Prior studies and clinical experience have established the safety and efficacy of subcutaneous insulin infusion (CSII) throughout the perioperative period.1,2 However, since FDA approval of the MiniMed 670G hybrid closed loop system (670G-HCL) in September 2016, there is limited clinical experience on the use of this system in the perioperative period, and there is currently no published data on the perioperative value of this system in individuals with type 1 diabetes (T1D) undergoing metabolic surgery. Metabolic surgery results in dramatic dietary restrictions, anatomical changes to the GI tract, and profound changes to intestinal hormone release and the body’s response to caloric intake. These changes lead to multiple challenges in the management of insulin delivery in the perioperative period.
We report a novel case of a 24-year-old female with uncomplicated T1D and obesity (BMI 40) using the 670G-HCL throughout the perioperative and 6 week post-operative period following laparoscopic sleeve gastrectomy. This case provides unique insights into how the 670G-HCL operates during a period of rapidly shifting metabolic changes.
Prior to admission for sleeve gastrectomy our patient, an experienced CSII user with a Carelink sensor estimated A1c of 6.9%, had been using the 670G-HCL for 4 months in addition to metformin XR 750 mg twice a day and liraglutide 1.8 mg subcutaneously daily. She weighed 218 pounds (99 kg) with BMI of 40 prior to surgery. She was admitted to Boston Medical Center for her procedure following a routine overnight fast. We elected to continue the 670G-HCL in “auto-mode” during the perioperative period, including during the procedure, but with a programmed 50% reduction in her “manual mode” basal insulin delivery rates, starting at midnight the night prior to prevent potential hypoglycemia, should the system enter into open loop basal insulin delivery.
Prior to surgery the percentage of time spent in auto-mode was 93% over a 14-day period (90% sensor wear/week) and her total daily insulin dose was 91 units with 50 units delivered as auto-basal (55%) and 41 units delivered as bolus/correctional insulin (45%). Throughout her 2-day hospital stay she continued uninterrupted in “auto-mode” with no immediate postoperative hypoglycemia despite consuming a diet of <30 g carbohydrate/day in the immediate postoperative period.
Six weeks after surgery, she had lost 28 pounds and weighted 190 pounds (86 kg). She was consuming a markedly reduced carbohydrate diet (approximately 75 g carbs/day in comparison to 135 g/day pre-op) and while no longer on liraglutide or metformin, her insulin requirements were dramatically reduced by over 50% (Table 1). The 14-day average total daily auto-basal insulin infusion prior to her week 6 follow up was 30 units/day, a 40% reduction in her auto-basal delivery in comparison to her preoperative needs, suggesting that the improvements in insulin sensitivity that are well known to occur in obese individuals with type 2 diabetes following bariatric surgery also occur in obese individuals with T1D and that these changes are well compensated for by the 670G HCL. This report furthers our understanding of the capacity of 670G HCL insulin delivery control algorithm to safely adjust to the dramatic metabolic and dietary changes that ensue following bariatric surgery.
Table 1.
Comparison of 14-Day Carelink Statistics From 6 Weeks Prior to Sleeve Gastrectomy and 6 Weeks Post–Sleeve Gastrectomy.
| Statistics | Preoperative | 6 weeks postoperative |
|---|---|---|
| Auto-mode/week | 93% | 97% |
| Sensor wear/week | 90% | 94% |
| Avg SG ± SD | 144 ± 45 mg/dL | 152 ± 35 mg/dL |
| Avg BG ± SD | 155 ± 67 mg/dL | 179 ± 53 mg/dL |
| eA1c | 6.6% | 6.9% |
| Time in range (70-180 mg/dl) | 79% | 81% |
| Hypoglycemia | ||
| Time <50 mg/dl | 0% | 0% |
| Time 50-70 mg/dl | 3% | 0% |
| Hyperglycemia | ||
| Time 180-250 mg/dl | 15% | 17% |
| Time 250-400 mg/dl | 3% | 2% |
| Total daily insulin dose (per day) | 91 units | 41 units |
| Bolus amount/day | 41 units (45%) | 11 units (27%) |
| Insulin: carb ratios | 12:00 am to 5:00 am: 5.0 | 12:00 am to 5:00 am: 8.0 |
| 5:00 am to 6:00 pm: 3.0 | 5:00 am to 6:00 pm: 8.0 | |
| 6:00 pm to 10:00 pm: 4.0 | 6:00 pm to 10:00 pm: 8.0 | |
| 10:00 pm to 12:00 am: 5.0 | 10:00 pm to 12:00 am: 8.0 | |
| Sensitivity factors | 12:00 am to 6:00 pm: 25 | 12:00 am to 6:00 pm: 50 |
| 6:00 pm to 12:00 am: 30 | 6:00 pm to 12:00 am: 50 | |
| Auto-basal/day | 50 units (55%) | 30 units (73%) |
| Meals/day (carbohydrates/day) | 2.9 (135 ± 62 g) | 3.2 (75 ± 23 g) |
Footnotes
Abbreviations: BMI, body mass index; CSII, continuous subcutaneous insulin infusion; FDA, US Food and Drug Administration; T1D, type 1 diabetes; 670G-HCL, MiniMed 670G hybrid closed loop system.
Declaration of Conflicting Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding: The author(s) received no financial support for the research, authorship, and/or publication of this article.
References
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