Gestational Diabetes Mellitus (GDM)

🔷 Introduction

Gestational Diabetes Mellitus (GDM) is defined as glucose intolerance of variable severity with onset or first recognition during pregnancy, usually diagnosed in the second or third trimester. It poses unique maternal and fetal risks and has major implications for anesthesia planning, particularly during labor analgesia, cesarean section, or non-obstetric surgery.

📌 Prevalence: 3–15% depending on population, diet, and screening criteria
📌 Resolution: Typically resolves postpartum, but increases risk for future type 2 DM

🔷 Etiopathogenesis

GDM occurs due to:

1. Increased insulin resistance in pregnancy
• Mediated by placental hormones (hPL, cortisol, progesterone, estrogen)
• Peak resistance in 3rd trimester

2. Inadequate β-cell compensation

• Fails to match insulin demands → Hyperglycemia

3. Placental anti-insulin hormones:

• Human Placental Lactogen (hPL)
• Cortisol
• Growth hormone
• Progesterone

🔍 These hormones are diabetogenic → They impair insulin sensitivity

🔷 Risk Factors

🔷 Diagnosis (as per DIPSI / ADA / WHO guidelines)

2-Hour Plasma Glucose Interpretation (Post 75g OGTT)

🔷 Maternal Complications

• Preeclampsia
• Infections (UTI, pyelonephritis)
• Polyhydramnios
• Increased cesarean rate
• Shoulder dystocia
• Birth trauma
• Postpartum hemorrhage (PPH)
• Progression to Type 2 DM later in life

🔷 Fetal Complications

🔷 Anesthetic Implications

🩺 Preoperative Evaluation

• Review blood glucose trends, HBA1c
• Evaluate for organ damage (neuropathy, nephropathy, retinopathy)
• Diabetic parturients face added risks due to autonomic neuropathy, which may manifest as hypertension, orthostatic hypotension, silent myocardial infarction, reduced heart rate variability, and blunted responses to drugs like atropine and propranolol. 
• They may also exhibit resting tachycardia, neurogenic bladder, a diminished cough reflex threshold, delayed gastric emptying (gastroparesis), and a higher prevalence of obstructive sleep apnea.

• Check for associated PIH, obesity, or difficult airway
• Investigate polyhydramnios or fetal macrosomia
• Confirm insulin regimen or oral hypoglycemics
• Monitor electrolytes (esp. K⁺ if insulin used)

🧪 Perioperative Blood Sugar Management

NICE Guidelines (Intrapartum Period):

• Check capillary blood glucose (CBG) hourly during labor and delivery in women with diabetes, aiming to keep levels within 4–7 mmol/L.
• If glucose levels fall outside this target range, initiate an intravenous infusion of insulin and dextrose to help maintain optimal glycemic control.
• A Variable Rate Intravenous Insulin Infusion (VRII) is initiated when target capillary blood glucose (CBG) levels cannot be maintained through adjustments in the patient’s regular medications. 
• It is administered along with a glucose-containing maintenance fluid, which helps suppress gluconeogenesis, lipolysis, and prevents ketoacidosis. Importantly, basal insulin therapy should be continued even after starting a VRII.
• The preferred substrate fluid when starting a Variable Rate Intravenous Insulin Infusion (VRII) is 5% glucose in 0.9% saline, supplemented with either 0.15% (20 mmol/L) or 0.30% (40 mmol/L) potassium chloride. 
• The inclusion of normal saline (sodium-rich) helps to prevent hyponatraemia. It is advised to begin the infusion of this substrate fluid at a rate of 50 mL/hour.

🧠 Choice of Anesthesia

1️⃣ Labor Analgesia

• Epidural preferred
• Reduces stress response and catecholamine surge
• May reduce risk of shoulder dystocia via relaxed perineum

⚠️ Check coagulopathy, infection, neuropathy before neuraxial block

2️⃣ Cesarean Section

• Regional (Spinal/CSE) anesthesia preferred
• Avoid hypotension (may compromise uteroplacental flow)
• Maintain euglycemia intraoperatively

3️⃣ General Anesthesia

• Used if regional is contraindicated or fails
• Risk of delayed gastric emptying → Use RSI
• Expect difficult intubation (esp. in obese GDM parturients)
• Ensure tight glucose control intra-op

• Ensure adequate venous access is available to allow for the administration of additional intravenous infusions such as fluids, phenylephrine, and oxytocin.
• The target capillary blood glucose (CBG) range during this period is 5–8 mmol/L. CBG should be monitored hourly, and if the patient is under general anesthesia, monitoring should be done every 30 minutes.

🔄 Postoperative Considerations

• Monitor glucose 4–6 hourly
• Restart antidiabetic medications post meals
• Watch for infections, wound healing issues
• Encourage breastfeeding (may reduce insulin need)

💉 Drug Considerations in GDM

🔷 Critical Care Considerations (In severe GDM)

• Diabetic ketoacidosis (DKA) may require ICU care
• Fluids, insulin infusion, electrolyte correction
• Monitor for ARDS, lactic acidosis, and sepsis
• Multidisciplinary approach involving obstetricians, endocrinologists, intensivists

🔷 Viva Triggers

• What’s the best anesthesia choice in a parturient with GDM?
• How do you manage intraoperative hypoglycemia?
• What are the risks of GA in uncontrolled GDM?
• Name insulin regimens used during labor.
• Explain how GDM affects fetus.

🔷 MCQ Nuggets