These  are  high  molecular  weight  substances  which  exert  colloidal  osmotic (oncotic) pressure, and when  infused  i.v. retain  fluid  in the  vascular compartment. 

They are used to correct hypovolemia due to loss of plasma/blood. 

Human  plasma  or  reconstituted  human  albumin  would  seem  to  be  the  best. However,  the  former  carries  risk  of  transmitting  serum  hepatitis,  AIDS,  etc.,  and the  latter  is  expensive.  

Therefore,  synthetic  colloids  are  more  often  used.  

The desirable properties of a plasma expander are given in the box. 

Desirable properties of plasma expander: 

1. Should exert oncotic pressure comparable to plasma. 
2.  Should  remain  in  circulation  and  not  leak  out  in  tissues,  or  be  too  rapidly disposed. 
3. Should be pharmacodynamically inert. 
4. Should not be pyrogenic or antigenic. 
5. Should not interfere with grouping and cross matching of blood. 
6. Should be stable, easily sterilizable and cheap. 

Substances employed are: 

Human Albumin 

Human  albumin:  

It  is  obtained  from  pooled  human  plasma;  100  ml  of  20% human albumin solution  is the osmotic equivalent of about 400  ml of  fresh  frozen plasma or 800  ml of whole blood.
It can be used without regard to patient’s blood group and does not interfere with coagulation. 
Unlike whole blood or plasma, it is free of  risk of transmitting serum  hepatitis because the preparation  is  heat treated. 
There is also no risk of sensitization with repeated infusions. 
The  20%  solution  draws  and  holds  additional  fluid  from  tissues:  crystalloid solutions  must  be  infused  concurrently  for  optimum  benefit.  
Apart  from  burns, hypovolemia,  shock,  etc.,  it  has  been  used  in  acute  hypoproteinaemia,  acute  liver failure  and  dialysis.  
Dilution  of  blood  using  albumin  and  crystalloid  solutions  can be used before cardiopulmonary bypass. Febrile reaction to human albumin occurs occasionally. 
It is expensive. 


It  is a polysaccharide obtained  from sugar beat, and  is available  in two forms. 
Dextran-70 (MW 70,000) Dextran-40 (MW 40,000; low MW dextran) The more commonly used preparation is dextran-70. 
It expands plasma volume for nearly 24 hours, and is slowly excreted by glomerular filtration as well as oxidized in the body over weeks. 
Some amount is deposited in RE cells. 
Dextran has nearly all the properties of an ideal plasma expander except: 
(a) It may interfere with blood grouping and cross-matching. 
(b)  Though  the  dextran  used  clinically  is  not  antigenic,  its  structure  is  similar  to other  antigenic  polysaccharides.  
Some  polysaccharide  reacting  antibodies,  if present,  may  cross  react  with  dextran  and  trigger  anaphylactic  reaction.  
Urticaria, itching, bronchospasm, fall in BP occur occasionally; anaphylactic shock is rare. 
(c)  It  can  interfere  with  coagulation  and  platelet  function,  and  thus  prolong bleeding time; should not be used in hypofibrinogenaemia, thrombocytopenia or in presence of bleeding. 

Polygeline  (Degraded  gelatin  polymer):  

It  is  a  polypeptide  with  average  MW 30,000  which  exerts  oncotic  pressure  similar  to  albumin  and  is  not  antigenic; hypersensitivity  reactions are rare, but should be watched  for. 
It does  not  interfere with grouping and cross-matching of blood and remains stable for three years. 
It is not  metabolized  in  the  body;  excreted  slowly  by  the  kidney.  
Expansion  of  plasma volume lasts for 12 hours. 
It is more expensive than dextran. 
It can also be used for priming of heart-lung and dialysis machines.  
Hypersensitivity reactions like flushing, rigor, urticaria, wheezing and hypotension can occur. 


It  is  a  complex  mixture  of  ethoxylated  amylopectin  of  various molecular  sizes;  average  MW  4.5  lac  (range  10,000  to  1  million).  
The  colloidal properties  of  6%hetastarch  approximate  those  of  human  albumin.  
Plasma  volume expands  slightly  in  excess  of  the  volume  infused.  
Haemodynamic  status  is improved  for  24  hour  or  more.  
Hetastarch  is  incompatible  with  many  drugs;  no injectable  drug  should  be  added  to  the  infusion.  
Blood  grouping  and  cross matching may be vitiated. 
Smaller molecules (MW < 50,000) are excreted rapidly by kidney; 40% of infused dose appears in urine in 24 hr. 
Larger molecules are slowly broken down to smaller ones and eliminated with a t½ of 17 days. 
Adverse  effects:  are  vomiting,  mild  fever,  itching,  chills,  flu  like  symptoms, swelling of salivary glands. Urticaria, periorbital edema and bronchospasm are the anaphylactoid reactions. 


These colloidal solutions are used primarily as substitutes for plasma in conditions where  plasma  has  been  lost  or  has  moved  to  extravascular  compartment,  e.g.  in burns  (acute  phase  only),  hypovolemic  and  endotoxin  shock,  severe  trauma  and extensive tissue damage. 
They can also be used as a temporary measure in cases of whole  blood  loss  till  the  same  can  be  arranged:  but  they  do  not  have  O2  carrying capacity.  
Apart  from  albumin,  other  plasma  expanders  should  not  be  used  for maintenance  of  plasma  volume  in  conditions  like  burns,  where  proteins  leakout with fluids for several days. 

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