Hypertension in Pregnancy for Undergraduates

1. Hypertension in Pregnancyfor Undergraduates Max Brinsmead MB BS PhD February 2015

2. This talk • 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

3. This talk(2) • 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?

4. How to Measure BP in a Pregnant Woman • Automated machines not recommended • 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

5. When is a Pregnant Woman Hypertensive? • >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 • Severe hypertension is >169 systolic and or diastolic >109 • Requires admission and urgent Rx • (However, the diagnosis is more important than the actual level of BP).

6. Differential Diagnosis of Hypertension in Pregnancy • Gestational Hypertension • Sustained hypertension after 20w of pregnancy without any other organ involvement. Returns to normal in 3m • Preeclampsia • Sustained hypertension after 20w of pregnancy with evidence of other organ involvement. Returns to normal in 3m • Chronic Hypertension • Hypertensive before 20w. 95% is Essential Hypertension Includes “White Coat Hypertension”

7. Systems involved in Preeclampsia • Renal • Significant proteinuria • S Creat >90 • Oliguria • Hepatic • Elevated transaminases • Epigastric or RUQ pain • Haematological • Thrombocytopenia • Haemolysis • DIC • CNS • Eclampsia or stroke • Hyperreflexia with sustained clonus • Severe headache or visual disturbance • Cardiovascular • Pulmonary oedema • Placental • IUGR • Abruption

8. Please note • I have not used the words “Pregnancy induced Hypertension” or PIH • No mention is made of oedema • Proteinuria is the most common manifestation of “other system involvement” • Evidence for other organ involvement in Pre eclampsia is a mix of symptoms, signs and tests

9. Some rare causes of preeclampsia before 20w Hydatidiform mole Fetal triploidy (with or without partial mole) Severe renal disease Lupus obstetric syndrome

10. Renal Disease in Pregnancy • Responsible for about 5% of chronic hypertension • Causes include: • 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

11. Some rare causes of hypertension • 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 • Phaeochromocytoma • Paroxysms of symptomatic hypertension • The clue to diagnosis is to think of it • Associated with high levels of catecholamines • Hyperaldosteronism • Also known as Conn’s disease

12. Pathophysiology of Pre eclampsia • Placental tissue • In 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

13. Pathophysiology of Pre eclampsia • Hypoperfusion 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

14. Pathophysiology WHY? • An ‘immunolgical’ response to pregnancy ---in ‘at risk’ or predisposed women • A response to a conceptus whose genetic material is 50% foreign (from the father) • A failure of ‘Blocking Antibody’ • This disease is still a mystery

15. Pathophysiology WHAT? • Contracted intravascular volume of mother • In reality a failure to increase plasma volume • ↑Sensitivity to pressure agents • Leaky capillaries • Reduced oncotic pressure • In part due to low serum albumen • Poor placental reserve • A fetus at risk of hypoxia and death

16. Tests for the Hypertensive Gravida • Blood tests • 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 • Urine Tests • 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

17. Management of Hypertensive Gravida • 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

18. Drugs for Hypertension in Pregnancy? Aldomet An old and safe drug Beta Blockers Labetalol widely used in Australia Oxyprenalol also shown in RCT to be useful Ca channel blockers Nifedipine Prazosin Relaxes pressor arterioles

19. Drugs for Hypertension in Pregnancy? Combination therapy of drugs from different classes is possible e.g. Aldomet + Beta blocker + Prazosin Do not use… Thiazide diuretics – reduce plasma volume Highly selective beta blokers – cause IUGR ACE inhibitors – may cause IUFD Aim for BP 130 -150 systolic and 80 – 100 diastolic

20. Drugs for Acute Hypertension in Pregnancy • IV Hydralazine • IV Labetalol • Not available in Australia • Nifedipine tablets crushed and oral • Repeat after 30 min • IV Diazoxide in small boluses

21. Which Drug is Best for Eclampsia? • First aid is more important than drugs • Protect from injury • Secure an airway • Administer oxygen • Then secure IV access • IV MgSO4 loading dose • Maintain by infusion • IV Diazepam only for status eclampticus • Monitor urine output, respirations, O2 saturation and deep tendon jerks

22. Who Requires Delivery? • Pre eclampsia >36 completed weeks • Uncontrollable hypertension • Deteriorating renal, hepatic or haematologic state • Eclampsia or imminently eclamptic • Fetus is compromised • Give steroids to mature the fetal lungs • APH - abruption

23. How to Deliver • Deliver vaginally if >37w and Cx is favourable • or 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 • Don’t overlook patient’s and family’s psychological needs

24. Intrapartum Care • Assess convulsive risk and consider prophylactic MgSO4 • Control BP with an epidural or IV Hydralazine • Careful fluid balance • Monitor the fetus • Avoid ergometrine

25. Postpartum Care • Things may get worse before they get better • Oliguria for 24 hours is common • Seizure risk is greatest for 48 hrs • 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

26. The Prognosis after Pre eclampsia • Mild pre eclampsia near term has a low recurrence risk • Unless there is a new partner or a long gap to the next pregnancy • Severe pre eclampsia prior to 34w has a 50- 66% recurrence risk • Most recover by 12w but these patients are at increased lifetime risk of hypertension and related disease

27. Risk factors for severe pre eclampsia • 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

28. The prevention of pre eclampsiawith low dose Aspirin • History of fetal death or severe IUGR • Patients who required delivery for pre eclampsia prior to 34w • You need to treat 4-5 to prevent one FDIU or severe IUGR • Does not increase the risk of APH or PPH • Conditions with high risk of pre eclampsia eg Lupus or homozygous for thrombophilia • These patients also require heparin • Also give Ca supplements 1.5 G/day

29. For the NICE Guideline go to http://pathways.nice.org.uk/pathways/hypertension-in-pregnancy

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