Will cover clinical considerations concerning the endocrine system as they pertain to the practice of anesthesia.
CLINICAL ANESTHESIA CONSIDERATIONS
While there are several pharmacologic agents that exert direct effects on the endocrine system and are discussed later in this section, most anesthesia management practices affecting the endocrine system are focused on preventing preoperative, intraoperative, or postoperative complications of various endocrine disorders, many of which were mentioned in the previous chapter.
A thorough preanesthesia evaluation is vital for the development of an individualized and effective anesthetic plan.1 Eliciting an accurate history of endocrine comorbidities is critical in delivering effective patient care. This chapter will discuss attention in the management of patients perioperatively with various endocrine disorders with a focus on physiological considerations.
As described previously, diabetes is the most common clinically encountered endocrine disease.2 As such, careful considerations must be made to manage patients who are either type 1 DM or type 2 DM. Related to the need to control blood glucose during operative procedures, insulin is always indicated for type 1 DM; however, various oral glucose regulators or insulin may be used to manage type 2 DM, given the progression and stage of the disease and if weight loss or dietary management preoperative is unsuccessful in optimizing the patient.
Insulin and Oral Glycemic Agents
Exogenous insulin can either be rapid, intermediated, or long-acting, with therapy potentially involving several basal injections as well as prandial insulin or continuous infusions subcutaneously.3 The objective of therapy is to control blood glucose levels and prevent ketoacidosis. In patients with type 2 DM, the glucose regulator that is preferred the most for initial therapy is metformin.
Additional oral agents may be added for better glucose control and prevention of macroangiopathic and microangiopathy disease, such as sulfonylureas, meglitinides, α-glucosidase inhibitors, thiazolidinediones, GLP-1 receptor agonists, DDP-4 inhibitors, or amylin agonists.4 Other agents include colesevelam (bile acid sequestrant) and bromocriptine mesylate (dopamine receptor agonist).
Perioperative Considerations of Diabetes Mellitus
In a diabetic patient with properly controlled glucose, special preoperative and intraoperative treatment may not be indicated. However, reducing the morning insulin dose by 30% to 50% is reasonable to prevent hypoglycemia since patients are fasting. Sulfonylurea drugs should not be taken the morning of the operation.4
Hypoglycemia in the perioperative setting may be related to several causes, including but not limited to the patient’s metabolic state, exogenous glucose administration, or neuroendocrine changes due to stress.
Blood glucose is usually measured preoperatively in order to evaluate the risk of developing severe dehydration, diabetic ketoacidosis, and/or coma, secondary to hyperosmolar hyperglycemic non-ketoacidosis. In critical care and perioperative settings, optimal levels of glucose control remain controversial.