Editor’s note: The ASA Monitor is pleased to introduce Dr. Gearhead, a new recurring column developed to provide anesthesiologists with a strong working knowledge of the latest patient wearables, implantable devices, and other medical technologies sure to be encountered in the OR or preoperative clinic.
According to the 2020 CDC National Diabetes Statistics Report, approximately 11% of the United States population had diabetes (asamonitor.pub/3zHi0G1). Insulin pumps and continuous glucose monitoring devices are becoming more popular among diabetics. A study in 2018 found that up to 40% of type 1 diabetics used one or both technologies (Curr Diab Rep 2021;21:7). This is an ever-expanding area within the medical device industry. It is difficult for the busy anesthesiologist to keep up with the rapidly advancing technology for managing diabetes. I will quickly review developments in insulin pumps and glucose monitoring to provide familiarity with the technology before your next encounter with a diabetic patient sporting the latest wearable technology.
According to the diabetesforecast.org 2020 Consumer Guide, there are seven different types of insulin pumps on the market, as well as a transcutaneous insulin delivery patch (asamonitor.pub/33jXUFJ). Most of the pumps are battery-driven, about the size of a deck of cards (or smaller), and require tubing that connects the insulin reservoir to the patient’s subcutaneous tissue. The insulin reservoir typically holds 200-300 units, except the “patch,” which holds less. Insulin pumps may be used alone or in tandem with a continuous glucose monitor (CGM). Insulin pumps that work with a CGM have the ability to regulate the insulin infusion and will slow or halt the infusion if the glucose level becomes too low (asamonitor.pub/33jXUFJ). There are also “pod-like” pumps with no actual tubing. Two of these types of pods can be worn for up to 48 hours. Lastly, the insulin “patch” can be worn for 24 hours and requires no battery (asamonitor.pub/33jXUFJ). There are two types of patch pumps: simple or full-featured. The simple insulin patch pumps are disposable, have a set basal rate, and boluses are given by pressing a button on the device. There is no ability to control or change the rate remotely. The full-feature insulin patch pumps include the ability to change basal rates. Not all patch pump styles are available in the U.S. (J Diabetes Sci Technol 20189;13:27-33). All other pumps have a programable basal rate to function as an electronic pancreas and the ability to give bolus doses with meals.
Continuous glucose monitors are small devices that continuously sample glucose in the interstitial fluid. They typically have three components: a sensor, a transmitter, and a receiver. The sensor is inserted by the wearer into fatty tissue, usually the abdomen. Most commonly there is an insertion device to facilitate placement. The sensor contains a small filament that interacts with interstitial glucose to initiate an electrical current. The transmitter transduces the current and sends the calculated glucose to the receiver. The receiver is a either a stand-alone handheld device or the user’s cell phone. In addition to displaying the real-time glucose reading, the software may provide a digital display of trends and glucose statistics. Some can send this information to another party, such as a physician or family member (asamonitor.pub/3zGxcDf).
The American Association of Clinical Endocrinology and the American Diabetes Association support hospitalized patients’ ability to utilize their insulin pumps and glucose monitors if they are mentally and physically able and they conform with institutional policies (Diabetes Care 2018;41:1579-89). During the perioperative period, the anesthesiologist should consider the length of surgery, type of anesthesia, type of diabetes, and type of surgical procedure. Also consider whether the patient is competent and knowledgeable about the pump or acutely ill and unable to work the device. Other important questions to ask: Where is the location of the procedure? Is there exposure to ionizing radiation? Are there institutional protocols that need to be followed (Curr Diab Rep 2021;21:7; Endocr Pract 2015;21:1269-76; J Diabetes Sci Technol 2018;12:880-9; J Diabetes Sci Technol 2020;14:1035-64)?
It is generally safe to continue the insulin pump on low-risk procedures under two hours with glucose monitoring and no ionizing radiation that could damage the apparatus. The anesthesiologist is not expected to operate all of the various types of pumps but should know how to disconnect if needed due to prolonged surgery, pump malfunction, or the need to convert to an intravenous insulin infusion. Insulin pumps are expensive, and there should be patient education and counseling on the possibility of pump damage or misplacement during the perioperative period. CGMs are not recommended during procedures unless the patient is awake and able to utilize the device. If there are abnormally high or low readings on a CGM, they should be confirmed with an actual blood glucose sample before treatment (J Diabetes Sci Technol 2020;14:1035-64).
It is reasonable to expect that patients with wearable devices will have a good understanding of the technology. If the anesthesiologist does not understand the insulin pump or glucose monitoring device, then the closest source of information about how the device works is likely the patient.