5. Dopamine
Dopamine was first synthesized in 1910 by George Barger
and James Ewens at Wellcome Laboratories in London,
England.
Dopamine has the chemical formula:
C6H3(OH)2-CH2-CH2-NH2
Its chemical name is "4-(2aminoethyl)benzene-1, 2-diol"
and its abbreviation is "DA."
As a member of the catecholamine family, dopamine is a
precursor to norepinephrine (noradrenaline) and then
epinephrine (adrenaline) in the biosynthetic pathways for
these neurotransmitters.
6. The market preparation of Inj. Dopamine is:
Inj. Dopamine: Each ampule contains 200
mg in 5ml
8. The effects of dopamine depend on the dose
administered. In lower doses (<4 μg/kg per
minute), dopamine increases renal blood
flow by stimulating dopaminergic (DA1)
receptors in the kidney and causes
peripheral vasodilation through DA2
receptors that inhibit the release of
norepinephrine.
9. At intermediate dosages (At intermediate dosages (5–105–10
μμg/kg/minuteg/kg/minute), dopamine improves), dopamine improves
cardiac function and increases bloodcardiac function and increases blood
pressure through increased βpressure through increased β11 receptorreceptor
activation without elevating myocardialactivation without elevating myocardial
oxygen consumption.oxygen consumption.
10. Recent study found that an average dose of 17
μg/kg per minute was needed to optimize
coronary perfusion pressure in a group of
patients that developed cardiogenic shock
after myocardial infarction. Dopamine at
such high levels increases myocardial oxygen
demand, produces tachycardia, and may
limit renal perfusion. It should be used with
caution in patients with cardiogenic shock
because it may adversely influence the
balance of myocardial oxygen delivery and
consumption.
11.
12. The market preperation of Inj. Dobutamine
is:
Inj. Dobutamine: Each ampule
contains 250 mg in 5 ml
14. Dobutamine is the inotropic drug of
choice for the management of
congestive heart failure and cardiogenic
shock. It is a β1-adrenergic agonist that
has minimum chronotropic and
peripheral vasoconstrictive effects. It
has a significant advantage over
dopamine in that it does not cause the
release of nor epinephrine.
15. Furthermore, it does not require the
presence of nor epinephrine at the nerve
terminals for effect. Because of its minimum
chronotropic effect, dobutamine can
improve ventricular performance without
significantly increasing myocardial oxygen
demand. Dobutamine’s greatest potential is
realized in patients with reduced cardiac
indices and increased filling pressures.
16. Because it is a vasodilator, dobutamine
reduces filling pressures and wall tensions in
patients with dilated ventricles. This permits
better myocardial nutrient flow during
diastole. A recent study found a 33%
improvement in cardiac index, a decrease in
systemic vascular resistance, and no change
in heart rate or systemic blood pressure
when dobutamine was given in doses that
averaged 8.5 μg/kg per minute.
17. The drug may be given in doses up to 40
μg/kg per minute without significantly
increasing heart rate. When three-
vessel coronary artery disease is
present, dobutamine may create a steal
and direct blood away from ischemic
areas.
18.
19. rommosuman@yahoo.com
Traits Dopamine Dobutamine
1. Chemical nature Dopamine is a
neurotransmitter and a
neurohormone
Dobutamine is a
sympathomimetic drug
2. Receptors Action depends on D1, β1, α (at
low dose) and β1, α, D1, β2 (at
high dose) receptors
Action depends on the
activity on β1, β2 and α1
receptors
3.Haemodynamic
Effect*
BP HR CO SVR PVR SBF BP HR CO SVR PVR SBF
↑/↑↑ ↔/↑ ↑/↑↑ ↑/↑↑ ↔/↑ ↔/↑ ↔/↓ ↑ ↑↑ ↓ ↓ ↔
4. In cardiogenic
shock
When SBP is 70-100 mmHg
with signs and symptoms of
shock
When SBP is > 100 mmHg
with no signs and symptoms
of shock
5. Septic shock As pressor agent alternative to
Nor adrenaline after initial
resuscitaion when MBP is Still
< 65mmHg
As ionotropes during initial
6 hours of resuscitation after
fluid management, Specially
in low cardiac output
* SVR=Systemic vascular resistance; PVR= Pulmonary vascular resistance; SBF= Splanchnic blood flow;
MBP= Mean blood pressure; SBF= Systemic blood flow.
22. In case of cardiogenic shock, we are
frequently practising Inotropes in wards,
preferably Inj. Dopamine and Inj.
Dobutamine. However, we are not using the
actual dose required to act as inotropes in
case of cardiogenic shock. The traditional
dose is much less than the actual dose, in
fact! But, we don’t even bother to think to
change it, rather practicing only as because
our ancestors used to practise it!!!
23.
24. 2 ampules Inj. Dopamine are mixed with 500 cc of
Inj. N/S or Inj. 5% DA.
So, 510 cc(500+2×5) fluid contains 400mg Dopamine,
i.e.
(510cc ×15 ×4)μd fluid contains (400 × 1000) μg
of Dopamine
Or,
30600 μd of fluid contains 400000 μg of
Dopamine
or
1 μd of fluid contains (400000 ÷ 30600) ≈13 μg of
Dopamine
25. So, when we use 32-40 μd/min of fluid
(Containing Inj. Dopamine) in average
weighted person, we actually give (13 × 32)
μg/min or, 416 μg/min, which is too less to
produce inotropic effect in cardiogenic
shock. Sometimes, the dose is increased
maximally up to 40 μg/min, i.e. 520
μg/min( In a 6okg weighted patient).
26.
27. EpinephrineEpinephrine Infusion starting from 0.05Infusion starting from 0.05μμg/kg/ming/kg/min
NorepinephrineNorepinephrine Infusion starting from 0.05Infusion starting from 0.05μμg/kg/ming/kg/min
DobutamineDobutamine Infusion starting from 2.5–25Infusion starting from 2.5–25μμg/kg/ming/kg/min
DopamineDopamine Infusion starting from 2.5–30Infusion starting from 2.5–30μμg/kg/ming/kg/min
Courtesy: Oxford Handbook
Of Critical Care Medicine
29. So, the heighest inotropic dose in
cardiogenic shock is 25-30 μg/min/kg.
In a average weighted (60kg) person we
can give (20 × 60) μg/min or, 1200 μg/min
!!! But we are only giving 520 μg/min!
The same is also true for Dobutamine.
30.
31.
32.
33.
34.
35. As we try to avoid extra fluid (In cardiogenic
shock)through infusion, we can concentrate
the drug, so that less amount of fluid is
required. For that reason, we can give the
inotropes in the following way:
Inj. N/S 90 CC + Inj. Dopamine 2 amp(400mg)
I.V @ 2.5-30 μd/min
Maximum dose will be I.V. @ 30 μd/min
36. If we add 2 ampules of Inj. Dopamine in 90 cc of
Inj. Normal saline, we can easily calculate the dose
as follows:
(90+10) or, 100 cc fluid contains 400 mg of
Dopamine
So, (400×1000) μg Dopamine is in = 100×4×15μd
fluid
400000 μg Dopamine = 6000 μd fluid
So, If we want to give Dopamine @2.5 μg/kg/min in
a patient of 60 kg, we should give 150 μg/min.
37. Now, 400000μg/min Dopamine = 6000μd/min of
fluid
So, 150 μg/min Dopamine = (6000÷400000)×150
= 2.25 μd/min
Therefore, the lowest dose of Inj. Dopamine, in a
patient of 60 kg with cardiogenic shock, will be
2.25 μd/min. The dose can be as high as ≈30 μd/min.
The same calculation can also be applicable for Inj.
Dobutamine!
38. S0, the regime should be Inj. Normal saline 90 cc
+ Inj. Dopamine (200mg) 2 ampules I.V. @ 3-
30μd/min.
And notthe Traditional one, i.e. Inj. Normal
saline(or, Inj. 5% DNS) 500 cc + Inj. Dopamine
(200mg) 2 ampules I.V. @ 32 (as if, its an
universal constant!!!) μd/min.
