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145 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What types of drugs are used to treat HTN?
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1. sympatholytics
2. ACE inhibitors 3. angiotensin receptor blockers 4. calcium channel blockers 5. vasodilators 6. diuretics |
vd casa
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What are some anesthesia concerns with antihypertensive drugs?
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1. attentuation of SNS activity
2. modification of response of sympathomimetic drugs 3. sedation |
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How is attenuation of SNS activity reflected?
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orthostatic hypotension and exaggerated SBP decreases during anesthesia
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Exaggerated SBP decreases during anesthesia are in response to what?
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1. acute blood loss
2. body position changes 3. decreased venous return d/t positive pressure ventilation |
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What population are beta blockers good for?
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1. young/middle age pts
2. pts w hx of CAD |
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How are beta blockers classified?
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1. whether they exhibit selective or nonselective properties
2. whether they possess intrinsic sympathomimetic activity |
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What is the mechanism of action of beta blockers with selective properties?
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They bind primarily to beta1 (cardiac) receptors.
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What is the mechanism of action of nonselective beta blockers?
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They have equal affinity for beta1 and beta2 receptors.
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How do beta blockers with intrinsic sympathomimetic activity activity work?
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1. Tend to produce less bradycardia
2. Less likely to produce vasospasm |
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How do NSAIDS affect the antihypertensive effects of beta blockers?
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The effect may be lessened.
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What patients are beta1 blockers preferred for?
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1. pulmonary disease
2. insulin-dependent diabetes 3. symptomatic peripheral vascular disease |
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Why are beta1 blocker preferred in pts with pulmonary disease, IDDM, and PVD?
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They are unlikely to produce bronchospasm, decrease peripheral blood flow, or mask hypoglycemia.
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What is a black box warning for beta blockers?
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NSAIDS may increase blood pressure.
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What are the side effects of beta blockers?
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1. bradycardia
2. CHF 3. bronchospasm 4. claudication 5. masking of hypoglycemia 6. sedation 7. impotence 8. angina pectoris from sudden discontinuation |
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Who should not be given beta blockers?
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asthmatic pts
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What type of blocker is Labetalol?
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nonselective B and A1 blocker
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How does Labetalol treat HTN?
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via direct vasodilation effect
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What are some side effects of labetalol?
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1. scalp tingling
2. urinary retention |
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What type of blocker is prazosin?
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selective post-synaptic A1 blocker
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How does prazosin treat HTN?
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vasodilation of arterial and venous vasculature
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How is prazosin most effective in treating HTN?
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when given in combination with a diuretic
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What are some other benefits of prasozin?
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1. decreased afterload in pts with CHF
2. pre-op prep in pts with pheochromocytoma 3. relief of vasospasm in Raynauds pts 4. decreases size of prostate gland in pts with BPH |
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What are the cardiovascular effects of prazosin?
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1. decreases SVR
2. decreases venous return 3. decreases cardiac output |
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What are some side effects of prazosin?
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1. vertigo
2. fluid retention 3. orthostatic hypotension |
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What population is prazosin good for?
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Young pts with moderately severe HTN
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What should you do with exaggerated hypotension during epidural anesthesia after the administration of prazosin?
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Give epi.
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How is prazosin metabolized?
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Via extensive first pass hepatic metabolism.
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What may happen if prazosin is given in combo with a beta blocker during anesthesia?
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Refractory hypotension.
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What are some effects of prazosin treatment?
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1. May increase plasma aminotransferase
2. May give a false positive for phochromocytoma |
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What type of sympatholytic is clonidine?
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Centrally acting selective partial A2 agonist
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Does clonidine cross the blood brain barrier?
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Yes.
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How does clonidine effect HTN?
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It decreases SNS from the CNS.
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What are the major uses of clonidine?
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1. Treatment of severe HTN
2. Treatment of renin-dependent disease |
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What are some other clinical uses of clonidine?
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1. Sedation
2. Decreases anesthetic requirements 3. Improves periop hemodynamics 4. Analgesia 5. Preanesthetic med 6. Prolongation of regional anesthesia 7. Protection against periop MI 8. Dx of pheochromoctyoma 9. Tx of opioid and alcohol withdrawal 10. Tx of shivering |
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Does the use of clonidine for sedation affect ventilation?
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No
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How does clonidine produce analgesia?
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It activates postsynaptic A2 receptors in the substantia gelatinosa of the spinal cord.
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What are the side effects of clonidine when used for epidurals or spinals?
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1. Hypotension
2. Sedation 3. Dry mouth |
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Why is clonidine used as a preanesthetic?
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1. Blunts reflex tachycardia during intubation
2. Decreases HR and BP during surgery 3. Decreases catecholamine levels 4. Decreases anesthetic requirements for MAC and injected drugs |
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How does clonidine interact with ephedrine?
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It augments the pressor response - decrease the dose by 1/2.
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How does clonidine prolong the effects of regional anesthesia?
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It prolongs the duration of sensory and motor block produced by the local anesthetics.
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How does clonidine affect the fetus when used in OB regional anesthesia?
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It causes fetal bradycardia.
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What effect does oral clonidine have when given before a spinal?
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It prolongs the sensory block.
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When is clonidine given to protect against perioperative MI? What dose is given?
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The night before or the same morning as the surgery and then for four days following the surgery. 0.2mg PO.
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How is clonidine used to diagnose pheochromoctyoma?
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Catecholamine levels will not go down in pts who have pheochromocytoma.
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How does clonidine treat withdrawal from opioids?
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It decreases SNS activity and catecholamine levels when naloxone is given to opioid addicts.
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How is clonidine used for alcoholics?
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It is given preop to prevent postop withdrawal syndrome.
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How does clonidine treat shivering?
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It inhibits central thermoregulatory control and decreases vasocontriction.
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What is the first treatment for shivering and why?
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Oxygen because of increased O2 requirements.
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What do alpha2A receptors mediate?
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1. Sedation
2. Analgesia 3. Sympatholysis |
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What do alpha2B receptors mediate?
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1. Vasoconstriction
2. Shivering |
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What do alpha2C receptors mediate?
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The startle response.
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Where does clonidine exhibit its sedative effect.
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By attaching to and blocking alpha2 receptors at the pontine locus ceruleus, which innervates the SNS at forebrain.
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How does clonidine work at the medullary vasomotor center?
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It stimulates alpha2-adrenergic inhibitory neurons and there is a decreases in SNS outflow from the CNS.
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How is decreased SNS activity manifested?
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1. Peripheral vasodilation
2. Decrease in SBP 3. Decrease in heart rate 4. Decrease in cardiac output |
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How does clonidine's ability to modify the function of potassium channels in the CNS affect the pt?
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There is a profound decrease in the amount of anesthesia needed due to hyperpolarized membranes.
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What are the effects of alpha2 receptors on blood vessels?
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They mediate vasocontriction.
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What are the effects of alpha2 receptors on peripheral SNS endings?
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They inhibit the release of norepi.
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What is the effect of neuroaxial placement of clonidine?
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It inhibits spinal substance P release and nociceptive neuron firing produced by noxious stimulation.
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How is sedation produced by drugs that act on alpha2 receptors?
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By decreasing SNS activity and the level of arousal.
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How do pts who have been treated with dexmedetomidine appear?
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Calm and easily aroused to full consciousness.
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How long does it take for clonidine to reach peak plasma concentrations?
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60-90 minutes.
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What is the elimination half-time of clonidine?
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9-12 hours.
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How is clonidine metabolized and eliminated?
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About 50% is metabolized by the liver and the rest is excreted unchanged in urine.
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What are the cardiovascular effects of clonidine?
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There is a decrease in SBP but compensatory homeostatic reflexes remain intact.
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What are the most common side effects of clonidine?
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1. Sedation
2. Xerostomia |
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How does clonidine affect MAC requirements?
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MAC requirements are decreased by nearly 50%.
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What can happen with abrupt discontinuation of clonidine?
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Rebound HTN.
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When does rebound HTN occur in relation to clonidine?
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8-36 hours after the last dose.
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What causes rebound HTN from clonidine?
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It's due to increased plasma concentrations of catecholamines and intense peripheral vasocontriction.
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What drugs may exaggerate the effects of rebound HTN caused by clonidine?
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1. Beta blockers
2. Tricyclic antidepressants |
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What can be used to treat rebound HTN caused by clonidine?
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1. Reinstitution of clonidine
2. Hydralazine 3. Nitroprusside 4. Labetalol |
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What are the side effects of clonidine on muscles?
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It produces skeletal muscle flaccidity with opioids but not NMBAs.
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What respiratory effects could occur if clonidine and fentanyl are given together?
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Increased ventilatory depression.
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Is dexmedetomidine more selective than clonidine?
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Yes, 7-10 times more selective at A2 receptors.
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What is the A2 antagonist used for the reversal of dexmedetomidine?
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Atipamezole.
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What is the elimination half-time of dexmedetomidine?
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2-3 hours.
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How does dexmedetomidine interact with opioids?
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It inhibits CYP450, thereby increasing the effects of opioids.
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How does dexmedetomidine affect MAC requirements?
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It decreases MAC requirements by >90%.
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Does dexmedetomidine affect ventilation?
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Yes, there is a mild depression of ventilation.
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How is dexmedetomidine metabolized?
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It is >90% protein bound and undergoes extensive hepatic metabolism.
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What are the clinical uses of dexmedetomidine?
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1. Pretreatment for surgery
2. Decreases MAC requirements 3. Analgesia 4. Sedation 5. Preservation of breathing 6. Decreases cardiac and delirium effects of ketamine 7. Treatment for shivering |
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How can the preservation of breathing caused by dexmedetomidine be beneficial?
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In pts with difficult airways.
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What are some side effects of dexmedetomidine?
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1. Severe bradycardia
2. Cardiac arrest when used with anesthesia |
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How is dexmedetomidine useful in the sedation of postop ICU pts?
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It can prevent withdrawal from benzos.
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Can dexmedetomidine be used for total IV anesthesia?
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Yes at doses of 5-10mcg/kg/hr IV.
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What type of HTN are ACE inhibitors more effective in treating?
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Systemic HTN secondary to increased renin production.
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ACE inhibitors are used as first-line therapy in what diagnosis?
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1. Systemic HTN
2. CHF 3. Mitral regurgitation |
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What is the mechanism of action of ACE inhibitors?
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The block the conversion of angiotensin I to angiotensin II. They also block the breakdown of bradykinin.
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What does angiotensin II do?
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It is a potent vasoconstrictor that is responsible for:
1. arterial smooth muscle constriction 2. increased aldosterone secretion 3. SNS stimulation |
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What are the effects of decreased aldosterone?
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Reduced sodium and water retention.
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What are the effects of blocking the breakdown of bradykinin?
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Bradykinin is an endogenous vasodilator substance, so if it is not broken down, it will maintain its vasodilatory effect.
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What are side effects of ACE inhibitors?
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1. Cough
2. Upper respiratory congestion 3. Rhinorrhea 4. Allergic symptoms 5. Decreased GFR 6. Hyperkalemia |
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When should ACE inhibitors be discontinued in relation to surgery?
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12-24 hours beforehand.
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What should be administered if respiratory distress occurs because of ACE inhibitors?
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Epi.
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What consideration should be made due to decreases in GFR from ACE inhibitors?
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They should be used with caution in pts with preexisiting renal dysfunction and are not recommended for pts with renal artery stenosis.
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What causes hyperkalemia induced by ACE inhibitors?
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Decreased production of aldosterone.
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How should you treat exaggerated hypotension caused by ACE inhibitors?
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1. Crystalloid fluid infusion
2. Sympathomimetics |
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What should you do if you have refractive hypotension caused by ACE inhibitors that has not responded to ephedrine?
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Administer terlipressin.
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Why is there a concern for administering ACE inhibitors to pts with diabetes?
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1. Increased insulin sensitivity
2. Hypoglycemia |
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How does Captopril work?
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By competitive inhibition of angiotensin I-converting enzyme.
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How does captopril affect potassium levels?
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There is slight hyperkalemia due to a decrease in aldosterone levels.
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What are the pharmacokinetics of captopril?
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1. 25-35% bound to protein
2. Urinary excretion of 50% |
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What are some cardiovascular effects of captopril?
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1. Decreased SVR
2. Sodium and water retention 3. Absence of compensatory reflex-mediated increase in HR |
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What are some general side effects of captopril?
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1. Rash or pruritis in 10%
2. Alteration or loss of taste in 2-4% |
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How is enalapril metabolized?
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It is a prodrug that is metabolized in the liver to its active form, enalaprilat.
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How do angiotensin II receptor inhibitors produce antihypertensive effects?
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By blocking the vasoconstrictive actions of angiotensin II without affecting ACE activity.
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Where does losartan work?
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It acts as an antagonist at angiotensin II receptors.
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How is losartan metabolized?
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Substantial first-pass hepatic metabolism through CP450.
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How does losartan produce its antihypertensive effects?
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Losartan and its active carboxylic acid metabolite block the vasoconstrictor and aldosterone-secretion effects of angiotensin II by selectively inhibiting the binding of angiotensin II to the AT1 receptors of vascular smooth muscles.
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What is a potential side effect of losartan?
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Hyperkalemia.
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What pts should not receive losartan?
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Pts with renal artery stenosis.
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How does losartan interact with lithium?
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It increases lithium absorption and may cause toxicity.
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What could happen if losartan is given during pregnancy?
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Fetal and neonatal morbitity as well as death due to its action on the renin-angiotensin system.
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When should losartan be discontinued for surgery?
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The day before.
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What is the most common side effect of calcium channel blockers?
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Decreased blood pressure.
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How are calcium channel blockers used for the treatment of HTN?
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As vasodilators in the treatment of essential HTN.
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What populations are particularly responsive to calcium channel blockers?
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1. Elderly
2. African Americans 3. Salt-sensitive pts |
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What drugs, if given in combination with calcium channel blockers, could increase the risk of MI?
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1. Nifedipine
2. Verapamil 3. Diltiazem |
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What make calcium channel blockers unique as a HTN drug?
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It does not require sodium restriction.
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Where do calcium channel blockers work?
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On smooth muscle cells.
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How do calcium channel blockers depend on calcium influx?
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It affects the normal resting tone and contractile response of smooth muscle.
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What other blockade do the effects of calcium channel blockers resemble? How so?
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Sodium channel blockade by local anesthetics; the drug acts from the inner side of the membrane.
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How do calcium channel blockers affect transmembrane calcium currents?
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It decreases them, resulting in long lasting relaxation.
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What is used to reverse calcium channel blockers?
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Elevation of plasma calcium concentrations.
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What circulations see more pronounced vasodilatory effects from hydralazine?
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1. Splanchnic
2. Coronary 3. Renal 4. Cerebral |
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What dosage of hydralazine is used for hypertensive crisis?
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2.5-10 mg IV.
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How long does it take for the effects of hydralazine to occur? How long does it last?
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Begins in 10-20 minutes and lasts 3-6 hours.
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How is hydralazine metabolized?
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Acetylation.
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What are the cardiovascular effects of hydralazine?
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1. Decreased diastolic pressure
2. Decreased SVR 3. Increased HR 4. Increased stroke volume 5. Increased cardiac output |
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What are some general side effects of hydralazine?
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1. Sodium and water retention
2. Vertigo 3. Diaphoresis 4. Nausea and vomiting |
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What syndrome can occur in 10-20% of pts treated with hydralazine?
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A systemic lupus erythematosus-like syndrome. It disappears when hydralazine is discontinued.
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What are the calcium channel blockers used for HTN?
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1. Amlodipine
2. Diltiazepam 3. Nifedipine 4. Verapamil |
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What is the oral dose for amlodipine?
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2.5, 5, and 10 mg
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What are the oral and parenteral doses for diltiazepam?
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Oral: 30, 60, and 90 mg
Parenteral: 5mg/ml |
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What is the oral dose of nifedipine?
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10, 20 mg
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What are the oral and parenteral doses of verapamil?
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Oral: 40, 80 mg
Parenteral: 2.5mg/ml |
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How does monoxidil affect HTN?
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It decreases SBP by direct relaxation of arteriolar smooth muscle.
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How is monoxidil absorbed after an oral dose?
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90% is absorbed from the GI tract.
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What are cardiovascular side effects of monoxidil?
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1. Increased HR
2. Increased cardiac output |
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What are some general side effects of monoxidil?
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1. Increased concentration of norepi and renin
2. Sodium and water retention |
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What is one potentially serious side effect of minoxidil therapy?
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Pericardial effusion and cardiac tamponade from accumulation of fluid in a serous cavity.
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What are some abnormalities seen on ECG with minoxidil therapy?
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1. Flat or inverted T-wave
2. Increased QRS complex |
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What 3 hormones are involved in rebound hypertension associated with discontinuation of clonidine?
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1. Catecholamines
2. Renin 3. Angiotensin II |
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Other than rebound HTN following sudden withdrawal of clonidine, what is your anesthetic concern for the pt on chronic clonidine therapy?
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Perioperative hypothermia.
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The pt is on clonidine, administration of what drugs may precipitate severe HTN during a surgical case?
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1. Ephedrine
2. Beta blockers |
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