Blood pressure elevation in children with orthopedic immobilization

At the bottom of the differential diagnosis list: unusual causes of pediatric hypertension

Hypertension affects 1-5% of children and adolescents, and the incidence has been increasing in association with obesity. However, secondary causes of hypertension such as renal parenchymal diseases, congenital abnormalities and renovascular disorders still remain the leading cause of pediatric hypertension, particularly in children under 12 years old. Other less common causes of hypertension in children and adolescents, including immobilization, burns, illicit and prescription drugs, dietary supplements, genetic disorders, and tumors will be addressed in this review.

Hypertension associated with skeletal traction in children

Since traction-associated hypertension seems to be a relatively unknown phenomenon, a survey was done of its incidence in children treated with skeletal traction for fractures and orthopaedic diseases. The correlation with hypercalcaemia, a possible aetiological factor, was also explored. Blood pressure was recorded three times a day with an automatic oscillometric unit during the stay in the hospital. Serum calcium, creatinine and total protein concentrations were measured once a week. Patients with pre-existing diseases or renal trauma were excluded. Arterial hypertension (systolic and/or diastolic) was found in 31/50 children (62%). In almost half of these the rise in systolic blood pressure was 10 mmHg or more above the 95th percentile. Hypertension occurred in most cases within the first 3 weeks of treatment; in 7 children it developed after 3 or more weeks of traction. All children became normotensive within 1 week after discontinuation of traction. Clinical symptoms were rare: two children complained of headache. In no instance had traction to be discontinued before the planned date because of hypertension. In the hypertensive group were more preschool children and more humeral fractures as compared to the normotensive group (n = 19). Hypercalcaemia occurred in 11 children and was equally distributed in hypertensive and in normotensive children. It is concluded that arterial hypertension is a frequent finding in children in traction, but its clinical relevance is uncertain. Hypercalcaemia is not a rare finding in immobilized children, but probably plays no causative role in traction-related hypertension.

Renal consequences of immobilisation in children with fractured femurs

Parameters of renal function and calcium homeostasis were studied in 8 children, immobilised for 5-9 weeks with fractured femurs, weekly during immobilisation and fourth weekly following mobilisation until all parameters returned to normal. During immobilisation 1 patient became hypercalcaemic, but all showed an increase in serum calcium and all developed hypercalciuria. During immobilisation all showed diminished urine osomolality after a 12-hour fast (mean 591 +/- 133 mOsm/kg) which improved 4-39 weeks after mobilisation (mean 973 +/- 87 mOsm/kg). Serum creatinine, urinary beta-2-microglobulin and renal ultrasound appearances were all normal. An inverse relationship, R = -0.70, was demonstrated between serum calcium and fasting urine osmolality during immobilisation. Three patients showed diminished urinary concentrating ability beyond 4 weeks after mobilisation. For 1 patient this defect persisted for 8 months and glomerular filtration rate was diminished 9 months after mobilisation, raising the possibility of long term renal damage in immobilised patients.

Mechanisms of elevated blood pressure in human essential hypertension

This review of the mechanisms of elevation of blood pressure in human essential hypertension first focuses on individual mechanisms and their interrelations. The authors then try to identify those forms of essential hypertension in which the major determinants are known. When the most significant processes associated with elevated blood pressure in individual patients are understood, a rational approach to therapy can be undertaken even though the ultimate cause of the disorder is not understood.