Dr. Mark R Slack , MD
Anesthesiology โข Manassas, VA
8700 Sudley Rd
Manassas, VA 201104418
This profile restates public CMS/NPPES data; T-MedInfo gives no medical advice — consult a licensed professional, and call 911 for emergencies.
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NPI assigned on July 11, 2006; this date does not establish years in practice.
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Published CMS data list 47 Original Medicare Part B services in 2024.
Source: CMS, Medicare Physician & Other Practitioners โ by Provider and Service, 2024. Published rows only; this is not a quality measure.
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Published Part B service records, 2024:
- 00142 โ Anesthesia for lens surgery: 16 service units.
- 00811 โ Anesthesia for other procedure on large bowel using an endoscope: 16 service units.
- 00731 โ Anesthesia for other procedure on esophagus, stomach, or upper small bowel using an endoscope: 15 service units.
Source: CMS, Medicare Physician & Other Practitioners โ by Provider and Service, 2024. Units differ by code; these are not visits or a measure of quality.
CPTยฎ only copyright 2023 American Medical Association. All rights reserved. Service names are shortened from CPT Consumer Friendly Descriptors (CMS data, 2024). CPT notice
See the full table ยท Guide: How to read Medicare Part B data
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Fewer Medicare Part B services than 95% of clinicians listed under Anesthesiology in Manassas, VA (2024, 11 clinicians with data). Median for this group: 136. Middle half: 93 to 280.
Fewer Medicare Part B services than 85% of clinicians listed under Anesthesiology in Virginia (2024, 795 clinicians with data). Median for this group: 165. Middle half: 75 to 288.
Source: CMS, Medicare Physician & Other Practitioners โ by Provider and Service, 2024. Billing and prescribing volume is not a quality rating.
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Medicare Part B services went from 19 in 2019 to 47 in 2024.
Source: CMS, Medicare Physician & Other Practitioners โ by Provider and Service, 2019โ2024.
Practice Location & Contact Primary Location
8700 Sudley Rd
Manassas, VA 201104418
Matched by practice address or phone in NPPES. A shared address or phone does not confirm that this clinician works there.
What Public CMS Data Show
Anesthesiology: NPPES taxonomy is a reported classification, not proof of board certification.
Medicare patients
91 people with Original Medicare in 2024
It gives a sense of how many people with Medicare this clinician treated that year.
Source: CMS, Medicare Physician & Other Practitioners โ by Provider, 2024.
Medicare-allowed amount
About $5,572 in 2024
The total amount Medicare approved for these services in 2024. It includes what Medicare paid and what patients or their other insurance owed, such as the deductible and coinsurance.
It shows the total cost of this clinician's Original Medicare services under Medicare's fee rules.
What this does not show: Medicare-allowed amount
This is not the clinician's income. Part of it can go to a clinic or group practice, staff, equipment or drugs. It is not the price you will pay.
Source: CMS, Medicare Physician & Other Practitioners โ by Provider and Service, 2024.
Paid by Medicare
About $4,251 in 2024
The part of the Medicare-allowed amount that Medicare itself paid in 2024, after patients' deductibles and coinsurance.
The gap between the allowed amount and this number is roughly what patients and their other insurance paid.
What this does not show: Paid by Medicare
This is not the clinician's income and not a measure of quality.
Source: CMS, Medicare Physician & Other Practitioners โ by Provider and Service, 2024.
Industry payments (Open Payments)
No Open Payments records are listed for this clinician for 2019โ2025.
NPI first issued
2006
The year this clinician's National Provider Identifier (NPI) was issued. An NPI is a unique 10-digit ID that US health care providers use for billing.
What this does not show: NPI first issued
NPIs have been issued only since 2005, so this year is not necessarily when the clinician started practicing.
Source: CMS NPPES NPI Registry.
Medicare assignment not listed
CMS data do not show whether this clinician accepts Medicare assignment. This does not mean they do not accept Medicare. Ask the office.
Medicare assignment applies to Original Medicare. It does not tell you whether the clinician is in a Medicare Advantage plan's network, accepts other insurance, or is taking new patients.
Source: CMS Doctors and Clinicians; Medicare.gov, โDoes your provider accept Medicare as full payment?โ
No telehealth indicator
CMS shows this indicator only when recent Medicare claims include telehealth services. The clinician may still offer telehealth; ask the office.
Source: CMS, Telehealth Indicator on Medicare Care Compare (fact sheet, January 2023); CMS Doctors and Clinicians.
Can order Medicare-covered services
CMS lists Dr. Slack as eligible to order or refer durable medical equipment (DME) for people with Medicare.
Medicare pays for these items and services only when they are ordered by an eligible clinician.
What this does not show: Can order Medicare-covered services
It does not mean the clinician offers these services directly.
Source: CMS Medicare Fee-For-Service Public Provider Enrollment (PECOS); CMS Order and Referring file.
Compared with the same specialty in Manassas and Virginia
Billing and prescribing volume is not a quality rating.
Medicare Part B services
Fewer Medicare Part B services than 95% of clinicians listed under Anesthesiology in Manassas, VA (2024, 11 clinicians with data). Median for this group: 136. Middle half: 93 to 280.
Fewer Medicare Part B services than 85% of clinicians listed under Anesthesiology in Virginia (2024, 795 clinicians with data). Median for this group: 165. Middle half: 75 to 288.
Medicare-allowed amount
A lower Medicare-allowed amount than 95% of clinicians listed under Anesthesiology in Manassas, VA (2024, 11 clinicians with data). Median for this group: $16,509. Middle half: $8,064 to $22,495.
A lower Medicare-allowed amount than 80% of clinicians listed under Anesthesiology in Virginia (2024, 795 clinicians with data). Median for this group: $18,247. Middle half: $8,186 to $31,387.
Paid by Medicare
A lower Medicare payment amount than 95% of clinicians listed under Anesthesiology in Manassas, VA (2024, 11 clinicians with data). Median for this group: $12,393. Middle half: $6,686 to $17,626.
A lower Medicare payment amount than 80% of clinicians listed under Anesthesiology in Virginia (2024, 795 clinicians with data). Median for this group: $14,436. Middle half: $6,510 to $24,871.
15 active clinicians are listed under Anesthesiology with a practice address in Manassas, VA (1,455 in Virginia).
Addresses are self-reported to NPPES and may be out of date.
Telehealth indicator in Manassas
0% of these 15 clinicians have the CMS telehealth indicator.
60% of these 15 clinicians are listed by CMS as accepting Medicare assignment.
CMS data by year
Changes may reflect reporting, coverage or privacy limits, not changes in care quality.
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Medicare Part B services
Medicare Part B services went from 19 in 2019 to 47 in 2024.
- 2019: 19
- 2021: 34
- 2022: 209
- 2023: 88
- 2024: 47
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Medicare-allowed amount
Medicare-allowed amount increased 113% from $2,611 in 2019 to $5,572 in 2024.
- 2019: $2,611
- 2021: $4,621
- 2022: $18,372
- 2023: $8,174
- 2024: $5,572
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Paid by Medicare
Paid by Medicare increased 102% from $2,109 in 2019 to $4,251 in 2024.
- 2019: $2,109
- 2021: $3,705
- 2022: $14,811
- 2023: $6,657
- 2024: $4,251
Sources: CMS Medicare Physician & Other Practitioners (2024), CMS Doctors and Clinicians, CMS NPPES NPI Registry. Specialty names follow the NUCC Health Care Provider Taxonomy.
Text: T-MedInfo ยท Report an error.
Performed Procedures & Service Volume
CPTยฎ is a registered trademark of the American Medical Association. CPT codes, descriptions and other data only are copyright 2018โ2023 American Medical Association. All rights reserved. Applicable FARS/HHSARS apply. Descriptions of CPT codes are the AMA's CPT Consumer Friendly Descriptors as published by CMS in the Medicare Physician & Other Practitioners โ by Provider and Service data, 2019โ2024; they are plain-language summaries, not for clinical coding or documentation. HCPCS Level II codes and descriptions are from CMS. Fee schedules, relative value units, conversion factors and/or related components are not assigned by the AMA, are not part of CPT, and the AMA is not recommending their use. The AMA does not directly or indirectly practice medicine or dispense medical services. The AMA assumes no liability for data contained or not contained herein.
| HCPCS Code | Services | Patients | Submitted Charge | Medicare Allowed |
|---|---|---|---|---|
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00142
Anesthesia for lens surgery
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16 | 16 | $1272.22 | $106.99 |
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00811
Anesthesia for other procedure on large bowel using an endoscope
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16 | 16 | $1377.14 | $118.79 |
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00731
Anesthesia for other procedure on esophagus, stomach, or upper small bowel using an endoscope
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15 | 15 | $1510.92 | $130.66 |
Source: CMS Part B by Provider and Service, 2024; services under 11 beneficiaries omitted by CMS. Privacy limits
Submitted charges are billed amounts, not a price quote for your visit.
Specialties & License Numbers Reported to NPPES
NUCC Taxonomy Code: 207L00000X
An anesthesiologist is trained to provide pain relief and maintenance, or restoration, of a stable condition during and immediately following an operation or an obstetric or diagnostic procedure. The anesthesiologist assesses the risk of the patient undergoing surgery and optimizes the patient's condition prior to, during and after surgery. In addition to these management responsibilities, the anesthesiologist provides medical management and consultation in pain management and critical care medicine. Anesthesiologists diagnose and treat acute, long-standing and cancer pain problems; diagnose and treat patients with critical illnesses or severe injuries; direct resuscitation in the care of patients with cardiac or respiratory emergencies, including the need for artificial ventilation; and supervise post-anesthesia recovery.
Additional State Medicaid & Healthcare Payer Identifiers
Medicare (PECOS) Enrollment & Ordering Eligibility
Source: CMS PECOSSources: CMS Provider Enrollment and Order and Referring. Medicare enrollment is a billing status, not an accreditation or quality rating.
Clinicians Sharing This Practice Address or Phone
Clinicians sharing this NPPES address, phone or fax; a shared contact does not mean they work together.
Internal Medicine - Gastroenterology
Doctor of Medicine (M.D.)
Emergency Medicine
Doctor of Medicine (M.D.)
Nurse Anesthetist, Certified Registered
Certified Registered Nurse Anesthetist
Nurse Anesthetist, Certified Registered
Certified Registered Nurse Anesthetist
Radiology - Diagnostic Radiology
Doctor of Medicine (M.D.)
Physician Assistant
Physician Assistant (Certified)
Career & Practice History Timeline
Changes recorded in monthly NPPES data files: addresses, names, credentials, specialties and NPI status
NPI status registered as active in NPPES database
Registered at 8700 SUDLEY RD, MANASSAS, VA 201104418 (Tel: 7033698000)
Registered at 3100 SPRING FOREST RD, STE 130, RALEIGH, NC 276162880 (Tel: 9198827908)
Recorded as MARK SLACK, MD
Anesthesiology (license number reported to NPPES: VA 0101044713)
NPI status registered as active in NPPES database
Registered at 1330 MURRAY DOWNS WAY, RESTON, VA 201941435 (Tel: 7036893776)
Registered at 1330 MURRAY DOWNS WAY, RESTON, VA 201941435 (Tel: 7036893776)
Recorded as MARK SLACK, MD
Anesthesiology (license number reported to NPPES: VA 0101044713)
First registered as active Individual Practitioner in NPPES Database.
NPI Administrative Meta
Other Anesthesiology Specialists in Manassas
- Dr. Ivan Harangozo, MD
- Dr. Luke Andries, MD
- Dr. Lee Eric Lorico, MD
- Dr. Alla Druker, MD
- Dr. Bindu Muthu, MD
- Dr. Robert Davis, MD
Mailing Address
3100 Spring Forest Rd, Ste 130
Raleigh, NC 276162880
Phone: 9198827908