By: Diari Gilliam, PharmD Candidate 2020 and Rachel Wolfe, PharmD, BCCCP
Diabetes is a metabolic disorder characterized by hyperglycemia due to impaired insulin secretion, insulin action, or a combination of both.1 In the United States, it is a frequently encountered disease state with an estimated incidence of 30.3 million in 2015.2 While it is well known that chronic hyperglycemia is associated with poor long term outcomes, such as retinopathy, nephropathy, and neuropathy, acute hyperglycemia in the surgical setting has also been associated with poor outcomes. Acute hyperglycemia in the surgical setting may precipitate surgical site infections, impaired wound healing, cardiovascular events, and even death.3-4 Due to the potential for these complications, perioperative glycemic control is essential.
The various transitions of care throughout the surgical continuum of care put patients at risk for sub-optimal perioperative glycemic control. A different team of providers will care for patients as they transition through the pre-admission, preoperative, intraoperative, recovery, and postoperative phases of care. Any miscommunication or omission of information concerning diabetic status or insulin use may result in perioperative hypo- or hyperglycemic events. This poses a significant threat to surgical outcomes and can be especially harmful in those with type 1 diabetes as they need a continuous exogenous source of insulin at all times. This article will provide a brief overview of the importance of perioperative glycemic control throughout the surgical continuum of care.
Diabetic patients are at an increased risk for hyperglycemia in the perioperative period due to the metabolic stress induced by surgery and anesthesia. Both alter the balance of glucose production and utilization due to the increased secretion of counterregulatory hormones such as catecholamines, cortisol, glucagon, and growth hormone.5 The collective effect of this imbalance results in increased lipolysis, gluconeogenesis, glycogenolysis, and simultaneously reduced insulin secretion.5 Increased glucose production coupled with insulin resistance creates a perfect storm for hyperglycemia and its associated complications. According to a study in patients undergoing abdominal surgery, insulin resistance persists for at least 5 days postoperatively.6 Therefore, it is important to develop an interprofessional approach to address glycemic control that can withstand the challenges of the multitude of care transitions inherent to the surgical environment.
When possible, preoperative optimization of a patient with diabetes should begin in the surgeon’s office and/or in the preoperative assessment clinic. Patients should be screened for indicators of uncontrolled diabetes such as hemoglobin A1c > 8.5%, hypoglycemic episodes (<70 mg/dL), or hyperglycemic episodes (>299 mg/dL).7 Additional indicators requiring selective attention would be outpatient use of concentrated insulin and insulin pump therapy, as these modalities are commonly associated with medication errors or suboptimal management within healthcare facilities.7 If patients present with any of these indicators, it is advisable to refer them to an endocrinologist for adequate optimization of their disease state and antidiabetic regimen prior to surgery and to create and communicate a management plan for the surgical continuum of care. For those who do not require further evaluation, explicit instructions should be given on how to take their antidiabetic medications the day prior to and the day of surgery (Table 1). Insulin-based regimens require the most modifications prior to surgery. Based on the type of insulin, different modifications may be necessary. For example, rapid and short-acting insulin should only be held on the day of surgery secondary to the restricted oral intake.7 Patients with insulin pumps should consult with their endocrinologist to discuss pump programming for surgery or make plans to disconnect on the day of surgery.7 It is important to note that if the insulin pump is disconnected at any time, there must be a plan in place to immediately provide another form of continuous insulin therapy for these patients. If patients undergo surgery with a connected infusion pump, they should be assessed preoperatively for their capacity to manage the pump after surgery.8 It is important to refer to institution policy regarding personal infusion pumps as not every institution allows their use.
Studies have shown that intraoperative hyperglycemia may play a role in postoperative complications such as infections, myocardial infarctions, and neurological and pulmonary dysfunction.3 A study on intensive intraoperative insulin therapy revealed that maintaining intraoperative glycemic targets between 80 mg/dL and 100 mg/dL is also associated with poor outcomes.9 While we lack nationwide consensus, recommendations from various organizations can be used to guide perioperative glucose targets (Table 2). To best achieve these targets, intraoperative management of hyperglycemia may require a continuous insulin infusion or subcutaneous rapid-acting insulin with monitoring every one to two hours. Intravenous push doses of short-acting insulin should be avoided when possible due to its short duration of action.
In the postoperative setting, patients often recover from anesthesia in the post-anesthesia care unit (PACU). Therapy in the PACU is influenced by the patient’s adherence to recommended adjustments to their home anti-diabetic regimen prior to surgery as well as the pre-and intra-operative regimen, making a thorough handoff essential. Obtaining a blood glucose value when the patient is admitted to and discharged from the PACU assists in determining the next steps of glycemic control.8 In this setting, various modalities may be utilized. Insulin drips can be titrated, insulin pumps may continue at a basal rate, and subcutaneous doses of intermediate- or short-acting insulin can be administered as necessary. Blood glucose monitoring in the PACU should mimic monitoring established on the inpatient divisions. Although the monitoring requirements may differ based on institution-specific and patient-specific factors, blood glucose is typically assessed every hour for continuous intravenous insulin infusions and approximately every four hours for subcutaneous insulin therapy. PACU glycemic control also addresses the therapeutic response to agents given perioperatively that may affect blood glucose. For example, studies have shown that dexamethasone, which may be administered to some patients pre- or intra-operatively to prevent postoperative nausea and vomiting or reduce inflammation, can increase the risk of postoperative hyperglycemia.14-16 In order to avoid acute hyperglycemia, clinicians may consider prescribing a dose of an intermediate-acting insulin in patients that receive greater than 10 mg of dexamethasone.14 Before discharging patients from the PACU and transitioning them to the next level of care, their history of perioperative glycemic control and diabetic status should be communicated to the next healthcare provider and any present family members. Patients being discharged to home should be instructed to monitor their blood glucose frequently while fasting or during times of minimal oral intake. Their home regimen may be re-initiated when they resume their normal diet.
In conclusion, perioperative glycemic control is essential to prevent poor outcomes in diabetic patients undergoing surgery. Institution specific protocols that foster multidisciplinary communication among various phases of care can streamline clinical decisions and communication. It is imperative that both the patient and the providers communicate effectively to achieve the best possible outcomes before, during, and after surgery.