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Effect of hemodilution on cochlear blood flow measured by laser-Doppler flowmetry
Insights
Hemodilution significantly increases cochlear blood flow in guinea pigs by reducing blood viscosity. This effect is most pronounced when hematocrit levels are around 20%, with minimal impact on blood pressure until lower levels.
Area of Science:
- Otolaryngology
- Physiology
- Cardiovascular Research
Background:
- Cochlear blood flow is crucial for auditory function.
- Hemodilution techniques are used to alter blood properties.
- Understanding hemodilution's impact on cochlear circulation is vital.
Purpose of the Study:
- To investigate the effects of hemodilution on cochlear blood flow in guinea pigs.
- To compare hypervolemic and normovolemic hemodilution methods.
- To assess the relationship between hematocrit levels and cochlear blood flow.
Main Methods:
- Guinea pigs underwent hypervolemic hemodilution using dextran 40.
- Normovolemic hemodilution was performed using dextran 75 exchange transfusions.
- Cochlear blood flow was measured using laser-Doppler flowmetry.
- Hematocrit and blood pressure were monitored throughout the study.
Main Results:
- Cochlear blood flow increased as hematocrit decreased, peaking at ~200% with hematocrit near 20%.
- Blood pressure remained stable until hematocrit dropped below 15%.
- Normovolemic hemodilution with dextran 75 showed fewer systemic disturbances and a more sustained effect than dextran 40.
Conclusions:
- Hemodilution enhances cochlear blood flow, likely due to reduced blood viscosity and increased cardiac output.
- Normovolemic hemodilution with dextran 75 is a preferable method for its systemic stability and duration.
- Findings support the role of hemodilution in managing cochlear blood flow.
Abstract:
The effect of hemodilution on cochlear blood flow was studied in guinea pigs. Hypervolemic hemodilution was accomplished by infusion of 10 mg/kg of body weight of dextran 40 (as a 10% solution in normal saline), which resulted in an average hematocrit decrease from 43 to 32%. Normovolemic hemodilution was accomplished by repeated exchange of 3 ml of whole blood with 3 ml of dextran 75 (6% solution in normal saline) every 5 minutes until the hematocrit reached approximately 5%. The cochlear blood flow was measured by laser-Doppler flowmetry. Irrespective of the dilutional technique, the cochlear blood flow increased as hematocrit decreased to a maximum of approximately 200% of original value at a hematocrit near 20%. The blood pressure was not significantly influenced by the hemodilution until hematocrit values below 15% were reached. The enhancement of cochlear blood flow is consistent with the expected reduction of blood viscosity and increase of cardiac output. Normovolemic hemodilution with dextran 75 causes a smaller disturbance of systemic circulation physiology and has a more lasting effect than dextran 40 infusion.