Unmet need: Potassium (K) is a mineral that controls nerve and muscle (including heart) function. Maintaining K within the normal range is important  to maintain a normal heart rhythm and maintain fluid and electrolyte balance in the body. Healthy kidneys remove excess K in the urine to maintain normal levels in the blood. When patients have advanced kidney disease, the kidneys cannot efficiently remove excess K, leading to high potassium levels (hyperkalaemia). The effects of hyperkalaemia include nausea, weakness, irregular heart rate, heart failure and sudden death. In patients who are on dialysis therapy or are approaching the need for dialysis, potassium levels can rise due to high potassium intake in the diet, medications and following surgery. Treatment of hyperkalaemia in these patients is urgent dialysis. Currently electrolytes, including K levels in the blood are measured in the labs and can take up to 24hours to receive the result (within 2 hours if requested urgently in the hospital setting). The ability to monitor K levels of patients in a similar fashion to a glucose meter - i.e a pin-prick test with immediate response - would offer a significant improvement to the current practice and allow immediate treatment.

Solution: Currently, portable monitors are utilised in various settings, including in the community to assess blood gases in patients with respiratory disease and in war zones to monitor measures of kidney function (creatinine). Such a device will provide a simple easy to use potassium monitor that will allow a rapid turnaround of potassium levels to aid patient/clinician discussion. The ultimate goal would be to have a monitor similar to a blood glucose monitor with disposable strips, and tailor made for renal patients that could be used by renal units, local clinics and patients.

The D4D team inLeedslooked at available technology to assess if a currently available product could be adapted to meet the needs of renal patients. This work showed that a hand-held blood analyser, used by a non-specialist, can provide repeatable, accurate results for potassium levels when compared to laboratory tests. However, this device is overly complex and expensive for the needs of renal patients, as it provides measurements for a large range of electrolytes and blood gasses. Work is ongoing to try to develop a smaller, simpler and cheaper device based on the same technology but tailored specifically for the needs of dialysis patients.

Areas where potassium monitor devices would be useful:

• In dialysis patients post-operatively, dialysis could be provided immediately if required rather than awaiting the lab result for several hours
• In dialysis patients whose vascular access (typically fistula) has failed, immediate decision can be made regarding requirement of urgent dialysis or whether an admission could be prevented (with the patient awaiting management of access problem as an out-patient), thereby improving patient experience
• In dialysis units, it would allow accurate decisions on dialysis time, dosage and choice of dialysis fluid to use.
• In patients with chronic kidney disease (CKD) (not on dialysis) and heart failure, medications to treat the latter can raise K levels. The effect of such medications can be assessed during the appointment time (either in cardiology clinics or GP surgery) and allow dosage adjustments and offer a more direct care rather than requiring follow up appointments.
• In patients with CKD, would aid patients in monitoring effects of their diet on K and thereby adjust diet as necessary.