[Water and electrolytes disorders after brain injury: mechanism and treatment]. / Désordres hydroélectrolytiques des agressions cérébrales : mécanismes et traitements.

Electrolyte disturbances are frequent after brain injuries, especially dysnatremia and dyskalemia. In neurological patients, usual clinical signs of hyponatremia are frequently confounded with clinical signs of the underlying disease. Natremia absolute value is less important than speed of onset of the trouble. Most often, hyponatremia is associated with hypotonicity and intracellular hyperhydration, which may exacerbate a cerebral edema. Distinction between inappropriate secretion of antidiuretic hormone (SIADH) and cerebral salt wasting syndrome (CSWS) may be difficult and is mainly based on assessment of patient's volemia, SIADH being associated with normal or hypervolemia and CSWS with hypovolemia. After subarachnoid haemorrhage, the most common disorder is CSWS. In this case, fluid restriction is strictly prohibited. Treatment of CSWS needs to compensate for the natriuresis and may justify the use of mineralocorticoid. It is important to avoid excessively rapid correction of hypernatremia, with a maximal speed of correction of 0.5 m mol/l/h. Serum sodium monitoring should be mandatory for the first ten postoperative days after pituitary adenoma surgery. Therapeutic barbiturate may be responsible for life threatening dyskalemia.

Human assay of antimotion sickness drugs.

The present study was undertaken to improve previous testing procedures, involving the use of a slow rotation room, for assessing the efficacy of antimotion sickness drugs which had validity for groups of subjects but not for each individual in the group. Three major changes were introduced: first, the use of an incremental increase in the intensity of the stressful stimuli of constant intensity; second, a systematic distribution of placebos, rather than a random distribution, in using a modified Latin-square design; third, categorizing the responses as "inconsquential," "beneficial," and "detrimental"--the range of the "placebo responses" was doubled to define the inconsequential range and response above or below were, respectively, beneficial or detrimental. Only drugs known to have antimotion sickness effectiveness were tested and the cardinal findings can be briefly summarized: 1) The group responses were similar to the data previously reported; 2) Great individual differences in response to antimotion sickness drugs were revealed, implying that individual assessments must be made for maximal benefits; 3) The fixed-dose combination of promethazine hydrochloride and ephedrine sulfate (25 mg each) proved to be outstanding as this combination of homergic drugs clearly exhibited a suprasummation effect; and 4) A few tests were conducted using larger than usual doses and the results supported previous findings that, for a maximal beneficial effect in response to a single dose, individuals may vary both with regard to the choice of drug and the amount administered.

Oxygen cost during exercise in simulated subgravity environments.

Oxygen cost (VO2) and heart rate (HR) were determined during treadmill walking in simulated subgravity environments. The long axis of the subject's body was suspended parallel to the floor in a slow rotation room with feet aligned on the surface of a treadmill mounted 90 degrees on the wall. Without rotation, the subjects were virtually weightless against the treadmill; with centrifugation, environments of 0.25, 0.5 and 1 G were simulated. VO2 (open circuit) and HR (ECG) were measured during the 5th minute of walking at 3.2, 4.7 and 6.1 km/h. Similar measurements were also determined during walking at 1/2-G using the inclined plane technique. VO2 per unit mass and HR were significantly reduced in all subgravity environments. However, net VO2 per unit weight carried and, therefore, mechanical efficiency was found to be independent of gravity. This supports the idea that the most probable cause for the decreased O2 cost with reduced gravity is less body weight carried.