A retrospective review of the ambulatory blood pressure patterns and diurnal urine production in subgroups of spinal cord injured patients.

STUDY

DESIGN

Retrospective study.

OBJECTIVES

To quantify diurnal blood pressure (BP) patterns and nocturnal hypertension and to measure diurnal urine production in spinal cord injury (SCI) patients with clinically significant disorders of BP control.

SETTING

A specialist state-based spinal cord service in Victoria, Australia.

METHODS

Medical records of patients with traumatic SCI who were referred to a specialist service for management of a BP disorder were examined. Ambulatory BP and nocturnal urine production were compared between groups of patients classified according to level, completeness and chronicity of SCI. Patients with night:day systolic BP <90% were classified as dippers, 90-100% as non-dippers and >100% as reversed dippers.

RESULTS

Patients (44 tetraplegic, 10 paraplegic) were predominantly males (92.6%) aged 41±2.5 years (mean±s.e.m.). Referral was for orthostatic intolerance (n=37), autonomic dysreflexia (n=6), nocturnal polyuria (n=4), elevated BP (n=1) and peripheral oedema (n=1). The average BP was 111.1±1.4/65.0±1.2 mm Hg. In 56% of patients (n=30), BP at night was higher than during the day and another 37% (n=20) were non-dippers. Nocturnal hypertension was present in 31% (n=17) of the patients. In the tetraplegic patients, urine flow rate was greater during the night than day (121±9.5 ml h(-1) vs 89±8.2 ml h(-1), P=0.025).

CONCLUSION

Ambulatory BP monitoring in patients with SCI and clinically significant BP disorders detected a high incidence of reversed dipping and nocturnal hypertension. We postulate elevated nocturnal BP may contribute to nocturnal diuresis that might cause relative volume depletion and thereby contribute to daytime orthostatic hypotension.