You'll be more successful at repotting houseplants from soil to hydroponics if you have a basic understanding of how plants grow.
The process plants use to grow is called photosynthesis (see box below.)
Photosynthesis - How Plants Grow
Water and minerals are absorbed at the roots and travel up to the plant's leaves. Using energy from the sun, the plant combines these elements with other chemical compounds to manufacture starch and sugar, which it uses to build new cells. During this process the leaves release oxygen and water vapor into the air. This is called photosynthesis.
The important part to understand here is "during photosynthesis plants release oxygen and moisture into the air." Releasing moisture and oxygen into the air is called "transpiration".
Transpiration (moisture and oxygen released into the air) accounts for 90% of the water used by a plant!
The plant's roots are called on to send water up to the leaves to replace the moisture lost. This is a big job for new roots!
The key to successful repotting from soil to hydropoinics is keeping moisture in the leaves by slowing the transpiration process.
Transpiration can be slowed by temperature and humidity. Cool temperatures at the leaves will slow the rate of transpiration naturally. Air temperatures in the 60-70 degree range is ideal.
Adequate humidity is also critical because dry air increases the rate of transpiration significantly. This forces new roots to function faster than they're capable of, stressing the plant.
Boost the humidity and your new transplant will benefit. For best results, try for humidity levels of at least 60% or more.
This is why large plants are more difficult to transfer. They have lots of leaves releasing lots of moisture, and removing the soil from the roots interrupts the flow of moisture up to the leaves. The plant becomes stressed and starts dropping leaves for survival.
Now that you have a general idea of how plants work, you'll have a better idea of what to do if your plant becomes stressed and transplanting from soil to hydroponics will be easier.