Hypermagnesemia as a cause of refractory hypotension, respiratory depression, and coma. 
Hypermagnesemia developed in a patient as a result of excess antacid ingestion, bowel obstruction, and renal failure.  Before the diagnosis was considered, refractory hypotension, respiratory depression, and coma developed, all of which were eventually reversed through the lowering of the serum magnesium concentration by hemodialysis.