Dr.U.P.RathnakarMD.DIH.PGDHM

[Plasma expanders]

MBBS iii Sem. 15 NOV 12

ShockCirculatory failure: oxygen delivery (DO2) fails to meet the metabolic requirements of the tissues

CO=

Capacity= Blood volume=

5L

5L5L

CO=

Capacity= Blood volume=

?3L

3L5L

Hypovolemic shock

Volume failure

Capacity=5L

Volume=3L

Hypovolemic shock

Capacity=5L

Volume=5LCardiogenic shock

Pump failure

CO= ?3LVolume failure

CO=

Capacity=

Blood volume=

3L

5L

8L

Distributive shock

Distribution failure

Capacity=5L

Volume=3L

Hypovolemic shock Cardiogenic shock

Capacity=5L

Volume=5L

Volume failure Pump failure

Capacity=5L

Volume=3L

Hypovolemic shock Cardiogenic shock

Capacity=5L

Volume=5L

Capacity=8L

Blood Volume=5L

Distributive shock

Capacity=5L

Volume=5L

Obstructive shock

Distribution failure

Volume failure Pump failure

CO= 3L

Stages of shock

Non-progressive stage

Progressive stage

Refractory [irreversible] stage

Distribution failure

Volume failure

Pump failure

Hypovolemic shock

Cardiogenic shock

Distributive shock

Obstructive shock

Pharmacotherapy of shock

1. Managing specific causes2. Managing associated

hemodynamic alterations3. Undertaking life saving &

life sustainable measures

Distribution failure

Pump failure

Distributive shock

Obstructive shock

Cardiogenic shock

Hypovolemic shock

Agents used to treat hemodynamic dysfunction:1.Sympathomimetic amines [Dopamine,

dobutamine etc.]2.Glucocorticoids3.Blood and plasma expanders

DopamineDose dependent action

2-5 ug/kg/min [D1]

5 to 10 [D1 & β1]

11-20 [β1]

More than 20 ug/kg/min[α1 ]

D1 receptors-renal, mesenteric, and cerebral circulations and increases blood flow

Increase in urinary sodium and water excretion

Stimulates β1-receptors in the heart & increase in cardiac output.

Cardiac

α-receptors-progressive vasoconstriction, and increase in ventricular afterload -limits the ability of dopamine to augment cardiac output.

DobutamineCardioselectivePostive inotropic1-10mcg/kg/min. i.v.

Nor-adrenalineWhen dopamine & dobutamine fail1-8mcg/min

AdrenalineAnaphylactic shock

GlucocorticoidsMethyl prednisolone, dexamethasone

1

2

3

4

Other drugs used in shockOxygenNaloxone [Opioid antagonist]VasoconstrictorsVasopressin

Volume replacements

1.Whole blood and plasma2.Plasma expandersa. Colloids

b. Crystalloids• Hydroxyethyl starch

Colloidal plasma expanders

Physiology of plasma expanders

Replace the lost volume. This way remaining RBCs can oxygenate body

tissue. Normal human blood has a significant excess

oxygen transport capability, -Provided blood volume is maintained by volume expanders,

Since the lost blood was replaced with a suitable fluid, the now diluted blood flows more easily, even in the small vessels. As a result of chemical changes, more oxygen is released to the tissues.

Ultimately red blood cell levels drop too low for adequate tissue oxygenation, even if volume expanders maintain circulatory volume.

Plasma expanders[Colloidal]

Colloidal plasma expanders-Substances of high Mol.Wt.-Remain long time in blood stream-Augment the volume of circulating fluid

-By increasing the osmotic pressure

Plasma expanders

Requirements of an ideal plasma expander:

1. Oncotic pressure comparable to plasma.

2. Remain in the circulation for an adequate period and

3. Disposed of either by metabolic degradation or by excretion.

4. Not antigenic or pyrogenic.5. Not interfere with grouping and cross

matching of blood.

Use of plasma expanders:Hypovolemic shock.Burns.Severe trauma.Endotoxin shock.

Contraindications:Severe anaemia.Cardiac failure.Pulmonary oedema.Renal insufficiency.

Dextran

It is a Polysaccharide[ made of many glucose molecules].

Dextran 70 (MW – 70,000) & Dextran 40 ( MW – 40,000).Oncotic pressure similar to plasma proteins and expands plasma volume for about 24 hours.

Large doses do not induce antibody formation.

They may interfere with coagulation and platelet function and also blood grouping.

Dextran – 70:Excreted very slowly by glomerular

filtration and some amount deposited in RE cells.

Dextran – 40Reduces blood viscosity.Excreted through renal tubules and

occasionally may produce acute renal failure. Precautions should be taken.

CautionDextran does not provide necessary

electrolytes and can cause hyponatremia or other electrolyte disturbances

Dextran- other usesAntithrombotic in microsurgeries In some eye drops as a lubricant To solubilize other factors, e.g. iron (=iron

dextran)Used in laboratory tests

Contraindications:Allergy.Heart failure.Acute oliguric renal failure.Hypofibrinogenemia.Thrombocytopenia.

Hydroxyethyl starch[HES]: Compared to dextrans –Maintains blood volume longer.Does not cause acute renal failure or

coagulation disturbances.Adverse effects:Anaphylactoid reactionsMild fever, Chilling, periorbital edema,

urticaria, itching and chills.

Polyvinylpyrrolidone[PVP]:Synthetic polymer,MW- 40,000.Interferes with blood grouping and cross

matching.Releases histamine.Binds to penicillin and insulin.

Gelatin polymer[Haemaccel]:Does not interfere with grouping and cross

matching.Expands plasma volume for about 12

hours.Not antigenicHypersensitivity and hypotension can

occur.

Crystalloids

Normal saline:Very limited duration of action.

Dextrose:Osmolality is lower than serum.Useful when kidney function is impaired.

Human albumin:Obtained from pooled human plasma.Crystalloid solutions must be infused

concurrently for better action.Does not interfere with coagulation.Used as a vehicle for transfusing packed

red cells.

Pharmacotherapy of shockDrug therapy aims at:Managing specific causesVolume,cardiac function,relieving obstruction etc.Managing associated hemodynamic

alterationsDopamine or dobutamine, glucocorticoids, volume replacements &expandersUndertaking life saving & life

sustainable measures

Shock & Plasma expandersEnlist the principles of pharmacotherapy of

shockEnumerate plasma expandersIndications and CIs of plasma expanders

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