Higher risk of cerebral palsy, seizures/epilepsy, visual- and hearing impairments, cancer, injury and child abuse in children with congenital anomalies: Data from the EUROlinkCAT study

AIM

The aim is to examine the risk of cerebral palsy, seizures/epilepsy, visual- and hearing impairments, cancer, injury/poisoning and child abuse in children with and without a congenital anomaly up to age 5 and 10 years.

METHODS

This is a population-based data linkage cohort study linking information from the European Surveillance of Congenital Anomalies network (EUROCAT) and birth registries to hospital discharge databases. We included 91 504 live born children with major congenital anomalies born from 1995 to 2014 from nine EUROCAT registries in five countries and 1 960 727 live born children without congenital anomalies (reference children). Prevalence and relative risk (RR) were estimated for each of the co-morbidities using Kaplan-Meier survival estimates.

RESULTS

Children with congenital anomalies had higher risks of the co-morbidities than reference children. The prevalences in the reference children were generally very low. The RR was 13.8 (95% CI 12.5-15.1) for cerebral palsy, 2.5 (95% CI 2.4-2.6) for seizures/epilepsy, 40.8 (95% CI 33.2-50.2) for visual impairments, 10.0 (95% CI 9.2-10.9) for hearing loss, 3.6 (95% CI 3.2-4.2) for cancer, 1.5 (95% CI 1.4-1.5) for injuries/poisoning and 2.4 (95% CI 1.7-3.4) for child abuse.

CONCLUSION

Children with congenital anomalies were more likely to be diagnosed with the specified co-morbidities compared to reference children.

Transesophageal echocardiography of cardiac function in Nile crocodiles - A novel tool for assessing complex hemodynamic patterns

BACKGROUND

The crocodilian heart is unique among reptiles with its four-chambered structure and complete intracardiac separation of pulmonary and systemic blood flows and pressures. Crocodiles have retained two aortic arches; one from each ventricle, that communicate via Foramen of Panizza, immediately distally from the aortic valves. Moreover, crocodiles can regulate vascular resistance in the pulmonary portion of the right ventricular outflow tract (RVOT). These unique features allow for a complex regulation of shunting between the pulmonary and systemic circulations. Studies on crocodile shunting have predominantly been based on invasive measurements, but here we report on the use of echocardiography.

METHODS

Experiments were performed on seven pentobarbital anaesthetized juvenile Nile crocodiles (length and mass of 192 ± 13 cm and 26 ± 5 kg, respectively). Echocardiographic imaging was performed using a transesophageal (TEE) approach. All images were EKG-gated.

RESULTS

We obtain excellent views of cardiac structures and central vasculature through the esophagus. Standard imaging planes were defined for both long- and short axis views of the left ventricle and truncus arteriosus. For the RV, only a short axis view could be obtained. Color Doppler was used to visualize flow. Pulsed waved Doppler for measuring flow profiles across the atrioventricular valves, in the two RVOTs and the left ventricular outflow tract. Shunting across the Foramen of Panizza could be visualized and gated to the EKG.

CONCLUSION

TEE can be used to image the unique features of the crocodile heart and allow for in-vivo imaging of the complex shunting hemodynamics, including timing of cardiac shunts.

Oral-only antibiotics for bone and joint infections in children: study protocol for a nationwide randomised open-label non-inferiority trial

INTRODUCTION

Children with bone and joint infections are traditionally treated with intravenous antibiotics for 3-10 days, followed by oral antibiotics. Oral-only treatment has not been tested in randomised trials.

METHODS AND ANALYSIS

Children (3 months to 18 years) will be randomised 1:1 with the experimental group receiving high-dose oral antibiotics and the control group receiving intravenous antibiotics with a shift in both groups to standard oral antibiotics after clinical and paraclinical improvement. Children in need of acute surgery or systemic features requiring intravenous therapy, including septic shock, are excluded. The primary outcome is defined as a normal blinded standardised clinical assessment 6 months after end of treatment. Secondary outcomes are non-acute treatment failure and recurrent infection. Outcomes will be compared by a non-inferiority assumption with an inferiority margin of 5%.

ETHICS AND DISSEMINATION

The trial has the potential to reduce unnecessary hospitalisation and use of intravenous antibiotics in children with bone or joint infections. Due to the close follow-up, exclusion of severely ill children and predefined criteria for discontinuation of the allocated therapy, we expect the risk of treatment failure to be minimal.

TRIAL REGISTRATION NUMBER

NCT04563325.

Hospital Length of Stay and Surgery among European Children with Rare Structural Congenital Anomalies-A Population-Based Data Linkage Study

Little is known about morbidity for children with rare structural congenital anomalies. This European, population-based data-linkage cohort study analysed data on hospitalisations and surgical procedures for 5948 children born 1995-2014 with 18 rare structural congenital anomalies from nine EUROCAT registries in five countries. In the first year of life, the median length of stay (LOS) ranged from 3.5 days (anotia) to 53.8 days (atresia of bile ducts). Generally, children with gastrointestinal anomalies, bladder anomalies and Prune-Belly had the longest LOS. At ages 1-4, the median LOS per year was ≤3 days for most anomalies. The proportion of children having surgery before age 5 years ranged from 40% to 100%. The median number of surgical procedures for those under 5 years was two or more for 14 of the 18 anomalies and the highest for children with Prune-Belly at 7.4 (95% CI 2.5-12.3). The median age at first surgery for children with atresia of bile ducts was 8.4 weeks (95% CI 7.6-9.2) which is older than international recommendations. Results from the subset of registries with data up to 10 years of age showed that the need for hospitalisations and surgery continued. The burden of disease in early childhood is high for children with rare structural congenital anomalies.

European study showed that children with congenital anomalies often underwent multiple surgical procedures at different ages across Europe

AIM

Children with congenital anomalies often require surgery but data on the burden of surgery for these children are limited.

METHODS

A population-based record-linkage study in Finland, Wales and regions of Denmark, England, Italy and Spain. A total of 91 504 children with congenital anomalies born in 1995-2014 were followed to their tenth birthday or the end of 2015. Electronic linkage to hospital databases provided data on inpatient surgical procedures and meta-analyses of surgical procedures were performed by age groups.

RESULTS

The percentage of children having surgery in the first year was 38% with some differences across regions and 14% also underwent surgery at age 1-4 years. Regional differences in age at the time of their first surgical procedure were observed for children with cleft palate, hydronephrosis, hypospadias, clubfoot and craniosynostosis. The children had a median of 2.0 (95% CI 1.98, 2.02) surgical procedures before age 5 years with children with oesophageal atresia having the highest median number of procedures (4.5; 95% CI 3.3, 5.8).

CONCLUSION

A third of children with congenital anomalies required surgery during infancy and often more than one procedure was needed before age 5 years. There was no European consensus on the preferred age for surgery for some anomalies.

Preterm birth and prescriptions for cardiovascular, antiseizure, antibiotics and antiasthmatic medication in children up to 10 years of age: a population-based data linkage cohort study across six European regions

OBJECTIVES

Preterm children are exposed to many medications in neonatal intensive care units, but little is known about the effect of prematurity on medication use throughout infancy and childhood. We examined prescriptions of cardiovascular medication (CVM), antiseizure medication (ASM), antiasthmatic medication and antibiotics issued/dispensed in the first 10 years of life for very and moderately preterm children compared with term.

DESIGN

Population-based data linkage cohort study linking information from birth records to prescription records.

SETTING

Six registries from five countries in the EUROlinkCAT study.

PARTICIPANTS

The study population included 1 722 912 children, of whom 10 820 (0.6%) were very preterm (<32 weeks gestational age (GA)), 92 814 (5.4%) were moderately preterm (32-36 weeks GA), 1 606 643 (93.3%) were born at term (≥37 weeks GA) and 0.7% had missing GA. Children with major or minor congenital anomalies were excluded (including patent ductus arteriosus).

MAIN OUTCOME MEASURES

Relative risk (RR) of receiving a prescription for CVM, ASM, antiasthmatic and antibiotics.

RESULTS

Very preterm children had a higher RR of receiving a prescription for CVM and ASM than preterm children. For all preterm children, the RR of having a CVM prescription was 3.58 (95% CI 2.06 to 6.23); 2.06 (95% CI 1.73 to 2.41) for ASM; 1.13 (95% CI 0.99 to 1.29) for antiasthmatics and 0.96 (95% CI 0.93 to 0.99) for antibiotics in the first year of life. Increased prescription of CVM, ASM and antiasthmatics persisted for all 10 years of follow-up. Although the RR was highest for CVM and ASM, in absolute numbers more children received prescriptions for antibiotics (42.34%, 95% CI 38.81% to 45.91%) and antiasthmatics (28.40%, 95% CI 16.07% to 42.649%) than for CVM (0.18%, 95% CI 0.12% to 0.25%) and ASM (0.16%, 95% CI 0.13% to 0.20%) in the first year of life.

CONCLUSION

Preterm children had a higher risk of being prescribed/dispensed CVM, ASM and antiasthmatics up to age 10. This study highlights a need for further research into morbidity beyond age 10.

Prescription of cardiovascular medication in children with congenital heart defects across six European Regions from 2000 to 2014: data from the EUROlinkCAT population-based cohort study

OBJECTIVES

Advances in surgical management strategies have substantially reduced fatality from congenital heart defects (CHD). Decreased infant mortality might be expected, consequentially to result in greater morbidity in older children due to complications later in childhood and adolescence. This study aims to evaluate the use of cardiovascular medication (CVM) as an indicator of disease burden in children born with CHD in the first 10 years of life.

DESIGN

Population-based cohort study.

SETTING

Six population-based registries from the European Surveillance of Congenital Anomalies (EUROCAT) network participated. Data from live born children with major congenital anomalies (CA) born from 2000 to 2014 were linked to prescription databases. Four groups of children were analysed: CA, CHD, severe CHD (sCHD) and ventricular septal defect (VSD) without sCHD. Live born children without CA were included as reference group.

PARTICIPANTS

We obtained data on 61 038 children born with a CA, including 19 678 with CHD, 3392 with sCHD, 12 728 children with VSD without sCHD, and 1 725 496 reference children.

RESULTS

Children born with sCHD were the most likely to receive a CVM prescription (42.9%, 95% CI, 26.3 to 58.5) in the first year of life compared with 13.3% (6.7 to 22.0) of children with any CHD, 5.9% (3.7 to 8.7) of children with any CA and 0.1% (0.0 to 0.1) of reference children. Medication was less likely to be prescribed after the first year of life for sCHD; 18.8% (14.8 to 23.1) for children 1-4 years and 15.8% (12.0 to 20.1) 5-9 years. Children with sCHD were most likely to receive a diuretic (36.4%, 18.6 to 54.5), an antihypertensive (6.9%, 3.7 to 11.3) or a beta-blocker (5.5%, 2.9 to9.2).

CONCLUSION

Almost half of all children with sCHD were prescribed CVM in their first year of life. For all four groups of children with anomalies, the proportion of children with a CVM prescription decreased with age.

The exaggerated natriuresis of essential hypertension occurs independently of changes in renal medullary blood flow

AIMS

In patients with essential hypertension, abnormal renal sodium handling includes exaggerated natriuresis in response to extracellular volume expansion. We tested the hypothesis that exaggerated natriuresis is associated with increases in medullary and/or cortical renal blood flow.

METHODS

Patients with mild essential hypertension, but no signs of end organ damage, and control subjects were studied after 4 days of dietary standardization (<60 mmol Na⁺  day^-1 ) preceded in patients by a 14-day drug washout period. On the study day, subjects received a 4-hour intravenous volume expansion with saline (2.1% of body mass). Renal medullary and cortical blood flows were measured by PET scanning using H₂ ¹⁵ O as tracer; anatomical regions of interest were defined by contrast-enhanced CT scanning.

RESULTS

In patients, arterial blood pressure increased during volume expansion (107 ± 2-114 ± 3 mm Hg, P < 0.05) in contrast to the control group (92 ± 2-92 ± 2 mm Hg). Renal sodium excretion increased more in patients than in controls (+133 ± 31 µmol min^-1 vs +61 ± 14 µmol min^-1 , respectively, P < 0.05) confirming exaggerated natriuresis. During volume expansion, renal medullary blood flow did not change significantly in patients (2.8 ± 0.4-2.5 ± 0.5 mL (g tissue)^-1  min^-1 ) or in controls (3.2 ± 0.3-3.1 ± 0.2 mL (g tissue)^-1 min^-1 ). In control subjects, renal cortical blood flow fell during volume expansion (4.1 ± 0.3-3.7 ± 0.2 mL (g tissue)^-1  min^-1 , P < 0.05) in contrast to patients in which deviations remained insignificant.

CONCLUSION

Exaggerated natriuresis, a hallmark of essential hypertension, is not mediated by increases in regional, renal blood flow.

Does mean arterial blood pressure scale with body mass in mammals? Effects of measurement of blood pressure

For at least the last 30 years, it has been discussed whether mean arterial blood pressure (MAP) is independent of body mass or whether it increases in accordance with the vertical height between the heart and the brain. The debate has centred on the most appropriate mathematical models for analysing allometric scaling and phylogenetic relationships; there has been previously little focus on evaluating the validity of underlying physiological data. Currently, the 2 most comprehensive scaling analyses are based on data from 47 species of mammals, based on 114 references. We reviewed all available references to determine under which physiological conditions MAP had been recorded. In 44 (38.6%) of the cited references, MAP was measured in anaesthetized animals. Data from conscious animals were reported in 59 (51.8%) of references; of these, 3 (2.6%) were radiotelemetric studies. In 5 species, data were reported from both anaesthetized and conscious animals, and the mean difference in the MAP between these settings was 20 ± 29 mm Hg. From a literature search, we identified MAP measurements performed by radiotelemetry in 11 of the 47 species included in the meta-analyses. A Bland-Altman analysis showed a bias of 1 mm Hg with 95% confidence interval (from -35 to 36 mm Hg); that is, the limits of agreement between radiotelemetric studies and studies in restrained animals were double the supposed difference in the MAP between the mouse and elephant. In conclusion, the existing literature does not provide evidence for either a positive or neutral scaling of arterial pressure to body mass across taxa.

The giraffe kidney tolerates high arterial blood pressure by high renal interstitial pressure and low glomerular filtration rate

BACKGROUND

The tallest animal on earth, the giraffe (Giraffa camelopardalis) is endowed with a mean arterial blood pressure (MAP) twice that of other mammals. The kidneys reside at heart level and show no sign of hypertension-related damage. We hypothesized that a species-specific evolutionary adaption in the giraffe kidney allows normal for size renal haemodynamics and glomerular filtration rate (GFR) despite a MAP double that of other mammals.

METHODS

Fourteen anaesthetized giraffes were instrumented with vascular and bladder catheters to measure glomerular filtration rate (GFR) and effective renal plasma flow (ERPF). Renal interstitial hydrostatic pressure (RIHP) was assessed by inserting a needle into the medullary parenchyma. Doppler ultrasound measurements provided renal artery resistive index (RI). Hormone concentrations as well as biomechanical, structural and histological characteristics of vascular and renal tissues were determined.

RESULTS

GFR averaged 342 ± 99 mL min(-1) and ERPF 1252 ± 305 mL min(-1) . RIHP varied between 45 and 140 mmHg. Renal pelvic pressure was 39 ± 2 mmHg and renal venous pressure 32 ± 4 mmHg. A valve-like structure at the junction of the renal and vena cava generated a pressure drop of 12 ± 2 mmHg. RI was 0.27. The renal capsule was durable with a calculated burst pressure of 600 mmHg. Plasma renin and AngII were 2.6 ± 0.5 mIU L(-1) and 9.1 ± 1.5 pg mL(-1) respectively.

CONCLUSION

In giraffes, GFR, ERPF and RI appear much lower than expected based on body mass. A strong renal capsule supports a RIHP, which is >10-fold that of other mammals effectively reducing the net filtration pressure and protecting against the high MAP.

Selective renal vasoconstriction, exaggerated natriuresis and excretion rates of exosomic proteins in essential hypertension

AIM

In essential hypertension (EH), the regulation of renal sodium excretion is aberrant. We hypothesized that in mild EH, (i) abnormal dynamics of plasma renin concentration (PRC) and atrial natriuretic peptide (ANP) are responsible for the exaggerated natriuresis, and (ii) exosomic protein patterns reflect the renal tubular abnormality involved in the dysregulation of sodium excretion.

METHODS

After 2-week drug washout and 4-day diet, systemic and renal hemodynamics, cardio-renal hormones, glomerular filtration and renal excretion were studied in male patients during saline loading (SL). Excretion rates of exosome-related urinary proteins including apical membrane transporters were determined by proteomics-based methods.

RESULTS

In patients, baseline renal vascular conductance was reduced (-44%, P < 0.001), but non-renal vascular conductances were normal while PRC was reduced and ANP elevated (both P < 0.01). SL induced exaggerated natriuresis and reduced PRC (P < 0.01), at normal suppression rate. SL increased arterial pressure in patients (+11 mmHg, P < 0.001), but not in controls; however, during time control, patients showed identical increases (+10 mmHg, P < 0.005) apparently dissociating arterial pressure from natriuresis. At baseline, excretion rates of 438 proteins ranged from 0.07 to 49.8 pmol (mmol creatinine)(-1); 12 proteins were found in all subjects, and 21 proteins were found in two or more patients, but not in controls. In patients, the excretion rate of retinoic acid-induced gene 2 protein was reduced, and excretion rates of other proteins showed increased variances compatible with pathophysiological and clinical applicability.

CONCLUSION

Essential hypertension patients exhibit selective renal vasoconstriction and individually varying excretion rates of several exosome-related proteins. Hormonal changes, rather than arterial pressure, seem to cause exaggeration of natriuresis.

Renal cortical and medullary blood flow during modest saline loading in humans

AIM

Renal medullary blood flow (RMBF) is considered an important element of sodium homeostasis, but the experimental evidence is incongruent. Studies in anaesthetized animals generally support the concept in contrast to measurements in conscious animals. We hypothesized that saline-induced natriuresis is associated with changes in RMBF in humans.

METHODS

After 4 days of low-sodium diet, healthy men were subjected to slow intravenous saline loading (12 μmol kg(-1) min(-1)) for 4 h. Renal medullary and cortical blood flow was determined by positron emission tomography with H(2)(15)O before and after saline infusion using two independent imaging processing methods. One based on a previously published algorithm (voxel peeling) and a novel method based on contrast-enhanced computed tomography (CT). Blood pressure was measured oscillometrically every 10 min. Cardiac output, heart rate and total peripheral resistance were recorded continuously.

RESULTS

Saline loading increased the urinary sodium excretion by 3.6-fold (21-76 μmol min(-1) , P < 0.01). The RMBF was 2.6 ± 0.2 mL g(-1) tissue min(-1) before and 2.7 ± 0.1 mL g(-1) tissue min(-1) after saline (n.s.). Cortical blood flow was 3.6 ± 0.1 before and 3.4 ± 0.2 after saline (n.s.). Mean arterial blood pressure did not change measurably (90 vs. 90 mmHg). Bland-Altman analysis suggested agreement between results obtained with voxel peeling (2.6 ± 0.2 mL g(-1) tissue min(-1)) and contrast-enhanced CT (2.0 ± 0.1 mL g(-1) tissue min(-1)).

CONCLUSION

In normal humans, changes in RMBF are not necessarily involved in the natriuretic response to modest saline loading. This result is in line with data from conscious rodents.

Pharmacological activation of KCa3.1/KCa2.3 channels produces endothelial hyperpolarization and lowers blood pressure in conscious dogs

BACKGROUND AND PURPOSE

In rodents, the endothelial KCa channels, KCa3.1 and KCa2.3, have been shown to play a crucial role in initiating endothelium-derived hyperpolarizing factor (EDHF) vasodilator responses. However, it is not known to what extent these channels are involved in blood pressure regulation in large mammals, which would also allow us to address safety issues. We therefore characterized canine endothelial KCa3.1 and KCa2.3 functions and evaluated the effect of the KCa3.1/KCa2.3 activator SKA-31 on blood pressure and heart rate in dogs.

EXPERIMENTAL APPROACH

Canine endothelial KCa3.1/KCa2.3 functions were studied by patch-clamp electrophysiology and wire myography in mesenteric arteries. Systemic cardiovascular actions of acute SKA-31 administration were monitored in conscious, unstressed beagle dogs.

KEY RESULTS

Mesenteric endothelial cells expressed functional KCa3.1 and KCa2.3 channels that were strongly activated by SKA-31. SKA-31 hyperpolarized the endothelial membrane and doubled endothelial hyperpolarization-dependent vasodilator responses in mesenteric arteries. SKA-31 (2 mg·kg(-1), i.v.) rapidly decreased the MAP by 28 ± 6 mmHg; this response was transient (8 ± 1 s), and the initial drop was followed by a fast and pronounced increase in HR (+109 ± 7 beats min(-1)) reflecting baroreceptor activation. SKA-31 significantly augmented similar transient depressor responses elicited by ACh (20 ng·kg(-1)) and doubled the magnitude of the response over time.

CONCLUSIONS AND IMPLICATIONS

Activation of endothelial KCa3.1 and KCa2.3 lowers arterial blood pressure in dogs by an immediate electrical vasodilator mechanism. The results support the concept that pharmacological activation of these channels may represent a potential unique endothelium-specific antihypertensive therapy.

Dexamethasone suppression test in depressive stroke patients

Depressive psychiatric patients often shown non-suppression to the dexamethasone suppression test (DST). Stroke patients shows a high frequency of depression. In the present study the DST was studied in 76 stroke patients and 26 controls. No difference was found in frequency of non-suppression to the DST between depressive and non-depressive stroke patients. It was found that postdexamethasone plasma cortisol level at 08 a.m. was significantly higher in patient with the lesion in the right hemisphere compared to patients with the lesion in the left hemisphere.

Bartter's syndrome--treatment with potassium, spironolactone and ACE-inhibitor

The treatment of Bartter's syndrome is fraught with difficulties, and there is no consensus concerning the pathogenetic mechanisms involved. Potassium depletion with hypokaliaemia is a dominant feature of the syndrome. In this case history, a 42-year-old woman suffering from Bartter's syndrome did not improve on several therapeutic trials. An impressive progress was noted, however, after intensive potassium repletion with subsequent potassium/spironolactone/ACE-inhibitor treatment. After 24 months her condition was unchanged with normal and stable Se-potassium concentration.

The renin-angiotensin system and kidney function during initial insulin treatment in diabetic man

Glomerular filtration rate, renal plasma flow, active renin, renin substrate and angiotensin II concentrations were monitored in nine consecutive patients (3 women, 6 men, mean age 31 years) with newly diagnosed, insulin-dependent diabetes. Measurements were performed before and during the initial eight days of intensive insulin treatment. All patients had ketonuria but none had acidosis. Glomerular filtration rate and renal plasma flow were significantly increased at the time of diagnosis as compared with values from normal subjects. A highly significant decline in glomerular filtration rate from 160 +/- 9 (SEM) to 133 +/- 5 ml/min x 1.73 m2 was seen during the initial eight days of treatment (p less than 0.01). Likewise renal plasma flow declined from 601 +/- 33 to 558 +/- 35 ml/min x 1.73 m2 (p less than 0.05). Plasma concentration of renin was within normal range at day 0, and remained unchanged during the eight day study. Also renin substrate concentration was normal and unchanged during the observation period, whereas angiotensin II concentration was low and unchanged. Our study does not support the suggestion that the renin-angiotensin system contributes to the hyperfiltration characteristically found in newly diagnosed insulin-dependent diabetic patients.

Metabolic and cardiovascular responses to epinephrine in diabetic autonomic neuropathy

Norepinephrine-induced vasoconstriction, which is mediated by alpha-adrenergic receptors, is accentuated in patients with autonomic neuropathy. In contrast, responses mediated by beta-adrenergic receptors, including vasodilatation and metabolic changes, have not been evaluated in these patients. To study these responses, we administered epinephrine in a graded intravenous infusion (0.5 to 5 micrograms per minute) to seven diabetic patients without neuropathy, seven diabetic patients with autonomic neuropathy, and seven normal subjects. Mean arterial pressure decreased significantly in the patients with autonomic neuropathy (P less than 0.01) but was unchanged in the other groups. Since cardiac output increased to a similar extent in the three groups, the decrease in blood pressure was due to a significantly larger decrease (P less than 0.01) in total peripheral vascular resistance in the patients with autonomic neuropathy. The heart rate increased significantly more during the infusions in the patients with neuropathy than in those without neuropathy. Epinephrine produced a greater increase in blood glucose, the glucose-appearance rate, lactate, glycerol, and free fatty acids in the patients with autonomic neuropathy than in the other groups (P less than 0.05). These findings indicate that several beta-receptor-mediated responses to epinephrine are enhanced in patients with diabetic autonomic neuropathy. The underlying mechanism remains to be elucidated.

Partial purification of human renin substrate

A two-step purification method is described for the preparation of renin substrate from human plasma. Pooled plasma from women on oral contraceptives is used for the purification. The overall yield of renin substrate is 57%, with a twenty-fold purification. The specific renin substrate content of the preparation, as determined by enzymatic degradation with an excess of human renin, is 2 mug angiotensin I per mg protein. The product has a very low endogenous renin activity and is free from angiotensinase activity. An additional purification step involving affinity chromatography is described. In pilot studies a renin substrate yield of 37% has been achieved, with a hundred-fold purification. The final product has a specific renin substrate content of 10 mug angiotensin I per mg protein. The preparation contains up to 12 different plasma proteins, nine of which have been identified and quantitated.