CGM-Assisted Management of PN

The objective of this investigation is to quantify dysglycemia associated with cycled parenteral nutrition (PN) and elevated glucose infusion rates (GIR) in infants with intestinal failure and PN-dependence, leveraging high-frequency continuous glucose monitor (CGM) sensor glucose values in a prospective, observational study.

Intestinal failure is a malabsorptive state which necessitates PN in its most severe form. PN is ideally transitioned from continuous (24 hr/day) to cycled PN (\<24 hr/day), requiring higher glucose infusion rates (GIR) to provide the same nutrition content over a shorter time-period. Patients on cycled PN, especially infants, are vulnerable to dysglycemia (abnormal glucose levels), specifically hyperglycemia during PN infusions (due to inadequate insulin relative to high GIR) and hypoglycemia when PN is cycled off (due to delayed insulin suppression after PN suspension). There is no established pediatric GIR threshold above which the risk of abnormal glucose levels significantly increases.

While current practice relies on intermittent blood glucose checks, continuous glucose monitors (CGM) measure high-frequency glucose profiles via minimally-invasive sensors, and are capable of precisely detecting clinically-actionable trends that may otherwise go unrecognized. The CGM sensor measures interstitial glucose, an accepted proxy for blood glucose in patients > 2 years old with diabetes or glycemic variability. CGM has been successfully used in infants and can fulfill the need for greater quantitative insight into glucose trends in metabolically and neurologically fragile populations, including infants with intestinal failure.

The investigators hypothesize that during high-GIR, cycled PN: a) trough glucose while PN is suspended is less than normal (statistically defined as 100 mg/dL), and b) average glucose while receiving the target (highest) GIR is greater than normal (statistically defined as 120 mg/dL).

Eligible infants will be identified among hospitalized infants at Boston Children's Hospital and followed by the Home Parenteral Nutrition (HPN) program and the Center for Advanced Intestinal Rehabilitation (CAIR). All enrolled participants will have a Dexcom G6 Pro CGM placed within 1 week prior to the anticipated initiation of PN cycling, and CGM will be worn using blinded mode for up to 30 days until target GIR cycled PN is reached (3 sensors maximum). If target GIR cycled PN is not reached following 3 sensor periods (up to 10 days per sensor), the parent/guardian will be approached to accept or decline participation in an optional extension phase. In the extension phase, the primary study will be repeated and CGM monitoring will continue until target GIR cycled PN is reached, up to an additional 3 sensor placements. No CGM will remain in place at the time of discharge.

The CGM readings will remain blinded to the clinical staff members, no real-time CGM alerts will be provided to the clinical staff. The clinical team will manage PN cycling and clinical blood glucose monitoring as per routine clinical practice. Chart review will occur throughout the study period to abstract necessary information about the participant's medical history and interval clinical events.

An initial CGM data review will be conducted by the research team within 72 hours of each sensor removal. The clinical team will be notified if there were intervals meeting the criteria of sustained sensor readings \< 50 mg/dL for greater than or equal to 15 minutes. The clinical team will be provided with the criteria for notification, the date/time stamps associated with those event(s), and information about interpreting CGM readings. We will provide this limited information to the clinical team because sustained CGM sensor readings \< 50 mg/dL may signify that the participant is at increased risk for hypoglycemia (blood glucose \< 70 mg/dL) on cycled PN. The study protocol does not require any blood glucose measurements or other clinical interventions.

Additionally, CGM may provide false low glucose readings when the tissue around the sensor is compressed (compression lows) such as when laying on the sensor during sleep. During study enrollment, a controlled amount of pressure will be applied to the CGM devices worn by CAMP participants during brief testing periods, which will be used to derive a mathematical model of compression lows in infants. These false low readings will be filtered out of the data for accurate data analysis of true low CGM readings. Specifically, the study team will perform brief tests applying pressure to the CGM device and a force sensor will be used to measure the force being applied to the CGM. Up to 1kg force will be applied to the CGM per attempt. There will be up to 2 attempts to apply force and measure a response per day, 3 days of attempts, 6 attempts total, for no more than 20 minutes per attempt. A successful response is defined as a drop in sensor glucose of at least 15 mg/dL sustained until pressure is released.