A retrospective study of hyponatremia in tetraplegic/paraplegic patients with a review of the literature.

The aetiology of hyponatremia in tetraplegic patients is multifactorial and includes not only general factors such as the use of diuretics and the intravenous infusion of hypotonic fluids, but also certain mechanisms which operate in the spinal cord injured: decreased renal water excretion due to both intrarenal and arginine vasopressin dependent mechanisms (resetting of the osmostat), coupled with habitually increased fluid intake, and the ingestion of a low salt diet. Between 1984 and 1993 we treated 28 episodes of hyponatremia in 19 patients (males: 10; females: 9). Fourteen were tetraplegic and five paraplegic (thoracic lesion in four and lumbar lesion in one). Six patients were asymptomatic during seven episodes of hyponatremia which were detected during routine blood tests. Seven patients were suffering from an acute chest infection, three had an acute urinary tract infection, one had an infected ischial pressure sore and a 69 year old paraplegic patient had bronchopneumonia as well as sepsis from a gangrenous pressure sore in the supraanal region. The time interval between the onset of paralysis and occurrence of the first episode of hypnoatremia was less than a month in only four of the patients. The lowest plasma sodium level observed was less than 100 mmol/l in two, between 100 and 110 mmol/l in four, between 111 and 120 mmol/l in eight patients, and between 121 and 128 mmol/l in 14 cases. Six patients also had hypokalemia (K+ < 3 mmol/l). Only one patient had and elevated plasma creatinine (201 umol/l). Treatment of sepsis and fluid restriction were the mainstay of treatment with only two patients receiving hypertonic saline. All patients with underlying sepsis were treated with antibiotics, usually administered intravenously. The outcome was good in 26 of the 28 episodes. Two patients died: a 68 year old tetraplegic patient with consolidation of the left lung, cystadenocarcinoma of both ovaries and squamous cell carcinoma of the forehead who presented with generalised oedema, with a plasma sodium level of 118 mmol/l, and potassium of 2.4 mmol/l and who was treated with 2 N saline + potassium + frusemide; she died 1 day later. The only other death was that of a 78 year old female tetraplegic patient who 2 days after sustaining cervical trauma developed hyponatremia because of intravenous infusion of hypotonic fluids given at another hospital, presumably to correct hypotension. She recovered from hyponatremia with fluid restriction, but 3 days later she succumbed to bronchopneumonia and respiratory insufficiency. No patient developed central pontine myelinolysis.(ABSTRACT TRUNCATED AT 400 WORDS)