what are vitamin b12 injections used for Injections: You Need To Know Vitamin B12 Injections: Hot Shots?

Cardiac output eventually returns to normal, plasma and extracellular fluid values return to slightly less than normal, but peripheral vascular resistance is reduced, resulting in lower blood pressure

Thats a subtle but important difference

The commenters stated that the current APC assignment does not adequately reflect the resource costs associated with these specialized contrast-enhanced ultrasound procedures

A commenter supported CMS' proposal to utilize this measure as specified with anonymous administration, supplying potential data collection options to address the anonymity requirement while emphasizing that the measure is evidence-based, has been tested to show moderate reliability, and has been endorsed by a CBE for the hospital outpatient department setting and has been adopted for the Hospital OQR Program

So on the narrow question does it stop working after N weeks, the honest answer is: no published evidence says it does, and the mechanism actually argues against it

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