Inotropes in medical practice

1. IONOTROPES AND IVC
DIAMETER
Dr.D.S.NIVETHAA
POST GRADUATE DEPARTMENT OF ANAESTHESIOLOGY

9. RECEPTOR DISTRIBUTION

10. EFFECTS OF SPECIFIC ADRENERGIC RECEPTOR
STIMULATION

12. EPINEPHRINE
Prototype sympathomimetic
synthesized stored andreleased from adrenal medulla
oral administration not effective- rapid metabolism in GI mucosaand liver
RECEPTORS STIMULATED-Beta 1-myocardium-raises BP, cardiac
output,myocardial oxygen demand by increasing contractility
Alpha 1- decreases splanchnic and renal blood flow but increases cpp by
increasing aortic diastolic bp
Beta 2- vasodilation in sk. muscle

13. ROUTES- SC/IV/IM
DOSE- to improve myocardial contractility 2-20 Mic/min(0.04-0.4
mic/kg/min)-4mic/ml dilution
Available preparation-1:1000(1mg/ml)
prefilled syringe 1:10000
1 in 1 lakh for paediatric use(10 mic/ml)
USES
1. Life threatening anaphylaxis-100-500 mcg
2. Severe asthma and bronchospasm- nebulization -5ml of 1:1000 (max 5 mg)
3. Cardiac arrest- 1mg every 3-5 mins

14. NOREPINEPHRINE
Precursor of epinephrine
Direct alpa 1 , beta 1 with little beta 2 activity
Beta 1 – myocardial contractility- inc BP
infusion- 2-20 mic/min(0.01-0.4mic/kg/min
should be infused in 5 D ( acidity-prevent oxidation of catecholamine)
DOC in septic shock-inc MAP,PVR

15. DOPAMINE
Precursor of norepinephrine
direct and indirect adrenergic and dopaminergic agonist
renal dose-0.5-3 mic/kg/min-DA1
3-10 mic/kg/min-beta 1
>10 mic/kg/min-PVR inc- alpha 1
used to improve cardiac output, maintain renal function

16. ISOPROTERENOL
Pure beta agonist
Beta 1-inc HR,CO,CONTRACTILITY,SBP
Beta 2-dec PVR,DBP
Dose- 1-5 mic/min
Metabolism-COMT in liver
Effective in patient with heart block

17. DOBUTAMINE
Synthetic catecholamine
Derived from isoproterenol
Potent alpha 1 agonist
Weak beta 1 &2 agonist
<5mic/kg/min-beta 1, alpha 1
>5mic/kg/min-alpha 1
>10 mic/kg/min- prone for arrhythmia

18. EPHEDRINE
Indirect acting synthetic sympathomimetic- alpha and beta
5-10 mg IV
Tachyphylaxis can occur
IV – inc HR,SBP
Hypotension due to Regional blockade and GA induction
Oral- treat bronchial asthma
IM-0.5 mg/kg- antiemetic

19. PHENYLEPHRINE
Hydroxy phenylethylamine
Direct alpha 1
Inc PVR,MAP
50-200 mic iv bolus
Infusion-20-100 mic/min
Nasal -1%-decongestant

20. DIGOXIN
Cardiac glycoside
Extracted from foxglove plant
60-80% oral bioavailability
Peak plasma conc- 1-3 hours following oral administration
100% iv bioavailability-attain peak plasma conc immediately
Excreted entirely by kidneys
Half life -1-2 days- inversely proportional to GFR(inc with age and renal
disease.

21. ORAL IV
ONSET OF ACTION 0.5-2hrs 10-30mins
PEAK EFFECT 6hrs 2-4hrs
Mechanism of action-selective and reversible cardiac sarcolemmal Na+_K+ ATPase
inhibitor
Increases intracellular calcium –responsible for ionotropic action
• Other benefits-
1. No change in heart rate
2. Decrease in LV preload and afterload
3. Decrease in wall tension
4. Decrease in oxygen consumption in failing heart

23. ECG findings obtained at therapeutic plasma concentrations include
 Prolonged PR interval-delayed Av nodal conduction
 Shortened QTc intervals-rapid ventricular repolarization
 ST depression-scaphoid/scooped out-decreased phase 3 depolarization of
cardiac action potentials.
 Diminished /inverted T wave
NARROW THERAPEUTIC RANGE

24. Digoxin toxicity
20% of patients treated with cardiac glycosides –report digitalis toxicity
AT RISK INDIVIDUALS:
-Renal dysfunction
-Diuretics-potassium depletion-arrhythmia
-Hyperventilation-decrease potassium 0.5mEq/L for 10mmHg decrease in
PaCO2
-Electrolyte imbalance –Hypokalemia,Hypercalcemia,Hypomagnesemia
-Hypoxemia induced sympathetic nervous system activity

25. Plasma conc < 0.5ng/ml-no toxicity
Therapeutic range-0.5-2.5ng/ml
Toxic range>3.0ng/ml
Treatment
- treat the underlying cause
-treat cardiac dysrhythmias
Phenytoin-0.5-1.5mg/kg IV over 5 mins
Lidocaine-1-2mg/kg IV
Atropine-35-70mic/kg IV
K+ supplementation-0.025-0.050 mEq/L
-Life threatening toxicity- digoxin antibodies
-Temporary artificial transvenous cardiac pacemaker-if complete heart
block is present.

39. THANK YOU