Cardiac - Inotropes & Pressors Flashcards
Adrenoreceptors and functions
(From LITFL)
A1 present in smooth muscle.
Causes vasoconstriction, relaxation of GI, contraction of GU
A2 present in CNS, arterioles, pancreas. Causes sedation, analgesia, vasodilation and inhibition of insulin release
B1 present in cardiac muscle and juxtaglomerular apparatus (JGA)
Causes ino/chrono/dromotropy (cAMP increases intracellular Ca2+) and in the JGA increases renin release.
B2 present in skeletal vascular and bronchial smooth muscle, liver and on cell membranes.
Causes vasodilation and bronchodilation, hepatic glycogenolysis, increases na+/k+ ATPase pump to increase intracellular K+
B3 present in fat, causes lipolyses and thermogenesis
MOA Epinephrine
B1- increased chrono/dromo/inotropy
B2- bronchodilation
Low doses B1&2>a1 decreased SVR
Higher doses A1>B1&2 increased SVR
Epinephrine dosages (adult)
Bradycardia/shock 2-20mcg/min
- UTD 1-40mcg
Anaphylaxis/bronchospasm 0.5mg IM, 50-100mcg IV/IO
Periarrest 10mcg IV/IO q2-3min
Intraarrest 1mg q3-5min
Epinephrine Formulary
CCP: 1mg/250mL= 4mcg/mL
OR
VCH: 3mg/250mL= 12mcg/mL
5mg/250mL= 20 mcg/mL
30mg/500mL= 60mcg/mL
Compatible with D5W, NS, LR, Ringer’s
Administer through central line or PIV for short-term
Pharmacokinetics of epinephrine
Onset: 30-90sec IM, 30sec IV
Peak: 4-10min IM, 3-5min IV
Duration: 5-10min
MOA of norepinephrine
“balanced inopressor”
A1: arteroconstriction (afterload/SVR), venoconstriction (SV/CO), and coronary artery constriction
A1>B1 and B2 effects
B1 increased contractility (and HR, but cancelled out by baroreflex-induced bradycardia)
B2 smooth vaso
Norepinephrine dosages (adult)
2-20mcg/min
*around 15mcg/min, consider layering in Vasopressin or other pressor
0.1mcg/kg/min up to 1mcg/kg/min
Norepinephrine indications
- Shock with hypotension refractory to fluid resuscitation (*vasodilatory)
- Cardiogenic shock with refractory hypotension
- Symptomatic bradycardia (? handbook)
Norepinephrine pharmacokinetics
Onset and peak immediate
Duration 1-2min
Norepinephrine infusions
4mg/250mL =16mcg/mL (single strength)
8mg/250mL = 32mcg/mL (double strength)
16mg/250mL= 64mcg/mL (quad strength)
central line access is preferred, can use peripheral IV for single strength through large bore
Compatible with NS, D5W, NS-D5W
Dobutamine MOA
Inodilator
(From AHA)
3:1 B1 to B2 affinity. Potent inotrope, with weaker chronotropy. Both A1 agonism and antagonism, with B2 stimulation, cause net effect of mild vasodilation. Higher doses cause vasoconstriction
Dobutamine indications
- Low cardiac index and low BP, but without hypotension (decompensated HF, cardiogenic shock, sepsis-induced myocardial dysfunction)
- Short-term management of patients with cardiogenic decompensation
MANY DRUG INTERACTIONS
Concomitant use with MAO inhibitors May cause prolonged HTN
Dobutamine dosages
2-20mcg/kg/min (max)
Dobutamine infusions
250mg/250mL= 1mg/mL (May appear pink due to oxidation, does not effect potency)
Compatible with N/S, D5W, NS-Dex combos, Ringer’s
Dobutamine pharmacokinetics
Onset: 1-10min
Peak: 10-20mins
Half-life: 2min
Dopamine MOA
Dose dependent:
Low: D1/D2 causes decreased SVR
Medium: additionally stimulates B1 (chrono and inotropy)
High: B1 and A1 increased SVR
Dopamine indications
- Symptomatic hypotension in the absence of hypovolemia (exp. Cardiogenic shock, bradycardia, sepsis, renal failure)
- post-arrest hypotension
- absence of more suitable agents
Dopamine pharmacokinetics
Onset 2-5min
Peak unknown
Duration <10min
Dopamine dosage (adult)
Low (dopaminergic) 2mcg/kg/min
Medium (b1) 5-10mcg/kg/min
High (a1 and b1) 10-20mcg/kg/min
Titrate by 2-5mcg/kg/min q 2-5min to effect
Dopamine infusion
400mg/250mL= 1600mcg/mL
800mg/250mL= 3200mcg/mL
Dopamine contraindications
Known/suspected pheochromocytoma
Tachydysrhythmia
Extreme caution with concurrent MAO inhibitors— may cause prolonged HTN
Norepinephrine contraindications
Mesenteric or peripheral vascular thrombosis, pregnancy, profound hypoxia or hypercarbia (may produce VT/VF)
Milrinone MOA
Inodilator, PDE inhibitor
Inhibits phosphoduesterase 3 from breaking down cAMP, causing inotropy in cardiac and vasodilation in vascular tissue
Milrinone indications
ADHF, inotropic support, cerebral vasospasm
Contraindications/cautions of Milrinone
Hypersensitivity, avoid use in severe obstructive aortic or pulmonic valvular disease. Caution with renal dysfunction.
Arrhythmias associated with use, correct electrolytes (especially hypoK and hypomag) before use.
Milrinone dosage
Short term management of CHF
- loading dose (optional) 50mcg/kg/10min
- maintenance 0.125 to 0.75 mcg/kg/min
Milrinone infusion
20mg/100mL= 200mcg/mL
40mg/100mL= 400mcg/mL
Compatible with N/S, D5W, NS 0.45%
Milrinone
Onset 5-15min
Half-life 2.3hrs
Isoproterenol MOA
Inodilator
B1 ino/chronotropy
B2 relaxation of bronchial, GI and uterine smooth muscle, vasodilation of peripheral vasculature
Little/no alpha affinity
Isoproterenol indications
Symptomatic bradycardia, AV blocks
Adjunct to fluid and electrolyte replacement therapy and other drugs/procedures in the treatment of low cardiac output states (ie. decompensated HF, cardiogenic shock)
Isoproterenol contraindications
Hypersensitivity to Isoproterenol and sulfites.
Tachyarrhythmias
Ventricular arrhythmias on inotropic support
Digitalis toxicity
MANY drug interactions and cautions with co-morbidities
Isoproterenol dosage
(handbook)
Bradycardia 2-10mcg/min
Heart block 2-20mcg/min
Isoproterenol infusions
1mg/250mL= 4mcg/mL
4mg/250mL= 16mcg/mL
Compatible with D5W, NS, dextrose 5% in Lactated Ringer’s, dextrose 5% in sodium chloride 0.9%, Lactated Ringer’s solution
Isoproterenol pharmacokinetics
Onset immediate
Duration 10-15min
Vasopressin MOA
ADH analogue, pure vasopressor
(Uptodate)
V1 constriction of vascular smooth muscle (increased SVR), baroreflex may cause decrease in HR
V2 increases water permeability at renal tubules- decreased urine volume and increased osmolality.
Pressor effects relatively preserved during hypoxic and acidotic conditions
Vasopressin indications
Vasodilatory shock states that remain hypotensive despite fluid resuscitation and catecholamines
Vasopressin dosages
0.03-0.04U/min
Titrate up by 0.005U/min q10-15 to a max of 0.1U/min
Vasopressin infusion
20U/100mL= 0.2U/mL
40U/100mL= 0.4U/mL
Compatible with NS and D5W
Vasopressin pharmacokinetics
Onset 30-60min
Duration: 20min
Phenylephrine MOA
Pure vasopressor
A1 increased SVR
May cause baroreflex reduction in HR
Phenylephrine indications
Acute hypotension despite adequate fluid volume replacement in airway management (ie. vasodilation in anesthesia, post-intubation hypotension)
Consider in aortic stenosis (increased SVR, reflex brady for filling time)
Phenylephrine contraindications/cautions
Hypersensitivity to phenyl or sulfites
Pheochromocytoma
Severe HTN or VT (also induced with rapid push)
Caution in bradycardia or underlying cardiovascular disease
Phenylephrine dosage
100mcg/20-30sec q 2-5min
