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Hypertension in Pregnancy

CHHS17/217

Canberra Hospital and Health Services

Clinical Guideline

Hypertension in Pregnancy

Contents

Contents1

Guideline Statement2

Scope2

Section 1 – Definition of terms2

Section 2 – Recording blood pressure in pregnancy3

Section 3 – Classification of blood pressure in pregnancy4

Section 4 – Risk factors for preeclampsia6

Section 5 – Investigation of new onset hypertension after 20 weeks gestation6

Section 6 – Management of preeclampsia and gestational hypertension8

Section 7 – Antihypertensive therapy10

Section 8 – Eclampsia12

Section 9 – Administration of Magnesium Sulphate (MgSO4)13

Section 11 – HELLP syndrome18

Section 13 – Chronic hypertension19

Section 14 – Chronic hypertension with superimposed preeclampsia19

Implementation19

Related Policies, Procedures, Guidelines and Legislation20

References20

Search Terms20

Guideline Statement

To provide maternity staff with clinical guidelines to inform the management of hypertensive disorders in pregnancy, during labour and in the postpartum period in order to reduce mortality and morbidity from hypertensive disorders and improve clinical outcomes.

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Scope

This document applies to the following Canberra Hospital Health Services (CHHS) staff working within their scope of practice:

Medical officers

Registered Midwives and Nurses

Students working under supervision


Section 1 – Definition of terms

Hypertension in Pregnancy:

systolic blood pressure greater than or equal to 140mmHg and/or

diastolic blood pressure greater than or equal to 90mmHg

These measurements should be confirmed by repeated readings over several hours.

Detecting a rise in blood pressure from ‘booking’ or preconception blood pressure rather than relying on an absolute value, has in the past been considered useful in diagnosing pre-eclampsia in women who do not reach systolic blood pressures of 140 mmHg or diastolic blood pressures of 90 mmHg. Current evidence does not demonstrate these women have an increased risk of adverse outcomes. However, in the presence of hyperuricaemia and proteinuria it is appropriate to closely monitor pregnant women with an increment in blood pressure of greater than or equal to 30mmHg systolic and/or 15 mmHg diastolic.

BP ≥ 160 mmHg Systolic or ≥110mmHg diastolic requires commencement of antihypertensive therapy

Severe Hypertension in Pregnancy:

systolic blood pressure greater than or equal to 170 mmHg and/or

diastolic blood pressure greater than or equal to 110 mmHg.

This represents a level of blood pressure above which cerebral auto regulation is overcome in normotensive individuals. Severe hypertension should be lowered promptly, albeit carefully, to prevent cerebral haemorrhage and hypertensive encephalopathy. This degree of hypertension therefore requires urgent assessment and management. It is important to acknowledge that systolic as well as diastolic hypertension increases the risk of cerebral haemorrhage.

White Coat Hypertension

May be defined as hypertension in a clinical setting and normal blood pressure away from the clinical setting. Can be determined by 24 hour ambulatory blood pressure monitoring. Women may be generally managed without medication by using ambulatory or home blood pressure monitoring.

Proteinuria

Defined as the urinary excretion of ≥ 0.3g protein in a 24 hour specimen. This will usually correlate with ≥ 30mg/dL (≥1+ reading on dipstick) in a random urine determination with no evidence of urinary tract infection.

Urine Protein Creatinine Ratio of ≥30mg of protein / mmol creatinine

Oedema

Oedema is no longer included in the definition of preeclampsia as it occurs equally in women with and without this condition. Rapid development of generalised oedema should alert the clinician to screen for preeclampsia.


Section 2 – Recording blood pressure in pregnancy

The woman should be seated comfortably with her legs resting on a flat surface. In labour, the blood pressure may be measured in the lower positioned arm in lateral recumbency. The supine posture should be avoided because of the supine hypotension syndrome.

Measurement of blood pressure should be undertaken in both arms at the initial visit to exclude rare vascular abnormalities such as aortic coarctation, subclavian stenosis and aortic dissection. Generally the variation in blood pressure between the upper limbs should be less than 10mmHg.

The systolic blood pressure is accepted as the first sound heard (Korotkoff 1) and the diastolic blood pressure the disappearance of sounds completely (Korotkoff 5). Where Korotkoff 5 is absent, Korotkoff 4 (muffling) should be accepted.

Correct cuff size is important for accurate blood pressure recording. A cuff size with an inflatable bladder covering 80% of the arm circumference should be used if the upper arm circumference is greater than 33cm. This helps to minimise over-diagnosis of hypertension during pregnancy.


Section 3 – Classification of blood pressure in pregnancy

The classifications of hypertensive disorders in pregnancy reflect the pathophysiology of the constituent conditions as well as the risks and potential outcomes for both mother and baby.

Classifications are as follows:

preeclampsia – eclampsia

gestational hypertension

chronic hypertension

· essential

· secondary

· white coat

Preeclampsia superimposed on chronic hypertension.

Preeclampsia

This is a multi-system disorder characterised by hypertension and involvement of one or more other organ systems and/or the fetus. Raised BP is commonly but not always the first manifestation. Proteinuria is also common but should not be considered mandatory to make the clinical diagnosis.

Diagnosis can be made when:

Hypertension arises after 20 weeks gestation – confirmed on 2 or more occasions

Accompanied by one or more of:

· significant proteinuria: random urine protein/creatinine ratio greater than or equal to 30mg/mmol.

· renal involvement: serum or plasma creatinine greater than or equal to 90 micromol/L or oliguria < 80mL/4 hours

· haematological involvement: thrombocytopenia, haemolysis, Disseminated Intravascular Coagulation

· Liver involvement: raised transaminases, severe epigastric or right upper quadrant pain

· neurological involvement: severe headache, persistent visual disturbances (photopsia, scotomata, cortical blindness, retinal vasospasm), hyperreflexia with sustained clonus, convulsions (eclampsia), stroke.

· pulmonary oedema

· intrauterine fetal growth restriction (IUGR).

Gestational hypertension

Gestational hypertension is characterised by the new onset of hypertension after 20 weeks gestation without any maternal or fetal features of preeclampsia, followed by return of blood pressure to normal within 3 months post-partum. At first presentation this diagnosis will include some women (up to 25%) who are in the process of developing preeclampsia but have not yet developed proteinuria or other manifestations. Some women initially diagnosed in this category will manifest persistent blood pressure elevation beyond 12 weeks post-partum and eventually be classified as having chronic hypertension.

Gestational hypertension near term is associated with little increase in the risk of adverse pregnancy outcomes. The earlier the gestation at presentation and the more severe the hypertension, the higher is the likelihood that the woman with gestational hypertension will progress to develop preeclampsia or an adverse pregnancy outcome. Severe hypertension (≥170/110mmHg) is associated with increased risk of adverse outcomes in pregnancy.

Chronic hypertension

Pre-existing hypertension is a strong risk factor for the development of preeclampsia and requires close clinical surveillance.

· Essential Hypertension – BP greater than 140/90 mmHg preconception or prior to 20 weeks without an underlying cause or BP less that 140/90 entering pregnancy on antihypertensive

· Secondary Hypertension due to:

· chronic kidney disease (e.g. glomerulonephritis, reflux nephropathy and adult polycystic kidney disease)

· renal artery stenosis

· systemic disease with renal involvement (e.g. diabetes mellitus, systemic lupus erythematosus)

· endocrine disorders (e.g. phaeochromocytoma, Cushing’s syndrome and primary hyperaldosteronism)

· coarctation of the aorta.

NOTE:

Aim to keep blood pressure lower than 150/100 mmHg in pregnant women with uncomplicated chronic hypertension but do not lower diastolic blood pressure below 80mmHg.

Preeclampsia superimposed on chronic hypertension

This is a diagnosed when a woman with pre-existing hypertension develops systemic features of preeclampsia, after 20 weeks gestation.

Ongoing assessment when hypertension in pregnancy exists

Classification

Modality

Frequency

Chronic Hypertension

Urinalysis for protein

Preeclampsia bloods

Each visit

If sudden increase in BP or new proteinuria

Gestational Hypertension


Preeclampsia bloods

1-2 x per week

Weekly

Preeclampsia


Preeclampsia bloods

At time of diagnosis: if non-proteinuric, repeat daily. Twice weekly or more frequent if unstable


Section 4 – Risk factors for preeclampsia

Moderate risk:

age 40 years or more

first pregnancy

multiple pregnancy

interval since last pregnancy of more than 10 years

body mass index of 35 or more at presentation

family history of preeclampsia.

High risk:

chronic hypertension

chronic kidney disease

hypertensive diseases during a previous pregnancy

diabetes

autoimmune disease.


Section 5 – Investigation of new onset hypertension after 20 weeks gestation

Any woman presenting with new hypertension after 20 weeks gestation should be assessed for signs and symptoms of preeclampsia. Initially, assessment and management in the Maternity Assessment Unit may be appropriate. If features of preeclampsia are detected admission to hospital is indicated. The presence of severe hypertension, headache, epigastric pain, oliguria or nausea and vomiting are ominous signs which should lead to urgent admission and management, as should any concern about fetal wellbeing.

Baseline assessments

Maternal

History and physical examination

Investigations:

· Bloods:

· Full blood count

· urea, creatinine, electrolytes

· uric acid

· liver function tests (including ALT and AST)

· Urine

· urine dipstick testing for proteinuria, with quantification by laboratory methods if >’1+’ (30mg/dl)

· urinalysis and microscopy on a carefully collected mid-stream urine sample

· spot urine protein: creatinine ratio if there is proteinuria on urinalysis

Hyperuricemia is a common but not diagnostic feature of preeclampsia. The literature regarding uric acid as a predictor of maternal and/or fetal complications in preeclampsia is conflicting although a recent meta-analysis did suggest its usefulness in the management of preeclampsia. It is important to use gestational corrected normal ranges which may correlate better with adverse events.

Upper limits for uric acid (based on mean+2SD) at different gestational ages

Gestation (wks)

24

32

36

38

Uricacid (mmol/L)

0.28

0.32

0.34

0.38

Fetal

Cardiotocograph

Ultrasound assessment of fetal growth, amniotic fluid volume and umbilical artery flows

Goals of antenatal monitoring are to:

control blood pressure

recognise preeclampsia early

prevent eclampsia

optimise clinical outcomes for both the woman and the baby.

Note:

Blood test abnormalities should be interpreted using pregnancy-specific ranges, some of which are gestation dependent.

If there is thrombocytopenia or falling haemoglobin, investigate for disseminated intravascular coagulation: (coagulation studies, blood film, Lactate Dehydrogenase (LDH), fibrinogen).

Patients with severe early onset preeclampsia warrant investigation for associated conditions e.g. systemic lupus erythematosus, underlying renal disease, antiphospholipid syndrome or thrombophilias. The timing of these investigations will be guided by the clinical features.

Phaeochromocytoma although rare, is potentially fatal and may present as preeclampsia. Measurement of fasting plasma free metanephrines/ normetanephrines or 24 hour urinary catecholamines should be undertaken in the presence of very labile hypertension.

Subsequent management will be based on the results of ongoing blood pressure measurement and these investigations.

Amongst women referred for assessment of new onset hypertension, a number will have normal blood pressure and investigations. Repeat assessment should be arranged within

3 – 7 days as many will subsequently develop preeclampsia.


Section 6 – Management of preeclampsia and gestational hypertension

Key Considerations in Management of Preeclampsia

Assessment of severity and Place of care

Timing and mode of delivery

Management of hypertension

Magnesium for treatment and prophylaxis of seizures

Fluid management

Thromboprophylaxis

Optimisation of fetal / neonatal condition

Post partum care and future pregnancy planning.

Assessment of severity and Place of care:

Outpatient management

Women with mild gestational hypertension can be cared for at home, as long as:

there are not obstetric contraindications

there are no geographic contraindications

there is no evidence of fetal compromise

maternal and fetal well being is monitored regularly in Maternity Assessment Unit (MAU) with obstetrician back up

BP monitored 1-2 times per week.

Note:

Any evidence of maternal and or fetal compromise or failure to respond to outpatient treatment requires hospitalisation.

Inpatient management

Admission to hospital allows close supervision of both mother and fetus as progress of the disorder is unpredictable. Outpatient monitoring may be appropriate in milder cases after a period of initial observation.

All patients with preeclampsia must be regarded as being at risk of major maternal and fetal complication. However, there are certain indicators of particular concern when they occur in a woman with definite preeclampsia:

HELLP syndrome – any component (see Section 11 on HELLP syndrome for further information)

severe hypertension refractory to usual treatment

renal impairment – creatinine greater than 90umol/L depending on clinical picture

pulmonary oedema

persistent neurological symptoms – headache/altered mental state/clonus

“preeclamptic angina” severe epigastric pain and/or vomiting with abnormal liver enzymes

fetal growth restriction

Preeclampsia usually pursues a course of deterioration, sometimes slowly and sometimes quickly. It may evolve from mild to moderate to severe over a period of hours or days, and requires frequent reassessment by medical staff.

Maternal:

evaluate patient to determine if the admission should be to Birthing or to the ward

· moderate hypertension usually appropriate to be admitted to antenatal ward

· Severe hypertension or high risk for eclampsia should be admitted to birthing unit

perform baseline laboratory evaluation (FBC, Serum creatinine, LDH, ALT, AST, Uric Acid and Urine protein/ creatinine ratio )

review by obstetric registrar/specialist, at least daily to evaluate the patient for evidence of maternal deterioration.

Fetal:

fetal surveillance by biophysical profile; Doppler studies and cardiotocography as appropriate. Cardiotocograph (CTG) if >28 weeks and consider CTG from viability (but discuss with obstetrician first).

Timing and mode of delivery:

Preeclampsia is a progressive disorder that will inevitably worsen if pregnancy continues. Current therapy does not improve the placental pathology nor alter the pathophysiology or natural history of preeclampsia. Birth is the definitive management and is followed by resolution of symptoms, generally over a few days but sometimes much longer. At a mature gestational age, birth should not be delayed. Additionally, it is important to control severe hypertension and other maternal derangements before subjecting the woman to the stresses of birth.

Prolongation of pregnancy in the presence of preeclampsia carries no benefit for the mother but is desirable at early gestations to improve the fetal prognosis because, in general, fetal outcome is proportional to gestation age at birth. In cases of preterm preeclampsia before 34 weeks, birth should be delayed for at least 24-48 hours, if maternal and fetal status permit, to allow fetal benefit from antenatal corticosteroids administered for lung maturation.

The timing of birth will be based upon a number of factors, maternal and/or fetal rather than a single absolute indication for birth thus decisions are on an individualised basis.

Table 3: Indications for birth in women with preeclampsia or gestational hypertension.

Maternal

Fetal

Gestational Age >37 weeks

Severe fetal growth restriction

Inability to control hypertension

Non-reassuring fetal status

Deteriorating platelet count

Deteriorating liver and renal function

Placental abruption

Persistent neurological symptoms

Persistent epigastric pain, nausea or vomiting with abnormal liver function tests

Acute pulmonary oedema

Continuation of pregnancy carries fetal risk and some stillbirths will occur despite careful monitoring. Preeclampsia presenting in the late preterm period, 34-36 weeks gestation, is associated with increasing risk of small for gestational age (SGA) neonates with a higher risk of delivery via caesarean section, respiratory distress syndrome and longer neonatal intensive care admissions. Therefore, antenatal steroid prophylaxis may be beneficial in this group.

A team approach, involving obstetrician, midwife, neonatologist, anaesthetist and physician provides the best chance of achieving a successful outcome for mother and baby. Regular and ongoing reassessment of both the maternal and fetal condition is required.


Section 7 – Antihypertensive therapy

Mild to moderate hypertension

Antihypertensive therapy should only be commenced following initial investigation and decision to initiate therapy should be made at registrar level or above.

Treatment of mild to moderate hypertension in the range 140 – 160/90-100mmHg should be considered once full clinical and laboratory assessment has occurred. Above these levels, treatment should be considered mandatory.

The maternal blood pressure must not be lowered too drastically because inadequate placental perfusion may occur where placental circulation has adapted to a higher blood pressure.

A number of drugs have demonstrated safety and efficacy in pregnancy. First line drugs include methyldopa and labetolol. Second line agents are hydralazine, nifedipine and prazosin.

Antihypertensives contraindicated in pregnancy include: Angiotensin Converting Enzyme (ACE) inhibitors and angiotensin receptor blockers (use has been associated with fetal death and neonatal renal failure).

Commonly used antihypertensives in pregnancy include:

Methyldopa (Common commencing doses of 250 BD or TDS with potential to increase to a maximum of 3g per day).

Labetalol (Common commencing doses of 100-200 BD or TDS with potential to increase).

Nifedipine (Common commencing dose 20mg slow release BD).

Acute treatment of severe hypertension

It is important to control severe hypertension at any gestation and post partum.

Antihypertensive treatment should be commenced in all women with a systolic blood pressure ≥170mmHg or a diastolic blood pressure ≥110mmHg or a mean Arterial Pressure >125mmHg due to the increased risk of intracerebral haemorrhage and eclampsia. Treatment should be administered promptly aiming for a gradual and sustained lowering of blood pressure. Avoid acute blood pressure drops to below a level of 140/80.

Potential treatments are:

Labetalol 100mg or 200 mg orally (check for response to treatment after 30 minutes)

Nifedipine 10mg orally (check for response to treatment after 30 minutes)

Hydralazine intravenously 5mg slowly with potential to repeat after 20- mins. (Dilute 20mg ampoule with normal saline to volume of 20mls giving concentration of 1mg per ml)

Labetalol intravenously 20-50mg bolus over 2 minutes.

Using IV hydralazine

Bolus administration

Dilute with 20mg ampoule with normal saline to give 20mg in 20 mls volume (concentration 1mg/mL)

Preparations not used within 24 hours of reconstitution should be discarded

Dosage and administration - 5 mg slow IV injection at approximately 1mg per minute

If necessary, repeat after an interval of 20 -30 minutes

If after 20 mg IV hydralazine BP still not sufficiently controlled, consider IV hydralazine or IV labetalol infusion.

Infusion

Preparation concentration is the same as IV hydralazine bolus

Use 10mL water for injection to reconstitute 60mg (3x20mg vials). Add to 50ml normal saline bag to give final volume of 60mL containing 60mg of hydralazine (1mg/mL concentration)

IV hydralazine infusion start at 5mLs per hour, titrate to systolic BP 140-150 mmHg.

Usual rate is 2 – 3mLs per hour, maximum rate 18mLs per hour.

Note:

Contraindications to hydralazine include: systemic lupus erythematosus, porphyria, severe tachycardia and heart failure with high cardiac output (e.g thyrotoxicosis).

Using IV labetalol

20mg bolus IV followed at 10 minute intervals by 20mg then 40mg doses until maximum of 300mg given

Or

labetalol 200mg in 50mls Normal Saline i.e 4mg /ml

Starting at 40mg /hour (10mls /hour) increasing rate as required up to maximum of 160 mg /hour (40mls /hour).

Prevention of eclampsia in the woman with preeclampsia

Magnesium sulphate should be considered for women with preeclampsia for whom there is concern about the risks of eclampsia. This is usually in the context of severe preeclampsia once a birth decision has been made and in the immediate postpartum period. In women with less severe disease the decision is less clear and will depend on individual case assessment.

Evidence indicates that magnesium sulphate is the superior drug to use in the prevention and the treatment of eclamptic seizures.

In the patient with known renal disease or myasthenia gravis however, phenytoin sodium is the anti-seizure medication of choice. Phenytoin sodium is administered in a total dose of 15mg/kg at an infusion rate of 40mg/min with continuous cardiac and blood pressure monitoring.


Section 8 – Eclampsia

Eclampsia complicates 1 in 200-300 cases of preeclampsia in Australia. There are no reliable clinical markers to predict eclampsia and conversely, the presence of neurological symptoms and/or signs is rarely associated with seizures. Seizures may occur antenatally, intra-partum or postnatally, usually within 24 hours of delivery but occasionally later. Hypertension and proteinuria may be absent prior to the seizure and not all women will have warning symptoms such as headache, visual disturbances or epigastric pain.

The further from delivery that the seizure occurs, the more carefully should other diagnoses be considered. Cerebral venous thrombosis in particular may occur in the first few days of the puerperium. It should be remembered that eclampsia is not the commonest cause of seizures in pregnancy and the differential diagnosis includes epilepsy and other medical problems that must be considered carefully, particularly when typical features of severe preeclampsia are lacking.

Management of Eclampsia

There are four main aspects to care of the woman who sustains eclampsia.

1. Resuscitation

Airway

Breathing

Circulation

2. Treating seizures and Prevention of further seizures

Eclamptic seizures are usually self-limiting; however intravenous magnesium sulphate is the agent of choice for treatment and prevention of eclamptic seizures. Following appropriate resuscitation, treatment should be continued with magnesium sulphate.

3. Control of Hypertension

Control of severe hypertension to level below 160/100 mmHg by parenteral therapy is essential as the threshold for further seizures is lowered after eclampsia, likely in association with vasogenic brain oedema. There is significant risk of the danger of cerebral haemorrhage if severe hypertension is not treated.

4. Birth

Once an eclamptic fit has occurred, stabilization of maternal condition is important prior to expediting delivery. There is no role, with currently available treatment, for continuation of pregnancy once eclampsia has occurred.


Section 9 – Administration of Magnesium Sulphate (MgSO4)

Magnesium sulphate therapy is recommended for use antepartum, intrapartum and postpartum for severe preeclampsia when any of the following situations are present:

Persistently elevated blood pressure despite adequate anti-hypertensive therapy and appropriate fluid management

Evidence of CNS dysfunction

Prevention of further seizures

Magnesium sulphate is usually given as an intravenous loading dose although the intramuscular route is equally effective. Monitoring should include blood pressure, respiratory rate, urine output, oxygen saturation and deep tendon reflexes.

Magnesium sulphate is excreted via the kidneys and extreme caution should be used in women with oliguria or renal impairment. Serum magnesium concentration should be closely monitored in this situation. Magnesium is not universally successful and the recurrence rate of seizures despite appropriate magnesium therapy is 10-15%.

Serum magnesium levels do not need to be measured routinely unless renal function is compromised.

Administration of Magnesium Sulphate (MgSO4)

Magnesium sulphate should not be prescribed for the prevention of eclampsia without discussion with the consultant obstetrician on call.

Dosing for treatment of eclampsia and for prophylaxis are the same:

4g loading dose, followed by an infusion of 1-2g/hr (usually 1g / hour but occasionally at higher rate by instruction from specialist).

In the event of a seizure whilst on prophylaxis, then a further bolus of 2-4 grams may be given intravenously over 10 – 20 mins.

Patient Observations / monitoring when using magnesium sulphate.

Before loading:

· Check:

· Blood pressure

· Pulse

· Respiratory rate (must be above 12per minute)

· Oxygen saturations

· Patella reflexes

· Check that Calcium gluconate10%/10ml ampoule is available

During Loading:

· Continuous electronic fetal monitoring

· Continuous oxygen saturation monitoring

After 10 minutes:

Blood pressure

Pulse

Respiratory rate (must be above 12per minute)

Oxygen saturations

Patella reflexes

After loading dose:

Blood pressure

Pulse

Respiratory rate (must be above 12per minute)

Oxygen saturations

Patella reflexes

Magnesium side effects Include:

Hypotension secondary to reductions in systemic vascular resistance

Facial flushing

Visual disturbances

Flushing at injection site

Chest pain

Nasal stuffiness

The following may also occur:

Electrocardiograph changes

Circulatory collapse

Gastrointestinal upset

Urinary retention

Magnesium toxicity

Tissue necrosis at the injection site

Magnesium sulphate contraindication or use with caution

Women treated with cardiac glycosides / digitalis

Concurrent use of central nervous depressants

Magnesium is excreted by the kidneys therefore serum levels should be checked in women with oliguria and those with renal impairment

Use of magnesium sulphate and Nifedipine may potentiate the drug actions and result in significant hypotension and neuromuscular blockade effects.

Administration of Magnesium Sulphate is by use of premixed bags of Magnesium Sulphate 40 Grams in 500mls volume as below:

Mainline:

Hartmanns or 0.9% Sodium Chloride (NaCl) at rate prescribed by medical officer.

(Total fluid input usually restricted to 1ml/kg bodyweight/hour)

Sideline:

Magnesium Sulphate loading then maintenance as described below:

1. Magnesium Sulphate (MgSO4) LOADING DOSE : 4g Magnesium Sulphate (MgSO4) over 20 minutes

· Infuse 150mL/hour for 20 minutes (i.e. the woman receives only 50mL) of the solution of 40g of MgSO4 in 500mL bag

· Via an infusion pump

· Select New guardrails drug

· Select magnesium ECLAMPSIA (magnesium Eclampsia 40g/500mL)

· Set rate at 150ml/hour

· Set VTBI at 50ml

Alert:

In the event of a Respiratory or Cardiac Arrest

· Cease magnesium sulphate

· Call code blue

· Administer Calcium Gluconate 10% in 10mls intravenously over 3 minutes.

2. Magnesium Sulphate (MgSO4) MAINTENANCE DOSE: 1 g Magnesium Sulphate (MgSO4) per hour

· Infuse 12.5 mls/hour of the solution of 40g of Magnesium Sulphate (MgSO4) in 500mL bag

· Set rate at 12.5ml/hour

· Dose =1 g/hour

· Set VTBI at 12.5ml/hour (total 50 mls)

MgSO4 Loading Dose – 4g MgSO4 over 20 minutes

1. Use premixed Magnesium Sulfate 40g in 500mL in Water for injection

2. Select Magnesium Maternity from Braun pump menu

3. Set VTBI at 50ml

4. Set Rate at 150ml/hr

MgSO4 Maintenance Dose – 1g MgSO4 per hour

1. Continue use of Magnesium Maternity from Braun pump menu

2. Set VTBI at 12.5mL/hr

3. Set Rate at 12.5mL/hr

4. Continue for at least 24 hours following birth, 24 hours after last seizure or whilst clinical reason present to continue, whichever is the later.

Treatment of further seizure – 2-4g MgSO4 over 10 minutes

· Continue use of Magnesium Maternity from Braun pump menu

· To give 2g MgSO4, set VTBI at 25ml and Rate at 150mL/hr; or

· To give 4g MgSO4, set VTBI at 50ml and Rate at 300mL/hr

Observations during Magnesium Sulphate Infusion:

Record as per MEWS chart and strict Fluid Balance Chart

Continuous

Maternal Heart Rate

Maternal Oxygen Saturation

Fetal Heart Rate

Document

15minutely intrapartum,

30-60minutely postpartum

½ to 1 hourly (as per MEWS and Medical Orders)

Blood Pressure

Maternal Heart Rate

Maternal Respiratory Rate

Maternal Oxygen Saturation

1 hourly

Temperature

Urine output

Deep Tendon Reflexes

Magnesium sulphate by infusion should usually be continued for a minimum of 24 hours after the last fit or for minimum of 24 hours post partum.

When a woman is on magnesium sulphate for prophylaxis of convulsions they should be reviewed by obstetric doctors clinically and an individualised plan of management be made with regard to frequency of ongoing blood testing and clinical reviews depending on severity of condition. Common intervals are 4, 6 ,8 or 12 hours.

Before planned discontinuation of MgSO4 therapy

Plan for discontinuation should be documented by obstetric registrar or specialist.

Blood pressure should be stable (consistently below 150/100).

Patient should be clinically improved (absence of headache, epigastric pain).

Fluid management

As vascular permeability is increased with preeclampsia and there is also often hypoalbuminaemia, administration of large volumes of intravenous fluid before or after delivery may cause pulmonary oedema.

Women admitted with preeclampsia should have fluid balance chart documented.

In those with severe preeclampsia it is recommended that the total fluid input should be limited to 1ml/kg/hour

Administration of fluid at an increased rate should be only by instruction from the obstetric registrar or specialist.

Thomboprophylaxis:

Preeclampsia is considered a major risk factor for venous thromboembolism.

Mechanical thromboprophylaxis such as graduated compression stockings should be recommended for all those who are hospitalised with preeclampsia.

Pharmacological prophylaxis is indicated, but may have to be withheld depending on some clinical circumstances e.g. timing of delivery, timing in relation to insertion and withdrawal of epidural and spinal cannulae .

Optimisation of fetal / neonatal condition

Depending on gestation and potential timing and mode of delivery consideration should be given to use of:

Corticosteroids

Mg S04 for neuroprotection

Post partum care

Antihypertensive therapy should be commenced if the BP is >150mmHg systolic or >100mmHg diastolic in the first four postpartum days. Options for antihypertensive therapy include:

labetolol 100mg BD TDS to start

atenolol 50mg daily – on rare occasions, may need increasing to 100mg/day

nifedipine 10mg BD increasing to 20mg TDS

enalapril 5-10mg daily

Resolution of preeclampsia

After birth, all clinical and laboratory derangements of preeclampsia recover, but there is often a delay of several days, and sometimes longer, in return to normality. On the first day or two after birth, liver enzyme elevations and thrombocytopenia will often worsen before they reverse. Hypertension may persist for days, weeks or even up to three months and will require monitoring and slow withdrawal of antihypertensive therapy. Resolution is still assured if the diagnosis was preeclampsia and there is no other underlying medical disorder. The woman and her family are often overwhelmed and distressed from their experience and appropriate counselling post partum should include psychological and family support.

All women who develop preeclampsia and gestational hypertension are at risk of these disorders in future pregnancies and should receive appropriate counselling before embarking upon another pregnancy.


Section 11 – HELLP syndrome

HELLP syndrome is a variant of severe preeclampsia (Haemolysis, Elevated Liver enzymes and Low Platelet) count. Maternal mortality is reported to be as high as 1-2%.

The elements of this variety of severe preeclampsia are:

haemolysis

elevated liver enzymes

thrombocytopenia

In a woman with preeclampsia, the presence of any one of the following is an indicator of severe disease, even if not suggested on other criteria such as severity of hypertension:

a maternal platelet count of <100 000 x 10₉/L

a transaminase level or LDH more than double the normal upper limit

haemolysis of any quantity.

Management of HELLP syndrome

Should be treated as severe pre eclampsia.

Attention should be given to:

· Antihypertensive therapy

· Prophylaxis to reduce risk of seizure

· Strict fluid restriction

· Monitoring blood indices initially every 4 to 6 hours then reduced frequency depending on clinical reviews.

If the platelet count is sufficiently low to present a hazard, a platelet transfusion should be considered (consult with consultant haematologist).


Section 13 – Chronic hypertension

Women with chronic hypertension have an increased risk of accelerated hypertension in the third trimester, superimposed preeclampsia, fetal growth restriction, placental abruption, premature delivery and stillbirth. Diagnosis can be difficult in women whose blood pressure before pregnancy or early in the first trimester is unknown. Very rarely preeclampsia can present before 20 weeks gestation and the physiological fall in blood pressure in the second trimester can obscure pre-existing chronic hypertension.

The woman with chronic hypertension, whether essential or secondary, should be referred to obstetric care early in pregnancy to establish a management plan. This usually involves baseline assessment followed by frequent checks of blood pressure and urinalysis in the third trimester.

Postpartum management of women with chronic hypertension

In many women with chronic hypertension or superimposed pre-eclampsia, blood pressure is unstable for 1-2 weeks postpartum and may be difficult to control. It may be particularly high on the third to the sixth postpartum day and it is often necessary to increase or commence antihypertensive medication at that time. All of the agents mentioned earlier are compatible with breast feeding, as are the ACE inhibitors enalapril, captropril and quinapril.


Section 14 – Chronic hypertension with superimposed preeclampsia

Chronic hypertension in pregnancy is a risk factor for the development of superimposed preeclampsia in the second half of pregnancy.

Management of superimposed preeclampsia should be as outlined above for preeclampsia.

It is recommended that all women with a hypertensive complication of pregnancy have a postpartum hypertension follow up. Depending on the severity of the hypertension this follow-up should be 2-6 weeks after discharge from hospital.


Implementation

This guideline will be referred to in existing provision of education and will be available via the Policy/Clinical Guidance and Policy Register.


Related Policies, Procedures, Guidelines and Legislation

Healthcare and Associated Infections Procedure

Patient identification - pathology specimen labelling procedure

Pathology Requests and Specimens procedure

Labour - 1st, 2nd and 3rd Stage Care Procedure

Human Rights Act 2004


References

1. Coghill A E, Hansen S, Littman A J. (2007) Risk factors for eclampsia: a population-based study in Washington State, 1987-2007. American Journal of Obstetrics and Gynecology.

2. Empson M, Lassere M, Craig J, Scott J. Prevention of recurrent miscarriage for women with antiphospholipid antibody or lupus anticoagulant. The Cochrane Database of Systematic Reviews 2005(8).

3. Le M, Tran BN. Perinatal Statistics in Western Australia, 2008: Twenty-sixth Annual Report of the Western Australian Midwives’ Notification System Department of Health- Government of Western Australia

4. Lisonkova S, Sabr Y, Mayer C, Young C, Skoll A, Joseph KS. (2014) Maternal morbidity associated with early-onset and late-onset preeclampsia. Obstet Gynecol. 2014 Oct; 124 (4):771-81

5. Lowe SA, Bowyer L, Lust K, McMahon LP, Morton MR, North RA, Paech MJ and Said JM. (2014). Guidelines for the management of hypertensive disorders of pregnancy. Society of Obstetric Medicine of Australia and New Zealand.

6. NICE. Hypertension in pregnancy: the management of hypertensive disorders during pregnancy. National Institute for Health and Clinical Excellence. 2012 (Clinical guideline 107).

7. Royal College of Obstetricians and Gynaecologists. Management of Pre Eclampsia/ Eclampsia. Greentop guidelines No 10(A),. 2010; London.

8. SOMANZ Guideline for the Management of Hypertensive Disorders in Pregnancy 2014: SOMANZ-Hypertension-Pregnancy-Guideline-April-2014.pdf


Search Terms

Hypertensive disorders of pregnancy, Preeclampsia, Eclampsia, Gestational hypertension, Magnesium sulphate


Disclaimer: This document has been developed by Health Directorate, Canberra Hospital and Health Services specifically for its own use. Use of this document and any reliance on the information contained therein by any third party is at his or her own risk and Health Directorate assumes no responsibility whatsoever.

(to be completed by the HCID Policy Team)

Date Amended

Section Amended

Approved By

Eg: 17 August 2014

Section 1

ED/CHHSPC Chair

Doc Number

Version

Issued

Review Date

Area Responsible

Page

CHHS17/217

1

08/09/2017

01/09/2022

WY&C Maternity

1 of 21

Do not refer to a paper based copy of this policy document. The most current version can be found on the ACT Health Policy Register

hypertension in pregnancy · web viewit should be remembered that eclampsia is not the commonest...

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