Hospital CKM | Continuous Potassium Monitoring Prototype

Why this product

ICU potassium is already managed as a continuous-risk variable. The data is still intermittent.

Potassium variability is associated with mortality in critical illness. Computerized potassium protocols reduce time outside target ranges and reduce hypo/hyperkalemia events. Hospital CKM turns that protocol logic into a sensor-backed surveillance product.

206,987Potassium measurements in a 10,451-patient ICU analysis linking potassium level, variability, and mortality.

23.3% → 19.9%In-hospital mortality change reported after computerized potassium control protocol implementation.

9.2% → 3.9%Time below 3.5 mmol/L after protocolized potassium control in critical-care data.

<2% CVReported potassium reproducibility benchmark for i-STAT point-of-care analyzer studies.

Clinical painICU teams respond to scheduled BMPs, blood gases, alarms, insulin shifts, CRRT prescriptions, diuretics, arrhythmias, and post-op physiology. Dangerous K+ movement can happen between samples.

Product thesisHospital CKM does not replace blood gas analyzers. It watches the interval between them and triggers earlier confirmation, protocol action, or line/circuit review.

Utilitarian ROIThe highest-value wedge is where the patient already has vascular access, dialysis/CRRT flow, or frequent lab sampling, and where a missed potassium trajectory changes the next hour of care.

ICU K+ variability Computerized protocol i-STAT benchmark

Product architecture

A closed disposable flow-cell with hospital-grade calibration controls.

The hospital version should not inherit wearable constraints. It gets a bigger cartridge, larger reference reservoir, calibration standard, temperature control, stronger diagnostics, and a bedrail reader with EHR-ready logs.

01 / DISPOSABLE

Inline K+ flow-cell

Single-patient closed cassette with K1/K2/K3 valinomycin ISEs, blank control, dual references, temperature, pressure, bubble detection, and standard/calibration loop.

02 / REUSABLE

Bedside reader

Guarded electrometer front end, 24-bit ADC, fluidic valve/pump control, optical/bubble checks, heating block, local display, battery backup, and network export.

03 / OUTPUT

Protocol trigger

Reports validated K+ trend, drift/QC state, rate of change, and confirmatory-test trigger. It never acts as autonomous potassium dosing.

Sample paths

Three deployment modes, one measurement stack.

Hospital CKM should be designed as a modular fluidic platform so the same sensor stack can be proven in the easiest matrix first, then advanced toward higher-acuity blood-contacting use.

PATH A

Dialysate / CRRT effluent

Lowest blood-contact risk. Tracks potassium exchange and prescription response around CRRT/dialysis workflows. Best first hospital feasibility path.

PATH B

Drawn-line micro-sample

Small periodic samples from arterial/venous access into a disposable measurement loop, then waste. Enables direct blood potassium trend without leaving sensor in the bloodstream.

PATH C

True inline blood

Highest clinical immediacy, highest burden: hemocompatibility, clotting, hemolysis, pressure drop, sterilization, line integration, and regulatory review.

Recommended startBuild Path A first: dialysate/CRRT/effluent and controlled blood-simulant rigs. It proves continuous electrolyte sensing without needing a first prototype in the blood path.

Clinical expansionMove to drawn-line micro-samples after bench performance and cassette sterility/containment are stable. True inline blood is the accuracy north star, not the first build.

In-line CRRT electrolytes CRRT electrolyte disturbances

Production-locked proof kit

One orderable first article, built from validated potassium sensing technology.

Potassium ISE chemistry is already used in clinical electrolyte and blood-gas analyzers. The Hospital CKM first article applies that validated measurement principle to a controlled dialysate/effluent-style flow cell with redundant channels, onboard QC, temperature compensation, and locked acceptance gates.

$2.8K-$4.2KLocked first-article order with duplicate wet-path parts, spare fittings, bench references, and enough consumables to confirm reproducibility without redesigning.

5-30 secRaw voltage sampling interval; report K+ after smoothing, temperature correction, QC, and agreement gates.

2-9 mmol/LBench validation span covering hypokalemia, normal range, hyperkalemia, dialysis/CRRT transitions, and failure states.

±0.2 mmol/LFirst-article acceptance target in clean electrolyte/dialysate matrices before moving to artificial plasma, micro-sample blood, or hospital comparator work.

Locked buildOrder and assemble one transparent PMMA/COC/COP flow-cell architecture with two identical wet-path sets, DropSens carbon electrodes coated with K+ ionophore membrane, bench Ag/AgCl references, LMP7721 guarded buffers, ADS124S08 multi-channel ADC, TMP117 temperature, Sensirion flow, pressure diagnostics, and KCl standards.

Pass conditionAcross repeated 3.0, 4.0, 5.5, 7.0, and 9.0 mmol/L steps, K1/K2/K3 must agree, the blank and dual references must stay within drift limits, step response must stabilize quickly, and the state machine must suppress output during bubbles, stale calibration, or reference movement.

Risk controlThe extra spend is part of the first-article order. It buys duplicate consumables, duplicate flow-cell bodies, and spare fittings up front so the first article can be assembled, repeated, and stress-tested from one locked design without being blocked by a trivial consumable failure.

Why ADS124S08I replaced the earlier single ADS1220 role with TI ADS124S08 because one 24-bit, 12-channel ADC can read triplicate K+, blank, references, temperature, and diagnostics. Verified package: VQFN-32 RHB, 5.0 x 5.0 mm, now reflected in the viewer.

TI ADS124S08 TI LMP7721 TI TMP117 K+ ionophore cocktail In-line dialysis electrolyte monitoring

Rendered first article

Inspect the bedside CKM architecture.

The 3D preview in the hero and this full viewer show the same first-article assembly: bedrail reader, disposable flow-cell, triplicate K-channel stack, reference/blank controls, KCl standards, pump/flow path, and waste capture.

Open full-screen viewer

Assembly validation

This is the first article to assemble, not just a concept image.

Use this checklist to validate that the ordered parts and fabricated flow-cell match the prototype before testing. Anything that fails here should block chemistry claims until the physical stack is corrected.

01 / CASSETTE

Wet path body

Transparent PMMA/COC/COP body, 120 x 44 x 14 mm modeled envelope, 86 mm long x 3.0 mm ID-equivalent channel, 0.61 mL main-channel volume, four 1/4-28-style ports for sample, standard, waste, and flush.

02 / CHEMISTRY

Electrode bay

DropSens DRP-110-U75 strip or equivalent fixture, 33.8 x 10.2 x 0.5 mm substrate, 4 mm working electrode pads coated as K1/K2/K3, blank membrane, and reference interface.

03 / READER

Electronics envelope

Reusable reader envelope 170 x 112 x 42 mm with LMP7721 guarded buffer array, ADS124S08 5 x 5 mm ADC package, TMP117 local temperature sensor, flow sensor, pump/driver, MCU logging, and isolated power path.

Mechanical and electrical checks before wet testing

Check	Acceptance condition	Why it matters
Channel alignment	Fluid path crosses K1/K2/K3, reference, and blank sensing zone without dead pockets or sharp trapped-bubble corners.	Prevents stagnant fluid and bubbles from looking like K+ movement.
Electrode seating	DRP-110 strip is fixed, sealed, and repeatably positioned over the channel; membrane disks remain wetted under flow.	Turns the render into a repeatable physical measurement geometry.
Reference isolation	Bench Ag/AgCl reference and reference sentinel have stable chloride contact and do not share a failure path.	Reference drift is the fastest way to create false accuracy.
Guarded analog path	LMP7721 inputs are guarded, clean, high impedance, and routed away from pump/valve/display noise before ADS124S08 digitization.	Potentiometric K+ signals are high impedance and can be ruined by leakage.
Flow instrumentation	SLF3S-0600F, pump, manual stopcocks, KCl standards, and waste capture route around the cassette without kinks or unmeasured bypass paths.	Validates that every K+ estimate corresponds to fresh known fluid.
Logging readiness	Before first wet run, log raw K1/K2/K3 mV, blank, reference delta, temperature, flow, pump state, sample label, and withheld-output reason.	Makes the first article auditable and reproducible from run one.

Workflow

The buyer is not buying a sensor. They are buying faster potassium control.

Hospital CKM should sit inside existing care pathways: blood gas confirmation, CRRT/dialysis prescription, insulin protocols, diuretic titration, telemetry, and medication review.

Clinical jobs

DKA / insulinWatch rapid intracellular K+ shifts between scheduled BMPs and blood gases.

CRRT / dialysisTrack potassium exchange and dialysate/replacement-fluid prescription response.

Cardiac surgeryDetect drift during post-bypass recovery, diuresis, insulin infusion, and arrhythmia risk windows.

ICU protocolProvide continuous surveillance that triggers a confirmatory sample or protocol escalation sooner.

Hard UI rules

GreenValidated trend, QC pass, recent comparator, stable references, in-range temperature.

AmberTrend usable but confirmation recommended: drift rising, calibration aging, rapid K+ movement.

RedUrgent clinical review: confirmed dangerous trajectory or discordance with comparator.

GrayWithhold output: clot/bubble/flow artifact, reference failure, calibration failure, hemolysis suspicion.

Validation gates

Hospital CKM only ships if it earns trust against existing analyzers.

The hospital bar is higher than the wearable bar. The product must prove analytical performance, hemocompatibility or safe sample isolation, workflow fit, alarm discipline, and clinical usefulness.

AnalyticalK+ slope, bias, precision, drift, hysteresis, temperature response, protein/fouling response, matrix effect, and calibration recovery across 2.0-9.0 mmol/L.

ComparatorDense paired samples against blood gas, i-STAT/POC, central lab, and dialysis/CRRT machine chemistry where applicable.

FluidicNo leaks, no unsafe pressure drop, bubble/clot detection, no hemolysis above accepted thresholds, and no blood-contacting reusable part.

SoftwareFail-closed state machine, audit log, calibration age, comparator age, alarm thresholds, and no autonomous dosing recommendation.

Human factorsNurse installation, sterile boundary, line-change workflow, alarm comprehension, and clinician response must pass simulation before patient feasibility.

First-article acceptance gates

Gate	Pass condition	Unlocks
KCl standards	3.0, 4.0, 5.5, 7.0, and 9.0 mmol/L steps track within the first-article error target and stabilize quickly.	Dialysate/CRRT matrix testing
Triplicate agreement	K1/K2/K3 agree within the preset mV/K+ window while the blank channel stays quiet.	Confidence score and majority-vote QC
Reference stability	Dual-reference delta stays inside drift limits across the run window and during calibration checks.	Longer duration runs and calibration aging
Flow artifact rejection	Bubble, stale-flow, and pressure anomalies suppress output instead of creating false potassium movement.	Enclosed reader and valve automation work
Dialysate matrix	Performance holds in CRRT/dialysate-like sodium, bicarbonate, temperature, and flow conditions.	Artificial plasma and drawn-line blood micro-sample planning

Expected data

The first useful dataset is raw mV truth, not a polished medical number.

Production readiness starts by logging everything needed to explain every potassium estimate, every suppressed estimate, and every calibration correction.

RAW SIGNAL

Electrode voltages

K1/K2/K3 open-circuit potential versus reference, blank membrane potential, reference A/B delta, ADC noise, settling time, and channel-to-channel agreement.

CONTEXT

Fluidic state

Flow rate, pump state, valve state, upstream/downstream pressure, bubble flag, calibration standard age, sample refresh estimate, and thermal state.

OUTPUT

Validated K+ trend

Temperature-corrected potassium estimate, confidence/QC state, rate of change, last comparator sample, reason for any withheld output, and alarm/confirmation trigger.

Bench expectationValinomycin ISE literature supports Nernstian or near-Nernstian slopes around 55-62 mV/decade, second-scale response in clean solutions, and low drift in controlled setups. The first article should prove repeatable step tracking with production-style QC logs.

Hospital barExisting point-of-care electrolyte analyzers already validate the core potassium ISE principle. Hospital CKM must validate continuous flow-cell behavior against blood gas/i-STAT/central lab and must report "confirm now" rather than act as a dosing device.

POC electrolyte performance K+ potentiometric drift example Screen-printed K+ ISE research

Hospital economics

The wedge is high-acuity beds where missed potassium drift is expensive.

This is not a consumer subscription. It is a per-patient disposable plus bedside reader platform for units already paying for blood gas cartridges, dialysis consumables, ICU telemetry, and adverse-event prevention.

ReaderReusable bedside module: analog front end, pump/valves, display, network export, battery backup.

CassetteSingle-patient disposable flow-cell with electrodes, references, fluid path, calibration reservoir, sterile packaging.

Use casesDKA, CRRT, dialysis transition, post-cardiac surgery, transplant induction, refeeding, high-risk arrhythmia beds.

ValueEarlier confirmation, fewer hours out of range, fewer unnecessary samples, better protocol adherence.

Buy now item	Why this part	Locked order cost	Scale target
Metrohm DropSens DRP-110-U75 pack	Fastest replicable carbon SPE substrate for K+ membrane experiments; 33.8 x 10.2 x 0.5 mm, 4 mm working electrode. One 75-pack is enough for coating practice, triplicate channels, and repeats.	$285	$2-$6 custom printed lane
Sigma/Supelco K+ ionophore cocktail / valinomycin membrane reagents	Known potassium-selective chemistry for biological and aqueous ISE work. Buy enough to coat multiple membranes from the same chemistry lot.	$150-$500Vendor quote/login pricing varies.	$0.50-$2 per cassette chemistry
Bench Ag/AgCl reference electrodes plus Ag/AgCl ink planning	Use bench references to lock first-article measurement quality, then translate to printed/reservoir references after drift behavior is known.	$150-$450	$1-$4 printed/reference reservoir
TI LMP7721 buffer array + guarded PCB/EVM path	3 fA input-bias electrometer buffers protect high-impedance ISE nodes. Buy enough channels for K1/K2/K3, blank, and references.	$150-$350Guarded layout and cleaning process matter more than chip price.	$12-$25 electronics
TI ADS124S08 24-bit 12-channel ADC	Replaces ADS1220 role; reads triplicate K+, blank, references, temperature, and diagnostics from one precision ADC.	$75-$250Prefer EVM/dev path for first article, then custom PCB.	$5.28+ at 1k IC volume
TI TMP117 temperature sensor	High-accuracy local temperature for Nernst compensation and QC gating; 2 x 2 mm package.	$10-$40	$2-$5
Sensirion SLF3S-0600F liquid flow sensor	Orderable microflow validation for sample refresh and valid trend windows; 48 x 15.5 x 8.9 mm.	$115-$205	$20-$45 integrated/OEM
Bartels mp6 micropump plus driver	Compact controlled flow for calibration/sample loop; 30 x 15 x 3.8 mm, 0-8 mL/min liquid.	$120-$250	$15-$35 OEM or alternate pump
Manual 3-way stopcocks now; Lee LHD valve bank later	Manual routing reduces first-article complexity. Add automated Lee valves after the chemistry and flow loop pass locked acceptance.	$30-$120 nowHold $150-$400 Lee valves until automation gate.	$25-$80 manifolded valves
Two transparent flow-cell bodies, fittings, tubing, KCl standards, waste capture	Physical bench loop: 1/4-28 fittings, PMMA/COC/COP flow body, KCl reservoirs, waste path. Two bodies avoid a redesign if one is damaged or contaminated.	$700-$1,200	$8-$25 molded cassette before sterile pack
Display/MCU/power/enclosure/logging harness	Prototype reader shell and logging/display control; production will be medically isolated and sealed.	$300-$600	$55-$120 reusable reader COGS share

Order now totalProduction-minded first article: approximately $2,800-$4,200 for the orderable stack plus duplicate wet-path consumables. The lean minimum remains around $1,800-$2,800, but the locked order is better because it gives assembly and repeat-test margin from day one.

At scaleDisposable cassette target COGS: roughly $18-$45 before sterile packaging and QA at low production maturity, with a long-term target around $12-$25. Reusable reader target COGS: roughly $180-$350 early, $90-$180 mature, excluding clinical service and support.

Order firstElectrodes, K+ membrane chemistry, KCl standards, bench references, LMP7721/ADS124S08/TMP117 dev hardware, Sensirion flow sensor, mp6 pump/driver, manual routing parts, fittings/tubing, waste capture, and two transparent flow-cell bodies. Defer custom sterile blood-path parts and automated valve banks until the locked first article passes.

Build to shipment

Make the shortest path to a useful hospital pilot.

The right sequence is not "build everything." It is retire the hardest unknowns in the order that creates a credible hospital feasibility package.

Bench CKM flow-cellBuild a transparent cassette with K1/K2/K3, reference, blank, temperature, pressure, bubble, and standard-loop ports. Test in KCl standards, dialysate, artificial plasma, and protein/fouling matrices.

CRRT/dialysate feasibilityProve continuous K+ tracking in dialysate/effluent-like matrices before blood-contacting designs. Show response to prescription-like potassium changes.

Micro-sample blood loopMove to drawn-line sample loops with waste capture. Compare against blood gas/i-STAT/central lab and quantify hemolysis, clotting, drift, and calibration recovery.

Simulation pilotRun ICU nurse and physician simulations: setup, alarm interpretation, comparator prompts, protocol response, and EHR-style event review.

Observational hospital studyNo care-driving claims. Collect paired comparator data, alarm logs, setup time, false alarms, and clinician response to trend information.

Boundaries

What Hospital CKM does and does not claim.

DOES CLAIM

Research architecture

A physically plausible hospital potassium trend monitor architecture with direct fluid access, redundant K+ sensing, onboard calibration, comparator-first validation, and fail-closed workflow.

DOES NOT CLAIM

Clinical readiness

No diagnosis, no autonomous dosing, no replacement of blood gas/lab potassium, no sterile patient use, no mortality reduction claim until analytical and clinical studies prove it.