Diabetes Mellitus

Pregestational diabetes mellitus

Gestational diabetes mellitus (GDM)

Obstetric diabetic clinic

Pregnant diabetic patients are best managed in a combined clinic run by an obstetrician, internal medicine specialist, nurse & dietician. Refer all pregnant diabetic women to this clinic as early as possible in the pregnancy.

PREGESTATIONAL DIABETES MELLITUS

This is diabetes that has been present before the current pregnancy. These women require tight control of their blood glucose levels from the time of conception, & should book for antenatal care as soon as pregnancy is confirmed. Pregestational optimization of blood glucose control is the ideal. Gestational diabetes (GDM) refers to diabetes diagnosed for the very first time during the index pregnancy.

First assessment

• Initial admission is not always required if blood glucose control is good 
• Take FBC, U&E; HbA₁C (<6,5% = good, 7-10 = average, >10 = poor control)
• Take urine for albumin:creatinine ratio
• Order baseline ultrasound scan
• Do fundoscopy & refer women with proliferative retinopathy to an ophthalmologist
• Convert all insulin dependent diabetics from Actraphane & other insulin combinations to equivalent dosages in one of the following regimens:
  • Three times daily short acting insulin & a night time dose of intermediate acting insulin
  • Alternatively, twice daily combined intermediate & short acting insulin (Humulin N and R)
• Women with type 2 diabetes may be converted from oral hypoglycaemic agents to Humulin N and R, or may remain on oral agents (eg metformin), individualized at the diabetic clinic

Hospital admission for glucose control

• Prescribe a 30-35 kcal/kg/day diabetic diet, with 50% low GI carbohydrate, 30% fat and 20% protein, and 80 g/day of fibre
• Perform six-point profiles (fingerprick capillary glucose before, and 1 hour after each meal of breakfast, lunch and supper)
• Using standard insulin regimen as described above, aim for:
  • Fasting capillary glucose values <5.3 mmol/L
  • 1-hour postprandial values <7.8 mmol/L
  • 2-hour postprandial values <6.4 mmol/L
• If on a twice daily regimen, add a midday dose if the total daily insulin requirement exceeds 120 units/day, or if control is difficult during the day
• Teach the woman to measure her own blood glucose and inject herself with insulin, and to understand recognition and treatment of hypoglycaemia.
• Discharge the woman once good control is achieved

Continuing antenatal care

• Outpatient 6-point blood glucose measurements are recorded daily by the woman (½ hour before, 1 and 2 hours after breakfast, lunch and supper)
• Attendance is 2-weekly to 32 weeks, then weekly until admission at 37 weeks
• Perform ultrasound scans for growth or macrosomia at 28 and 34 weeks
• Do NST weekly from 32 weeks
• Admit to hospital at 37 weeks, with 6-point profiles and NST on alternate days

Labour and delivery

• Aim for induction of labour at 38 weeks if there are no complications
• Consider earlier induction with poor obstetric history, poor control, IUGR, hypertension, fetal macrosomia, retinopathy, nephropathy, and neuropathy
• Preterm induction may require prophylactic betamethasone 12 mg IMI daily for two doses, with a supplemental insulin sliding scale
• Caesarean section should be done for estimated fetal weight >4 kg
• Elective caesarean section should be done as early as possible in the day
• Standard methods of induction are used
• Give only the Humulin N dose on the morning of planned delivery
• Transfer to a high care area for induction when in labour, keep nil per os
• Measure hourly fingerprick capillary glucose levels during labour
• Run 5% dextrose-saline 1000 mL with 20 mmoL of KCL and 10 units of rapid acting soluble insulin (Humulin R) at 100 mL/hour; and monitor capillary glucose levels hourly. Insulin is given as follows:
  • <4 mmol/L:  no insulin
  • 4-7 mmol/L: 10 units insulin in 1 L at 100 mL/hour (1 unit/hour)
  • >7 mmol/L: 20 units insulin in 1 L at 100 mL/hour (2 units /hour)
• Give oxytocin, if needed, through a separate 200 mL infusion bag
• Monitor fetus with continuous CTG

Postpartum care

• After caesarean section, give 5% dextrose-saline with 20 mmoL of potassium chloride – 3 L in the first 24 hours
• Measure 4 hourly fingerprick capillary glucose
• Give a 4 hourly sliding scale of SC Humulin R based on blood glucose level
• Note that insulin requirements drop sharply among women with GDM

• Re-introduce pre-pregnancy insulin or oral hypoglycaemic drugs cautiously as appetite may be poor and insulin requirements may be low in the first few days after delivery
• Discharge the woman to be followed up at her normal diabetic care provider, with a discharge summary
• Breastfeeding mothers may need less insulin or an increased dietary intake
• For contraception, tubal ligation, progestin, low-dose combined contraceptives and intrauterine devices are acceptable.

Diabetic ketoacidosis in pregnancy

Diagnosis

• Clinical features include polyuria, polydipsia, abdominal pain, weakness, vomiting, hyperventilation, dehydration, tachycardia, hypotension, disorientation, and coma
• Tests reveal blood glucose ≥17 mmol/L, glycosuria and ketonuria, arterial blood pH <7.3, serum bicarbonate <15 mmol/L, base excess > -7, and raised serum urea

General measures

• Admit the woman to a high care area and record all findings on an ICU chart
• Nurse in left lateral position
• Monitor fetal heart rate by CTG
• Insert a large bore (16G) intravenous cannula
• Take blood for glucose, ketones, FBC, U&E, culture, and ABG.  Repeat glucose and U&E hourly at first, and venous blood gas 2 hourly
• Insert a urinary catheter and monitor urine output hourly
• Send a catheter specimen of urine for MCS
• Use CVP and peripheral arterial lines only for severe acidosis or hypotension
• Search for predisposing factors and sites of infection
• Do not hesitate to consult internal medicine specialists for advice

Specific measures

1. Fluids

• Give normal saline 1 L for the first half-hour, followed by normal saline over one hour. For hyperosmolar nonketotic coma follow with half-normal saline
• Continue rehydration at 1 L/1-2 hours (6-12 L in 12-24 hours) depending on clinical response. Add potassium (below). Aim for urine output of 1 mL/kg/hour, provided renal function is normal
• If sodium level rises to >150 mmol/L or when glucose falls to <15 mmol/L, change to 5% dextrose water with potassium (below) at 150-300 mL/hour

2. Potassium

• Withhold potassium if ECG shows hyperkalaemia or potassium >5.5 mmol/L
• Once rehydration has commenced and urine output is satisfactory, replace potassium. Never exceed 20 mmol potassium per hour IV.

3. Phosphate

• Replace phosphate when supplementing potassium initially
• Infuse potassium phosphate 20 mmol/L IV over one hour

4. Insulin – use low dose Humulin R

• Delay giving insulin until potassium level is known to be >3.5 mmol/L
• Give 10 units IV followed by a continuous infusion at 5-10 units/hour, or hourly boluses of 5-10 units IV
• If fall in blood glucose is <4 mmol/hour, double the insulin dose
• Change to SC sliding scale insulin if base excess > -7 mmol/L
• Once the patient is fully alert, commence twice daily SC insulin

4. Sodium bicarbonate

• Only give sodium bicarbonate if pH <7.0 and serum potassium >4.0 mmol/L
• Add 25-50 mL 8.5% solution to 200 mL water or 0.45% saline with 10 mmol postassium and run in over one hour; can repeat until pH >7.0.

GESTATIONAL DIABETES MELLITUS (GDM) 

This is glucose intolerance that develops during pregnancy, or is noted for the first time during the current pregnancy. 

Screening and diagnosis

Screening is based on history taking at antenatal clinic and the presence of glycosuria at clinic visits. Random blood glucose testing may be done if there is strong suspicion of diabetes. A random level ≥11 mmol/L is diagnostic. An oral glucose tolerance test (OGTT) is done in the presence of significant risk factors.

An OGTT is usually done from 24 weeks onwards. Blood glucose levels in gestational diabetics may only become abnormal in the third trimester, so an OGTT may delayed to 28 weeks for some women, or repeated at 28 weeks if an earlier OGTT was negative.

Screening for GDM

• Glycosuria 1+ on two occasions, or 2+ on one occasion.
• Family history of diabetes
• Previous gestational diabetes
• Weight ≥100 kg or BMI > 40 kg/m².
• Previous unexplained stillbirth.
• Previous macrosomic baby (weight > 4 000 g).
• Maternal age >40 years.
• Polycystic ovarian syndrome.
• Acanthosis nigricans.
• Polyhydramnios in current pregnancy.

Diagnostic criteria

• Random plasma glucose > 11 mmol/L OR
• A fasting plasma glucose ≥ 5.6 mmol/L, OR
• A plasma glucose of ≥ 7.8 mmol/L two hours after a 75 g OGTT, performed after overnight fasting, from 24 weeks’ gestation onwards.

Management of GDM

Management is the same as for pregestational diabetes mellitus except:

• Ophthalmologic examination is usually not required
• Some women can be successfully treated with diabetic diet alone
• Insulin is usually stopped after delivery
• A 75 g OGTT is usually done 6 weeks after delivery, or an HbA₁C at 12 weeks postpartum