5.2 Diabetic Emergencies (DKA & HHS)

Introduction to Diabetic Emergencies

Diabetic emergencies are critical, life-threatening conditions resulting from severe insulin deficiency and insulin resistance. The two primary emergencies managed by the AGACNP are Diabetic Ketoacidosis (DKA) and Hyperosmolar Hyperglycemic State (HHS). While they share underlying pathogenic mechanisms of relative or absolute insulin deficiency combined with excess counter-regulatory hormones (glucagon, catecholamines, cortisol, growth hormone), their clinical presentations, laboratory profiles, and management nuances differ significantly.

Diabetic Ketoacidosis (DKA)

DKA most commonly occurs in patients with Type 1 Diabetes Mellitus, though it can occur in Type 2 under severe stress. It is triggered by an absolute or profound relative insulin deficiency. Common precipitants include infection (pneumonia, UTI), non-adherence to insulin therapy, myocardial infarction, trauma, or the onset of new diabetes.

The pathogenesis of DKA involves three concurrent processes:

1. Hyperglycemia: Lack of insulin prevents cellular glucose uptake, while excess glucagon stimulates hepatic gluconeogenesis and glycogenolysis. This profound hyperglycemia leads to an osmotic diuresis, resulting in severe dehydration and loss of electrolytes (sodium, potassium, magnesium, phosphate).
2. Ketogenesis: Without insulin to suppress lipolysis, free fatty acids are released from adipose tissue and transported to the liver. Here, they undergo beta-oxidation to form ketone bodies (acetoacetate and beta-hydroxybutyrate).
3. Metabolic Acidosis: The accumulation of ketoacids consumes bicarbonate, leading to a high anion gap metabolic acidosis.

Clinically, patients present with polyuria, polydipsia, weight loss, nausea, vomiting, and diffuse abdominal pain. On examination, signs of volume depletion are evident. Respiratory compensation for the metabolic acidosis manifests as deep, rapid Kussmaul respirations. A fruity odor (acetone) may be detected on the breath.

Laboratory diagnostic criteria for DKA include:

• Hyperglycemia (blood glucose typically > 250 mg/dL). Note: "Euglycemic DKA" can occur, particularly with SGLT2 inhibitors.
• Metabolic acidosis (pH < 7.30 and serum bicarbonate < 18 mEq/L).
• Elevated anion gap (typically > 10-12).
• Positive serum or urine ketones (beta-hydroxybutyrate is the most accurate marker).

Hyperosmolar Hyperglycemic State (HHS)

HHS typically affects older patients with Type 2 Diabetes Mellitus. In HHS, there is enough residual insulin secretion to suppress significant ketogenesis and lipolysis, preventing severe acidosis. However, the insulin level is insufficient to facilitate glucose utilization or suppress hepatic glucose production.

The resultant hyperglycemia is much more profound than in DKA, often exceeding 600-1000 mg/dL. This extreme hyperglycemia causes a massive osmotic diuresis, leading to profound dehydration and hyperosmolarity. Fluid deficits in HHS are typically much greater than in DKA (often 8-10 liters).

The clinical presentation of HHS is more insidious, developing over days to weeks. Symptoms are dominated by severe volume depletion and neurological manifestations. Patients exhibit profound lethargy, altered mental status, and focal neurologic deficits that can mimic a stroke, progressing to coma if untreated.

Laboratory criteria for HHS include:

• Extreme hyperglycemia (blood glucose > 600 mg/dL).
• Profound hyperosmolarity (effective serum osmolality > 320 mOsm/kg).
• Absent or minimal ketonemia/ketonuria.
• Arterial pH > 7.30 and serum bicarbonate > 18 mEq/L (minimal or no acidosis).

DKA vs. HHS: A Clinical Comparison

Management Strategies for DKA and HHS

The management of both DKA and HHS revolves around three pillars: fluid resuscitation, insulin therapy, and electrolyte replacement.

1. Fluid Resuscitation: This is the most critical initial step. Patients are profoundly dehydrated. Intravenous fluids restore intravascular volume, improve renal perfusion, and reduce blood glucose and counter-regulatory hormones independently of insulin.

• Begin with aggressive isotonic saline (0.9% NaCl) at 15-20 mL/kg/hr for the first 1-2 hours.
• Subsequent fluid choice depends on the corrected serum sodium. (Corrected Na = measured Na + 1.6 mEq/L for every 100 mg/dL glucose above 100 mg/dL). If corrected Na is normal or high, switch to 0.45% NaCl.
• Once blood glucose reaches 200 mg/dL in DKA (or 300 mg/dL in HHS), change fluids to contain 5% dextrose (e.g., D5W/0.45% NaCl). This is crucial to prevent hypoglycemia while continuing insulin therapy to clear ketones.

2. Insulin Therapy: Intravenous insulin suppresses lipolysis and ketogenesis, and promotes cellular glucose uptake.

• Ensure serum potassium is ≥ 3.3 mEq/L before starting insulin, as insulin drives potassium intracellularly and can precipitate life-threatening hypokalemia.
• Initiate a continuous regular insulin infusion at 0.1 units/kg/hr. A loading dose of 0.1 units/kg IV bolus is optional but often omitted.
• The goal is a steady decline in glucose of 50-75 mg/dL per hour.
• Do not stop the insulin drip just because glucose normalizes; the primary goal in DKA is the resolution of the ketoacidosis (closure of the anion gap).

3. Electrolyte Replacement: Potassium is the most critical electrolyte to manage.

• Despite a total body deficit of potassium (due to osmotic diuresis), initial serum potassium levels may be normal or elevated due to extracellular shift caused by acidosis and insulin deficiency.
• Once insulin and fluids are started, serum potassium will plummet rapidly.
• If initial K+ is < 3.3 mEq/L, hold insulin and give IV potassium until K+ > 3.3 mEq/L.
• If K+ is 3.3 - 5.2 mEq/L, add 20-30 mEq of potassium to each liter of IV fluid to maintain serum levels between 4.0 and 5.0 mEq/L.
• If K+ is > 5.2 mEq/L, hold potassium but check levels every 2 hours.
• Phosphate and magnesium should also be monitored and replaced as needed, though routine phosphate replacement is not generally recommended unless levels drop below 1.0 mg/dL or there is cardiac/respiratory dysfunction.

Resolution: DKA is considered resolved when the anion gap is closed (< 12 mEq/L), blood glucose is < 200 mg/dL, and the patient is able to tolerate oral intake. At this point, transition to a subcutaneous basal-bolus insulin regimen is required. Ensure a 1-2 hour overlap between the administration of subcutaneous basal insulin and the discontinuation of the IV insulin infusion to prevent rebound ketoacidosis. HHS is resolved when serum osmolality normalizes and mental status returns to baseline.