a syndrome of symptomatic hypercalcemia and hypermagnesemia has previously been described in dialysis patients in the 1960s . it was attributed to failure in water treatment systems of that era and was termed the  hard water syndrome [ 1 , 2 ] . we present a case of life - threatening hypercalcemia in a home nocturnal hemodialysis patient that resulted from a technical error . the patient is a 46-year - old woman with diabetic nephropathy on home nocturnal hemodialysis for 6 years . she presented to the emergency room with a history of vomiting , profuse sweating and progressive deterioration in sensorium , which started 1 h after initiation of dialysis the previous night . because of the change in her status , her husband stopped the dialysis 3 h after initiation . in the emergency room , she was stuporous , had a heart rate of 48 b.p.m . and blood pressure of 98/56 mmhg . her laboratory investigation showed a serum sodium of 128 mmol / l , potassium 4.7 mmol / l and creatinine 266 mol / l ( 3.02 mg / dl ) . the serum magnesium was also elevated at 2.09 mmol / l ( 5.1 meq / l ) . her blood work 1 month prior to the present episode showed a serum calcium of 2.18 mmol / l ( 8.7 mg / dl ) , serum phosphate of 1.26 mmol / l ( 2.18 mg / dl ) and an intact parathyroid hormone 22.85 pg / ml . she was initiated on urgent hemodialysis with a low - calcium bath . over a period of the next 6 h , her clinical status improved and at the end of 10 h of dialysis , her calcium had normalized to 2.57 mmol / l ( 10.3 mg / dl ) . note bradycardia ( heart rate 50 b.p.m . ) and shortened qtc interval ( 357 ms ) . note normal heart rate ( 82 b.p.m . ) and qtc interval ( 449 ms ) . investigation as to the cause of the hypercalcemia revealed that the reverse osmosis machine used for dialysis at home was changed 1 day prior to the patient s presentation to the hospital . it was found that the drain port of the reverse osmosis machine was mistakenly connected to the dialysis machine and the product water for dialyzate was connected to the drain ( figure 2 ) . the results from the reverse osmosis drain that was incorrectly connected to the dialysis machine input showed a conductivity of 400416 s , caused by the high calcium concentration in the sample . thus , the drain water from the reverse osmosis machine that contained a very high concentration of calcium was used in the dialyzate , resulting in acute hypercalcemia . reverse osmosis machine bottom panel : note port for product water on the left ( arrow ) and port for drain water on the right ( arrowhead ) . in this case , the patient presented with acute life - threatening hypercalcemia related to human technical error . in a dialysis patient , these were excluded in our patient as the sequence of events suggested that the hypercalcemia was acute and had developed soon after initiation of dialysis . as the patient had been well before the start of dialysis , it was very likely that the dialysis process was responsible for the change in clinical status . the reverse osmosis machine had just been replaced at the patient s home , which also heightened our suspicion of a technical fault in the dialysis process as the underlying cause of the patient s problem . the detection of the reversal of the connections in the reverse osmosis machine confirmed our suspicion . reported a patient who developed severe hypercalcemia due to an inadvertent hose reversal in the reverse osmosis machine used for dialysis in hospital . in our case , when the reverse osmosis machine used for the patient s dialysis at home was examined , we discovered that the ports for connection of the processed and drain water were similar in appearance and close to each other . this case led us to evaluate the quality assurance aspect of our home hemodialysis programme . as nocturnal hemodialysis is a novel form of therapy , there are few validated benchmarks to evaluate a program from a patient or technical perspective . most of the quality assurance guidelines for nocturnal home hemodialysis programs focus on outcomes from a patient 's perspective . technical guidelines for setting up home dialysis units are lacking . we reevaluated the training program for our technicians and mandated all dialysis setups to be cross - checked by another technician before any clinical use . we also ensured that the ports for connection of the hoses to the reverse osmosis machines were color coded so as to avoid a similar incident in the future . this case illustrates the complexities involved in the care of a patient on home hemodialysis and how a human error can lead to catastrophic events emphasizing the importance of quality assurance in the delivery of complex medical care in the home setting .
life - threatening hypercalcemia in dialysis patients is very unusual . 
 we present a case where life - threatening hypercalcemia in a home hemodialysis patient resulted from a technical mistake . 
 a 46-year - old woman , on home nocturnal hemodialysis , presented to the emergency room with history of altered sensorium , vomiting and sweating , which started 1 h after initiation of dialysis the previous night . 
 serum calcium was 6.5 
 mmol / l . 
 she improved with 10 h of low - calcium hemodialysis . 
 investigation revealed that the drain port of the reverse osmosis machine was connected to the dialysis machine and the product water was connected to the drain leading to acute hypercalcemia .