Neonatal Hypertension Research Articles

1609 POST-NEONATAL HYPERTENSION SCREENING IN NICU GRADUATES WHO HAVE HAD INDWELLING UMBILICAL ARTERY (UA) CATHETERS

Most reported neonatal hypertension has been renovascular in origin, with the majority caused by renal artery thrombosis as the result of indwelling UA catheters. The incidence of such catheter related hypertension during the neonatal period is reported to be about 3%. But the long term, post neonatal effect of UA catheterization on the kidney is not known. We have systematically followed the blood pressure (BP) of 112 NICU graduates who have had indwelling catheter during the past 3 years. BP was measured by Roche Doppler ultrasound BP monitor on each scheduled follow-up visit (1 month, 3 months, 6 months, 1 year, 1½ yers, 2 years and 3 years). Post neonatal hypertension were defined as a BP of over 113 mmHg at age 4 wks or older (95th percentile of Brompton study). Seventy-nine percent were preterm, 14% term and 7% post term infants. Infants with congenital heart diseases and increased intracranial pressure were excluded from the study. Duration of follow-up was between 1 to 3 years. Mean BP at 1 to 3 months of age was 75.4 mmHg, at 3 to 6 months was 78.0 mmHg, at 6 mos to 1 year was 81.1 mmHg, at 1-2 years was 88.1 mmHg and at 2 to 3 years was 83.6 mmHg. No one was found to be hypertensive during the study period. We conclude that if NICU graduates survive the neonatal period without hypertension, the chance of developing hypertension during the next 3 years is minimal.

1536 NEONATAL HYPERTENSION: A NATIONAL SURVEY

Umbilical arterial catheter(UAC) placement has been implicated in the etiology of neonatal hypertension(HBP). 119/163(73%) of NICUs responded to a survey regarding UAC care and placement and the incidence and outcome of HBP. Respondents identified 581 HBP among 70,186 admissions, defined as BP 95/63(mean 71 mmHg) for infants >1500gms, and 82/51(mean 60) for those <1500gms who accounted for 25% of HBP. 94% of HBP had UAC prior to or during HBP which complicated 0.82% of admissions(range 0 to 8%). HBP incidence was calculated according to UAC site and whether maintained with constant infusion(CI) or intermittent flushes(IF). A comparable number of units preferred high UACs (T6-T10) to low UACs (L3-L5). Thromboembolism of the renal artery was stated as the most common etiology of HBP(63%), with heart failure the most common manifestation(44%), followed then by renal failure, respiratory distress, encephalopathy and retinopathy. 68% of centers initiated treatment for HBP alone, the rest required evidence of systemic symptoms. A favorable long term outcome was reported for 90% of HBP. These data suggest that both UAC position and its specific care influence the incidence of HBP, the greatest risk occurring with high UAC and intermittent heparin flushes.

AIKALOSIS ATIENUATES HYPOXIC PULYONARY VASOCONSTRICTION IN NEO NATAL LAMBS

Hyperventilation (respiratory alkalosis)is an important treatment for persistent pulmonary hypertension in neonates. The precise way that hyperventilation attenuates hypoxic pulmonary vasoconstriction is unclear. We studied the effect of alkalosis on hypoxia-induced pulmonary vasoconstriction in 13 acutely instrumented neonatal lambs. We specifically examined the relative roles of a metabolic alkalosis (MA) vs a respiratory alkalosis (RA). After stabilization in each experimental situation, the lambs were made acutely hypoxic by a 1-minute inhalation of 5% O2-95% N2. The control pulmonary vasoconstrictor response to hypoxia was measured at both the beginning and end of each experiment and was compared to the responses observed after hyperventilation (RA) and after bicarbonate infusion (MA-normal PaCO2). The table gives the mean changes before and during hypoxia. Data consider different from control 1 when p<.05 by 2-way ANOVA. Hypoxic pulmonary vasoconstriction was significantly milder whenever the animal was alkalotic - regardless of whether the alkalosis was respiratory or metabolic. Although the rise in PVR was smaller during MA than during RA, there was no significant difference between the effects of the two types of alkalosis. In summary, the elevated pH rather than decreased PaCO2 during hyperventilation appears to be the major factor in blunting hypoxic pulmonary vasoconstriction.

SIX-YEAR FOLLOWUP OF NEONATAL RENOVASCULAR (NRH) HYPERTENSION

Neonatal hypertension is often associated with renal artery thrombosis after use of umbilical artery catheters. Although infants with NRH usually respond to medical therapy, their prognosis is unclear; longterm followup of 11 infants is presented. Mean birthweight was 2914 gm; pre-treatment blood pressure, 161/100 mmHg, and age of onset, 7.8 days. 9 of 11 infants had umbilical artery catheters. A renal abnormality was noted on renal scan or angiography in 9 of 11 infants. 7 of 10 infants studied had elevated peripheral plasma renin activity (PRA). All infants became normotensive with diuretic and/or antihypertensive agents and remained so when weaned off drugs. 2 infants died at 3 months of age of SIDS and pneumonia. The remaining have been followed for 5.5 to 7.5 years. 2 children, neither small for gestational age, have heights and weights below the 5th percentile for age. One child has a creatinine clearance of 62 ml/min/1.73 m2. PRA in 8 children studied is normal. Renal ultrasound, intravenous pyelography, and renal scan demonstrate persistent renal abnormalities in 7 of 9 children. Neonates with NRH responded well to antihypertensive medication, remained normotensive off medications, but had significant abnormalities in renal size and function which persisted over a 6 year period. Because their ultimate prognosis is unclear, longterm followup of infants with NRH is indicated.

THE EFFECT OF CHRONIC PROPRANOLOL (P) ON THE GROWTH AND ENDOCRINE FUNCTION OF NEWBORN PUPPIES

Top of pageAbstract The effect of P, commonly employed in the treatment of neonatal hypertension, on growth, development and endocrine function of developing infants has not been examined. Beagle littermates, age 1 week, were placed in one of three groups: P 3 mg/kg/BID, P 9 mg/kg/BID, or control (C). Measurements of blood pressure, weight, and length were done weekly or bi-weekly. At 3 and 6 months of age fasting puppies were given, on different days, 0.5 gm/kg of glucose IV and 0.1 U/kg insulin IV for determination of glucose and insulin tolerance respectively. Fasting T3 and T4 levels were determined. Animals were sacrificed at 6 months and wet organ weights obtained. Blood pressure was significantly lower in P treated animals (p <.001). There were no significant differences between P and C animals in body or individual organ size. After IV insulin, P animals had greater falls in serum glucose (p <.02) compared to C animals at 3 months (42.5% vs 33.6%) and at 6 months (33.6% vs 26.4%). In P animals glucose disappearance rate was slower at 3 months (.009 vs .011, p <.05) and T4 levels were lower at 6 months (2.85 mcg/dl vs 3.51 mcg/dl, p <.05). In summary, chronic β blockade with P had no effect on body or organ growth of newborn puppies. However, significant abnormalities were observed in thyroid function and in glucose homeostasis, suggesting the need for additional studies on the safety of chronic β blockade in developing infants.

HYPERTENSION REDEFINED FOR CRITICALLY ILL NEONATES

The diagnosis of neonatal hypertension(HTN) has been complicated by the limited available normative data and hence, arbitrary assignment of the upper limit of normal blood pressure(BP). Our objective was to determine a normative data base. BPs were recorded every 8 hrs for up to 30 days in 121 preterm and 61 term infants who required an umbilical artery catheter(UAC). Dinamap was used after discontinuation of UAC. Infants were grouped as follows: <1.0 kg (n=17), 1.0-1.5 kg (n=41), 1.5-2.5 kg (n=63) and >2.5 kg (n=61). In each group, mean arterial pressure(MAP) rose steeply over the first 5 days. At all times, BP was higher in infants with the greater birth weight(BW). Predictive equations for MAP as a function of postnatal age(PNA) best fit a curvilinear relationship (MAP=a+b.ln[day]). The following tabulates the MAP(mmHg) and 95% confidence limits for single measurements. Both PNA and BW markedly influence BP values. By prior definition(MAP >70 × 3 days) 10% of these asymptomatic neonates would be hypertensive. The present criteria reduces the incidence to 2% which is in accordance with our previous report of symptomatic HTN. This dynamic definition of the range of BP with respect to BW and PNA more precisely identifies HTN in sick neonates.

Hypertensive retinopathy in the newborn infant

Hypertension (blood pressure greater than 70 mm Hg on three days) was noted in 1.2% of all neonatal admissions to the intensive and intermediate care nurseries. During this investigation of neonatal hypertension, a retinopathy identical to that seen in hypertensive adults was noted. Indirect ophthalmoscopy was performed in 21 neonates with elevated blood pressure. Eleven of these patients demonstrated some or all of the following abnormalities: increased ratio of venous to arterial caliber, vascular tortuosity (including arteriovenous crossing changes), superficial and deep hemorrhages, and exudates. These findings appeared to resolve after control of the hypertension. The specificity of this constellation of lesions for hypertensive retinopathy and their possible clinical significance are explained in light of what is known about hypertensive retinopathy in adults.

Neonatal Renovascular Hypertension—A Complication of Aortic Monitoring Catheters

Two critically ill neonates with severe removascular hypertension as a complication of aortic monitoring catheter are presented. They did not respond to intensive medical therapy for hypertension. In spite of their precarious general condition, nephrectomy was undertaken with complete relief of symptoms.

Treatment of neonatal hypertension with Captopril

C A P T O P R I L (SQ 14,225) is an an t ihype r t ens ive agent which acts p r imar i ly by inh ib i t ing the enzyme that converts ang io tens in I to ang io tens in II. It has b e e n effective in the t r ea tmen t o f m a n y hype r t ens ive adul ts wi th high and n o r m a l ren in hyper t ens ion , re f rac tory to o the r fo rms o f therapy . 1 ~ Recent ly , Cap topr i l has b e e n used to t reat severe ly hyper t ens ive ch i ldren? . ~ We repor t he re three cases o f severe h igh r en in h y p e r t e n s i o n in n e w b o r n infants , all o f w h o m r e s p o n d e d to Cap topr i l t he r apy w h e n o the r modal i t i es o f t r e a t m e n t had failed.

Neonatal renovascular hypertension—A complication of aortic monitoring catheters

Two critically ill neonates with severe renovascular hypertension as a complication of aortic monitoring catheter are presented. They did not respond to intensive medical therapy for hypertension. In spite of their precarious general condition, nephrectomy was undertaken with complete relief of symptoms.

Nonsurgical Management of Renovascular Hypertension in the Neonate

Over an 18-month period nine infants in a neonatal intensive care unit developed hypertension (blood pressure, 115/88 to 280/140 mm Hg) at 2 to 45 days of age. Eight of the nine infants had indwelling umbilical artery catheters prior to onset of hypertension; six of the nine infants had evidence of a patent ductus arteriosus. Peripheral plasma renin activity was greater than 300 ng/ml/3 hr in six of eight infants. Angiograms were abnormal in six of seven infants and computerized renal scans were abnormal in all nine infants. One infant had congenital renal artery stenosis. Eight of nine infants had evidence of unilateral or bilateral renal artery thrombi which were felt to have emanated from an umbilical artery catheter or a ductus arteriosus. Hypertension in all infants was successfully controlled medically (follow-up of 3 to 27 months; mean, 14.4 months). Blood pressures remained normal when medication was discontinued. In our experience, neonatal renovascular hypertension is no longer uncommon, responds to aggressive medical management, and rarely requires early nephrectomy. Neonatal renovascular hypertension was usually associated with umbilical artery catheters positioned above the level of the renal arteries.

Neonatal Hypertension

The pathophysiology, clinical course, and laboratory features of neonatal hypertension are reviewed. The author’s experience with 17 newborns with hypertension provide the basis for an approach to evaluation and management.

Neonatal Hypertension Associated with Renal Artery Hypoplasia

A newborn infant was presented with severe hypertension, associated with congenital hypoplasia See Images in the PDF file of the abdominal aorta and bilateral renal hypoplasia.