Early life determinants of adult blood pressure

PURPOSE OF REVIEW: While treating high blood pressure in middle age is beneficial in terms of reducing the occurrence of cardiovascular disease, treated and well controlled hypertensive adults still have a substantial excess mortality and reduced survival compared with normotensives. Therefore, identification of the means of preventing hypertension in earlier life is an important objective. There is increasing evidence that adult blood pressure is determined by a range of characteristics from the intrauterine period, through infancy and childhood. The purpose of this review is to provide a summary of the current evidence concerning the early life determinants of adult blood pressure. RECENT FINDINGS: Children from poorer socioeconomic positions, those whose mothers experience pregnancy-induced hypertension, those whose mothers smoke throughout pregnancy, those with low birthweight, who are not breast-fed, who have high sodium diets in infancy and who are obese in childhood or adolescence tend to have higher blood pressure in adulthood. However, the mechanisms linking these early life factors to later blood pressure and the most appropriate means of preventing adult hypertension by intervening in early life are unclear. SUMMARY: There is clear evidence that early life factors are important determinants of adult blood pressure. However, there is a need for randomized trials with sufficient resources for long-term follow-up to assess the effects that interventions such as preventing pregnancy-induced hypertension, reducing maternal smoking, increasing breast-feeding, reducing salt consumption in infancy and preventing childhood obesity have on adult blood pressure and cardiovascular disease.     

Progression of renal insufficiency: role of blood pressure

The effect of blood pressure on progression of renal insufficiency was examined in a large group of patients who eventually required dialysis. Out of 198 consecutive new chronic dialysis patients, 86 had sufficient data predialysis to determine rates of progression of renal insufficiency by reciprocal creatinine versus time plots. Average plasma creatinine at first contact was 3.8 +/- 0.2 mg/dl and at the time of dialysis was 11.4 +/- 0.4 mg/dl. Mean duration of follow-up was 33.4 +/- 2.5 months and the average rate of decline in reciprocal creatinine was -0.009 +/- 0.001 dl/mg month. Patients were stratified by average value of diastolic blood pressure measured in clinic. Patients in the lowest quartile had a rate of decline in reciprocal creatinine of -0.007 +/- 0.001 dl/mg month, which was slower than that of patients in the third and fourth quartiles, -0.010 +/- 0.001 and -0.011 +/- -0.002 dl/mg month, respectively (P less than 0.05). In individual patients, a mean diastolic BP of less than 90 mm Hg was associated with a rate of decline in reciprocal creatinine of -0.006 +/- 0.001 dl/mg month which was significantly less than the rate of -0.009 +/- 0.001 when the diastolic BP was greater than 90 mm Hg. Thus, in a large group of patients who have progressed to ESRD, there is an association between control of diastolic blood pressure and a slower rate of decline in renal function.     

Retinoic acid enhances nephron endowment in rats exposed to maternal protein restriction

A reduced nephron complement at birth renders the kidney susceptible to renal disease in adulthood. Retinoic acid (RA; the active metabolite of vitamin A) is linked to nephrogenesis in vitro and in vivo. The aim of this study was to determine the effect of administration of retinoic acid in midgestation in rats on nephron endowment in offspring exposed to maternal protein restriction. Rats were fed either a normal-protein diet (NPD) or a low-protein diet (LPD) during pregnancy and lactation. Half of the dams in the LPD group were injected intraperitoneally with retinoic acid (20 mg/kg) during gestation at embryonic day 11.5. At 4 weeks of age, the offspring were anesthetized and perfusion-fixed, and nephron number estimated using unbiased stereological techniques. Body weight and kidney volume was significantly reduced in all LPD offspring. There was a significant 29% reduction in nephron number in the LPD group compared with the NPD offspring, whereas the number of nephrons in kidneys from the LPD + RA offspring was not significantly different compared with controls. In conclusion, administration of a single bolus dose of retinoic acid during midgestation restored nephron endowment to normal in offspring exposed to maternal protein restriction.     

Ambulatory blood pressure monitoring: mean blood pressure and blood pressure load

Ambulatory blood pressure monitoring (ABPM) is commonly used to diagnose pediatric hypertension. Using ABPM, hypertension is usually defined as a mean BP greater than the 95th percentile for height. A BP load >30% (% of BP readings greater than the 95th percentile) is also used for the diagnosis of hypertension. The objective of this study was to determine the agreement between mean BP greater than the 95th percentile and 30% BP load for the diagnosis of hypertension using ABPM. All ABPM records (n =1,009) of patients referred for hypertension to a pediatric center were retrieved. Scans were excluded if: age was >19 and height <115 cm or >185 cm. Mean BP and BP loads were calculated for 728 scans. Agreement between mean BP greater than the 95th percentile for height and various BP loads were calculated using the kappa coefficient. The kappa coefficient of agreement between mean BP greater than the 95th percentile and 30% BP load was 0.56 and 0.57 for daytime systolic and diastolic BP, respectively. The agreement between mean night-time BP greater than the 95th percentile and 30% BP load was 0.70 and 0.66 for systolic and diastolic BP, respectively. Agreement between mean BP greater than the 95th percentile and 30% BP load is only moderate to good. Maximum agreement between mean BP greater than the 95th percentile and BP load is achieved at 50% BP load.     

Amelioration of experimental glomerulonephritis by dietary protein restriction

We have examined the effects of various levels of dietary protein intake on the course of nephrotoxic serum nephritis in the rat by feeding low (4.6% casein), standard (23% casein), and high (57.5% casein) protein diets which were identical in calorie, mineral, and electrolyte content. Nephritic rats on a high protein diet manifested heavy proteinuria, hypoalbuminemia, hypercholesterolemia, azotemia, and elevated serum creatinine levels. In those subjected to dietary protein restriction, proteinuria remitted and azotemia did not develop. While mesangial widening, interstitial abnormalities, and segmental proliferation and sclerosis of glomeruli occurred regularly in nephritic rats fed high protein diets, histologic abnormalities were virtually absent in those on low protein intake. Animals on a standard protein intake manifested histologic and clinical features intermediate in severity. We conclude that the renal functional and histologic consequences of nephrotoxic serum nephritis can be averted by dietary protein restriction.     

Increasing maternal blood pressure with ephedrine increases uterine artery blood flow velocity during uterine contraction

BACKGROUND: During labor, ephedrine is widely used to prevent or to treat maternal arterial hypotension and restore uterine perfusion pressure to avoid intrapartum fetal asphyxia. However, the effects of ephedrine on uterine blood flow have not been studied during uterine contractions. The purpose of the study was to assess the effects of ephedrine on uterine artery velocities and resistance index using the Doppler technique during the active phase of labor. METHODS: Ten normotensive, healthy parturients with uncomplicated pregnancies at term received intravenous ephedrine during labor to increase mean arterial pressure up to a maximum of 20% above their baseline pressure. Peak systolic and end-diastolic Doppler flow velocities and resistance indices were measured in the uterine artery before and immediately after administration of bolus intravenous ephedrine and after ephedrine washout. Umbilical and fetal middle cerebral arterial resistance indices and fetal heart rate were also calculated. RESULTS: After ephedrine administration, mean arterial pressure increased by 17 +/- 4%. End-diastolic flow velocity in the uterine artery at peak amplitude of uterine contraction was restored to 74% of the value observed in the absence of contraction. The systolic velocity was totally restored, and the uterine resistance index was significantly decreased, compared with the values in the absence of contraction. Between uterine contractions, ephedrine induced similar but less marked effects. Fetal hemodynamic parameters were not altered by ephedrine administration. CONCLUSIONS: Bolus administration of intravenous ephedrine reversed the dramatic decrease in diastolic uteroplacental blood flow velocity and the increase in resistance index during uterine contraction, without altering fetal hemodynamic parameters. This suggests that the increase in uterine perfusion pressure during labor could in part restore uterine blood flow to the placenta during uterine contraction.     

Reduction of remnant nephron hypermetabolism by protein restriction

To study the metabolic mechanisms involved in the protective effect of dietary protein restriction on the progression of chronic renal failure, experiments were performed in Sprague-Dawley rats subjected to five-sixths nephrectomy and pair-fed on isocaloric low (4%) protein (LP) or high (50%) protein (HP) diets. Protein restriction reduced the severity of uremia, with lower blood urea nitrogen (BUN) concentrations (8.9 +/- 1.1 v 30.0 +/- 2.9 mmol/L [25 +/- 3 v 84 +/- 8 mg/dL] both n = 12, P less than 0.01), and resulted in lower mortality at 2 weeks (0% v 33%, P less than 0.05), 4 weeks (16% v 58%, P less than 0.05), and 10 weeks (16 v 83%, P less than 0.01). Isolated perfusion of the remnant kidney at 3 weeks demonstrated reduced O2 consumption (QO2) (0.77 +/- 0.2 v 2.56 +/- 0.5 mumol/min/g, both n = 7, P less than 0.05) in the absence of significant differences in inulin clearance (239 +/- 53 v 341 +/- 39 microL/min/g, NS) and net sodium reabsorption (34 +/- 8 v 49 +/- 6 mumol/min/g, NS) in rats fed the LP diet. A lower renal QO2 in protein-restricted animals was also demonstrated in vivo (4.1 +/- 0.9 v 13.8 +/- 2.7 mumol/min/g, P less than 0.01). In vivo P-31 nuclear magnetic resonance (NMR) studies of remnant kidneys did not demonstrate any difference in the steady-state tissue concentrations of adenosine triphosphate (ATP) or inorganic phosphate between rats fed LP and HP diets. Dietary protein restriction decreases the severity of uremia and diminishes renal QO2 in the remnant kidney model.(ABSTRACT TRUNCATED AT 250 WORDS)     

成年人围手术期血压目标控制研究进展

围手术期低血压经常发生,是外科患者发生术后器官功能不全和死亡的重要促进因素。文章回顾近年来围手术期血压控制水平与器官损伤相关的文献研究,从而为围手术期血压管理目标提供参考以减少术后器官功能不全的发生。目前缺少围手术期血压控制目标的共识,血压控制目标是一个动态管理的过程,不应视为一个固定值。血压目标设定的最终目的是维持器...     

Validation of inflationary non-invasive blood pressure monitoring in adult surgical patients

Oscillometric determination of blood pressure may be advantageous, as cuff inflation requires lower cuff pressure and shorter duration than deflation. In this observational study, we compared the blood pressure value, cuff pressure, and duration of cuff inflation between a prototype of inflationary non-invasive blood pressure (NIBP) and conventional deflationary NIBP in adult patients during anesthesia. Three hundred and twenty-three pairs of measurements were obtained from 64 subjects. The bias and precision of systolic pressure and diastolic pressure were 2.9 ± 8.3 and 5.6 ± 6.1 mmHg, respectively. Inflationary NIBP could better determine NIBP with lower cuff pressure than deflationary NIBP (124 ± 22 vs. 160 ± 33 mmHg, p < 0.05). Inflationary NIBP could also determine NIBP more quickly (13.0 ± 2.3 vs. 32.7 ± 13.6 s, p < 0.05). These data suggest that inflationary NIBP may reduce cuff-related discomfort and complications, and has reasonable accuracy compared to deflationary NIBP in adult surgical patients.     

Nephron number and blood pressure in rat offspring with maternal high-protein diet

This study investigated the effects of a high-protein diet during pregnancy on nephron endowment and subsequent levels of blood pressure in the offspring. Female WKY rats were fed either a normal (20%, NPD) or a high (54%, HPD) protein diet during pregnancy. Male offspring were paired at birth. At 4 weeks of age, 1 of the pair was randomly chosen for perfusion fixation, and total glomerular number, and thereby nephron number, was estimated using an unbiased stereological technique. The other rat of the pair was allowed to grow to 30 weeks of age, during which time tail cuff systolic blood pressure was monitored twice weekly. There was no effect of the HPD on birth weight (NPD 4.23+/-0.53 g, HPD 4.26+/-0.45 g, mean+/-SD), kidney weight (NPD 0.372+/-0.049 g, HPD 0.337+/-0.090 g), or total nephron number (NPD 27,191+/-3,512, HPD 26,738+/-4,735). Systolic blood pressure at 30 weeks was 170+/-14 mmHg in NPD and 169+/-14 in HPD offspring. These findings show that a HPD during pregnancy did not lead to an increase in birth weight, kidney weight, or nephron endowment, nor did the HPD affect adult blood pressure.     

Use of a neonatal noninvasive blood pressure module on adult patients

A clinical and statistical comparison of systolic, mean and diastolic arterial blood pressures was made between a non-invasive technique using a neonatal oscillometric blood pressure monitor attached to the thumb versus an invasive technique using a catheter inserted into the ipsilateral radial artery in 18 patients undergoing general anaesthesia for major surgery. In 1258 readings, the mean differences between the pressures obtained (invasive versus non-invasive) were + 9.1–7.9, and—0.7 mmHg for systolic, diastolic and mean pressures respectively. Oscillometric blood pressure measurement using the thumb appears to be an acceptable method for monitoring blood pressure during anaesthesia and has advantages over conventional cuff placement on the upper arm.     

Increased systolic daily ambulatory blood pressure in adult women born preterm

We have studied 24-h ambulatory blood pressure and kidney function in three groups of adult women: (1) born full term but with birth weights below the 3rd percentile for gestational age (n =18), (2) born preterm before gestational week 33 (median birth weight 1,250 g, range 950–2,040 g) (ex-preterm, n =14), and (3) those born full term with normal birth weights (comparison group n =17). We have previously published the results from the study. We recalculated the daily ambulatory blood pressure and redefined the time interval from 6:00–24:00 to 8:00–20:00, since this better corresponds to daily active life. We found significantly increased mean daily systolic ambulatory blood pressure in the ex-preterm group. The result supports the suggestion that disturbance and/or disruption of the normal prenatal milieu seem to affect arterial blood pressure in adult life.