HETASTARCH
Chemistry - A synthetic polymer derived from a waxy starch, hetastarch is composed primarily ofamylopectin. To avoid degradation by serum amylase, hydroxyethyl ether groups are added to theglucose units. It has an average molecular weight of 450, 000, but ranges in size from about MW10, 000 - 1, 000, 000. Hetastarch occurs as a white powder. It is very soluble in water and insoluble inalcohol. Hetastarch may also be known as hydroxyethyl starch or HES.
The commercially available colloidal solution appears as a clear, pale yellow to amber solution. In500 ml of the commercial preparation containing hetastarch 6% and 0.9% sodium chloride, thereare 77 mEq of sodium and chloride. It has an osmolality of 310 mOsm/L and a pH of about 5.5.
Uses, Indications - In hypovolemic patients where total protein is less than 3.5 g/dl and crystalloidtherapy is likely to reduce this level further, colloid therapy (plasma, dextran or hetastarch) shouldbe considered as part of intravascular volume restoration. It is often used when colloid therapy isrequired and blood products are unavailable or when time is of the essence and the wait for crossmatching is unacceptable. Because of the expense, hetastarch is generally used only in small animals.
Because of the danger of volume overload, use of hetastarch for the treatment of of shock notaccompanied by hypovolemia may be hazardous. As it has no oxygen carrying capacity, hetastarchis not a replacement for whole blood or red blood cells.
Because of its effect on platelets, hetastarch should be used with caution in patients with thrombocytopenia and it should be used with extreme caution in patients undergoing CNS surgery.
Because of its effects on indirect serum bilirubin levels, hetastarch should be used with caution in patients with liver disease.
Because of the threat of volume overload, hetastarch should be used in caution in patients with renal dysfunction, congestive heart failure or pulmonary edema.
Hetastarch's safety during pregnancy has not been established, but no untoward effects have apparently been reported thus far.
When given via rapid infusion to cats, hetastarch may cause signs of nausea and vomiting. Ifadministered over 15-30 minutes, these signs are eliminated. At recommended dosages, hetastarchmay cause minor changes in clotting times and platelet counts due to direct (precipitation of factor
VIII) and dilutional causes. Clinically these effects are usually insignificant, but patients withpreexisting coagulapathies may be predisposed to further bleeding.
In humans, increases in serum indirect bilirubins have occurred occasionally in humans. No effecton other liver function tests were noted and the increases subsided over several days. Serumamylase levels may be falsely elevated for several days after hetastarch is administered. Whileclinically insignificant, the changes may preclude using serum amylase to diagnosis or monitorpatients with acute pancreatitis.
Circulatory overload leading to pulmonary edema is possible, particularly when large dosages areadministered to patients with diminished renal function. Do not give intramuscularly as bleeding, bruising, or hematomas may occur.
Overdosage - Overdosage could result in volume overload in susceptible patients. Dose andmonitor fluid status carefully.
The commercially available colloidal solution appears as a clear, pale yellow to amber solution. In500 ml of the commercial preparation containing hetastarch 6% and 0.9% sodium chloride, thereare 77 mEq of sodium and chloride. It has an osmolality of 310 mOsm/L and a pH of about 5.5.
Storage, Stability, Compatibility
Hetastarch 6% in 0.9% NaCl should be stored at temperaturesless than 40°C; freezing should be avoided. Exposure to temperature extremes may result in formation of a crystalline precipitate or a color change to a turbid deep brown. Should this occur, do not use.Pharmacology - HETASTARCH
Hetastarch acts as a plasma volume expander by increasing the oncotic pressurewithin the intravascular space similarly to either dextran or albumin. Maximum volume expansionoccurs within a few minutes of the completion of infusion. Duration of effect is variable, but maypersist for 24 hours or more. When added to whole blood in humans, hetastarch causes an increasein erythrocyte sedimentation rate.Uses, Indications - In hypovolemic patients where total protein is less than 3.5 g/dl and crystalloidtherapy is likely to reduce this level further, colloid therapy (plasma, dextran or hetastarch) shouldbe considered as part of intravascular volume restoration. It is often used when colloid therapy isrequired and blood products are unavailable or when time is of the essence and the wait for crossmatching is unacceptable. Because of the expense, hetastarch is generally used only in small animals.
Pharmacokinetics - HETASTARCH
Lower molecular weight molecules (less than 50, 000) are rapidly excreted bythe kidneys, larger molecules are slowly degraded enzymatically to a size where they then can beexcreted. About 40% of a dose is excreted in the first 24 hours after infusion. After about 2 weeks, practically all the drug is excreted.Contraindications, Precautions, Reproductive Safety
In humans, hetastarch is contraindicatedin patients with severe heart failure, severe bleeding disorders and patients in oliguric or anuric renalfailure.Because of the danger of volume overload, use of hetastarch for the treatment of of shock notaccompanied by hypovolemia may be hazardous. As it has no oxygen carrying capacity, hetastarchis not a replacement for whole blood or red blood cells.
Because of its effect on platelets, hetastarch should be used with caution in patients with thrombocytopenia and it should be used with extreme caution in patients undergoing CNS surgery.
Because of its effects on indirect serum bilirubin levels, hetastarch should be used with caution in patients with liver disease.
Because of the threat of volume overload, hetastarch should be used in caution in patients with renal dysfunction, congestive heart failure or pulmonary edema.
Hetastarch's safety during pregnancy has not been established, but no untoward effects have apparently been reported thus far.
Adverse Effects, Warnings
Hetastarch can affect platelet function and clotting tests can be transiently prolonged. It is less antigenic than dextran, but can cause sensitivity reactions and interfere with antigen-antibody testing. Anaphylactic reactions and coagulopathies are considered to occur rarely, however.When given via rapid infusion to cats, hetastarch may cause signs of nausea and vomiting. Ifadministered over 15-30 minutes, these signs are eliminated. At recommended dosages, hetastarchmay cause minor changes in clotting times and platelet counts due to direct (precipitation of factor
VIII) and dilutional causes. Clinically these effects are usually insignificant, but patients withpreexisting coagulapathies may be predisposed to further bleeding.
In humans, increases in serum indirect bilirubins have occurred occasionally in humans. No effecton other liver function tests were noted and the increases subsided over several days. Serumamylase levels may be falsely elevated for several days after hetastarch is administered. Whileclinically insignificant, the changes may preclude using serum amylase to diagnosis or monitorpatients with acute pancreatitis.
Circulatory overload leading to pulmonary edema is possible, particularly when large dosages areadministered to patients with diminished renal function. Do not give intramuscularly as bleeding, bruising, or hematomas may occur.
Overdosage - Overdosage could result in volume overload in susceptible patients. Dose andmonitor fluid status carefully.