Postural hypotension and abnormalities of salt and water metabolism in myelopathy patients

Abstract

To describe the clinical manifestations of postural hypotension (PH) in myelopathy patients a standardized interview and chart review were carried out. Of 232 myelopathy patients with more than 2 years of paralysis seen during a 2 year period, 30 had been treated for PH. All PH patients were paralysed at levels higher than thoracic 7. The highest risk patients were tetraplegic, motor complete, 24 of 73 (33%). The common symptoms of PH were those of reduced consciousness (100%), strength (75%), vision (56%) and breath (53%). Precipitating factors were hot weather (77%) bowel care (33%) and meals (30%). Symptoms worsened with the duration of paralysis in 12 patients. Chronic hyponatremia was found in 54% of the PH patients and 16% of those without, P50.001. Of ®ve PH-hyponatremic patients with urine sodium and osmolality determinations, ®ve continued to retain water (4150 mOsm/kg) while four failed to conserve salt (419 mmol Na/L). PH is common among myelopathy patients with higher levels of paralysis, symptoms are variable, and abnormal salt and water metabolism often coexist.

Orthostatic hypotension following spinal cord injury: understanding clinical pathophysiology

“…66 In patients with chronic SCI, there is evidence of impaired water and sodium retention in the seated position, and limited salt and water intake. 25,74 Hyponatremia is also reported in acute SCI. 75 Thus, hyponatremia, probably secondary to supraphysiological ADH activity in SCI, 51 is common among acute and chronic SCI patients.…”

“…6 However, it has also been shown that autonomic dysreflexia can present in the early phases of SCI, 23,24 and that orthostatic hypotension can persist for years, and often becomes worse with time. 25 Numerous investigators identified various possible mechanisms that are likely to be responsible for the abnormal sympathetic cardiovascular control following SCI (Table 1). Firstly, there is a loss of descending supraspinal sympathetic excitatory and inhibitory control.…”

“…75 Thus, hyponatremia, probably secondary to supraphysiological ADH activity in SCI, 51 is common among acute and chronic SCI patients. 25,75,76 The combination of increased ADH secretion, low sodium intake, high sodium excretion and the resulting hyponatremia are likely to predispose towards small plasma volumes in SCI patients, and this, in turn, would exacerbate episodes of orthostatic hypotension in these individuals.…”

Unstable baseline blood pressure in chronic tetraplegia

“…[4][5][6] Both of these responses are clinically recognized in patients with the higher, more extensive spinal cord lesions. 3,4 It is reasonable to suspect that BP is unstable subclinically as well in the tetraplegic patient. This expectation is supported by the unstable cutaneous blood flow recently demonstrated in asymptomatic tetraplegic patients.…”

Salt wasting, hypotension, polydipsia, and hyponatremia and the level of spinal cord injury

“…Attention to both salt and water metabolism in patients with the syndrome described could improve circulation to critical areas such as the brain, the skin, the kidneys, and the lungs. 35 …”