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PubMed1975

Blood substitutes.

Substitutes for whole blood include blood fractions such as plasma, serum albumin and other fluids of various kinds which are not derived from blood but are used as plasma volume expanders; these, include the usual crystaloid intravenous solutions. Since in comparison to blood far more of these later solutions are given intravenously, a thorough knowledge of plasma volume expanders is essential. The first use of such expanders in human patients was by Hogan in 1915. He used colloidal gelatin and noted an improvement in blood pressure in shock. In 1945, Gronwall and Ingelman advocated the use of dextran in shock. The reguirements for an acceptable plasma substitute are: a satisfactory colloidal osmotic pressure, constand composition at reasonable cost, a viscosity suitable for intravenous administration, stability in prolonged storage at variable temperatures, and sterilization by autoclaving. Such substances must be either fully excreted or metabolized, and must cause no early or late tissue damage. They must be non-antigenic and pyrogen free. They must cause no change in the blood such as haemolysis, R.B.C. agglutination, increased sedimentation rate and no impairment of haemostasis. The presently available plasma expanders include blood derivatives (plasma, albumin), modified protein (gelatin, oxypolygelatin), polymerized carbohydrates (dextran) and plastics (polyvinyl pyrrolidone-PVP). All these substances expand plasma volume, decrease haematocrit and plasma proteins, increase sedimentation rate and blood pressure. Dextran, PVP and geletin do not alter hepatic function. Dextran and gelatin have no deleterious effects on renal function. Features of the clinically used plasma expanders are: 1. Fresh Frozen Plasma Fresh frozen plasma contains all clotting factors except platelets. The risk of the transmission of hepatitis is present as it is with whole blood. 2. Plasma Protein Fractions Plasma protein fractions are free of hepatitis virus, but may cause arteriolar dilatation and hypotension. 3. Serum Albumin Serum albumin is a concentrated blood protein fraction. It is salt poor, stable and does not transmit the virus of hepatitis. Since it has a high oncotic pressure it is necessary to give significant quantities of clear fluids with it. It is expensive, scarce, and dilutes the clotting factors. It is, however, a first choice for emergency treatment of shock; 4. Dextran The dextrans may be of medium or low molecular weight. They are inexpensive and readily available, and do not transmit the virus of hepatitis. In large amounts they cause a coagulation defect and may be antigenic. Continued.

Blood Proteins↗
PubMed1979

Hemodilution and oxygen transport to tissue in shock.

Shock was induced in sixty dogs by laparotomy, splenectomy and exteriorization of the small intestine for three hours. Resuscitation following different plasma substitutes was assessed by measuring hemodynamic parameters (mean arterial blood pressure, plasma volume, oxygen consumption, cardiac output and hematocrit). To justify a comparison, the colloids (albumin, ACD-plasma, dextran 40, dextran 70, gelatine) were given at the same concentration and dose (3.5 % solutions in saline at a dose of 1.5 g/kg or 43 ml/kg). Ringer's acetate was given in a three times larger volume (129 ml/kg). After reposition of the intestine, the infusion was given over a 20 minute period. During shock hemoconcentration developed, increasing from 50 to 59 % in hematocrit; mean arterial blood pressure dropped from 144 to 95 mm Hg; plasma volume decreased to 67 %; total body oxygen consumption decreased to 59 % and cardiac output to 21 % of initial values. Reposition of the intestine did not in itself improve these values. Ringer's acetate was effective up to about 30 minutes after infusion but did not differ from no infusion at four hours. Gelatine and ACD-Plasma had a similar effect up to two hours. Albumin, dextran 40 and dextran 70 increased and maintained plasma volume and oxygen consumption at preexperimental levels for up to at least four hours. It is concluded that a single infusion of albumin, dextran 40 or dextran 70 is superior to ACD-plasma gelatine or Ringer's acetate in restoring and maintaining oxygen consumption and hemodynamic functions, when given in comparable doses and volumes.

Animals↗
PubMed1975

Artificial blood and the National Blood Policy.

Artificial blood will become important to the extent that it is safer, more effective, more economical, and more readily available than natural substances. If physicians would accept blood substitutes, their use might help to eliminate prevailing shortages of blood and increasing needs for plasma. The high demand for albumin, one of the safest biologics known, is pushing the requirement for plasma to higher levels every year. The albumin situation illustrates both the value placed on hemotherapeutic agents of proven safety and the problem of mobilizing sufficient blood resources for their production. The solutions to this problem and others addressed by the National Blood Policy will involve both scientific efforts and improvements in the operation and organization of blood service systems. Thus, the search for blood and plasma substitutes must be viewed as just one of a set of management and scientific approaches to meeting the need for safe, effective hemotherapuetic agents.

Blood Banks↗