Vasodilators Flashcards
Sodium Nitroprusside (Nipride)
MOA
&
Receptors
Nitric Oxide Donors
Exogenous NO donor:
NO stimulates conversion of
GMP to cGMP by guanylate cyclase;
↑ cGMP levels cause ↓ intracellular Ca++,
causing vascular smooth muscle relaxation
Arterial & venous dilator
Sodium Nitroprusside (Nipride)
Indications
&
Effects
Nitric Oxide Donors
HTN: Controlled ↓BP is needed
Pulmonary venous congestion: ↓ PVR
Pheochromocytoma, Spinal Surgeries, HTN Emergencies & Carotid Surgeries
Arterial vasodilators counteract effects of vasoconstriction; ↓ SVR
Venous vasodilators alleviate pulmonary/systemic congestion;
↓ venous return
Sodium Nitroprusside (Nipride)
Dosing
Nitric Oxide Donors
Infusion:
0.3-2 mcg/kg/min
Sodium Nitroprusside (Nipride)
Onset
Duration
Nitric Oxide Donors
Onset
Immediate
Duration
Transient
Sodium Nitroprusside (Nipride)
Side Effects
&
Considerations
Nitric Oxide Donors
↓BP: Potent vasodilator
can significantly drop BP
Dissociates immediately into CN & NO to produce methemoglobin &
CYANIDE poisoning
Methemoglobinemia Tx:
Methylene Blue;
IV: 1-2 mg/kg over 5 min
MAX: 7-8 mg/kg
Maintenance of hemodynamics
during surgical cases
Requires continuous administration
Requires arterial line monitoring
Nitroglycerin (Nitrostat)
MOA
&
Receptors
Nitric Oxide Donors
Exogenous NO donor:
NO stimulates conversion of
GMP to cGMP by guanylate cyclase;
↑ cGMP levels cause ↓ intracellular Ca++, causing vascular smooth muscle relaxation
Primarily venous dilator;
Dilates the large coronary arteries
Nitroglycerin (Nitrostat)
Indications
&
Effects
Nitric Oxide Donors
Acute MI;
HTN & Pulmonary venous congestion;
Relaxes Sphincter of Oddi Spasm;
Relaxes uterus to release retained placenta post-delivery
Venous vasodilators; ↓ venous return
High doses can cause arterial vasodilation; ↓ SVR
Nitroglycerin (Nitrostat)
Dosing
Nitric Oxide Donors
Infusion
Initial dose: 5-10 mcg/min
Titrate to desired MAP/SBP
Nitroglycerin (Nitrostat)
Onset
Duration
1/2 Time
Nitric Oxide Donors
Onset
Rapid
Duration
3-5 min
1/2 Time
1-4 min
Nitroglycerin (Nitrostat)
Side Effects
&
Considerations
Nitric Oxide Donors
↓BP: Potent venodilator
HA related to profound venodilation
Tachyphylaxis: w/in 24 hrs;
12-15 hrs drug-free interval may be needed to reverse tolerance
Maintenance of hemodynamics
during surgical cases
Requires continuous administration
Requires arterial line monitoring
Hydralazine (Apresoline)
MOA
&
Receptors
Direct Vasodilator
Direct-acting smooth muscle relaxant
& acts as a vasodilator primarily
in resistance arterioles
Inhibition of inositol trisphosphate (IP3) induced Ca++ release from the sarcoplasmic reticulum in arterial smooth muscle cells
Selective for resistance arterioles
Hydralazine (Apresoline)
Indications
&
Effects
Direct Vasodilator
HTN
Arterial vasodilation; ↓ SVR
Hydralazine (Apresoline)
Dosing
Direct Vasodilator
IV: 2.5 mg
Hydralazine (Apresoline)
Onset
Duration
1/2 Time
Direct Vasodilator
Onset
Slow; peaks 1 hr
Duration
~12 hrs
1/2 Time
3-7 hrs
Hydralazine (Apresoline)
Side Effects
&
Considerations
Direct Vasodilator
Extreme/profound ↓BP; rebound ↑HR
Caution: use w/ elderly pts
Maintenance of hemodynamics
during surgical cases
Nicardipine (Cardene)
MOA
&
Receptors
Calcium Channel Blocker
Dihydropyridine
Binds to receptors on voltage-gated
(L-type) Ca++ channels
↓ Ca++ influx inhibits
excitation-contraction coupling
** Selective for arteriolar beds**
Nicardipine (Cardene)
Indications
&
Effects
Calcium Channel Blocker
Short term control of HTN
Arterial vasodilation;
↓ SVR & ↓ BP
No significant change in HR d/t
no effect on SA/AV node
Slight myocardial depression
Greatest coronary artery dilation
Moderate peripheral artery dilation
Nicardipine (Cardene)
Dosing
Calcium Channel Blocker
Infusion
Initial: 5 mg/hr
Titrated: 2.5 mg/hr
Q5 min to MAX 15 mg/hr
Nicardipine (Cardene)
Onset
Duration
1/2 Life
Calcium Channel Blocker
Onset
IV: 1-3 min
Duration
IV: ≤8 hrs
1/2 Life
3-5 hrs
Nicardipine (Cardene)
Side Effects
&
Considerations
Calcium Channel Blocker
Dose-dependentt ↓BP;
requires continuous
hemodynamic monitoring
Maintenance of hemodynamics
during surgical cases
Verapamil (Calan)
MOA
&
Receptors
Calcium Channel Blocker
Phenylalkylamines
Cardiac selective inhibition of voltage-gated Ca++ channels is frequency-dependent;
↓ Ca++ influx inhibits
excitation-contraction coupling
Selective for AV node
Verapamil (Calan)
Indications
&
Effects
Calcium Channel Blocker
Tachycardia; HTN
Marked delay conduction thru the AV node
& moderate SA node depression
Moderate myocardial depression
Moderate coronary artery dilation
Moderate peripheral artery dilation
Verapamil (Calan)
Dosing
Calcium Channel Blocker
IV: 5-10 mg over 2 min
Can give 2nd dose after 15 min
Verapamil (Calan)
Onset
Duration
1/2 Life
Calcium Channel Blocker
Onset
1-3 min
Duration
0.5-6 hrs
1/2 Life
3-7 hrs
