Tuesday, January 12, 2016

Management of Hypertension in Pregnancy

  • Hypertension in pregnancy defined as a systolic blood pressure (BP) ≥140 mmHg and/or a diastolic BP ≥ 90 mmHg. 
  • An increase of 15 mmHg and 30 mmHg diastolic and systolic BP levels above baseline BP respectively is no longer recognised as hypertension if absolute values are below 140/90 mmHg. 
  • But close observation is warranted, especially if proteinuria and hyperuricaemia are also present

PRECONCEPTION
  • Atenolol has been shown to lead to fetal growth restriction. The use of ARBs, ACEIs and thiazide diuretics are associated with fetal anomaly and are therefore contraindicated in pregnancy.
  • The drugs of choice in pregnancy are still methyldopa and labetalol.
  • Labetalol safety : not know to be harmful except possibly in the first trimester, and breastfeeding infants should be monitored as there is a risk of possible toxicity due to alpha and beta-blockade
  • Pregnant women with uncomplicated chronic hypertension, target BP is lower than 150/100 mmHg. In the presence of target organ damage secondary to chronic hypertension, the aim is to maintain the BP below 140/90 mmHg.

WOMAN AT RISK OF PRE-ECLAMPSIA
  • High risk patients should be prescribed aspirin (75mg–100mg daily) from 12 weeks gestation until delivery
  • Moderate risk patients, aspirin prophylaxis must be commenced before 16 weeks gestation for optimal effectiveness
  • Low dietary calcium intake (less than 600 mg day), high calcium supplementation of 1.5g/day significantly reduces the risk of eclampsia, severe gestational hypertension, and severe preeclamptic complication index
  • Combined vitamins C and E (i.e. tocopherol from soybean) should be avoided because they significantly increase the incidence of low birth weight without any preventive effect against preeclampsia.

SEVERE PRE-ECLAMPSIA
  • Anti-hypertensive treatment should be initiated if diastolic BP is persistently ≥100 mmHg. The target BP to achieve is DBP between 80-100 mmHg.
  • Diuretics are generally contraindicated as they reduce plasma volume, may cause intrauterine growth restriction (IUGR) and may possibly increase perinatal mortality
  • In the event of an acute hypertensive crisis IV hydrallazine (2.5-5 mg bolus or infusion)orIV labetalol (10-20 mg slow bolus over 5 minutes or infusion), or Oral nifedipine (10mg stat dose). Sublingual nifedipine is no longer recommended.
  • High calcium supplementation of 1.5 g/day significantly reduces the risk of eclampsia, severe gestational hypertension and severe preeclamptic complication index in pregnant women with low dietary calcium intake.
  • Pregnant women who are at high risk of developing preeclampsia should be referred to an obstetrician. Specialist management will include Doppler ultrasonography and aspirin pharmacoprophylaxis.

ECLAMPTIC FIT
  • Prevention of eclampsia and to abort an eclamptic fit - Parenteral magnesium sulphate. It provides fetal neuroprotection following preterm birth with a significant reduction in the incidence of cerebral palsy
  • Alternative : IV diazepam, but it is inferior in efficacy compared to magnesium sulphate

POSTPARTUM CARE
  • Antihypertensives should be tapered down and not stopped suddenly
  • Preeclampsia Patient – usually need approximately 2 weeks of antihypertensives after postpartum
  • Gestational Hypertension Patient – usually need approximately 1 week of antihypertensives


REFERENCES
1.       Malaysia Clinical Practice Guidelines 2013- Management of Hypertension, 4TH edition. 2013
2.       Hypertension in pregnancy: Evidence Update May 2012 http://www.nice.org.uk/guidance/cg107/evidence/evidence-updates-134790445

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