A RETROSPECTIVE STUDY OF HYPONATREMIA IN TETRAPLEGIA PARAPLEGIC PATIENTS WITH A REVIEW OF THE LITERATURE

The aetiology of hyponatremia in tetraplegic patients is multifactoria l and includes not only general factors such as the use of diuretics a nd the intravenous infusion of hypotonic fluids, but also certain mech anisms which operate in the spinal cord injured: decreased renal water excretion due to both intrarenal and arginine vasopressin dependent m echanisms (resetting of the osmostat), coupled with habitually increas ed fluid intake, and the ingestion of a low salt diet. Between 1984 an d 1993 we treated 28 episodes of hyponatremia in 19 patients (males: 1 0; females: 9). Fourteen were tetraplegic and five paraplegic (thoraci c lesion in four and lumbar lesion in one). Six patients were asymptom atic 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 inf ected ischial pressure sore and a 69 year old paraplegic patient had b ronchopneumonia as well as sepsis from a gangrenous pressure sore in t he supraanal region. The time interval between the onset of paralysis and occurrence of the first episode of hypnoatremia was less than a mo nth in only four of the patients. The lowest plasma sodium level obser ved was less than 100 mmol/l in two, between 100 and 110 mmol/l in fou r, between 111 and 120 mmol/l in eight patients, and between 121 and 1 28 mmol/l in 14 cases. Six patients also had hypokalemia (K+ < 3 mmol/ l). Only one patient had an elevated plasma creatinine (201 umol/l). T reatment of sepsis and fluid restriction were the mainstay of treatmen t with only two patients receiving hypertonic saline. All patients wit h underlying sepsis were treated with antibiotics, usually administere d intravenously. The outcome was good in 26 of the 28 episodes. Two pa tients died: a 68 year old tetraplegic patient with consolidation of t he left lung, cystadenocarcinoma of both ovaries and squamous cell car cinoma of the forehead who presented with generalised oedema, with a p lasma sodium level of 118 mmol/l, and potassium of 2.4 mmol/l and who was treated with 2 N saline + postassium + frusemide; she died 1 day l ater. The only other death was that of a 78 year old female tetraplegi c patient who 2 days after sustaining cervical trauma developed hypona tremia because of intravenous infusion of hypotonic fluids given at an other 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. No patient with a severe degree of hypon atremia (sodium < 100 mmol/l) had respiratory involvement requiring ve ntilatory assistance. In conclusion, hyponatremia is seen in tetrapleg ic patients often in association with sepsis either in the lungs or in the urinary tract, and is best managed by treatment of the predisposi ng factor(s) along with fluid restriction.