11.1 Diabetes Mellitus: Glycemic Control, Insulin Therapy & Complications

11.1 Diabetes Mellitus: Glycemic Control, Insulin Therapy & Complications

Pathophysiology & Diagnostic Standards in Singapore Practice

Diabetes Mellitus (DM) is a chronic metabolic disorder characterized by persistent hyperglycemia resulting from defects in insulin secretion, insulin action, or both. In Singapore, diabetes represents a major public health priority under the Ministry of Health (MOH) national "War on Diabetes" initiative. Effective management requires a thorough understanding of disease mechanisms, diagnostic criteria, and strict adherence to nursing safety protocols.

• Type 1 Diabetes Mellitus (T1DM): Characterized by autoimmune destruction of pancreatic beta cells in the Islets of Langerhans, leading to absolute insulin deficiency. Patients require lifelong exogenous insulin replacement and are highly prone to Diabetic Ketoacidosis (DKA).
• Type 2 Diabetes Mellitus (T2DM): Characterized by peripheral insulin resistance combined with a progressive decline in pancreatic beta-cell insulin secretion. T2DM accounts for over 90% of diabetes cases in Singapore and is strongly associated with central obesity, physical inactivity, and metabolic syndrome.

According to the MOH Clinical Practice Guidelines (CPG) on Diabetes Mellitus, diagnostic thresholds using venous plasma samples are defined as follows:

• Fasting Plasma Glucose (FPG): $\ge 7.0 \text{ mmol/L}$ (following an 8-hour fast).
• 2-Hour Post-OGTT (Oral Glucose Tolerance Test): $\ge 11.1 \text{ mmol/L}$ following a 75g anhydrous glucose load.
• Glycated Hemoglobin (HbA1c): $\ge 6.5%$ (48 mmol/mol), measured using a standardized NGSP-certified assay.
• Random Plasma Glucose: $\ge 11.1 \text{ mmol/L}$ in a patient presenting with classic symptoms of hyperglycemia (polyuria, polydipsia, polyphagia, unexplained weight loss).

MOH HbA1c Glycemic Targets

Glycemic management must be individualized based on patient age, comorbidities, and hypoglycemia risk:

• General Adult Target: $\text{HbA1c} < 7.0%$ to reduce long-term microvascular and macrovascular risk.
• Tight Glycemic Target (6.0% – 6.5%): Younger patients, newly diagnosed T2DM, long life expectancy, and absent micro/macrovascular complications without significant hypoglycemia risk.
• Relaxed Target (7.5% – 8.0%): Frail elderly patients, severe hypoglycemic unawareness, advanced microvascular or macrovascular complications, extensive comorbidities, or limited life expectancy.

---

Pharmacotherapy & Insulin Management Protocols

Pharmacological intervention in T2DM progresses from oral hypoglycemic agents (OHAs) to combination therapies and injectable agents when glycemic targets are not achieved.

Oral & Non-Insulin Injectable Agents

Insulin Types & Action Profiles

Insulin therapy is required in all T1DM patients and T2DM patients failing oral therapy or experiencing severe glycemic decompensation.

SNB Medication Safety & Administration Technique

1. High-Alert Medication Safety: Under Singapore Nursing Board (SNB) Medication Administration Standards, subcutaneous and IV insulin are classified as High-Alert Medications. Independent double-checking by two Registered Nurses (RNs) is mandatory for concentration, dose verification, syringe calibration (U-100), and patient identification.
2. Mixing Insulin Protocol ("Clear before Cloudy"): When combining Regular (short-acting) and NPH (intermediate-acting) insulin in a single syringe:
   • Inject air into the NPH (cloudy) vial equal to the NPH dose (do not touch liquid).
   • Inject air into the Regular (clear) vial equal to the Regular dose.
   • Withdraw the Regular (clear) insulin dose first.
   • Withdraw the NPH (cloudy) insulin dose second.
   • Rationale: Prevents contamination of the short-acting clear vial with intermediate-acting cloudy NPH, which would alter the rapid onset profile.
3. Lipodystrophy Prevention: Rotate injection sites systematically within the same anatomical area (abdomen, thigh, upper arm) at least 1 cm apart. Inject at a $90^\circ$ angle ($45^\circ$ for thin individuals). Avoid injecting into hypertrophy or atrophy nodules to ensure consistent absorption.

---

Acute Hypoglycemia Protocol (MOH Rule of 15)

Hypoglycemia is defined as a Capillary Blood Glucose (CBG) reading of $< 4.0 \text{ mmol/L}$ (or symptomatic blood glucose drop).

Clinical Manifestations

• Autonomic Symptoms (adrenergic/cholinergic response): Tremors, palpitations, diaphoresis, anxiety, hunger, paresthesia.
• Neuroglycopenic Symptoms (brain glucose deprivation): Confusion, dizziness, slurred speech, visual disturbances, lethargy, seizures, loss of consciousness.

Singapore Hospital Emergency Rescue Protocol

• Conscious & Able to Swallow safely:
  1. Administer 15g fast-acting simple carbohydrate (e.g., 150 mL fruit juice, 3–4 glucose tablets, or 3 teaspoons of sugar dissolved in water).
  2. Rest patient; recheck CBG in 15 minutes ("Rule of 15").
  3. If CBG remains $< 4.0 \text{ mmol/L}$, repeat 15g fast-acting carbohydrate. Recheck CBG in 15 min.
  4. Once CBG $> 4.0 \text{ mmol/L}$, provide a complex carbohydrate snack (e.g., 2 plain biscuits, slice of bread, or scheduled main meal) to maintain normoglycemia.
• Unconscious, Altered Mental State, or NPO:
  1. Secure airway and call for immediate medical assistance / Resuscitation Team.
  2. Establish IV access. Administer IV 20% Dextrose 40–50 mL (or IV 50% Dextrose 20–30 mL) over 1–3 minutes via large peripheral vein (vesicant precaution).
  3. If IV access unavailable: Administer IM or SC Glucagon 1 mg (position patient in lateral recovery position due to risk of emesis upon awakening).
  4. Recheck CBG every 15 minutes until CBG $> 4.0 \text{ mmol/L}$ and patient recovers consciousness.

---

Chronic Complications & Preventive Surveillance

Chronic diabetic complications are categorized into microvascular and macrovascular pathology:

Microvascular Complications

1. Diabetic Retinopathy: Leading cause of blindness in working-age Singaporeans. Requires annual Singapore Integrated Diabetic Retinopathy Screening (SIDRP) fundus photography.
2. Diabetic Nephropathy: Characterized by persistent microalbuminuria. Screened annually via urine Albumin-to-Creatinine Ratio (uACR; abnormal if $> 2.5 \text{ mg/mmol}$ in men, $> 3.5 \text{ mg/mmol}$ in women) and serum eGFR. Target Blood Pressure per MOH CPG is $< 130/80 \text{ mmHg}$, using ACE inhibitors (e.g., Enalapril) or ARBs (e.g., Losartan) for renal protection.
3. Diabetic Peripheral Neuropathy: Loss of protective sensation assessed using the 10g Semmes-Weinstein Monofilament Test at 10 anatomical sites on each foot.

Comprehensive Diabetic Foot Assessment & Patient Education

• Daily Foot Inspection: Inspect soles, heels, and interdigital spaces for calluses, blisters, erythema, or fissures.
• Foot Hygiene: Wash feet daily in lukewarm water; dry thoroughly, especially between toes. Apply emollient to dry skin but avoid applying lotion between toes to prevent fungal maceration.
• Footwear: Never walk barefoot. Wear custom-fitted, broad-toed supportive shoes with seamless cotton socks.
• Nail Care: Cut toenails straight across; file sharp edges. Never cut cuticles or dig into nail corners.

Clinical Nursing Scenario

Scenario: A 64-year-old Malay male with T2DM on twice-daily premixed insulin (Mixtard 30/70, 24 units AM, 12 units PM) is admitted for elective laparoscopic cholecystectomy. At 11:30 AM, while awaiting surgery (NPO status), he becomes diaphoretic, confused, and tachycardic (HR 118 bpm). Bedside CBG measures $2.8 \text{ mmol/L}$. Action: As the patient is NPO and confused, the nurse immediately secures IV access and administers IV 20% Dextrose 50 mL over 3 minutes as per hospital protocol. The nurse rechecks CBG 15 minutes later (result: $4.6 \text{ mmol/L}$), notifies the surgical/endocrine team, documents the incident, and maintains IV 5% Dextrose infusion while NPO.