Hypertension in Pregnancy

1. Hypertensive disorders of pregnancy
Chronic hypertension • Systolic pressure ≥140 mm
Hg &/or diastolic pressure
≥90 mm Hg prior to
conception or at <20 weeks
gestation
Gestational
hypertension
• New-onset elevated blood
pressure at
≥20 weeks gestation
• No proteinuria or signs of
end-organdamage
Preeclampsia • New-onset elevated blood
pressure at
≥20 weeks gestation
AND
• Proteinuria OR signs of
end-organdamage
Eclampsia • Preeclampsia
AND
• New-onset tonic-clonic seizures
Chronic
hypertension
with
superimposed
preeclampsia
Chronic hypertension AND 1 of the
following:
• New-onset proteinuria or
worsening ofexisting
proteinuria at ≥20 weeks
gestation
• Sudden worsening of
hypertension
• Signs of end-organ damage

2. 2
Preeclampsia
Risk factors • Nulliparity
• Obesity
• Preexisting medical condition (eg,
SLE, chronichypertension)
• Multiple gestation
• Advanced maternal age
Definition • New-onset hypertension* (SBP ≥140 or
DBP
≥90 mm Hg)
at ≥20 weeks
AND
• Proteinuria OR signs/symptoms of
other end-organ damage
Severe
features
• Severe-range hypertension (SBP ≥160 or
DBP
≥110 mm Hg)
• Platelets <100,000/mm3
• Creatinine >1.1 mg/dL or 2x normal
• Elevated transaminases >2x upper limit
of normal
• Pulmonary edema
• Vision or cerebral symptoms (eg,
headache)
Management • <37 weeks & no severe features:
expectant
• ≥37 weeks (or ≥34 weeks with severe
features):delivery
• Severe-range blood pressure: IV
labetalol, IVhydralazine,
PO nifedipine
• Seizure prophylaxis: magnesium sulfate
*On 2 measurements ≥4 hr apart.

3. 3
Obstetric complications of hypertension
Maternal • Superimposed preeclampsia
• Cesarean delivery
• Abruptio placentae
• Postpartum hemorrhage
• Maternal mortality
Fetal • Fetal growth restriction ± oligohydramnios
• Preterm delivery
• Intrauterine fetal demise
• Perinatal mortality
Preeclampsia prevention
Definition • New-onset hypertension &
proteinuria &/orend-organ
damage at >20 weeks gestation
High risk • Prior preeclampsia
• Chronic kidney disease
• Chronic hypertension
• Diabetes mellitus
• Multiple gestation
• Autoimmune disease
Moderate
risk
• Obesity
• Advanced maternal age
• Nulliparity
Prevention • Low-dose aspirin at 12 weeks gestation

4. 4
Treatment of preeclampsia
Drug Indication
Hydralazine IV,
labetalol IV or
nifedipine PO
Lower blood pressure
acutely todecrease
stroke risk
Magnesium sulfate IV or IM Prevent or treat eclamptic
seizures
Treatment of Severe Blood Pressures
Labetalol
Initial dose: 20 mg IV bolus over 2 minutes
If BP remains > 160/110 then repeat 10 minutes later at 40 mg and 10
minutes later at 80 mg. If still > 160/110 switch to hydralazine
Maximum daily IV dose 200mg
Nifedipine
10 to 20 mg po; repeat in 30 min if needed
Can also use 10 to 20 mg orally every two to six hours
Hydralazine
Initial dose 5 mg or 10 mg IV or 2 minutes and may repeat with 10 mg
IV in 20 minutes if >160/110

5. 5
Drug Dose Route Onset of action Adverse effects
Hydralazine 5–10 mg Intravenous bolus repeated after
20 min if blood pressure remains
>160/110 mmHg
20 min Flushing, headache, nausea,
hypotension, tachycardia
Labetalol 20–80 mg Intravenous bolus over 2 min,
repeat after 10 min if blood
pressure remains >160/110mmHg
5 min Bradycardia, hypotension,
fetal bradycardia
Labetalol 200 mg Oral 30–45 min Bradycardia, bronchospasm,
headache
Nifedipine 10 mg Oral 30–45 min Headache, flushing
Magnesium Dosage and Monitoring
• 4gram IV load over 15 to 20 minutes, followed by infusion of 2
grams/hour
Drug Dose Route Onset of Action Adverse effects
Magnesium 4 g Intravenous bolus over 20 min Flushing, respiratory depression
sulphate 20 min followed by 1 g/hour Caution in renal impairment as
infusion, typically continued magnesium is excreted renally
for 24 hours and toxicity may occur

6. 6
Magnesium toxicity
Clinical
features
• Mild: nausea, flushing, headache,
hyporeflexia
• Moderate: areflexia, hypocalcemia,
somnolence
• Severe: respiratory paralysis, cardiac arrest
Treatment • Stop magnesium therapy
• Give IV calcium gluconate bolus
Magnesium Levels
Normal 1.3 to 2.6
Therapeutic 4 to 8
Loss of patellar reflex 8 to 10
Somnolence 10 to 12
Respiratory depression 12 to 17
Paralysis 15 to 17
Cardiac arrest 30 to 35
Antidote is calcium gluconate one gram IV over three
minutes

7. 7
** Asthma, overt cardiac failure, severe bradycardia, heart block
Management of Severe Pre-eclampsia
Blood Pressure Target
 Aim for systolic lesson than 150mmHg
 Reduction of diastolic by 10mmHg to below 100mmHg. Avoid sudden drop in DBP to less than
80mmHg
General Measures
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Manage in maternity HDU
Use maternity HDU chart and MEOWS
Involve both Consultant Obstetrician & Consultant in Obstetric Anaesthesia
Consider requesting input from critical care outreach and/or intensive care
Insert IV cannula
Intravenous fluid by volumetric pump
Give Ranitidine 150mg 6 hourly
Inform Neonatal team if gestation is below 36 weeks
Discuss Neonatal care in pre-term birth
Control of Blood Pressure
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First Line
Labetalol 200mg orally if can tolerate, before venous access. If no contraindication **
If no response within 30 minutes or cannot tolerate oral therapy give IV Labetalol
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Labetalol 50mg slow IV over at least 5 minutes
Repeat Labetalol at 10min intervals if DBP has not reduced as desired. Total maximum dose of
Labetalol is 200mg
Maintenance of Blood Pressure ( <150/110 mm HG)
Following reduction in BP commence Labetalol infusion 5mg per/ml. Rate 4ml/per hour via
syringe pump.
 The infusion can be doubled every half hour to a maximum of 32ml (160mg)/hour until BP

8. 8
Seizure Prophylaxis
Loading Dose
 4g Magnesium Sulphate slow IV over 10mins
 Administer via syringe pump
Maintenance
 Magnesium Sulphate 1g /hour for 24 hours or until delivered whichever is longer
Important Observations
 Continuous pulse oximetry
 Hourly urine output
 Hourly respiratory rate
 Five Hourly deep tendon reflexes
Every 5 hours the following observations
 Biceps reflex present
 Respiratory rate is >12/min
 Urine output >100ml previous 4 hrs; 97% magnesium is excreted in urine;
presence of oliguria can lead to toxic levels.
Side Effects
Discontinue magnesium sulphate if:-
 Motor Paralysis
 Absent tendon reflexes
 Respiratory Depression
 Cardiac Arrythmia
If side effects occur, administer 10ml 10% calcium gluconate IV.
No need to measure Magnesium levels with the above

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