Antihypertensives Flashcards
Many patients present to the OR on various ________
HTN agents
What is the drug classes commonly used to treat hypertension? (4)
thiazide diuretics, CCB (dihydropyridine), ACE-I, ARB, beta-blocker
Patients with systemic HTN can be sensitive to anesthetic agents; challenging for anesthesia provider: ________
Roller coaster anesthetics
What is the continuation of antihypertensive meds for surgery? When is this not the case?
Antihypertensive meds are continued up to time of surgery; held for severe bradycardia or hypotension
What antihypertensive medications must be held prior to surgery?
Ace inhibitors the exception: commonly held 12-24 hrs before surgery (patients can develop refractory hypotension intraoperatively
What are some medications that can cause refractory hypotension intraoperatively when given with ACE inhibitors?
sometimes minimal effect using ephedrine or phenylephrine; vasopressin effective)
When are β-Adrenergic Receptor Blockers indicated?
Indicated in long-term tx of patients w/ CAD & HF
What is the classification for β-Adrenergic Receptor Blockers?
Classified as nonselective or cardioselective
When are cardioselective β-Adrenergic Receptor Blockers prefered?
cardioselective drug preferred in pulmonary disease, IDDM, & symptomatic PVD
What are general side effects of β-Adrenergic Receptor Blockers?
bradycardia, heart block, CHF, bronchospasm, claudication, masking hypoglycemia, sedation, impotence, abrupt withdrawal issues
What is the use of metoprolol?
Metoprolol used to control HR (cardioselective)
What is MOA of labetalol?
: nonselective beta and alpha-1 adrenergic blocker
What is the use of labetalol in anesthesia?
used to tx hypertensive emergencies & type B aortic dissections
What is the onset of labetalol?
Onset 1-5 min
What is the clinical half life of labetalol?
clinical half-life 1-4 hrs
What are the side effects of Labetalol?
- Less reflex tachycardia and less negative inotropy
- Decreases HR d/t beta-blocking activity
- Orthostatic hypotension
What is the use of esmolol?
control HR and blunt sympathetic responses that are episodic during an anesthetic (ideal anesthetic drug, quick on-quick off)
What is the target receptors of Prazosin, terazosin, doxazocin?
peripheral-acting, oral, selective postsynaptic a-1 adrenergic receptor blockers
What is the effect of Prazosin, terazosin, doxazocin?
arterial & venous vasodilation
What is the MOA of phenoxybenzamine and phentolamine?
(nonselective alpha blockers) by not affecting presynaptic α-2 receptors
What is the affect of phenoxybenzamine and phentolamine?
no reflex increase in CO or renin
What is the use of Prazosin?
used for HTN, afterload reduction for CHF and alpha blockade in preop management of pheochromocytoma (”a before b”)
What is Prazosin most commonly used for in males?
HTN in males with BPH
What are the side effects of Prazosin?
orthostatic hypotension, vertigo, fluid retention
What medications can interfere with the anti-HTN effects of Prazosin?
NSAIDS may interfere with anti-HTN effects
What can be exaggerated when Prazosin and epidurals? What is the treatment? What can occur when combined with BB?
- Hypotension with epidural may be exaggerated
- Phenylephrine may not be effective; may require epinephrine
- When combined with B-blockers could result in refractory hypotension
What is the receptors targets of Clonidine?
central acting, partial α2- adrenergic agonist
What is the effect of Clonidine?
d/t decreased sympathetic output from the CNS
What is the clinical use of Clonidine?
Tx of patients w/severe HTN
What is the formularies of Clonidine?
Oral and transdermal use
What is the clinical effects of Clonidine?
Affects systolic more than diastolic, maintains homeostatic CV reflexes (no orthostatic hypotension or hypotension during exercise)
What id the MOA of Clonidine?
Clonidine binds to α2 receptors in medullary vasomotor center to decrease SNS outflow
What effect does Clonidine and anesthetics have?
Decreases anesthetic requirements by modifying K+ channels in CNS (decreases MAC by nearly 50%)
What impact does neurxial administration have with Clonidine?
inhibits nociceptive neuron firing and spinal substance P release
What is the side effects of Clonidine?
sedation and xerostomia (dry mouth)
What is the effects of Clonidine that is abruptly withdrawal? What is this treated with?
Rebound HTN with abrupt discontinuation- better treated with hydralazine, SNP or labetalol (given the alpha blockade), restart clonidine
What is true about Clonidine and DEX?
Both clonidine and DEX reduce the sympathetic hyperactivity following ETOH and opioid withdrawal
Overview of commonly used antihypertensive drugs.
Describe the Renin-Angiotensin-Aldosterone Pathway.
What is the MOA of ACE Inhibitors?
Decrease the production of angiotensin II by inhibiting the activity angiotensin-converting enzyme
What does Angiotensin II produce?
produces vasoconstriction through release of Ca++ from SR in vascular smooth muscle
What do ACE Inhibitors prevent?
prevent breakdown of bradykinin
What is bradykinin?
an endogenous vasodilator
What are side effects of ACE Inhibitors?
cough (most common), upper respiratory congestion, rhinorrhea
Why do allergy-like symptoms occur with ACE Inhibitors?
d/t inhibiting breakdown of bradykinin
What is the life threatening side effects of ACE Inhibitors?
ANGIOEDEMA
What are the effects of ACE Inhibitors?
Decreases GFR; caution with renal dysfunction, renal artery stenosis
What is the electrolyte abnormality associated with ACE Inhibitors?
Hyperkalemia (from decreased aldosterone); highest risk in patients with CHF or renal insufficiency
What effect do ACE Inhibitors have on the kidneys?
Decreased renal perfusion and increase sympathetic activity result in increase in renin
What do ACE Inhibitors lack?
The agents lack many of the CNS side effects seen with the other centrally acting anti-HTN agents
What do ACE Inhibitors treat?
Treat systemic HTN, CHF, mitral regurg.
What do ACE Inhibitors delay?
Delay progression of diabetic renal disease
Why do ACE Inhibitors need to be held before anesthesia?
Common to hold these agents 12-24 hrs before surgery due to profound hypotension following induction
Profound hypotension from ACE Inhibitors associated with anesthesia can be treated with?
May be responsive to crystalloids, catecholamine or vasopressin administration
What are examples of ACE inhibitors?
- Benazepril (Lotensin)
- Captopril
- Enalapril (Vasotec)
- Fosinopril
- Lisinopril (Prinivil, Zestril)
- Moexipril
- Perindopril
- Quinapril (Accupril)
- Ramipril (Altace)
- Trandolapril
What is the MOA of Angiotensin II Receptor Blockers (ARB’s)?
Block the vasoconstrictive effects of angiotensin II without blocking ACE activity
Angiotensin II Receptor Blockers (ARB’s): Similar anti-HTN and treatment regimen as __________
ACE inhibitors
What is differ with Angiotensin II Receptor Blockers (ARB’s) then with ACE inhibitors?
Differ mainly from ACE inhibitors as they do not cause the troublesome cough (since ACE activity not affected, bradykinin is broken down)
What is a postop side effect commonly associated with Angiotensin II Receptor Blockers (ARB’s)?
Hypotension following surgery similar concern and need to hold preop
What are examples of Angiotensin II Receptor Blockers (ARB’s)?
- Azilsartan (Edarbi)
- Candesartan (Atacand)
- Eprosartan.
- Irbesartan (Avapro)
- Losartan (Cozaar)
- Olmesartan (Benicar)
- Telmisartan (Micardis)
- Valsartan (Diovan)
What is the MOA of Calcium Channel Blocking Drugs ?
Inhibit calcium influx through voltage-sensitive L-type calcium channels in vascular smooth muscle causing vasodilation
What are the two classes of Calcium Channel Blocking Drugs?
Dihydropyridine class & Nondihydropyridine class
What are examples of Dihydropyridine class of Calcium Channel Blocking Drugs?
potent vasodilators (nifedipine, amlodipine, nicardipine, clevidipine)
What are examples of Nondihydropyridine class of Calcium Channel Blocking Drugs?
verapamil and diltiazem
What are the effects of verapamil and diltiazem?
less potent vasodilators, both have negative inotropic & chronotropic activity
What are the clinical indications of verapamil and diltiazem?
antihypertensive and antiarrhythmic activity
What is the clinical use of Nicardipine & clevidipine?
available as continuous IV infusions for tx of HTN emergencies
What are the components of Nicardipine & clevidipine infusions?
- both can be rapidly titrated
- short half lives
What impact is seen with Nicardipine and liver issues?
- hepatic metabolism
- prolonged half-life & elevated plasma concentrations in pts w/hepatic impairment
What is the metabolism of clevidipine?
metabolized by plasma esterases to inactive metabolites
What is the effect of Clevidipine with hepatic or renal dysfunction?
dosing doesn’t have to be adjusted in hepatic or renal dysfunction
What is true about Clevidipine?
deemed a potent & safe alternative to existing parenteral vasodilators
What are the adverse effects of Clevidipine and nicardipine?
reflex tachycardia, negative inotropy (as do other CCBs within dihydropyridine class)
What Clevidipine and nicardipine inhibit?
•Inhibit hypoxic pulmonary vasoconstriction (HPV) – as do other potent vasodilators
Clevidipine visually looks like _________
Clevidipine
When is clevidipine contraindicated? What can this precipitate?
relatively contraindicated in severe aortic stenosis d/t lowered coronary perfusion pressure which precipitates myocardial ischemia
What are phosphodiesterases (PDEs)?
enzymes which mediate the breakdown of intracellular cAMP & cGMP which regulate intracellular calcium
What does inhibition of PDE cause?
causes vascular smooth muscle relaxation
What are the effects of PDE3 inhibition?
- positive inotropy d/t intracellular calcium mobilization
- combined inotropic & vasodilator actions
What is the clinical use of PDE3 inhibitors?
tx of heart failure in ICU & OR settings: amrinone, milrinone
What are PDE5 inhibitors?
sildenafil, tadalafil, vardenafil
What is the clinical uses of PDE5 inhibitors?
tx pulmonary HTN & erectile dysfunction
What is the available forms of PDE5 inhibitors?
PO forms
What happens when PDE inhibitors are combined with vasofilators?
When combined with other vasodilators can be significant BP lowering agents
What has been associated with PDE inhibitors and anesthesia?
- Reports of blindness/visual changes after anesthesia
- Could be related that the ophthalmic and central retinal arteries have an autoregulation of their own blood flow without any autonomic nerve supply
What can sildenafil increase?
sildenafil also increases IOP
