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Hydralazine (Brand Name: Apresoline®)
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Description and indication
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- Hydralazine is a vasodilator that causes relaxation of arteriolar smooth muscle, which results in a lowering of blood pressure.
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- Hydralazine is used for the treatment of hypertensive states - especially hypertension associated with pregnancy (pre-eclampsia or eclampsia).
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Presentation
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Apresoline® ampoules: 20mg dry powder for reconstitution (white crystalline powder)
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Route of Administration
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- IV injection: Administered by slow intravenous injection over 30 seconds (in order to avoid precipitous decreases in mean arterial pressure with a critical reduction in cerebral or uteroplacental perfusion).
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- IV infusion: May also be given by continuous infusion. Dilute with sodium chloride 0.9%.
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Reconstitution
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IV injection
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- 20mg ampoule powder: Add 1mL of sterile water for injection to the ampoule and mix until dissolved (= 20mg/mL)
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IV infusion
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- Need 3 ampoules of hydralazine 20mg powder.
- Reconstitute each 20mg ampoule powder with 1mL of sterile water for injection until dissolved.
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- Using 60mL syringe: draw up 3mL of reconstituted hydralazine solution (3 ampoules = 60mg)
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- Further dilute this 3mL solution with sodium chloride 0.9% to make 60mL volume (= 60mg/60mL)
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This solution gives a final concentration of 1mg/1mL (= 60mg/60mL)
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Dose
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Slow IV injection:
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- The initial dose is 5 to 10 mg. If it is necessary to repeat the injection, this should be done after an interval of 20 to 30 minutes.
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Continuous IV infusion:
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Prior to commencement the medical staff should explain to the patient the reason for medication, the continuous observation required and potential side effects (common - headache & flushing).
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Loading dose:
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- Administer hydralazine at 1mg/min (i.e. 1mL/min of the prepared solution) to obtain a diastolic BP of 90 -100mmHg.
- Once BP has reached this level then commence maintenance regimen.
- There is rarely a need to lower the BP further than this, and doing so may compromise the placental blood flow and fetus.
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- Record blood pressure readings every minute on MR/40366 chart during administration.
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Maintenance regimen:
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- Continue infusing hydralazine at 1 - 10mg/hr to maintain a diastolic BP of 90 - 100mmHg.
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- Continue observation of BP every 15minutes until stable.
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- Maintain observation of BP every 30minutes during critical phase.
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Nursing / Midwifery responsibilities
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Record on MR/43066: Frequent Observation and Fluid Balance Chart
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Incompatabilities
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Glucose 5%, aminophylline, ampicillin, diazoxide, frusemide, glyceryl trinitrate, methohexitone, phenobarbitone.
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Side effects
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Common at the start of treatment (especially if the dose is raised rapidly):
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- Tachycardia, palpitation, anginal symptoms, flushing, headache, dizziness, nasal congestion and gastrointestinal disturbances. Such reactions generally subside with further course of treatment.
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Contraindications
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- Hypersensitivity to hydralazine
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- See full product information for extensive list
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Monitoring
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- Blood pressure and heart rate should be monitored.
- Severe hypotension may respond to placing the patient in the supine position with the feet raised.
- The viable fetus MUST be continuously monitored with CTG before, during and after administration of hydralazine.
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Links
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References
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- References (link to separate web page)
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Revised and published: 10 January 2008
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Royal Women's Hospital Clinical Practice Guidelines (CPGs) are intended to provide guidance to health care professionals, based on a thorough evaluation of research evidence, on the practical assessment and management of specific clinical issues or situations. The guidelines allow some flexibility on the part of the health care professional based on the needs of the specific patient for whom they are caring.
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