2. An isotonic solution which is used to ;
-Substitute the blood to provide safe hemodilution.
-Fill the circuit line.
-De-air.
Purpose :
Adequate flow rates can be rapidly achieved on initiation of cpb without risk of
air embolism.
3. Prime Volume:
The volume is determined by both;
-Caliber.
-Length of tubing.
*Per kg 20ml gives safe hemodilution.
*30-35% of patient blood.
4. Administration Of Priming Fluids:
The first trials of CPB usage in practice
suggested to use fresh blood to fill the CPB
circuit, this caused an overload in blood banks
and limited the ability to execute the number
of procedures planned.
5. As an alternative for using fresh blood, stored blood which
was preserved in a citrate solution was used. However, the
use of fresh or citrated homologous blood to fill CPB circuits
was associated with a complex conditions at the start of the
perfusion including arterial hypertension and a drop in the
venous return.
Other complications included excessive hemolysis,
denaturation of proteins ,transfusion reactions, viral particle
transmission, and increased postoperative morbidity.
6. The issue of selecting the right priming solution for
cardiopulmonary bypass circuit is imperative.
Basically, priming solutions can be classified into two
categories crystalloids and
colloids.
The crystalloids include dextrose, balanced
crystalloid fluids (e.g. Plasma-Lyte, Ringer's) , and
mannitol, and the colloids include albumin,
dextran's, gelatins, and hydroxyethyl starch (Haes-
Steril).
7. The crystalloids are a volume expanding solutions
that mimic the normal plasma electrolyte
concentrations, can be used with effective
hemodilution but they lack oncotic activity.
Otherwise, colloids have ability to maintain the
oncotic pressure and reducing tissue oedema, but
their use may be associated with increased
incidence of anaphylactoid reactions and clinical
coagulopathy.
8. Crystalloid Fluid:
Crystalloids have minor components that are easily mixed and
dissolve in a solution. The components (solutes) may be
electrolytes(e.g. Normal saline, Ringer's Lactate or Solution) or
nonelectrolytes (e.g. Dextrose) which are composed of small
molecules that have ability to transit across the semipermeable
membrane and mobility from bloodstream into cells and body tissues.
This ability may increase the fluid volume in both interstitial and
intravascular spaces, but the general effect of the crystalloid fluids is to
expand the interstitial volume rather than the plasma volume.
9. DEXTROSE:
Dextrose was one of the first crystalloids that was
used as priming solution for filling cardiopulmonary
bypass circuits following the abandonment of blood
priming. Dextrose 5% in Water is isotonic and
acidotic(pH 5.0) .
10. When comparing the use of crystalloid fluids with the
banked blood use as priming solution for
cardiopulmonary bypass circuits, the crystalloids
have a beneficial effects on reducing the mechanical
damage to erythrocytes and on improving
intraoperative and postoperative diuresis.
Furthermore ,crystalloid prime containing dextrose
has also led to decreased peri-operative fluid
requirement and reduced postoperative fluid
retention .
11. Disadvantages of using dextrose as a priming
solution:
1- may cause systemic metabolic acidosis.
2- may increase the level of blood glucose, especially in
diabetic patients.
3- Possibility of increase the risk of neurological complications
of cardiopulmonary bypass.
12. Balanced crystalloid fluids:
Balanced crystalloids are fluids that have a neutral
pH as Plasma-Lyte solution (pH 7.4), or slightly
low pH (slightly acidotic) as Ringer's (pH 6.6),
which are isotonic and consist of electrolyte ions
approximately similar to that of human plasma.
13. Ringer's lactate:
Ringer's Lactate , or Hartmann's (Ringer's
solution), is a typical example of a balanced
crystalloid. Ringer's lactate contains lactate as a
source of bicarbonate. But, as lactate may be
converted into glucose in vivo through the
gluconeogenic pathway, as result of that we
must be careful when using a large volume of
fluid containing lactate in diabetic patients.
14. Plasma-Lyte:
Plasma-Lyte solution, which contains acetate
and gluconate for bicarbonate production, and
magnesium (intracellular cation) which is
important in cellular process of energy
transfer and in myocardial ATP metabolism.
15. Mannitol:
Mannitol is a hypertonic, acidotic (pH 4.5 –7.0), and low molecular weight
(182 Da) crystalloid. It widely used in clinical practice to stimulate diuresis.
Mannitol is used also as a volume expander, initially it draws the fluid across
the capillary to the plasma. Then the mannitol diffuses rapidly into the
interstitial fluid and draws water from the body cells to extracellular phase,
resulting increase in the volume of the extracellular phase or compartment.
Mannitol have a protective effect on renal function, and have a beneficial
effects on all organs, including the brain and heart. Mannitol is commonly
used with circuit prime of cardiopulmonary bypass. The amount usually
administered is 0.5-1 g/kg . The diuretic effect of mannitol continue for up to
12 h. It is classified as an osmatic diuretic.
