The failed moderate sedation code would be to indicate that is the reason you are not billing for example 99144 and are billing 01936 done by a separate provider using MAC or general anesthesia, but this might be something that the provider fails to documents the reason conscious sedation can not be used and instead MAC or general by a separate provider.
With other specified anxiety disorders, I think "other" versus "unspecified" would be for a condition that ICD-10 does not have a specific entry to describe the condition, I don't know if having anxiety about having a needle placed in your spinal region is a condition or more just a general concern about the pain that has to be endured and the concern about dural puncture or other complications that could result. So I think other or unspecified would be ok but Anxiety NOS (not otherwise specified) the generic form of having anxiety about having injection procedure can be just an unspecified code. And not think that the clearinghouse will be holding the claim for that diagnosis. Below is excerpt from AIHMA & CMS regarding unspecified ICD-10 codes and the coverage. In regards to Z79.891, I think Z79.891 might mean the patient has had tolerance for certain medications that might affect a response to a lower level of sedation for the patient.
F41.8
Other specified anxiety disorders
Anxiety depression (mild or not persistent)
Anxiety hysteria
Mixed anxiety and depressive disorder
Below is a CMS link
https://www.cms.gov/Medicare/Coding/ICD10/Downloads/ICD-10Overview.pdf
In both ICD-9-CM and ICD-10-CM, sign/symptom and unspecified codes have acceptable, even necessary, uses. While you should report specific
diagnosis codes when they are supported by the available medical record documentation and clinical knowledge of the patient’s health condition, in some instances signs/ symptoms or unspecified codes are the best choice to accurately reflect the health care encounter. You should code each health care encounter to the level of certainty known for that encounter.
If a definitive diagnosis has not been established by the end of the encounter, it is appropriate to report codes for sign(s) and/or symptom(s) in lieu of a definitive diagnosis. When sufficient clinical information is not known or available about a particular health condition to assign a more specific code, it is acceptable to report the appropriate unspecified code (for example, a diagnosis of pneumonia has been determined but the specific type has not been determined). In fact, you should report unspecified codes when such codes
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most accurately reflect what is known about the patient’s condition at the time of that particular encounter. It is inappropriate to select a specific code that is not supported by the medical record documentation or to conduct medically unnecessary diagnostic testing to determine a more specific code.
Below is from AIHMA
http://bok.ahima.org/PdfView?oid=300625
Using Sign/Symptom and Unspecified Codes
Sign/symptom and “unspecified” codes have acceptable, even necessary, uses. While specific
diagnosis codes should be reported when they are supported by the available medical record documentation and clinical knowledge of the patient’s health condition, there are instances when signs/symptoms or unspecified codes are the best choices for accurately reflecting the healthcare encounter. Each healthcare encounter should be coded to the level of certainty known for that encounter.
If a definitive diagnosis has not been established by the end of the encounter, it is appropriate to report codes for sign(s) and/or symptom(s) in lieu of a definitive diagnosis. When sufficient clinical information is not known or available about a particular health condition to assign a more specific code, it is acceptable to report the appropriate “unspecified” code (e.g., a diagnosis of pneumonia has been determined, but not the specific type). Unspecified codes should be reported when they are the codes that most accurately reflects what is known about the patient’s condition at the time of that particular encounter. It would be inappropriate to select a specific code that is not supported by the medical record documentation.