SODIUM NITROPRUSSIDE

• Accelerated hypertension
• Sodium nitroprusside is a very potent agent
• use only on the advice of a renal SpR/consultant
• use only on wards (e.g. critical care unit/CCU) where continuous monitoring of BP (preferably via arterial line) is possible

• Sodium nitroprusside 50 mg ampoules/vials for reconstitution

• Glucose 5%

• Administer sodium nitroprusside either in a 50 mL syringe via a syringe pump, or in 250 mL or 500 mL bags using a controlled infusion device for precise control of flow rate
• choice of bag size or use of syringe pump depend on dosage, patient weight and fluid status and availability of equipment
• Take care to avoid extravasation. Check infusion site regularly

How to start and adjust doses

• Initially 0.3 microgram/kg/min by IV infusion
• increase to 0.5 microgram/kg/min
• then in increments of 0.5 microgram/kg/min according to response allowing 5–10 min between each increment
• Maximum dose = 8 microgram/kg/min

Infusion via syringe pump

• Reconstitute sodium nitroprusside with 2 mL of glucose 5%
• Withdraw resulting solution and make up to 50 mL with glucose 5% (50 mg in 50 mL = 1 mg/mL)
• mix thoroughly
• Infusion solution has a faint orange-brownish tint. If it is highly coloured do not use
• Sodium nitroprusside must be protected from light
• immediately wrap syringe and tubing with foil provided
• infusion solution is then stable for up to 24 hr from time of preparation

Infusion in a bag via a controlled-infusion device

• Infusion solution has a faint orange-brownish tint. If it is highly coloured, do not use
• Sodium nitroprusside must be protected from light
• immediately wrap infusion bag and all parts of administration set with foil provided
• infusion solution is then stable for up to 24 hr from time of preparation

• Aim to reduce diastolic BP to 110–115 mmHg over several hours
• Patients already taking antihypertensive drugs and the elderly will be more sensitive to sodium nitroprusside
• If BP not adequately reduced within 10 min at maximum dosage, discontinue infusion – see Accelerated (malignant) hypertension guideline for alternative

Monitoring

• Monitor BP and symptoms carefully
• Over-rapid reduction in BP may produce the following symptoms:
• headache, dizziness, perspiration
• nausea, retching, abdominal pain
• palpitations, apprehension, retrosternal discomfort
• If these occur, reduce infusion rate in decrements of 0.5 microgram/kg/min

Length of treatment

• Sodium nitroprusside is metabolised to free cyanide, converted in the liver to thiocyanate
• if response obtained, continue therapy only for a few hours to avoid risk of toxicity
• If therapy required for >24 hr, consult manufacturer's literature on monitoring and management of potential toxicity
• signs of toxicity include tachycardia, sweating, hyperventilation, arrhythmias, marked metabolic acidosis

Withdrawal

• Start oral antihypertensive therapy while BP is being controlled by sodium nitroprusside
• When finally withdrawing sodium nitroprusside, to prevent rebound increase in BP, reduce infusion rate gradually
• reduce by 25–30% every 5 min, rechecking BP before each decrement