Clinical physiology - pharmacology: The wet brain: Drug-induced hyponatremia

Abstract

A 72-year-old male has a history of hypertension, diabetes mellitus, ischemic cardiomyopathy and degenerative osteoarthritis. He is treated with digoxin 0.25 mg qd, hydrochlorothiazide 50 mg qd, chlorpropamide 250 mg qd, propranolol 120 mg bid, ibuprofen 400 mg qid and amitriptyline 25 mg tid. His past medical history is also significant for prostatism with overflow incontinence and endogenous depression. Over a four-week period he develops memory loss for recent and past events, occasional urinary incontinence, three episodes of falling and evidence of weight loss. Is there sufficient evidence in the history to implicate a reversible form of memory loss? If yes, does the index of suspicion point to (a) normal pressure hydrocephalus, (b) meningioma, (c) aneurysm, (d) multiple medications? First, it is necessary to understand that of all of the secondary or reversible forms of dementia, medications comprise the number one cause. In this person's history it is most likely that he has a secondary or reversible form of dementia due to at least one and, possibly, more medications. The physical exam revealed a cachectic and illappearing elderly male. He was lethargic but arousable. His mucous membranes, axillae and groins were moist. Blood pressure taken in the supine position was 150/80. His pulse was 77 and regular. The lungs were clear. His heart was enlarged percussion to the anterior axillary line and was associated with an $3S4 gallop. Examination of the abdomen revealed a palpable liver edge three centimeters below the right costal margin and a palpable liver edge three centimeters below the right costal margin and a palpable urinary bladder up to the umbilicus. The stool was heme positive. He had no edema. Neurological examination revealed the patient to be oriented to person and place but he was easily confused and occasionally replied incoherently. His strength was symmetrical and intact. The deep tendon reflexes were diffusely decreased but there was no B abinski reflex, tremor or asterixis. Do the physical findings confirm a dementia or an acute confusional state (delirium)? The physical exam points more to an acute confusional state which could be superimposed on a dementia process. One cannot ascertain this in the setting of delirium. One needs to find the cause of the delirium which in this case may be drugs or a surgically correctable lesion and then once rectified, neuropsychological testing could be performed to elucidate the presence of primary dementia, i.e. Alzheirner's, Binswanger's, etc. Laboratory evaluation revealed: Bicarbonate 34.5 mEq/L Sodium 102 meq/1 Chloride 51 meq/1 Bicarbonate 34.5 mEq/L Potassium 2.7 meq/1