Plasma expanders are agents that have relatively high molecular weight and boost the plasma volume by increasing the osmotic pressure. They are used to treat patients who have suffered haemorrhage or shock.
Plasma expanders are agents that have relatively high molecular weight and boost the plasma volume by increasing the osmotic pressure. They are used to treat patients who have suffered haemorrhage or shock.
There are two main types of Volume Expanders:
1. Crystalloids – Crystalloids are aqueous solutions of mineral salts or other water-soluble molecules. E.g. normal saline, dextrose, Ringer’s solution etc.
2. Colloids – Colloids are larger insoluble molecules, such as dextran, human albumin, gelatin, blood. Blood itself is a colloid.
What do they do?
Crystalloid | Colloid |
Inexpensive | Increase plasma volume |
Use for maintenance fluid and initial resuscitations | Less peripheral edema |
Restore 3rd space loss | Smaller volumes for resuscitation |
Intravascular half-life 20-30 minutes | Intravascular hal-life 3-6 hrs |
A buffer is a solution that can resist pH change upon the addition of an acidic or basic component. It is able to neutralize small amounts of added acid or base, thus maintaining the pH of the solution relatively stable
Human blood contains a buffer of carbonic acid (H2CO 3) and bicarbonate anion (HCO 3 –) in order to maintain blood pH between 7.35 and 7.45, as a value higher than 7.8 or lower than 6.8 can lead to death. In this buffer, hydronium and bicarbonate anion are in equilibrium with carbonic acid
There are several buffer systems in the body. The most important include:
(1) Bicarbonate buffer (HCO3–/CO2)
(2) Haemoglobin buffer (in erythrocytes)
(3) Phosphate buffer
(4) Proteins
(5) Ammonium buffer.
Buffers in the Human Body. Blood contains large amounts of carbonic acid, a weak acid, and bicarbonate, a base. Together they help maintain the bloods pH at 7.4. If blood pH falls below 6.8 or rises above 7.8, one can become sick or die
A buffer is simply a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid. Buffers work by reacting with any added acid or base to control the pH.