The script makes it clear that the stasis unit Picard has requested isn't normally intended for medical use but is in fact some manner of scientific study apparatus (perhaps for storing gases or samples from nebulae) and that the unit can be jerry-rigged to work as a crude medical stasis chamber, presumably because they both work on the same scientific principles;
BEVERLY : Captain... Arkaria Base does not have the medical storage units I requested. I have seven living tissue samples that
won't survive the baryon sweep anymore than you or I would. I've tried
to reason with them, but --
PICARD : Have Mister LaForge transport a stasis unit from the astrophysics lab. You should be able to convert it to store tissue
The key word here is convert.
The excellent (and moderately canon) Star Trek TNG Technical Manual indicates that "stasis" technology works by slowing atomic motion, something which would be invaluable in the study of various forms of matter and antimatter found in astrophysical phenomena;
The technology that has given rise to the QCRD is similar to that of the transporter, SIF, IDF, and other devices that manipulate matter on
the quantum level. The conversion process sees the inlet of normal
matter, stretched out into thin rivulets no more than 0.000003 cm
across. The rivulets are pressure-fed into the QCRD under magnetic
suspension, where groups of them are chilled to within 0.001 degree of
absolute zero, and exposed to a short-period stasis field to further
limit molecular vibration. As the stasis field decays, focused
subspace fields drive deep within the subatomic structure to flip the
charges and spins of the "frozen" protons, neutrons, and electrons.
The flipped matter, now antimatter, is magnetically removed for
storage. The system can normally process 0.08 m3/hr.