Date Published: September 6, 2011
Publisher: Hindawi Publishing Corporation
Author(s): Sara M. Alexanian, Marie E. McDonnell, Shamsuddin Akhtar.
Hyperglycemia in the surgical population is a recognized risk factor for postoperative complications; however, there is little literature to date regarding the management of hyperglycemia in the perioperative period. Here, we detail the strategies that our institutions have employed to identify and treat hyperglycemia in patients with diabetes who present for surgery. Our approach focuses on the recognition of hyperglycemia and metabolic abnormalities, control of glucose levels via insulin infusion when needed, monitoring for hypoglycemia and a comprehensive multidisciplinary approach that provides standardized recommendations for patients at all points in care as they transition from the preoperative clinic into the operating room, and then into the hospital.
Studies have demonstrated that hyperglycemia occurs in a significant percentage of hospitalized patients; seventy percent of patients with diabetes admitted with acute coronary syndrome and 80% of cardiac surgery patients in the perioperative period may develop hyperglycemia . Over the past few decades, there has been mounting evidence that hyperglycemia in hospitalized patients leads directly to adverse consequences. In particular, the literature indicates a role for glycemic control in surgical patients, where postoperative hyperglycemia is associated with an increased risk of infection, renal and pulmonary complications, and also mortality [2–7]. More recent studies have addressed the effects of hyperglycemia perioperatively and confirmed similar associations [8–11]. One study demonstrated that for every 20 mg/dL increase in the mean intraoperative glucose, the risk of an adverse outcome increased by more than 30% .
Because the perioperative time period involves care by multiple and different physician groups, a multidisciplinary team approach is key to the creation of a successful protocol. Depending on institutional practice, this may include representatives from endocrinology, anesthesiology, surgery, nursing, preoperative clinic, pharmacy, and information technology (IT). Every transition point for the patient should be addressed, from the preoperative assessment clinic with standardized recommendations for antihyperglycemic medications before surgery, to transition to in-hospital postoperative care as well as discharge preparation and education. It is important that a standardized protocol for the treatment of hypoglycemia be included whenever a hyperglycemia protocol is instituted.
Hypoglycemia and the fear of hypoglycemia remain a major barrier in the care of hospitalized patients. In prospective studies, the incidence of significant hypoglycemia is reported to be up to six times higher in intensive glucose control groups. Recent data has demonstrated a relationship between hypoglycemia, morbidity, and mortality [40–44], though whether the hypoglycemia is causal, or a sign of critical illness has yet to be established [43, 45]. Physicians have a heightened and appropriate concern for patients who are sedated as they will be unable to report symptoms, and the signs of hypoglycemia may be masked. For patient safety, a standard treatment algorithm for hypoglycemia must be included as part of the glycemic protocol. Patients on intravenous insulin infusions in the OR should have a glucose checked at a minimum every sixty minutes, and more often as clinically indicated. Monitoring methods can include the use of point-of-care glucose meters or blood samples such as venous blood gases during the procedure. One of the drawbacks of glucose meter use is the variance between meter readings and laboratory sample (allowed to be up to 20% by FDA regulations). The FDA is currently reviewing these limits, and revised regulations may be forthcoming. Many patient factors are known to affect the accuracy of the reading, including pH, oxygenation status, and anemia among others, and this has been shown to be a particular issue in critically ill patients [46, 47]. Additionally, when a glucose value is in the hypoglycemic range, the accuracy is further decreased [47–49]. Caregivers using these devices need to be educated about their limitations and a value that is not consistent with the clinical picture needs to be verified by a central laboratory method. This issue is another reason not to target a glucose value in the normoglycemic range but only treat if glucose is more than 180 mg/dL .
Currently no evidence-based guidelines exist regarding when to cancel a surgical procedure due to hyperglycemia. Given the multitude of patient factors involved as well as the variety of surgical procedures and procedure urgency, it is unlikely that recommendations based on outcomes will be forthcoming. Providers need to weigh several issues when considering this question. First of all, the urgency of surgery should be considered. Secondly, hyperglycemia could represent an unstable metabolic state, such as diabetic ketoacidosis, which should be rapidly assessed in the preoperative area. Elective surgery in unstable metabolic state is not recommended. Furthermore, the chronic glycemic state of the patient should be considered. In our experience, most patients who present for elective surgery with a glucose >300 mg/dL have had similar values documented as an outpatient and are a representation of chronically poor control, as opposed to a new illness. In this situation, there are opportunities for providers to identify and address the problem prior to the patient arriving in the preoperative area. Another consideration is that the hyperglycemia may be caused by the illness for which the patient presented for surgery (for example, osteomyelitis), which would not be expected to improve until the patient undergoes surgery. Providers need, therefore, to assess the patient for stability, the need for the procedure, the risks of the procedure, and the ability of the patient to achieve glucose control if the surgery is postponed. We have used a cutoff of 300 mg/dL (Boston Medical Center) as a trigger in the preoperative area for evaluation for ketoacidosis either via urine ketone dipstick or whole blood chemistry. At Yale New-Haven Hospital, no cutoff value to trigger evaluation for ketoacidosis has been set. It has been left to the discretion of the physician. However, it is recommended to postpone nonurgent/emergent surgery if the glucose is >400 mg/dL. At Boston Medical Center, it is recommend to postpone nonurgent procedures if the glucose is >500 mg/dL, or at the discretion of the physician at lower levels based on the risks and urgency of the procedure.
The multidisciplinary nature of a perioperative protocol necessitates education over the course of time and in different formats. At Boston Medical Center, this included surgical and anesthesiology grand rounds to review data and recommendations and later a joint conference regarding the practical implementation of the protocol. There were nursing in-services as well as training in the use of glucose meters and point-of-care testing with ketostix. Nurses without prior ICU experience also needed training in insulin infusion administration. At all steps, the physician groups were given updates at conferences and via emails. We also developed an educational video that was available for viewing on the hospital intranet. The endocrinology team was trained in the protocol to provide support when issues arose. In order to assess the safety of our protocol and to identify unforeseen issues, a three-month pilot of the protocol was performed in one OR area prior to it being used hospital wide. The leadership group focused on the efficacy at achieving glycemic control and the incidence of hypoglycemia, as well as any needed adjustments to nursing orders before deciding to expand the program. Pilot results have been previously published . At Yale New Haven hospital, similar education was employed, and an initial protocol was tried in the cardiothoracic ICU and then introduced to the perioperative services. We are in the process of analyzing the data for our in-hospital population. Table 2 summarizes the main challenges that arose during the creation and implementation of these protocols and how they were addressed.
There is currently a lack of evidence to guide providers regarding the details of perioperative glycemic management. We provide this information to report our experience and inform the literature, not as a formula we wish to recommend as the ideal or only way to approach the issue. Below, we describe the patient flow that occurs at each of our institutions for an example patient. A comparison of the two programs is provided in Table 3.
With the increasing prevalence of diabetes, practitioners will continue to face the challenge of managing hyperglycemia in patients during all aspects of the hospital stay. We note that especially during the perioperative time where several physician specialties are involved and many care transitions will occur, it is critical that a multidisciplinary team be utilized in addressing this issue. Variation in institutional resources, staff, and existing hospital practice will mean that there is no “one size fits all” approach. Many unanswered questions remain as well as future research opportunities to determine optimal intraoperative glucose targets, when to postpone surgery, and specific populations who may show greater or less benefit from insulin therapy. Here, we provide our experience and await more data to further refine our practice.
The authors have nothing to disclose.