Download Questions and Answers about Hypertension in Pregnancy

Hypertension in Pregnancy
for Undergraduates
Max Brinsmead MB BS PhD
February 2015
This talk
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How to measure BP
When is a pregnant woman hypertensive
What is the Differential Diagnosis
What tests are required and how do you
interpret them
Risk factors for pre-eclampsia
Pathophysiology of pre eclampsia
How to manage the hypertensive gravida
Drugs to lower BP in pregnancy
This talk(2)
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When to deliver
Best practice intrapartum care
Who requires an anticonvulsant?
What is the best drug for Eclampsia?
Best practice postpartum care
Prognosis after pre-eclampsia
Can pre-eclampsia be prevented?
How to Measure BP in a Pregnant Woman
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Automated machines not recommended
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Unless calibrated against a mercury sphygmomanometer in
the individual patient
Appropriate sized cuff
Seated for 2 - 3 minutes with feet supported
Both arms first visit
Palpate systolic and go 20 mm higher
Deflate slowly 2 mm every sec
Use Korotkoff 5 (or 4 if 5 absent) for diastolic
Repeated measures may be required
Ambulatory monitoring useful for White Coat
Hypertension
When is a Pregnant Woman
Hypertensive?
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>140/90 on >one occasion
(Rise of >30 systolic or >15 diastolic)
Knowledge of prior BP very important
 No longer accepted as a diagnostic point
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Severe hypertension is >169 systolic and
or diastolic >109
 Requires
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admission and urgent Rx
(However, the diagnosis is more
important than the actual level of BP).
Differential Diagnosis of Hypertension
in Pregnancy
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Gestational Hypertension
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Preeclampsia
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Sustained hypertension after 20w of pregnancy without any
other organ involvement. Returns to normal in 3m
Sustained hypertension after 20w of pregnancy with
evidence of other organ involvement. Returns to normal in
3m
Chronic Hypertension
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Hypertensive before 20w. 95% is Essential Hypertension
Includes “White Coat Hypertension”
Systems involved in Preeclampsia
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Renal
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Hepatic
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Eclampsia or stroke
Hyperreflexia with sustained clonus
Severe headache or visual disturbance
Cardiovascular
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Thrombocytopenia
Haemolysis
DIC
CNS
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Elevated transaminases
Epigastric or RUQ pain
Haematological
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Significant proteinuria
S Creat >90
Oliguria
Pulmonary oedema
Placental
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IUGR
Abruption
Please note
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I have not used the words “Pregnancy induced
Hypertension” or PIH
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No mention is made of oedema
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Proteinuria is the most common manifestation of
“other system involvement”
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Evidence for other organ involvement in Pre
eclampsia is a mix of symptoms, signs and tests
Some rare causes of preeclampsia
before 20w
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Hydatidiform mole
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Fetal triploidy (with or without partial mole)
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Severe renal disease
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Lupus obstetric syndrome
Renal Disease in Pregnancy
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Responsible for about 5% of chronic hypertension
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Causes include:
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chronic or recurrent infection
glomerulonephritis
renal artery stenosis
Must be assessed by creatinine clearance (CC)
which doubles in normal pregnancy
When CC falls below 50% the prognosis for a
pregnancy is very bad
Monitoring for superimposed pre eclampsia can
be difficult if there is chronic proteinuria
Some rare causes of hypertension
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Coarctation of the aorta
 Sometimes
the clue is to measure BP in both arms
 There is a systolic murmur that can be heard in the
back
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Phaeochromocytoma
 Paroxysms
of symptomatic hypertension
 The clue to diagnosis is to think of it
 Associated with high levels of catecholamines
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Hyperaldosteronism
 Also
known as Conn’s disease
Pathophysiology of Pre eclampsia
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Placental tissue
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healthy pregnancies cytotrophoblast
infiltrates the decidual portion of the uterine
spiral arteries
 In order to increase maternal blood flow to the
placenta
 In patients destined to develop pre eclampsia
this fails to occur
 This results in placental hypoperfusion
 These changes occur at <16 weeks gestation
but the pre eclampsia may not be manifest until
much later in the pregnancy
Pathophysiology of Pre eclampsia
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Hypoperfusion
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of the Placenta
Becomes worse as pregnancy progresses
The abnormal uterine vasculature is unable to
accommodate the normal rise in blood flow to
the fetus/placenta that occurs with increasing
gestational age.
Late placental changes consistent with
ischemia include atherosis (lipid-laden cells in
the wall arterioles), fibrinoid necrosis,
thrombosis, sclerotic narrowing of arterioles,
and placental infarction
Pathophysiology WHY?
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An ‘immunolgical’ response to pregnancy
---in ‘at risk’ or predisposed women
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A response to a conceptus whose genetic
material is 50% foreign (from the father)
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A failure of ‘Blocking Antibody’
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This disease is still a mystery
Pathophysiology WHAT?
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Contracted intravascular volume of mother
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reality a failure to increase plasma volume
↑Sensitivity to pressure agents
 Leaky capillaries
 Reduced oncotic pressure
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 In
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part due to low serum albumen
Poor placental reserve
A
fetus at risk of hypoxia and death
Tests for the Hypertensive Gravida
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Blood tests
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Urine Tests
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FBC - look at HB, Haematocrit and Platelets
UEC - look at Creatinine Should be < 0.07 (or 70)
URATE - equivalent to weeks of gestation
Liver enzymes – AST & ALT should be <70. Ignore ALP
UMCS - exclude UTI and look for casts
Protein:Creatinine ratio from spot test (>30 significant)
24 hr protein excretion (>300 mg/day significant)
Assess fetal welfare by CTG & Scan for
amniotic fluid volume & umbilical artery
Dopplers
Management of Hypertensive
Gravida
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Hospitalise if pre-eclamptic
Discharge if “just BP”
Bed rest only when there is proteinuria
Control BP to protect mother from severe
hypertension
Role of antihypertensive agents for mild &
moderate chronic hypertension is still
controversial
Delivery will cure pre eclampsia and
gestational hypertension
Remember thromboprophylaxis
Drugs for Hypertension in
Pregnancy?
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Aldomet
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An old and safe drug
Beta Blockers
Labetalol widely used in Australia
 Oxyprenalol also shown in RCT to be useful
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Ca channel blockers
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Nifedipine
Prazosin
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Relaxes pressor arterioles
Drugs for Hypertension in
Pregnancy?
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Combination therapy of drugs from
different classes is possible e.g.
 Aldomet
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+ Beta blocker + Prazosin
Do not use…
diuretics – reduce plasma volume
 Highly selective beta blokers – cause IUGR
 ACE inhibitors – may cause IUFD
 Thiazide
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Aim for BP 130 -150 systolic and 80 –
100 diastolic
Drugs for Acute Hypertension in
Pregnancy
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IV Hydralazine
IV Labetalol
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Nifedipine tablets crushed and oral
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Not available in Australia
Repeat after 30 min
IV Diazoxide in small boluses
Which Drug is Best for Eclampsia?
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First aid is more important than drugs
Protect from injury
 Secure an airway
 Administer oxygen
 Then secure IV access
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IV MgSO4 loading dose
Maintain by infusion
IV Diazepam only for status eclampticus
Monitor urine output, respirations, O2
saturation and deep tendon jerks
Who Requires Delivery?
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Pre eclampsia >36 completed weeks
Uncontrollable hypertension
Deteriorating renal, hepatic or haematologic
state
Eclampsia or imminently eclamptic
Fetus is compromised
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Give steroids to mature the fetal lungs
APH - abruption
How to Deliver
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Deliver vaginally if >37w and Cx is favourable
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can be ripened
Caesarean only if the above not met
Elective CS usually at gestations <35w
Inappropriate attempts at delivery when it is
not indicated is an invitation to CS (and more
CS)
Deliver in an environment that can cope with
a severe multisystem disease
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Don’t overlook patient’s and family’s psychological needs
Intrapartum Care
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Assess convulsive risk and consider
prophylactic MgSO4
Control BP with an epidural or IV Hydralazine
Careful fluid balance
Monitor the fetus
Avoid ergometrine
Postpartum Care
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Things may get worse before they get
better
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Seizure risk is greatest for 48 hrs
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Oliguria for 24 hours is common
Continue MgSO4 infusion for 24 hrs
Avoid NSAIDs
Treat any BP >150/100
OK to discharge 3 days after BP
control
Follow up weekly to 6w then 3m
The Prognosis after Pre eclampsia
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Mild pre eclampsia near term has a low
recurrence risk
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Unless there is a new partner or a long gap to the next
pregnancy
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Severe pre eclampsia prior to 34w has a 5066% recurrence risk
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Most recover by 12w but these patients are at
increased lifetime risk of hypertension and
related disease
Risk factors for severe pre eclampsia
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Previous pre eclampsia at <35w
Renal disease
Thombophilias
Autoimmune disease e.g. SLE
Diabetes
Multiple pregnancy
Severe alloimmunisation
Family history of pre eclampsia
Obesity
Increasing maternal age
The prevention of pre eclampsia
with low dose Aspirin
History of fetal death or severe IUGR
 Patients who required delivery for pre
eclampsia prior to 34w
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You need to treat 4-5 to prevent one FDIU or
severe IUGR
 Does not increase the risk of APH or PPH
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Conditions with high risk of pre eclampsia
eg Lupus or homozygous for thrombophilia
 These
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patients also require heparin
Also give Ca supplements 1.5 G/day
For the NICE Guideline go
to
http://pathways.nice.org.uk/pathways/hyperten
sion-in-pregnancy
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