HYPERTENSION (Blood Pressure in Childhood)

Starship Children’s Health Clinical Guideline Note: The electronic version of this guideline is the version currently in use. Any printed version can not be assumed to be current. Please remember to read our disclaimer.

HYPERTENSION (Blood Pressure in Childhood)          

Measurement of Blood Pressure Normal Blood Pressure When should BP be measured? Definition of Hypertension Signs & Symptoms Causes of Transient Hypertension Causes of Sustained Hypertension Investigation of the Hypertensive Child Hypertensive Urgency Hypertensive Emergency

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Management of the Hypertensive Emergency Management of Primary Hypertension Recommended Reading Appendix 1 – Tables of Blood Pressure Levels for Age & Height Appendix 2 – Neonatal BP Values Appendix 3 - Oral antihypertensive drugs for management of hypertension in children References

An elevated blood pressure level in childhood can predict an increased cardiovascular risk in adult life. The increasing prevalence of childhood obesity necessitates regular surveillance of blood pressure to detect abnormal blood pressure and hence increased cardiovascular risk. Identifying hypertension in children allows for treatment, assessment of target organ damage and investigation of aetiology.

Measurement of Blood Pressure Devices The most common methods are: (1) Aneroid sphygmomanometry (manual blood pressure) (2) Oscillometry using automated devices such as DINAMAP (Critikon). Mercury manometers are no longer in routine clinical use. Aneroid devices are not as accurate as mercury manometers and require regular calibration. Oscillometry detects arterial pulsations by transducer. The mean arterial pressure is measured, and systolic and diastolic recordings are calculated from a mathematical formula. There is good agreement between DINAMAP readings and blood pressures obtained by invasive central aortic measurements. DINAMAP values are generally 6-7 mm Hg higher for systolic and 2-4 mm Hg lower for diastolic. DINAMAP recordings have the potential for less variability, less error and greater reproducibility. DINAMAP measurements may be inaccurate in low birth weight or preterm infants where it may overestimate BP. Ambulatory blood pressure monitoring is also available for investigation of those with suspected hypertension, those at risk of developing hypertension or difficult to mange blood pressure. Appropriate Cuff Size This refers to the size of the inflatable bladder. The correct size is based on the diameter (thickness) of the arm, not the age of the child. Length is not as important. The widest cuff that can be applied to the arm should be used, with the bladder covering at least two thirds of the upper arm, and the length of the cuff should completely encircle the arm. Small cuffs result in a spuriously high BP, whereas the risk of a spuriously low blood pressure from too large a cuff is minimal. It is better to use a cuff which too large than one that is too small.

Author: Editor:

Dr William Wong Dr Raewyn Gavin

Hypertension (Blood Pressure in Childhood)

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Nephrology December 2009

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HYPERTENSION (Blood Pressure in Childhood) The cuff should be at heart level. Blood pressure should be measured on the arm only. There are no significant differences in BP between supine and erect as long as the cuff is at heart level and the child is volume replete. Technique The child should be seated in a quiet room for at least 5 minutes before taking the blood pressure. The right arm is preferred for consistency and because of the possibility of aortic coarctation (falsely low recording in the left arm.) Blood pressure should not be measured routinely on the leg as this may result in a false high reading. Definition of Systolic and Diastolic BP Systolic BP = 1st Korotkoff sound (K1). Diastolic BP = K5 in young children, K4 in adolescents. Use K4 (muffling of the sounds) in young children if K5 is very low, in which case record both.

Variables Affecting the Measurement of BP Several variables can affect BP measurement including:  Patient behaviour (anxiety, cooperation)  Medications (beta-agonists, steroids)  Observer variability (detection of Korotkoff sounds)  Cuff size (as above). There are significant variations in published normal measurements due to these differences.

Normal Blood Pressure Current normative data is based on auscultation and there is no normative blood pressure data that is based on recordings measured from oscillometric devices. There is limited data available on infants and young children. There is no significant difference between sexes in the first 5 years of life. Blood pressures rise gradually from 2 to 5 yrs of age, at a rate of approximately 1 mm Hg per year, and at a rate of 1.5 mm Hg per year from 7 to 11 years of age. In older children a wide variation of "normal values" are reported. Approximately 40% of the variability of BP in children is related to height, weight, triceps skin fold thickness, and arm circumference. The Fourth Report on the Diagnosis, Evaluation and Treatment of High Blood Pressure in Children and Adolescents presents new data and the reader is advised to consult this extensive report. See Appendix for BP tables

When Should BP be Measured? It should be an integral part of the physical examination. Measure it 4 to 5 times in early school age, after which only children with "high" BP (>75th centile) need following. Measure BP more often in "high risk" children: IDDM, obesity, hyper-lipoproteinemia (child or parent), periodically high BP, risk factors in a parent (severe hypertension, early stroke or MI), renal disease, syndromes known to be associated with hypertension. Author: Editor:



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HYPERTENSION (Blood Pressure in Childhood) Definition of Hypertension A single moderately elevated measurement does not indicate hypertension. There must be repeated evaluation under basal conditions, over time. A very high blood pressure measurement requires urgent evaluation and treatment. The 4th report definitions are as follows: Pre hypertension

(previously borderline hypertension) is defined as an average SBP and/or average DBP between 90th and 95th centile. This group is considered at increased risk for hypertension.

Hypertension

Average systolic and/or diastolic BP > 95th centile for age, sex and height obtained on at least 3 occasions.

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Stage 1 hypertension average SBP ± DBP 95 to 99% for age and sex with no end organ damage.

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Stage 2 hypertension: average SBP ± DBP ³ 99% ± end organ damage.

A patient with BP levels >95th centile in a clinic setting, who is normotensive outside the clinic setting has “white coat” hypertension If a statistical definition of hypertension is used, then potentially 5% of children have hypertension, a prevalence which is not supported in clinical studies where 1-2% of children have hypertension.

Signs and Symptoms of Hypertension The signs and symptoms of hypertension vary enormously. The underlying disease causing hypertension may also have symptoms.  

Neonates: Respiratory distress, sweating, irritability, pallor/cyanosis, failure to thrive, sepsislike picture, cardiac failure, apnoea, vomiting, seizures Older children: Fatigue, encephalopathy, headache, heart murmur, blurred vision, anorexia, nausea, epistaxis, weakness (facial palsy), weight loss / gain, polydipsia / polyuria, tiredness, enuresis, abdominal pain, haematuria, short stature. Acute hypertension in older children may be heralded by, Bell’s palsy, headaches, seizures, sudden visual loss, epistaxis or abdominal pain.

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HYPERTENSION (Blood Pressure in Childhood) Causes of Transient Hypertension         

Acute glomerulonephritis, Henoch-Schonlein nephritis, haemolytic uraemic syndrome, other causes of acute renal failure. Post urologic surgery or renal transplantation. Acute hypovolaemia (nephrotic relapse, burns, adrenal + GI saline depletion). Acute hypervolaemia (excessive administration of blood, saline or plasma). CNS disease (tumour, infection, seizures, injury). Guillain-Barre syndrome. Hypercalcaemia. Lead Poisoning. Medications (steroids, sympathomimetics, contraceptive pill).

Causes of Sustained Hypertension  

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Coarctation of aorta. Renin-dependent hypertension: o Renovascular o Renal parenchymal: coarse renal scarring (reflux nephropathy, obstructive uropathy, neuropathic bladder), glomerulonephritis, polycystic kidney disease, hemolytic uraemic syndrome. o Renal tumour. o Catecholamine-excess hypertension (pheochromocytoma, neuroblastoma). Corticosteroid excess (Congenital adrenal hyperplasia, Cushing’s or Conn’s syndrome). Essential hypertension.

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HYPERTENSION (Blood Pressure in Childhood) Investigation of the Hypertensive Child The level and urgency of investigation depend on the rapidity of onset, severity, and age. The younger the child, and the more severe the hypertension, the more likely there is an underlying cause. Initial investigation is focussed on the kidneys, as 80% have a renal abnormality. You must also search for evidence of end organ damage. First line Investigations   

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Medical history (symptoms of hypertension, medications, trauma, growth) Family history (renal or CVS disease, endocrine tumours, phakomatoses) Examination - Mental state and coma score (Encephalopathy). - Optic Fundi (papillodema, haemorrhage, exudates). - Visual acuity and pupillary responses (Visual impairment). - Tone, power and reflexes (Hemiparesis, Bell’s palsy). - Tachycardia, gallop rhythm, hepatomegaly, crackles(Congestive heart failure). - Abdominal masses or bruits (Renal enlargement ,R Art stenosis). - Signs of virilisation or cushingoid habitus (CAH, Cushing’s syndrome). - Skin (neurofibromatosis) Urinalysis (urinary sediment, microscopy and culture) Cardiac investigations (CXR, ECG, echocardiogram) Renal function (U&E, creatinine, chloride, acid base, FBC, GFR estimation) Renal Ultrasound including Doppler study of renal arteries

Second Line Investigations     

Further imaging of the urinary tract (DMSA scan, MCU) Imaging of renal vasculature (CT angiography or MR. Angiography) Urine catecholamines Plasma renin and aldosterone ESR and ANA

Other Investigations (on advice from renal team) 

Renal vein renin sampling, arteriography, isotope scan for pheochromocytoma

NOTE: A normal ECG does not exclude left ventricular hypertrophy

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HYPERTENSION (Blood Pressure in Childhood) Hypertensive urgency Hypertensive urgency is defined as a significant elevation of blood pressure without evidence of end organ injury. Patients are symptomatic with headaches or nausea but without end organ involvement. The patient is clinically stable. Treatment with oral hypotensive agents is indicated if BP is above the 99th centile for age, height and gender, on three occasions 30 minutes apart. See Appendix for BP tables. The choice of agents are: Beta blockers (labetolol, atentolol) Vasodilators (isradipine, felodipine, amlodipine, minoxidil) Angiotensin converting enzyme inhibitors (captopril, lisinopril, enalapril) Diuretic if volume overload is evident. Sublingual nifedipine is unpredictable and should be avoided. Suggested drugs: Oral 

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Isradapine: 0.1 mg/kg/dose q 6- 8h. Hospital only. Will need to be changed to a different medication if patient requires outpatient antihypertensive therapy. NOT TO BE USED AS A MAINTENANCE MEDICATION Labetalol: - See dosing table Appendix 2 Enalapril: - See dosing table Appendix 2

Intravenous  Hydralazine: 0.15mg/kg iv q 3-4 hourly. Short acting rapid onset medication. Should not be used as maintenance medication. This can be given on the ward. Longer acting drugs such as amlodipine, lisinopril may be started but will not provide acute control of blood pressure

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HYPERTENSION (Blood Pressure in Childhood) Hypertensive Emergency Defined as a severe elevation of blood pressure associated with a clinical picture of rapid and progressive central nervous system, visual, myocardial, haematological or renal deterioration. Fibrinoid necrosis of arterioles with retinal exudates and haemorrhages occur. Congestive heart failure may occur, with infants being particularly prone to this complication. There is no specific level of BP that constitutes a hypertensive emergency. It is defined as a blood pressure high enough to cause acute injury to target organs    

Heart Brain Kidney Eye

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left ventricular failure hypertensive encephalopathy (9 - 33% of children) renal failure retinopathy

The most common causes in children are renal scarring from reflux nephropathy, and acute nephritis. Children are more prone to hypertensive encephalopathy than adults, and you must differentiate this from stroke or subarachnoid haemorrhage.

Management of the Hypertensive Emergency  

Admit the child to PICU. Consult paediatric nephrologist and intensivist on call

Acute severe hypertension requires urgent treatment to prevent end organ damage. In chronic severe hypertension, slow smooth BP reduction is strongly recommended. It is often difficult to know whether hypertension is acute or chronic at the first presentation. Signs of end organ damage are more likely in chronic hypertension (eyes, heart, kidney), and less likely to be present in acute severe hypertension. There is a high risk of neurological sequelae (spinal infarction, blindness) if anti-hypertensive drugs cause a precipitous fall in blood pressure.      

Sublingual nifedipine is unpredictable and should be avoided if the duration of hypertension is unclear and there are signs of end organ damage. Reduce blood pressure urgently. Secure IV access before commencing therapy Monitor BP and pupillary responses frequently during therapy Use continuous intra-arterial pressure monitoring. Dinamap is a second option in children aged over 5 years Aim to reduce blood pressure by one third of the total planned reduction in the first 24 hours, and the remaining 2/3 over the next 48 to 72 hours Formatted: Bullets and Numbering

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HYPERTENSION (Blood Pressure in Childhood) 

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The choice of intravenous antihypertensive drug is at the discretion of the treating physician. These need to given in ICU. o IV Labetalol: a bolus of 0.2 - 1 mg/kg, followed by a constant infusion (1 mg / ml in 0.9% NaCl). Begin infusion at 1 mg/kg/hour. Increase the infusion rate at 10 -15 minute intervals until there is an effect. If there is no effect at a dose of 2.5 mg/kg/hour, choose another agent. o IV Sodium nitroprusside infusion (0.5-10micrograms/kg/min) may be used as a second option. In this case, intra-arterial blood pressure monitoring is mandatory o IV Hydralazine as per above If BP falls too rapidly, give boluses of normal saline

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Avoid using ACE inhibitors until a renovascular cause has been excluded

Management of Primary Hypertension     

Weight reduction is the mainstay in obesity related hypertension. Dietary modification with emphasis on sodium intake reduction is strongly encouraged in those who have blood pressures in the prehypertensive range as well those with established hypertension. Lifestyle changes are integral to the successful treatment of hypertension. Pharmacological therapy is indicated when primary interventions are unsuccessful. Single agents which are suitable for daily dosing is preferred. Examples are ACE inhibitors, calcium channel blockers,  blockers. The goal for pharmacological therapy is reduction of blood pressure to