1. Clinical Overview
Hydroxyethyl starch (HES) 6% w/v is a synthetic, colloidal plasma volume expander derived from waxy maize or potato starch. It is a polydisperse solution of hydroxyethyl-substituted amylopectin with a molar substitution (MS) typically around 0.4-0.5 (e.g., HES 130/0.4 or HES 200/0.5). In the Indian context, it is primarily used for intravascular volume replacement in hypovolemic states, particularly in surgical and critical care settings. Its use has become more restricted globally and in India due to emerging safety concerns regarding renal impairment and mortality in septic and critically ill patients.
| Onset | Duration | Bioavailability |
|---|---|---|
| Immediate upon intravenous infusion. | Volume expansion effect lasts 4 to 6 hours, depending on the specific HES type (e.g., HES 130/0.4 has a shorter duration than HES 200/0.5). | 100% (administered intravenously). |
2. Mechanism of Action
HES molecules are large, osmotically active polymers that, when infused intravenously, increase the colloid osmotic pressure (oncotic pressure) in the intravascular compartment. This creates an osmotic gradient that draws fluid from the interstitial space into the bloodstream, thereby expanding plasma volume. The volume-expanding effect is greater than the volume infused (plasma expansion effect of 100-140% of the infused volume).
3. Indications & Uses
- Treatment of hypovolemia (volume deficiency) when crystalloids alone are not sufficient or considered inadequate.
- Plasma volume expansion in the setting of acute blood loss (e.g., trauma, surgery).
4. Dosage & Administration
Adult Dosage: Initial dose: 500-1000 mL (approx. 10-20 mL/kg) administered by IV infusion. The total daily dose should generally not exceed 33 mL/kg (approx. 2000-2500 mL for a 70 kg adult). Infusion rate is adjusted based on hemodynamic response (BP, CVP, urine output).
Administration: For IV infusion only. Use a sterile infusion set. Can be administered without dilution. Must be inspected for particulate matter and discoloration before use. Do not mix with other drugs in the same infusion line/bag. The infusion rate should be titrated to the patient's hemodynamic status (BP, heart rate, CVP). Monitor urine output, renal function, and coagulation parameters closely.
5. Side Effects
Common side effects may include:
- Dilutional coagulopathy (increased bleeding time, aPTT).
- Hemodilution (decreased hematocrit, serum proteins).
- Pruritus (itching), often severe and delayed onset (weeks after infusion), due to tissue storage.
- Mild fluid overload.
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Anticoagulants (Heparin, Warfarin, DOACs) | Additive effect on coagulation impairment, increasing risk of bleeding. | Major |
| Antiplatelet drugs (Aspirin, Clopidogrel) | Increased risk of bleeding. | Moderate |
| ACE Inhibitors (e.g., Ramipril, Enalapril) | Increased risk of anaphylactoid reactions. | Moderate |
| Diuretics (Furosemide) | Concomitant use may enhance diuresis but also increase risk of renal impairment. | Moderate |
| Other Plasma Expanders (Albumin, Gelatins) | Additive volume expansion effect, risk of overload. | Moderate |
7. Patient Counselling
- Inform your doctor about any history of kidney disease, heart disease, liver problems, or bleeding disorders.
- Report any itching that develops, especially if it starts days or weeks after the infusion.
- Inform all healthcare providers that you have received HES, especially if surgery is planned later.
8. Toxicology & Storage
Overdose: Symptoms of severe hypervolaemia: acute pulmonary edema, dyspnea, tachycardia, hypertension followed by hypotension, peripheral edema, congestive heart failure. Coagulopathy leading to bleeding. Severe electrolyte imbalances.
Storage: Store below 25°C. Do not freeze. Protect from light. Keep the container in the outer carton. The solution should be clear and slightly yellow. Do not use if the solution is cloudy, discolored, or contains particles. Once the infusion bag/bottle is opened, use immediately. Discard any unused portion.