Thursday, October 29, 2015

Hypertension in pregnancy

Hypertension in pregnancy 
 NICE published guidance in 2010 on the management of hypertension in pregnancy.
 They also made recommendations on reducing the risk of hypertensive disorders developing in the first place.
 Women who are at high risk of developing pre-eclampsia should take aspirin 75mg od from 12 weeks until the birth of the baby. High risk groups include:

 hypertensive disease during previous pregnancies
 chronic kidney disease
 autoimmune disorders such as SLE or antiphospholipid syndrome
 type 1 or 2 diabetes mellitus
 The classification of hypertension in pregnancy is complicated and varies.
 Remember, in normal pregnancy:
 blood pressure usually falls in the first trimester (particularly the diastolic), and continues to fall until 20-24 weeks
 after this time the blood pressure usually increases to pre-pregnancy levels by term
 Hypertension in pregnancy in usually defined as:
 systolic > 140 mmHg or diastolic > 90 mmHg
 or an increase above booking readings of > 30 mmHg systolic or > 15 mmHg diastolic
After establishing that the patient is hypertensive they should be categorized into one of the following groups: 

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A=Pre-existing hypertension :

A history of hypertension before pregnancy or an elevated blood pressure > 140/90 mmHg before 20 weeks gestation No proteinuria, no oedema Occurs in 3-5% of pregnancies and is more common in older women
B=Pregnancy-induced HTN (PIH, also known as gestational HTN):
Hypertension (as defined above) occurring in the second half of pregnancy (i.e. after 20 weeks) No proteinuria, no oedema Occurs in around 5-7% of pregnancies Resolves following birth (typically after one month). Women with PIH are at increased risk of future pre-eclampsia or hypertension later in life
Pregnancy-induced hypertension in association with proteinuria (> 0.3g / 24 hours) Oedema may occur but is now less commonly used as a criteria Occurs in around 5% of pregnancies
- Pre-eclampsia is a condition seen after 20 weeks gestation characterised by:
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  Pregnancy-induced hypertension in association with
  Proteinuria (> 0.3g / 24 hours).
  Oedema used to be third element of the classic triad but is now often not included in the definition as it is not specific 
 Pre-eclampsia is important as it predisposes to the following problems:
  fetal: prematurity, intrauterine growth retardation
  eclampsia
  haemorrhage: placental abruption, intra-abdominal, intra-cerebral 
 cardiac failure
  multi-organ failure
Risk factors: 

  > 40 years old
  nulliparity (or new partner)
  multiple pregnancy
  body mass index > 30 kg/m^2
  diabetes mellitus 
 pregnancy interval of more than 10 years
  family history of pre-eclampsia
  previous history of pre-eclampsia
  pre-existing vascular disease such as hypertension or renal disease
 Features of severe pre-eclampsia: 
 hypertension: typically > 170/110 mmHg and proteinuria as above
  proteinuria: dipstick ++/+++
  headache
  visual disturbance
  papilloedema
  RUQ/epigastric pain
  hyperreflexia 
 platelet count < 100 * 106/l, abnormal liver enzymes or HELLP syndrome Management:
  consensus guidelines recommend treating blood pressure > 160/110 mmHg although many clinicians have a lower threshold
  Oral labetalol is now first-line following the 2010 NICE guidelines.
  Nifedipine and hydralazine may also be used
  Delivery of the baby is the most important and definitive management step. The timing depends on the individual clinical scenario
 Eclampsia may be defined as the development of seizures in association pre-eclampsia.
 To recap, pre-eclampsia is defined as:
1) condition seen after 20 weeks gestation
2) pregnancy-induced hypertension
3) proteinuria

Magnesium sulphate is used to both prevent seizures in patients with severe pre-eclampsia and treat seizures once they develop. Guidelines on its use suggest the following:
1) should be given once a decision to deliver has been made
2) in eclampsia an IV bolus of 4g over 5-10 minutes should be given followed by an infusion of 1g / hour
3) urine output, reflexes, respiratory rate and oxygen saturations should be monitored during treatment
4) treatment should continue for 24 hours after last seizure or delivery (around 40% of seizures occur post-partum)
Other important aspects of treating severe pre-eclampsia/eclampsia include fluid restriction to avoid the potentially serious consequences of fluid overload
Centrally acting antihypertensives
Examples of centrally acting antihypertensives include:
 methyldopa: used in the management of hypertension during pregnancy
 moxonidine: used in the management of essential hypertension when conventional antihypertensives have failed to control blood pressure
 clonidine: the antihypertensive effect is mediated through stimulating alpha-2 adrenoceptors in the vasomotor centre


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