11.2 Management of Diabetic Ketoacidosis (DKA) & Hyperosmolar Hyperglycemic State (HHS)

11.2 Management of Diabetic Ketoacidosis (DKA) & Hyperosmolar Hyperglycemic State (HHS)

Pathophysiology & Differential Diagnosis of Hyperglycemic Emergencies

Diabetic Ketoacidosis (DKA) and Hyperosmolar Hyperglycemic State (HHS) are acute, life-threatening metabolic complications of diabetes mellitus requiring rapid recognition, intensive monitoring, and protocolized resuscitation in emergency and high-dependency units across Singapore hospitals.

Pathophysiologic Mechanisms

• Diabetic Ketoacidosis (DKA): Triggered by absolute or relative insulin deficiency combined with counter-regulatory hormone excess (glucagon, catecholamines, cortisol, growth hormone). Unopposed lipolysis leads to the breakdown of adipose tissue into free fatty acids (FFAs). In the liver, FFAs undergo $\beta$-oxidation to form ketone bodies ($\beta$-hydroxybutyrate and acetoacetate), inducing metabolic acidosis with an elevated anion gap. DKA predominantly affects Type 1 Diabetes Mellitus patients, though it occurs in Type 2 DM under severe physiological stress (infections, myocardial infarction, stroke).
• Hyperosmolar Hyperglycemic State (HHS): Characterized by severe hyperglycemia, hyperosmolality, and profound dehydration in the absence of significant ketoacidosis. HHS typically occurs in older patients with Type 2 DM. Residual endogenous insulin is sufficient to suppress lipolysis and hepatic ketogenesis, preventing severe ketoacidosis, but insufficient to facilitate peripheral glucose uptake. Extreme hyperglycemia leads to massive osmotic diuresis, fluid deficits of 9–12 liters (10–15% of total body weight), hyperosmolality, and progressive neurological impairment.

Comparative Diagnostic Criteria

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Fluid Resuscitation & Glucose Management Protocols

The primary therapeutic objective in DKA and HHS is intravascular volume expansion, restoration of renal perfusion, gradual reduction of serum osmolality, and clearance of ketones.

Fluid Resuscitation Sequence

1. Initial Volume Expansion: Infuse 0.9% Sodium Chloride (Normal Saline) at $1000 \text{ mL/hr}$ ($15–20 \text{ mL/kg/hr}$) during the first hour to restore hemodynamic stability and renal perfusion.
2. Subsequent Fluid Selection: Calculate corrected serum sodium: $\text{Corrected } Na^+ = \text{Measured } Na^+ + 0.3 \times (\text{Glucose} - 5.5 \text{ mmol/L})$
   • If corrected $Na^+$ is normal or elevated ($\ge 135 \text{ mmol/L}$): Switch to 0.45% Sodium Chloride (Half-Normal Saline) at $250–500 \text{ mL/hr}$.
   • If corrected $Na^+$ is low ($< 135 \text{ mmol/L}$): Continue 0.9% Sodium Chloride at $250–500 \text{ mL/hr}$.
3. Addition of Dextrose (Preventing Cerebral Edema):
   • In DKA: When CBG reaches $14.0 \text{ mmol/L}$, add 5% Dextrose in 0.45% NaCl (or 5% Dextrose in 0.9% NaCl) and reduce the continuous IV insulin infusion rate to $0.02–0.05 \text{ units/kg/hr}$.
   • In HHS: When CBG reaches $16.7 \text{ mmol/L}$, add 5% Dextrose to IV hydration fluids.
   • Rationale: Maintaining CBG between 10.0 and 14.0 mmol/L in DKA (13.9–16.7 mmol/L in HHS) while continuing insulin suppresses lipolysis and ketogenesis while avoiding rapid drops in plasma osmolality that trigger osmotic shift into brain parenchymal cells, causing fatal cerebral edema.

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Continuous Insulin Therapy & Potassium Safety Guidelines

Potassium Safety Threshold (MOH & SNB Critical Standard)

Insulin causes an intracellular shift of glucose and potassium by activating the $Na^+/K^+$-ATPase pump. Administering IV insulin in the presence of hypokalemia leads to precipitous drops in serum potassium, triggering lethal ventricular dysrhythmias and respiratory muscle paralysis.

• Serum $K^+ < 3.5 \text{ mmol/L}$: HOLD IV INSULIN INFUSION IMMEDIATELY. Administer IV Potassium Chloride (KCl) at $20–30 \text{ mEq/hr}$ (via central line or dedicated infusion pump under continuous telemetry) until serum $K^+ \ge 3.5 \text{ mmol/L}$.
• Serum $K^+$ 3.5 – 5.2 mmol/L: Initiate or continue IV insulin infusion. Add $20–30 \text{ mEq}$ KCl per liter of IV infusion fluid to maintain serum potassium between $4.0 \text{ and } 5.0 \text{ mmol/L}$.
• Serum $K^+ > 5.2 \text{ mmol/L}$: Initiate IV insulin infusion. Do not add KCl to IV fluids. Monitor serum potassium every 2 hours until levels fall below $5.2 \text{ mmol/L}$.

Insulin Infusion Protocol

• Bolus vs Continuous: Current guidelines recommend continuous fixed-rate IV Regular Insulin infusion at $0.1 \text{ units/kg/hr}$ (e.g., 7 units/hr for a 70 kg adult). An initial IV bolus ($0.1 \text{ units/kg}$) is optional.
• Target Rate of Glucose Reduction: Capillary blood glucose should decrease at a steady rate of $3.0 \text{ to } 5.0 \text{ mmol/L per hour}$. If glucose fails to decline by $3.0 \text{ mmol/L}$ in the first hour, verify IV line patency, infusion pump settings, and double the insulin infusion rate.

Sodium Bicarbonate Indications

Sodium bicarbonate administration is not recommended for routine DKA resuscitation. It is indicated only when initial arterial $\text{pH} < 6.90$.

• Risks of Bicarbonate Therapy: Paradoxical central nervous system acidosis (due to rapid diffusion of $CO_2$ across the blood-brain barrier), severe hypokalemia, delayed ketone clearance, and tissue hypoxia (left-shift of oxyhemoglobin dissociation curve).

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DKA Resolution Criteria & Subcutaneous Transition Protocol

DKA is considered resolved when all of the following laboratory criteria are met:

1. Capillary Blood Glucose $< 11.1 \text{ mmol/L}$.
2. Serum Bicarbonate $\ge 18 \text{ mEq/L}$.
3. Venous Blood $\text{pH} > 7.30$.
4. Normal Anion Gap ($\le 12 \text{ mEq/L}$).

Subcutaneous Insulin Transition Protocol

To prevent rebound hyperglycemia and recurrent ketoacidosis, never abruptly discontinue the IV insulin infusion.

• Basal Subcutaneous Overlap: Administer long-acting subcutaneous basal insulin (e.g., Insulin Glargine or Degludec) 1 to 2 hours prior to stopping the IV insulin infusion.
• Timing: Schedule the transition to coincide with a mealtime when the patient is alert, non-nauseated, and able to eat oral food.

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Critical Nursing Complications & Clinical Scenario

Cerebral Edema Vigilance

Cerebral edema is a devastating complication occurring primarily in children and young adults during DKA treatment, caused by rapid osmolality reduction.

• Warning Signs: Severe headache, lethargy, confusion, bradycardia, hypertension (Cushing's triad), incontinence, and papilledema.
• Immediate Nursing Actions: Elevate head of bed to $30^\circ$, immediately notify physician, slow IV infusion rate, and administer IV Mannitol $0.5–1.0 \text{ g/kg}$ or 3% Hypertonic Saline as ordered.

Clinical Nursing Scenario

Scenario: A 22-year-old female university student with T1DM presents to the Emergency Department with a 2-day history of fever, nausea, vomiting, and abdominal pain. On arrival: GCS 14 (drowsy), BP 92/58 mmHg, HR 128 bpm, RR 32 breaths/min (deep, rapid Kussmaul breathing with sweet fruity breath odor). STAT bloods: CBG $26.4 \text{ mmol/L}$, Venous $\text{pH } 7.12$, $HCO_3^- \text{ 9.2 mEq/L}$, Serum $K^+ \text{ 3.1 mmol/L}$, Anion Gap $22 \text{ mEq/L}$. Nursing Action: Recognizing severe DKA with critical hypokalemia ($K^+ < 3.5 \text{ mmol/L}$), the RN immediately initiates IV 0.9% Normal Saline at $1000 \text{ mL/hr}$ but withholds the ordered IV insulin infusion. The RN alerts the medical officer, inserts a dedicated IV line for potassium replacement, and infuses IV KCl at $20 \text{ mEq/hr}$. After 2 hours, repeat serum $K^+$ is $3.8 \text{ mmol/L}$. The RN then safely commences continuous IV Regular Insulin at $0.1 \text{ units/kg/hr}$ while adding $20 \text{ mEq}$ KCl per liter of IV maintenance fluid, conducting hourly CBG and neurological observations.