Modern automated insulin delivery systems have transformed type 1 diabetes management by optimizing glycemic variability and reducing patient burden. However, unexpected device failures can still lead to life-threatening complications. In particular, clinicians are increasingly encountering cases of hybrid closed-loop DKA when physical delivery fails despite automated algorithmic adjustments. This article reviews a recent clinical report of a patient using an advanced automated insulin pump who developed acute ketoacidosis. The case underscores how material reuse, subtle structural deterioration, and technology limitations converge to impair insulin infusion.

Clinical Case Presentation and Acute Management

A forty-five-year-old woman with long-standing type 1 diabetes mellitus presented to the emergency department exhibiting mild ketoacidosis. Notably, the patient utilized an advanced hybrid closed-loop system to regulate subcutaneous insulin delivery. She reported generalized malaise, nausea, and persistent hyperglycemia over several hours without overt fever, infection, or dietary indiscretion. Diagnostic evaluation revealed venous acidosis, ketonemia, and elevated blood glucose levels. Consequently, the medical team admitted the patient and initiated metabolic resuscitation according to current institutional diabetic ketoacidosis protocols.

Physicians administered intravenous crystalloid fluids alongside a continuous regular insulin infusion. Furthermore, nursing staff monitored capillary ketones, electrolytes, and arterial blood gases at scheduled hourly intervals. Because the clinical team acted promptly, the patient achieved complete resolution of metabolic acidosis within eighteen hours. Her anion gap normalized smoothly, and clinicians resumed subcutaneous basal therapy safely. However, standard clinical workups initially failed to identify any infectious or inflammatory trigger for the decompensation. Throughout the resuscitation process, the treating clinicians remained perplexed by the acute onset of ketoacidosis, given the patient's immaculate history of adherence and the absence of concurrent systemic illness. Therefore, endocrinologists scrutinized continuous glucose monitoring tracings and automated pump transmission logs to locate the true root cause of the acute event.

Mechanisms of Single-Use Material Degradation

Subsequent engineering and visual inspection of the patient's delivery hardware unmasked the precipitating defect. The patient had reloaded and reused a disposable insulin reservoir cartridge intended exclusively for single use. Specifically, she experienced an unexpected shortage of original manufacturer supplies, prompting her to refill the plastic cartridge manually. Although the cartridge appeared superficially intact, microscopic evaluation revealed progressive structural deterioration along the internal plunger seal and delivery neck.

Repeated mechanical stress degrades the silicone lubrication and polymeric tolerances inside disposable reservoirs. Consequently, the pump motor drive piston exerted uneven friction against the distorted cartridge walls. This mechanical resistance caused microscopic piston slippage and micro-leakage around the plunger gasket during basal pulses. Therefore, the device failed to infuse the programmed micro-boluses of rapid-acting insulin into the subcutaneous tissue. In addition, repeated sterilization and manual refilling introduce particulate matter and micro-tears in delicate luer-lock fittings. Consequently, the plastic housing suffered microscopic distortion after multiple re-insertions, compromising the airtight seal necessary for precise delivery. Over time, plastic fatigue compromises hydraulic pressure, leading to partial or complete occlusion without triggering high-pressure motor stall sensors. Thus, physical degradation directly undermined therapeutic insulin delivery.

Algorithm Limitations in Detecting Hybrid Closed-Loop DKA

Advanced hybrid closed-loop systems rely on sophisticated mathematical algorithms that dynamically adjust basal delivery based on real-time interstitial sensor readings. When sensor glucose values climb persistently, the automated algorithm responds by escalating basal rates and delivering automated correction boluses. However, the system assumes that mechanical hardware faithfully translates electronic dosing commands into actual subcutaneous drug delivery. In this scenario, the algorithm commanded repeated corrective insulin pulses, but the degraded cartridge prevented physical delivery.

Consequently, the automated system entered a deceptive cycle of escalating algorithmic delivery against non-responsive, climbing glucose levels. Because standard commercial systems lack inline flow sensors, the controller cannot directly measure actual fluid movement through the cannula. The internal software only detects motor resistance spikes that exceed pre-set mechanical pressure thresholds. Because the mechanical failure involved piston slipping and gasket deformation rather than a total distal blockage, line pressure remained below the alarm threshold. Therefore, the device never emitted an occlusion alert to warn the patient. Thus, the algorithm continued to display successful insulin delivery on screen, creating a false sense of security for the patient while systemic insulinopenia progressed unchecked. Furthermore, because rapid-acting insulin analogues have short half-lives, absolute insulin deficiency developed within four to six hours, culminating in rapid ketoacidosis.

Risks of Material Shortages and Off-Label Practice

This clinical emergency highlights a widespread yet under-recognized challenge in contemporary diabetes care. Patients living with chronic illnesses often confront supply chain interruptions, distribution delays, and steep out-of-pocket expenses for specialized consumables. Consequently, individuals occasionally adopt off-label conservation strategies, such as refilling single-use reservoirs or prolonging infusion set wear beyond recommended intervals. While patients undertake these measures out of logistical desperation or economic necessity, the clinical risks remain exceptionally severe.

Consequently, financial barriers and distribution bottlenecks force vulnerable individuals to make hazardous clinical trade-offs without fully comprehending the lethal mechanical consequences. Moreover, medical manufacturers engineer single-use diabetes consumables using precise biocompatible polymers that maintain stability for only one fill cycle. When patients introduce needles into cartridges repeatedly, they alter internal pressures and cause microscopic silicone displacement. Additionally, insulin preservatives can degrade plastic components over prolonged contact, increasing the risk of insulin fibril aggregation and cartridge binding. Therefore, clinicians must routinely ask non-judgmental questions regarding supply access during routine visits. Healthcare teams must identify supply vulnerabilities before patients resort to hazardous hardware reuse. When supply shortages occur, clinicians must provide clear guidance rather than letting patients navigate equipment constraints unsupported.

Preventive Protocols and Patient Education Priorities

To prevent catastrophic mechanical failures, endocrinologists and diabetes educators must establish robust patient safety protocols. Clinicians must educate all automated insulin delivery users on the absolute hazards of reusing single-use cartridges and infusion sets. Furthermore, education curricula must reinforce the foundational troubleshooting rule: unexplained, persistent hyperglycemia resistant to correction boluses requires an immediate hardware change. Patients should never assume the algorithm will overcome physical delivery bottlenecks.

Additionally, every patient utilizing an automated pump system must maintain an emergency contingency kit containing rapid-acting and long-acting injectable insulin pens. If glucose levels exceed 250 mg/dL with positive blood ketones, patients should immediately administer a manual subcutaneous injection using an insulin syringe or pen. This bypasses the entire mechanical delivery system while the patient investigates potential pump hardware failure. Moreover, clinicians should help patients formulate formal back-up plans during supply shortages, including temporary transitions to multiple daily injection regimens. Furthermore, clinics must maintain updated registry lists of patients on advanced automated systems to provide emergency outreach during regional supply crises or product recalls. By combining technological vigilance with rapid clinical contingency protocols, healthcare teams can successfully prevent avoidable episodes of ketoacidosis.

Why did the automated system fail to alert the user about the mechanical failure?

Automated insulin delivery systems detect blockages using internal motor pressure sensors that trigger when downstream line resistance spikes. In this case, structural deformation of the reused cartridge caused piston slippage and micro-leakage rather than a complete physical blockage. Because hydraulic pressure remained below the pre-programmed alarm threshold, the algorithm continued calculating and commanding insulin deliveries unaware that the physical medication was failing to enter subcutaneous tissue.

What immediate actions should automated pump users take during persistent hyperglycemia?

When pump users encounter persistent hyperglycemia exceeding 250 mg/dL that fails to respond to automated or manual correction boluses, they must check blood ketone levels immediately. If ketones are elevated, the patient should administer a correction dose using a standard syringe or pen rather than relying on the pump. Subsequently, they must replace the entire infusion set, cartridge, and insulin vial before resuming automated pump therapy.

How should clinicians manage patients facing insulin pump supply shortages?

Clinicians must proactively provide structured contingency plans whenever patients encounter supply interruptions. Rather than allowing patients to reuse single-use consumables, healthcare providers should transition them to temporary multiple daily injection regimens using basal and rapid-acting insulin pens. Furthermore, clinics should maintain emergency sample supplies, connect patients with manufacturer assistance programs, and ensure patients retain active, unexpired prescriptions for conventional injection equipment to prevent dangerous off-label reuse practices.

Disclaimer: This content is for informational and educational purposes only and should not be considered medical advice. Always consult a qualified healthcare professional regarding any medical condition or treatment. Refer to the latest local and national guidelines for clinical practice.

References

López Calles A et al. Diabetic ketoacidosis associated with the reuse of single-use materials in a patient with type 1 diabetes mellitus treated with an advanced hybrid closed-loop system: A case report. Endocrinol Diabetes Nutr (Engl Ed). 2026 Nov 07. doi: undefined. PMID: 42998935.

Boughton CK, Hovorka R. New aspects of automated insulin delivery systems in type 1 diabetes. Lancet Diabetes Endocrinol. 2021;9(4):250-262.

American Diabetes Association Professional Practice Committee. 7. Diabetes Technology: Standards of Care in Diabetes—2024. Diabetes Care. 2024;47(Suppl. 1):S126-S144.