure (BP) and the risk for progression to hypertension (HTN) is of increasing concern in children and adolescents. Indeed, it is increasingly recognized that target organ injury may begin with even low levels of BP elevation. Sodium intake has long been recognized as a modifiable risk factor for HTN. While it seems clear that sodium impacts BP in children, its effects may be enhanced by other factors including obesity and increasing age. Evidence from animal and human studies indicates that sodium may have adverse consequences on the cardiovascular system independent of HTN. Thus, moderation of sodium intake over a lifetime may reduce risk for cardiovascular morbidity in adulthood. An appetite for salt is acquired, and intake beyond our need is almost universal. Considering that eating habits in childhood have been shown to track into adulthood, modest sodium intake should be advocated as part of a healthy lifestyle.

Recurrent Page kidney in a child with a congenital solitary kidney requiring capsular artery embolization

We report an unusual case of a child with a congenital solitary functional kidney complicated by a sports-related posttraumatic Page kidney. The child developed severe hypertension and renal insufficiency requiring percutaneous intervention to preserve renal function. The literature is sparse with no definitive guidelines for the treatment of Page kidney. Following the initial unsuccessful treatment with percutaneous drainage and sclerotherapy procedures, the child ultimately required catheter-directed particle embolization of the capsular arteries to resolve a recurrent subscapsular hematoma definitively. This was successful in preserving renal function and stabilization of the clinical manifestations of the Page kidney.

Concepts guiding therapy for hypertension in children

Increasing attention has been focused on identifying children with prehypertension and hypertension (HTN). Obesity and low birthweight are two risk factors that predispose children to develop HTN during their childhood years or later as adults. Early onset of pre-HTN and HTN increases the lifetime risk for cardiovascular sequelae. Lifestyle modification should be part of the initial recommendations for management of all hypertensive children. In those children requiring pharmacologic therapy, the choice of medication should be guided by the etiology of HTN, the needs of the child and the risk and benefit profiles of the various drug classes. The long-term impact of antihypertensive therapy in children is not known. Concerns regarding the effects of HTN and its treatment on cognitive function are of particular importance in the growing child and warrant further study. Ongoing investigations that offer promise for innovative therapeutic approaches in the future are discussed.

Stress-induced sodium retention and hypertension: a review and hypothesis

Hypertension--an important health problem in industrialized nations--is particularly significant in blacks and obese individuals, in whom it is hypothesized to result from impaired renal sodium regulation. We reviewed studies that identified individuals with impaired sodium regulation by examining the natriuretic response to mental stress. A significant percentage of black and obese individuals retain or have a diminished natriuretic response to mental stress despite increased blood pressure (BP). This contributes a volume component to the normal resistance-mediated BP increase, and BP remains elevated after the stressor ceases until the volume expansion diminishes. The stress exposes these individuals to greater cardiovascular load. This response pattern has been linked to renin-angiotensin-aldosterone system activity, and is associated with premature target-organ damage. Assessing stress-induced sodium retention provides a method to identify patients with impaired sodium regulation without using a dietary protocol that poses adherence difficulties, or complicated laboratory assessments. Furthermore, research using this technique indicates the effectiveness of renin-angiotensin-aldosterone system blockers in correcting impaired sodium regulation and consequent hypertension in these individuals.

Racial differences in microalbumin excretion in healthy adolescents

It has been suggested that "normal" levels of urine albumin excretion rate (AER) may be predictive of an increased risk for progression of hypertension, cardiovascular morbidity, and mortality. No data are available on the effect of race and gender on AER in normal youth. We evaluated AER in timed urine samples in subjects participating in a study of stress-induced pressure natriuresis. A total of 317 healthy, normotensive adolescents aged 15 to 18 years (155 males and 162 females; 216 blacks and 101 whites) participated in a 5-hour testing protocol, which included a 1-hour period of mental stress preceded and followed by a 2-hour rest period. AER (micrograms per minute) was determined after 60 minutes of rest, and log transformation was used to normalize the data. AER was significantly higher in blacks as compared with whites (P=0.006). We also found a race-by-sex interaction, which was driven by the low albumin excretion in white females (P=0.036). Indexing urine albumin to creatinine excretion revealed the same pattern. Among blacks, AER was also higher in subjects who demonstrated impaired stress-induced pressure natriuresis versus those with normal sodium excretion (P=0.024). AER was related to blood pressure only in African-American males. The relative elevation of AER in normotensive black adolescents and the association with impaired pressure natriuresis and blood pressure is noteworthy. These findings suggest that albumin excretion may be a marker for a population at increased risk for the development of vascular and renal injury even before the manifestation of hypertension.

Prevalence, prevention, and treatment of microalbuminuria and proteinuria in children with sickle cell disease

Microalbuminuria (MA) and proteinuria (P) are believed to be precursors of sickle cell nephropathy. We analyzed our longitudinal data on MA/P in children with sickle cell disease (SS) to define the age of onset, association with age, sex, and hemoglobin, and to explore the safety and efficacy of hydroxyurea and angiotensin converting enzyme inhibitor (ACEI) therapy. Data on 191 patients with SS (ages 3 to 20 y) with a mean follow up of 2.19 years+/-2.05 were available. Urine MA was measured yearly with follow-up testing if abnormal. Prevalence of MA/P was 19.4%. Increasing age and lower hemoglobin levels were related to MA/P but sex was not. Microalbumin excretion normalized in 44% of patients treated with hydroxyurea and 56% of patients treated with ACEI. Hyperkalemia developed in 4 ACEI patients resulting in discontinuation of treatment in 3 children. In summary, MA/P often develops in childhood and preventive and treatment strategies for sickle cell nephropathy should be a focus of pediatric programs. Our preliminary data suggest that although both hydroxyurea and ACEI therapy may be beneficial for MA/P, hyperkalemia may limit the utility of ACEI.

Acute renal failure during lisinopril and losartan therapy for proteinuria

The use of combined therapy with an angiotensin-converting enzyme (ACE) inhibitor and an angiotensin II receptor blocker (ARB) for treatment of proteinuria has been gaining support. Limited data are available regarding this treatment in the pediatric population. This report describes a case of acute compromise of renal function associated with hypotension in a 7-year-old boy treated with the ACE inhibitor lisinopril and the ARB losartan. It emphasizes the need for close surveillance of renal function and blood pressure during such therapy even in patients with relative preservation of renal function. Further investigation into the utility and safety of dual therapy with an ACE inhibitor plus an ARB in pediatric patients is warranted. Key Words: renal failure, proteinuria, angiotensin-converting enzyme inhibitor, ACEI, angiotensin II receptor blocker, ARB.

Ethnic and Gender Differences in Ambulatory Blood Pressure Trajectories

Background— Cross-sectional studies demonstrated ethnic and gender differences in ambulatory blood pressure patterns, but little is known about the longitudinal development of these differences.

Methods and Results— Twenty-four-hour ambulatory blood pressure was measured up to 12 times (5 times on average) over a 15-year period in 312 African Americans (AAs) and 351 European Americans aged 7 to 30 years. Multivariate individual growth curves across age were created for daytime and nighttime blood pressure jointly. For both daytime and nighttime systolic blood pressure (SBP), AAs and males had higher levels ( P <0.001) than European Americans and females. Males also showed a greater increase with age ( P <0.001) than females. For nighttime SBP, a faster increase of SBP with age ( P <0.01) in AAs was additionally observed. The ethnic difference in nighttime SBP levels and its increase with age were significantly larger than in daytime SBP. For daytime and nighttime diastolic blood pressure, AAs had higher levels than European Americans ( P <0.001), and this difference was significantly larger at night. From late adolescence onward, males showed a greater increase in diastolic blood pressure with age than females. Ethnic and gender differences persisted after adjustment for height, body mass index, socioeconomic status, and stress-related coping styles. Family history of essential hypertension explained ethnic differences in daytime SBP.

Conclusions— We observed significant ethnic and gender differences in longitudinal trajectories of ambulatory blood pressure in youth and young adults. The blunted nocturnal decline and its exacerbation with age in AAs corroborate and extend findings of cross-sectional studies.

Obesity and renal transplant outcome: a report of the North American Pediatric Renal Transplant Cooperative Study

OBJECTIVE

Obesity is increasing in the end-stage renal disease population. Studies that have evaluated the effect of obesity on transplant outcomes in adults have yielded varying results. This issue has received little attention in the pediatric population.

METHODS

We performed a retrospective study of the effect of obesity on pediatric renal transplant outcomes using the North American Pediatric Renal Transplant Cooperative Study database. Registry data from 1987 through 2002 on 6658 children aged 2 to 17 years were analyzed. Obesity was defined by a BMI >95th percentile for age.

RESULTS

Overall, 9.7% were obese with an increase noted in recent years (12.4% after 1995 vs 8% before 1995). Obese children were significantly younger and shorter and had been on dialysis for a longer time than nonobese children. There was no significant difference in the overall patient and allograft survival between the 2 groups. However, obese children aged 6 to 12 years had higher risk for death than nonobese patients (adjusted relative risk: 3.65 for living donor; adjusted relative risk: 2.94 for cadaver), and death was more likely as a result of cardiopulmonary disease (27% in obese vs 17% in nonobese). Overall, graft loss as a result of thrombosis was more common in obese as compared with nonobese (19% vs 10%).

CONCLUSIONS

Obesity is an increasing problem in children who present for transplantation and may have an adverse effect on allograft and patient survival.

Nephrotic syndrome after conversion to alternate day steroids in two children with a history of recurrent FSGS

FSGS is a common indication for kidney transplantation in children. However, transplantation is often complicated by recurrence of FSGS in the transplanted kidney, resulting in nephrotic syndrome and an increased risk of graft loss. Acute treatment strategies for recurrent FSGS include plasmapheresis and increased immunosuppressive therapy. There is little information on the long-term management of immunosuppression in these patients. We describe two children who were successfully treated with plasmapheresis for recurrent FSGS that occurred immediately post-transplant. Nephrotic syndrome reappeared years later when the patients were converted from daily to alternate day prednisone. In children with a history of FSGS, caution is necessary when altering the dosing schedule of prednisone.

Acquired free protein S deficiency in children with steroid resistant nephrosis

Plasma and urine concentrations of protein S were measured in five children with steroid-resistant nephrotic syndrome. It was found that plasma free protein S was reduced in three out of the five patients studied. Thus, acquired free protein S deficiency does occur in children with nephrotic syndrome and is one of many factors which may place them at risk for a thromboembolic event.

Tissue differences in antioxidant enzyme gene expression in response to endotoxin

The effect of endotoxin on antioxidant gene expression and antioxidant enzyme activity in homogenates of the heart, liver, and kidney from Sprague-Dawley rats was compared by quantitation of m-RNA and enzyme activities. Alterations in the message level for Cu-Zn superoxide dismutase (SOD), Mn SOD, and catalase varied with the tissue type, length of exposure to endotoxin, and dose of endotoxin. In general, endotoxin treatment reduced Cu-Zn SOD expression in the heart and liver, but had no noticeable effect in the kidney. Mn SOD message levels were increased in the heart and kidney but decreased in the liver. Catalase expression was reduced in the kidney and increased marginally in the heart and liver. With regard to enzyme activity, endotoxin treatment reduced Cu-Zn SOD activity in the heart, liver, and kidney. Mn SOD activity showed little change in the heart, but increased in the liver and, to a lesser extent, in the kidney. Catalase activity showed little change in the heart and kidney but was decreased at 12 h in the liver. The differing responses of tissues to the oxidant stress of endotoxin exposure should be considered when evaluating the effect of endotoxin on antioxidant enzymes.

Effect of rifampin on Staphylococcus aureus colonization in children on chronic peritoneal dialysis

The efficacy of rifampin in eliminating Staphylococcus aureus colonization was evaluated in a pediatric peritoneal dialysis population. Six children with documented nasal colonization were treated for 7 days with rifampin and cloxacillin. Although antimicrobial therapy eliminated nasal carriage in all patients, recolonization occurred in 66%. Exit site colonization proved difficult to eradicate with negative cultures documented in only 3 of 5 children after rifampin/cloxacillin therapy. Although S. aureus carriage is a risk factor for S. aureus infections, efforts to eradicate carriage with rifampin are hindered by rapid recolonization.

Impairment of peroxisomal beta-oxidation system by endotoxin treatment

It is now clear that peroxisomes play a crucial role in many cellular processes, including the beta-oxidation of very long chain fatty acids. Recently, mammalian peroxisomes have been shown to contain the antioxidant enzymes, superoxide dismutase and glutathione peroxidase, in addition to catalase. The presence of these enzymes in peroxisomes suggests that peroxisomes undergo oxidative stress in normal and disease states. As an indicator of the potential impact of an oxidative stress on peroxisomal functions, we evaluated the effect of endotoxin exposure on the beta-oxidation enzyme system in rat liver. Peroxisomes were isolated from liver homogenates by differential and density gradient centrifugations. Endotoxin treatment decreased the beta-oxidation of lignoceric acid to 56% of control values (p < 0.01). The specific activity of the rate limiting enzyme in the system, acyl-CoA oxidase, was decreased to 73% of control values (p < 0.05). Immunoblot analysis revealed a 25% decrease in the 21KD subunit of the acyl-CoA oxidase protein. In contrast, the protein levels of the other enzymes in the pathway, trifunctional protein and 3-ketoacyl-CoA thiolase, were increased by 10 and 15%, respectively. These findings suggest that impairment of beta-oxidation of lignoceric acid by endotoxin treatment is due primarily to a reduction in the activity and protein level of the key enzyme, acyl-CoA oxidase. Oxidative stresses such as endotoxin exposure may have deleterious effects on important peroxisomal functions, such as beta-oxidation of very long chain fatty acids.

Tumor necrosis factor alpha modulates parathyroid hormone action in UMR-106-01 osteoblastic cells

Tumor necrosis factor (TNF-alpha) has been shown to play an important role in local control of bone remodeling. The interaction of TNF-alpha and PTH was evaluated in UMR-106-01 cells, a phenotypic osteoblastic osteosarcoma cell line. We examined the influence of TNF-alpha on the two signal transduction systems triggered by PTH in UMR-106-01 cells, adenylate cyclase and free cytosolic calcium ([Ca2+]i). cAMP generation was inhibited in TNF-alpha-pretreated cells by 69, 61, 34, and 21% at PTH concentrations of 0.1, 1, 10, and 100 nM, respectively. Inhibition was seen at TNF-alpha doses of 100-1500 units/ml after a minimum incubation time of 12 h. TNF-alpha inhibition of the PTH-stimulated increase in [Ca2+]i was even more pronounced: treated cells showed no change in baseline [Ca2+]i after stimulation with 40 nM PTH. Treatment with TNF-alpha was also found to inhibit both arms of the PTH response in the nontransformed osteoblastic cell line, MC3T3-E1. TNF-alpha treatment did not alter cAMP generation in response to PGE2. TNF-alpha inhibition of the PTH-stimulated cAMP response was reversed completely by addition of cholera toxin (5 micrograms/ml) and partially by forskolin (10 microM) but not pertussis toxin (100 and 500 ng/ml). Scatchard analysis using PTHrP revealed that TNF-alpha treatment reduced the number of receptors but had no effect on KD. These findings suggest that TNF-alpha inhibits the osteoblastic response to PTH at least in part because of a reduction in receptor number. Further investigation is indicated to provide insight into the interaction of calciotropic hormones and cytokines in vivo.

Peroxisomal participation in the cellular response to the oxidative stress of endotoxin

Exposure to a sublethal dose of endotoxin offers protection against subsequent oxidative stresses. The cellular mechanisms involved in generating this effect are not well understood. We evaluated the effect of endotoxin on antioxidant enzymes in liver peroxisomes. Peroxisomes have recently been shown to contain superoxide dismutase (SOD) and glutathione peroxidase (GPX) in addition to catalase. Peroxisomes were isolated from liver homogenates by differential and density gradient centrifugations. Endotoxin treatment increased the specific activity of SOD and GPX in peroxisomes to 208% and 175% of control activity, respectively. These findings correlated with increases in peroxisomal SOD and GPX proteins observed by immunoblot. Although the quantity of catalase protein was increased when assessed by immunoblot analysis, the specific activity of catalase was decreased to 68% of control activity. Activation of catalase with ethanol only restored catalase activity to control levels suggesting that catalase had undergone irreversible inactivation. The observed increase in GPX activity may represent a compensatory mechanism triggered by accumulating H2O2. The data presented here suggest for the first time that mammalian peroxisomal antioxidant enzymes are altered during the oxidative injury of endotoxin treatment.

Acute peritoneal dialysis utilizing a non-luminal channeled catheter in infants

Acute peritoneal dialysis in unstable infants is at times plagued by early catheter malfunction secondary to omental plugging in both rigid acute catheters and conventional Tenckhoff catheters. This problem is inherent to the design of catheters using sideports for outflow and is enhanced by the tenacity of the omentum in this population in walling off foreign bodies. We have modified and utilized a non-luminal, channeled surgical drain for acute peritoneal dialysis in infants to avoid this problem. Five infants ranging in age from 2 days to 7 months were dialyzed acutely in a Pediatric Intensive Care Unit setting for periods ranging from 5 to 34 days utilizing this modified catheter. The infants ranged in weights from 1.96 to 8 Kg. Catheters were placed by a surgeon and peritoneal dialysis was initiated using a Y-setup. In none of the patients was there loss of catheter function secondary to omental plugging. Three patients subsequently died of their underlying illness and two recovered renal function. Two acute catheters were subsequently changed to conventional Tenckhoff catheters when it became apparent that dialysis would need to be performed for a prolonged time. The acute catheter which was used has a four channel cloverleaf appearance when cut in cross section with no central lumen. There is a transition to a luminal catheter outside the peritoneal cavity. The advantage of the cloverleaf configuration is the ability to exchange fluid along its entire intraperitoneal length, thereby excluding a defined area of catheter sideports where omentum can occlude the system causing a ball valve phenomenon.(ABSTRACT TRUNCATED AT 250 WORDS)

Vesicoureteral reflux and urinary tract infections in renal transplant recipients

Fifty-six children who received kidney transplants were evaluated for postoperative vesicoureteral reflux and frequency of urinary tract infection. Two methods of ureteral implantation were compared: a nonantireflux extravesicular ureteroneocystostomy and an antireflux intravesicular ureteroneocystostomy. Reflux was found in 79% of children who had the nonantireflux procedure vs 19% of children who had the antireflux procedure. This disparity was present regardless of sex and age. Infections occurred at a rate of one per 11 patient-months after the nonantireflux procedure vs one per 40 patient-months after the antireflux procedure. Regardless of surgical technique, the incidence of infection was higher in children with reflux. The potentially harmful effect of infection with reflux warrants concern. Because of the need to maximize allograft function for a longer time period, an antireflux procedure is recommended in all pediatric kidney transplants.