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59 Cards in this Set
- Front
- Back
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Objectives
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1.Describe the mechanism of action nitric oxide and where it is released.
2.Describe the metabolism of nitroprusside. 3. List the signs of cyanide toxicity. 4. Describe methemoglobinemia and the treatment 5. Describe the treatments of cyanide toxicity. 6. Describe the mechanism of action of nitroglycerin and its cardiovascular effects? 7. Describe the mechanism of action of hydralazine, Minoxidil, and Diaoxide. Give an example of it use. 8. Describe the mechanism of action of trimethaphan and how is it used. 9. Describe the mechanism of action of adenosine. Give an example of its use. 10. Describe controlled hypotension? What procedures benefit from controlled hypotension? 11.Contraindications? Complications? What is a safe level of hypotension? |
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Vasodilators treat ___ ___ and produce controlled ___.
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HTN crisis, hypotension.
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Name another effect of vasodilators.
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Facilitate left ventricular forward stroke volume, esp in pts with regurgitant valvular heart lesions or acute cardiac failure.
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Conceptually, how do vasodilators decrease systemic blood pressure?
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By decreasing SVR (arterial vasodilators) or by decreasing systemic venous return and cardiac output (venous return).
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What is nitric oxide (NO) and where is it released?
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Naturally occurring potent vasodilator released from endothelial cells (endothelium-derived releasing factor).
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Describe the half-life of NO.
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Ultrashort (<5 sec).
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What is inhaled NO and how is it used?
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Selective pulmonary vasodilator used for tx of reversible pulmonary HTN.
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Name three other uses for NO.
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Improve oxygenation in ARDS and one lung ventilation, also has antiinflammatory effects.
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Describe the dosing of Nitroprusside.
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IV, start small at 0.5mcg/kg/min, rarely exceed 3mcg/kg/min.
Bolus dosing may be effective in blunting the hypertensive 1-2mcg/kg |
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Nitroprusside is mixed in ___.
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D5W.
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Administration considerations for nitroprusside?
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Must be stored away from light-active ingredients decompose.
Always give with infusion pump. Nearly always have art line. Avoid administering in same line as sympathomimetics. |
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Nitroprusside may cause what GI effect?
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N/V.
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Describe the metabolism of SNP.
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SNP + OXYHGB = (SNP) + METHEMOGLOBIN 5CN
1. CN- + METHEMOGLOBIN---CYANMETHEMOGLOBIN (Rhondanase, B12) 2. CN- +THIOSULFATE---------THIOCYANATE 3. CN- +CYTOCHROME OXIDASE = CYANIDE TOXICITY |
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Early sign of cyanide toxicity?
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Tachyphylaxis.
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5 other signs of cyanide tox?
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Methhemoglobinemia, increased MVO2 content, tachycardia, increased ICP, met acidosis.
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What infusion doses should be avoided to minimize the risk of cyanide toxicity with SNP?
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Infusions of 8-10mcg/kg/min for greater than 3 hours.
Chronic administration should not be greater than 0.5mcg/kg/min. |
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How is cyanide tox treated?
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1. Discontinuation of infusion.
2. Administer oxygen. 3. Treat acidosis. 4. Sodium thiosulfate-150mg/kg over 15min 5. 3% sodium nitrate, 5mg/kg over 5 min 6. Methoglobinemia can be treated with methlene blue 1-2 mg/kg of 1% solution over 5min. |
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What is important to remember while administering methlene blue?
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Pulse ox will not work while administering.
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What are the indications for nitroglycerin?
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Angina
HTN Myocardial ischemia |
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What is the MOA of nitroglycerin?
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Relaxes vascular smooth muscle with venous pooling.
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Nitroglycerin is metabolized to ___ ___ to increase ___, decrease ___, and cause ___ ___ ___ ___.
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nitric oxide; cGMP; intracellular calcium; vascular smooth muscle relaxation.
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What are the coronary effects of nitroglycerin?
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1. decreases preload
2. decrease left end-diastolic pressure 3. decrease MO2 demand 4. increase endocardial perfusion 5. relieves coronary spasm 6. redistributes coronary BF to ischemic areas |
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Respiratory effects of nitroglycerin?
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Relaxes bronchial smooth muscle.
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GI/GU effects of nitroglycerin?
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Relaxes sphincter of Oddi.
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How is nitroglycerin supplied and how is it administered?
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In a glass bottle with special tubing and diluted to 100mcg/ml.
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Potency compared to nitroprusside?
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Not as potent.
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Nitroglycerin can potentiate the effects of ___.
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Pancuronium.
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Nitroglycerin may cause ___ in awake patients.
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Headache.
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Describe dosing of nitroglycerin.
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*Diluted to 100mcg/ml
*0.5-10mcg/kg/min *SL peak in 4 min *Transdermal sustained release for 24 hours *Can give small bolus if needed until drip is ready (50mcg, if BP is high) |
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Hydralazine MOA?
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Direct relaxation of arterial smooth muscle.
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Hydralazine indication?
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Duh...HTN.
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Hydralazine causes ___ and ___. Use when pt has what condition?
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Decreased BP and tachycardia. Use when pt is bradycardia and hypertensive.
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Effects of hydralazine on the heart?
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Increases MRO2 demand and can cause coronary steal.
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Why may hydralazine cause coronary steal.
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Because it does not dilate epicardial arteries.
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CNS effects of hydralazine?
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Increases ICP.
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Dosing of hydralazine?
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IV 5-20mg up to 15min, lasts 2-4 hours.
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How is hydralazine prepared?
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20mg/1ml
Mix Iml in 3ml of NS for 5mg/ml. |
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Can hydralazine be used in the gravid patient?
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Yes, for pregnancy induced HTN.
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What is Minoxidil (Rogaine, Loniten)?
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Direct acting peripheral vasodilator.
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MOA of minoxidil?
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Blocks the uptake of calcium in the cell membranes and reduces systolic and diastolic BP.
Activates the SNS and renin-angiotensin-aldosterone system. |
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Three results of administration of minoxidil?
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Increased HR, CO, sodium retention.
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Dose of minoxidil?
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Max dose 100mg per day PO.
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MOA of diazoxide (hyperstat, proglycem)?
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Directly relaxes arterial smooth muscle and decreases pancreatic secretion of insulin.
Competes for calcium at receptor sites. |
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Cardiac effects of diazoxide?
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Reflex tachycardia.
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Dosing of diazoxide?
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1-3mg/kg up to 150mg IV.
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Onset, peak and t1/2 of diazoxide?
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30-60 sec.
5min. 21-45 hours. |
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What factors affect the hypotensive effects of diazoxide and how?
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These drugs increase the hypotensive effects of diazoxide: vasoactive drugs, general anesthetics, and acute blood loss.
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What lab should be monitored perioperatively with diazoxide?
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Glucose.
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How does trimethephan work?
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Peripherally vasodilation by direct smooth muscle relaxation and by blockade of acetylcholine receptors in autonomic ganglia.
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What is controlled with trimethephan?
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Autonomic hyperreflexia in patients with upper spinal cord injuries.
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With what NMB does tirmethephan interact and how?
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Can double succinycholine by inhibiting plasma cholinesterase.
Also potentiates ND muscle blockade. |
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What is adenosine?
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Potent vasodilator.
Purine endogenous to all cells of the body. |
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MOA of adenosine?
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Acts on receptors located in several vascular beds and on AV node.
Opens K channels, hyperpolarizing nodal tissues and making it less likely to fire. Leads to AV block and slows sinus rate. |
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Indications of adenosine?
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Potent vasodilator that can be used for reduction of BP under anesthesia.
Only approved by FDA for SVT. |
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Dosing of adenosine?
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60-120mcg/kg/min for controlled HTN.
6mg over 1-2sec, then 12mg 1-2sec. May repeat once. |
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Adenosine affects afterload or preload?
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Afterload.
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How is adenosine metabolized?
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Erythrocytes and vascular endothelial cells metabolize it to inosine and adenosine monophosphate.
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What is a possible negative cardiac effect of adenosine?
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Coronary vasodilation can lead to coronary steal in pt's with CAD, myocardial ischemia.
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What types of drugs competitively antagonize adenosine?
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Methylxanthines (aminophylline).
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