<PAGE>
                                                                  EXHIBIT 10.15


                      FIRST AMENDMENT TO CREDIT AGREEMENT


         THIS FIRST AMENDMENT TO CREDIT AGREEMENT (this "Amendment"), dated
January 30, 2004, is made and entered into on the terms and conditions
hereinafter set forth, by and among SYMBION, INC., a Delaware corporation, the
several lenders who are parties to the Credit Agreement (as hereinafter
defined), as lenders (the "Lenders"), and BANK OF AMERICA, N.A., a national
banking association ("Bank of America"), as administrative agent for the Lenders
and the Issuing Bank (in such capacity, the "Administrative Agent") and as
Issuing Bank.

                                   RECITALS:

         1.       Pursuant to a Credit Agreement dated as of July 18, 2003,
among the Borrower, the Lenders party thereto and Bank of America, as
Administrative Agent and as Issuing Bank (as the same heretofore has been or
hereafter may be further amended, restated, supplemented, extended, renewed,
replaced or otherwise modified from time to time, the "Credit Agreement"), the
Lenders agreed to make Loans to the Borrower and to purchase participations in
Letters of Credit issued for the account of the Borrower, and the Issuing Bank
agreed to issue such Letters of Credit, all as more specifically described in
the Credit Agreement.

         2.       The parties hereto desire to amend the Credit Agreement in
certain respects, as more particularly hereinafter set forth.

                                  AGREEMENTS:

         NOW, THEREFORE, in consideration of the mutual covenants and
agreements hereinafter set forth, and for other good and valuable
consideration, the receipt and sufficiency of all of which are hereby
acknowledged, the parties hereto agree as follows:

         1.       AMENDMENT OF SECTION 1.1. Section 1.1 of the Credit Agreement
is hereby amended by amending and restating the existing definitions of the
terms identified below to read as follows:

                  "EBITDA" shall mean, for the Borrower and its Subsidiaries on
         a consolidated basis for any period, the sum of Consolidated Net
         Income plus (a) the following, without duplication and to the extent
         deducted in computing Consolidated Net Income: (1) Interest Expense,
         (2) federal, state, local and foreign income, value-added and similar
         tax expense, (3) depreciation, and (4) amortization of intangible
         assets and other non-cash charges, less (b) any non-cash items
         increasing Consolidated Net Income for such period (except to the
         extent cash relating to such item has been received after the date of
         this Agreement); provided, however, that to the extent that EBITDA
         attributable to Permitted Non-Guarantor Entities exceeds twenty
         percent (20%) of EBITDA for the Borrower and its Subsidiaries on a
         consolidated basis, the excess shall be excluded from "EBITDA" for


<PAGE>
         purposes of determining compliance with the requirements of Sections
         10.1.2, 10.1.3 and 10.1.5.

                  "Permitted Acquisition" shall mean any Asset Acquisition by
         the Borrower or any Subsidiary of the Borrower that complies with all
         of the following requirements, as applicable:

                           (a)      the assets to be acquired shall consist
                  primarily of (i) a Center or (ii) the Capital Stock of a
                  Person whose primary asset is (A) a Center or (B) Capital
                  Stock of a Subsidiary of such Person whose primary asset is a
                  Center;

                           (b)      the Borrower shall have complied with the
                  provisions of Section 8.2.4;

                           (c)      the Borrower or a Subsidiary of the
                  Borrower is the surviving entity in the transaction;

                           (d)      all assets acquired in the transaction are
                  held or acquired by the Borrower or a Person who is or as a
                  part of the transaction will become a Subsidiary of the
                  Borrower and has complied with the provisions of Section 8.18
                  prior to or contemporaneously with the consummation of the
                  transaction;

                           (e)      at the time of such Asset Acquisition and
                  after giving Pro Forma Effect thereto and to any other
                  relevant transaction occurring during the then most recent
                  twelve (12) month period, (1) no Default shall have occurred
                  or be continuing or would result therefrom, and (2) the
                  Senior Funded Indebtedness to EBITDA Ratio shall not exceed
                  2.25 to 1.00, both as confirmed by a certificate of a
                  Responsible Officer of the Borrower in form and substance
                  satisfactory to the Administrative Agent;

                           (f)      with respect to an Asset Acquisition
                  primarily in exchange for cash (including Indebtedness
                  incurred or assumed) (1) the total consideration (including
                  Indebtedness incurred or assumed) for any one Asset
                  Acquisition made pursuant to this clause (f) shall not exceed
                  $15,000,000, and (2) as of the date of such Asset
                  Acquisition, the total consideration (including Indebtedness
                  incurred or assumed) for such Asset Acquisition and all other
                  Asset Acquisitions made pursuant to this clause (f) during
                  the immediately preceding twelve months, together with the
                  aggregate amount of all Investments made in Permitted
                  Non-Guarantor Entities by the Borrower or any of its
                  Subsidiaries during such period, shall not exceed an amount
                  equal to EBITDA for the Last Four Fiscal Quarters (taking
                  into account EBITDA during the Last Four Fiscal Quarters
                  attributable to (i) any Asset Acquisitions made during the
                  Last Four Fiscal Quarters but without giving Pro Forma Effect
                  to such Asset Acquisitions, and (ii) Investments made in
                  Permitted Non-Guarantor Entities during the Last Four Fiscal
                  Quarters), as established pursuant to Compliance Certificates
                  delivered to the Administrative Agent as provided herein; and


                                      -2-
<PAGE>
                           (g)      with respect to an Asset Acquisition
                  primarily in exchange for Capital Stock of the Borrower, (1)
                  if such Capital Stock consists of equity securities other
                  than common stock, all terms, conditions and provisions of
                  those equity securities shall be satisfactory to Requisite
                  Lenders, in their discretion, and (2) as of the date of such
                  Asset Acquisition, the total consideration (including
                  Indebtedness incurred or assumed) for such Asset Acquisition
                  and all other Asset Acquisitions made pursuant to this clause
                  (g) during the immediately preceding twelve months shall not
                  exceed an amount equal to the difference between (x) one
                  hundred fifty percent (150%) of EBITDA for the Last Four
                  Fiscal Quarters (taking into account EBITDA during the Last
                  Four Fiscal Quarters attributable to (i) any Asset
                  Acquisitions made during the Last Four Fiscal Quarters but
                  without giving Pro Forma Effect to such Asset Acquisitions,
                  and (ii) Investments made in Permitted Non-Guarantor Entities
                  during the Last Four Fiscal Quarters), as established
                  pursuant to Compliance Certificates delivered to the
                  Administrative Agent as provided herein, and (y) the sum of
                  (A) the total consideration (including Indebtedness incurred
                  or assumed) paid in connection with all Asset Acquisitions
                  made during such period pursuant to the preceding clause (f)
                  and (B) the aggregate amount of all Investments made by the
                  Borrower or any of its Subsidiaries in Permitted
                  Non-Guarantor Entities during such period.

                  "Permitted Non-Guarantor Entity" shall mean a Person that
         meets all of the following requirements:

                           (a)      Such Person shall be a Person in which the
                  Borrower and its Subsidiaries own Capital Stock, but is not a
                  Subsidiary of the Borrower, and the remaining Capital Stock
                  of which is owned by a hospital or hospital system or
                  individual physicians or Persons owned or controlled by
                  individual physicians.

                           (b)      There shall be no restriction on the
                  ability of such Person to pay dividends or make distributions
                  of its available cash (i.e., cash remaining after debt
                  service, payment of expenses and the establishment of
                  reasonable reserves) to holders of its Capital Stock, other
                  than pursuant to the law under which such Person is
                  organized.

                           (c)      Such Person shall be engaged exclusively in
                  the ownership or operation of a Center.

                           (d)      The aggregate face amount of Contingent
                  Obligations of the Borrower and its Subsidiaries incurred
                  after July 18, 2003 with respect to Indebtedness of such
                  Persons shall not exceed $5,000,000.

                           (e)      As of the date of the making of any
                  Investment by the Borrower or any of its Subsidiaries in a
                  Permitted Non-Guarantor Entity, the aggregate amount of such
                  Investment, together with (1) the aggregate amount of all
                  other Investments by the Borrower or any of its Subsidiaries
                  in Permitted Non-


                                      -3-
<PAGE>
                  Guarantor Entities during the immediately preceding twelve
                  months and (2) the total consideration (including
                  Indebtedness incurred or assumed) for all Asset Acquisitions
                  made pursuant to clause (f) of the definition of "Permitted
                  Acquisition" during such period, shall not exceed an amount
                  equal to EBITDA for the Last Four Fiscal Quarters (taking
                  into account EBITDA during the Last Four Fiscal Quarters
                  attributable to (i) any Asset Acquisitions made during the
                  Last Four Fiscal Quarters but without giving Pro Forma Effect
                  to such Asset Acquisitions, and (ii) Investments made in
                  Permitted Non-Guarantor Entities during the Last Four Fiscal
                  Quarters), as established pursuant to Compliance Certificates
                  delivered to the Administrative Agent as provided herein.

                           (f)      As of the date of the making of any
                  Investment by the Borrower or any of its Subsidiaries in a
                  Permitted Non-Guarantor Entity, the aggregate amount of such
                  Investment, together with (1) the aggregate amount of all
                  other Investments by the Borrower or any of its Subsidiaries
                  in Permitted Non-Guarantor Entities during the immediately
                  preceding twelve months and (2) the total consideration
                  (including Indebtedness incurred or assumed) for all
                  Permitted Acquisitions made during such period, shall not
                  exceed an amount equal to one hundred fifty percent (150%) of
                  EBITDA for the Last Four Fiscal Quarters (taking into account
                  EBITDA during the Last Four Fiscal Quarters attributable to
                  (i) any Asset Acquisitions made during the Last Four Fiscal
                  Quarters but without giving Pro Forma Effect to such Asset
                  Acquisitions, and (ii) Investments made in Permitted
                  Non-Guarantor Entities during the Last Four Fiscal Quarters),
                  as established pursuant to Compliance Certificates delivered
                  to the Administrative Agent as provided herein.

         2.       AMENDMENT OF SECTION 9.3. Section 9.3 of the Credit Agreement
is hereby amended by (a) deleting "and" at the end of clause (d), (b) deleting
the period at the end of clause (e), and substituting in lieu thereof "; and",
and (c) adding the following new clause (f):

                           (f)      the sale of Capital Stock of a Permitted
                  Non-Guarantor Entity if after the sale of such Capital Stock
                  such Permitted Non-Guarantor Entity would continue to
                  constitute a Permitted Non-Guarantor Entity in compliance
                  with all applicable provisions of this Agreement.

         3.       AMENDMENT OF SECTION 10.1.2. Section 10.1.2 of the Credit
Agreement is hereby amended to read as follows:

                  10.1.2.  Funded Indebtedness to EBITDA Ratio. Permit the
         Funded Indebtedness to EBITDA Ratio as of the end of any Fiscal
         Quarter to be greater than 3.00 to 1.00.

         4.       AMENDMENT OF SECTION 10.1.4. Section 10.1.4 of the Credit
Agreement is hereby amended to read as follows:


                                      -4-
<PAGE>
                  10.1.4.  Funded Indebtedness to Capitalization Ratio. Permit
         the Funded Indebtedness to Capitalization Ratio as of the end of any
         Fiscal Quarter to be greater than 0.50 to 1.00.

         5.       AMENDMENT TO SUBSECTION 14.16(B). Subsection 14.16(b) of the
Credit Agreement is hereby amended by adding the following immediately after
the reference to "Section 9.6," in the second line of Section 14.16(b):

                           "or if any Capital Stock of a Permitted
                  Non-Guarantor Entity shall be Disposed of in a transaction
                  permitted by clause (f) of Section 9.3,"

         6.       REPLACEMENT OF EXHIBIT 1.1A. The Credit Agreement is hereby
amended by replacing Exhibit 1.1A thereto with Exhibit 1.1A to this Amendment.

         7.       SPECIAL AGREEMENTS REGARDING SCHEDULED ACQUISITION. It is
understood and agreed that the Scheduled Acquisition regarding Valley ASC, Inc.
shall be disregarded for purposes of the consideration limitations set forth in
paragraphs (f) and (g) of the definition of "Permitted Acquisition" and the
investment limitation set forth in paragraph (d) of the definition of
"Permitted Non-Guarantor Entity". It is further understood and agreed that the
Scheduled Acquisition regarding Valley ASC, Inc. shall be deemed to be a
Permitted Acquisition for purposes of subsection 9.8(a) of the Credit
Agreement.

         8.       EVIDENCE OF AUTHORIZATION, ETC. The Borrower shall provide,
or shall cause to be provided, to the Administrative Agent such evidence
(including but not limited to opinions of legal counsel to the Borrower and the
Guarantors) as the Administrative Agent reasonably may require to confirm (a)
the existence of the Borrower and the Guarantors, (b) the authorization of this
Agreement and the transactions that are the subject hereof, (c) the execution
and delivery by the Borrower and the Guarantors of this Agreement and any
documents executed pursuant hereto or in connection herewith, and (d) the
enforceability against the Borrower and the Guarantors of this Agreement and
any documents executed pursuant hereto.

         9.       CONDITIONS TO EFFECTIVENESS. This Amendment shall be
effective only upon the satisfaction of the following conditions:

                  (A)      the Borrower shall have consummated an initial
         public offering of its common Capital Stock on terms and conditions
         reasonably acceptable to the Administrative Agent, and as a result
         thereof shall have received cash proceeds, net of cash underwriting
         fees and cash payments to holders of the Borrower's Series A and
         Series B convertible preferred stock in connection with the conversion
         of these shares to common stock, in a minimum amount of $50,000,000;

                  (B)      the Borrower, the Administrative Agent, the Issuing
         Bank and Requisite Lenders shall have executed and delivered a
         counterpart of this Amendment;

                  (C)      the Subsidiary Guarantors shall have executed and
         delivered the Consent of Subsidiary Guarantors appended to this
         Amendment (the "Guarantor Consent");


                                      -5-
<PAGE>
                  (D)      each of the representations and warranties of the
         Borrower contained in Section 10 shall be true and correct as of the
         date as of which all of the other conditions contained in this Section
         9 shall have been satisfied;

                  (E)      in consideration of the agreements of the Lenders
         contained herein, the Borrower shall have paid to the Administrative
         Agent, for distribution to each Lender, such fees as shall have been
         agreed to by the Borrower, the Administrative Agent and the Lenders:

                  (F)      the Administrative Agent shall have received legal
         opinions of Waller Lansden Dortch & Davis PLLC, counsel to the
         Borrower and its Subsidiaries, regarding customary matters (including
         the enforceability of this Amendment, the Guarantor Consent and the
         Credit Agreement (as modified hereby), and no conflict with law or
         material agreements); and

                  (G)      the Administrative Agent shall have received such
         other documents, instruments, certificates, opinions and approvals as
         it reasonably may have requested.

         10.      REPRESENTATIONS AND WARRANTIES OF THE BORROWER. As an
inducement to the Lenders, the Issuing Bank and the Administrative Agent to
enter into this Amendment, the Borrower hereby represents and warrants that, on
and as of the date hereof:

                  (A)      The representations and warranties contained in the
         Credit Agreement and the other Loan Documents are true and correct,
         except for (1) representations and warranties that expressly relate to
         an earlier date, which remain true and correct as of said earlier
         date, and (2) representations and warranties that have become untrue
         or incorrect solely because of changes permitted by the terms of the
         Credit Agreement and the other Loan Documents, and

                  (B)      Both before and after giving effect to this
         Amendment and the transactions contemplated hereby, no Default or
         Event of Default has occurred and is continuing.

                  (C)      The Borrower has the requisite corporate power and
         authority to execute and deliver this Amendment and to enter into and
         perform its obligations hereunder and under the Credit Agreement (as
         modified hereby). Each of the Subsidiary Guarantors has the requisite
         corporate or other organizational power and authority to execute and
         deliver the Guarantor Consent. The execution, delivery and performance
         (i) by the Borrower of this Amendment and the Credit Agreement (as
         modified hereby) and the transactions contemplated hereby and thereby
         and (ii) by the Subsidiary Guarantors of the Guarantor Consent, in
         each case, have been duly approved by all necessary corporate or other
         organizational action of such Person, and no other corporate or other
         organizational proceedings on the part of each such Person are
         necessary to consummate such transactions.


                                      -6-
<PAGE>
                  (D)      This Amendment has been duly executed and delivered
         by the Borrower. The Guarantor Consent has been duly executed and
         delivered by each of the Subsidiary Guarantors. Each of this
         Amendment, the Guarantor Consent and, after giving effect to this
         Amendment, the Credit Agreement and the other Loan Documents, (i) is
         the legal, valid and binding obligation of each Credit Party party
         hereto and thereto, enforceable against such Credit Party in
         accordance with its terms, and (ii) is in full force and effect.
         Neither the execution, delivery or performance of this Amendment or of
         the Guarantor Consent or the performance of the Credit Agreement (as
         modified hereby), nor the consummation of the transactions
         contemplated hereby or thereby, will adversely affect the validity,
         perfection or priority of the Administrative Agent's Lien on any of
         the Collateral or its ability to enforce its rights and remedies with
         respect thereto. This Amendment is effective to amend the Credit
         Agreement as provided therein (assuming the due authorization,
         execution and delivery of this Amendment by each Lender party hereto).

                  (E)      All necessary consents, approvals and authorizations
         of, filings with and acts by or with respect to all Governmental
         Authorities and other Persons required to be obtained, made or taken
         in connection with the execution, delivery, performance, validity or
         enforceability of this Amendment, the Guarantor Consent and the Credit
         Agreement (as modified hereby), or otherwise in connection with the
         transactions contemplated hereby and thereby, have been obtained, made
         or taken and remain in effect.

                  (F)      The execution and delivery of this Amendment and the
         Guarantor Consent, the transactions contemplated by this Amendment and
         by the Credit Agreement (as modified hereby), the performance by the
         Borrower of its obligations hereunder and under the Credit Agreement
         (as modified hereby) and the performance by the Subsidiary Guarantors
         of their respective obligations under the Guarantor Consent (i) do not
         conflict with or violate any Requirement of Law or any Contractual
         Obligation of the Borrower or any Subsidiary of the Borrower, except
         to the extent that any such violation or conflict will not have a
         Material Adverse Effect, and (ii) do not conflict with, constitute a
         default or require any consent under, or result in the creation of any
         Lien upon any property or assets of the Borrower or any Subsidiary of
         the Borrower pursuant to any Contractual Obligation of the Borrower or
         such Subsidiary (other than Liens in favor of the Administrative
         Agent, the Lenders and the Issuing Bank), except to the extent that
         any such conflict or default or the failure to obtain any necessary
         consent will not have a Material Adverse Effect.

         11.      EFFECT OF AMENDMENT; CONTINUING EFFECTIVENESS OF CREDIT
AGREEMENT AND LOAN DOCUMENTS.

                  (A)      Neither this Amendment nor any other indulgences
         that may have been granted to the Borrower or any Guarantor by the
         Administrative Agent, the Issuing Bank or any Lender shall constitute
         a course of dealing or otherwise obligate the Administrative Agent,
         the Issuing Bank or any Lender to modify, expand or extend the
         agreements contained herein, to agree to any other amendments to the
         Credit Agreement


                                      -7-
<PAGE>
         or to grant any consent to, waiver of or indulgence with respect to
         any other noncompliance with any provision of the Loan Documents.

                  (B)      Upon and after the effectiveness of this Amendment,
         each reference in the Credit Agreement to "this Agreement",
         "hereunder", "hereof" or words of like import referring to the Credit
         Agreement, and each reference in the other Loan Documents to "the
         Credit Agreement", "thereunder", "thereof" or words of like import
         referring to the Credit Agreement, shall mean and be a reference to
         the Credit Agreement as modified hereby. This Amendment shall
         constitute a Loan Document for all purposes of the Credit Agreement
         and the other Loan Documents.

                  (C)      Any noncompliance by the Borrower with any of the
         covenants, terms, conditions or provisions of this Amendment shall
         constitute an Event of Default.

                  (D)      Except to the extent amended or modified hereby, the
         Credit Agreement, the other Loan Documents and all terms, conditions
         and provisions thereof shall continue in full force and effect in all
         respects and shall be construed in accordance with the modifications
         of the Credit Agreement effected hereby. Without limiting the
         generality of the foregoing, the Security Documents and all of the
         Collateral described therein secure and shall continue to secure the
         payment of all Obligations, in each case taking into account the
         modifications of the Credit Agreement effected hereby.

         12.      FURTHER ACTIONS. Each of the parties to this Amendment agrees
that at any time and from time to time upon written request of any other party,
it will execute and deliver such further documents and do such further acts and
things as such other party reasonably may request in order to effect the
intents and purposes of this Amendment.

         13.      COUNTERPARTS. This Amendment may be executed in multiple
counterparts or copies, each of which shall be deemed an original hereof for
all purposes. One or more counterparts or copies of this Amendment may be
executed by one or more of the parties hereto, and some different counterparts
or copies executed by one or more of the other parties. Each counterpart or
copy hereof executed by any party hereto shall be binding upon the party
executing same even though other parties may execute one or more different
counterparts or copies, and all counterparts or copies hereof so executed shall
constitute but one and the same agreement. Each party hereto, by execution of
one or more counterparts or copies hereof, expressly authorizes and directs any
other party hereto to detach the signature pages and any corresponding
acknowledgment, attestation, witness or similar pages relating thereto from any
such counterpart or copy hereof executed by the authorizing party and affix
same to one or more other identical counterparts or copies hereof so that upon
execution of multiple counterparts or copies hereof by all parties hereto,
there shall be one or more counterparts or copies hereof to which is(are)
attached signature pages containing signatures of all parties hereto and any
corresponding acknowledgment, attestation, witness or similar pages relating
thereto.


                                      -8-
<PAGE>
         14.      MISCELLANEOUS.

                  (A)      This Amendment shall be governed by, construed and
         enforced in accordance with the laws of the State of Tennessee,
         without reference to the conflicts or choice of law principles
         thereof.

                  (B)      The headings in this Amendment and the usage herein
         of defined terms are for convenience of reference only, and shall not
         be construed as amplifying, limiting or otherwise affecting the
         substantive provisions hereof.

                  (C)      All references herein to the preamble, the recitals
         or sections, paragraphs, subparagraphs, annexes or exhibits are to the
         preamble, recitals, sections, paragraphs, subparagraphs, annexes and
         exhibits of or to this Amendment unless otherwise specified. The words
         "hereof", "herein" and "hereunder" and words of similar import, when
         used in this Amendment, refer to this Amendment as a whole and not to
         any particular provision of this Amendment.

                  (D)      Any reference herein to any instrument, document or
         agreement, by whatever terminology used, shall be deemed to include
         any and all amendments, modifications, supplements, extensions,
         renewals, substitutions and/or replacements thereof as the context may
         require.

                  (E)      When used herein, (1) the singular shall include the
         plural, and vice versa, and the use of the masculine, feminine or
         neuter gender shall include all other genders, as appropriate, (2)
         "include", "includes" and "including" shall be deemed to be followed
         by "without limitation" regardless of whether such words or words of
         like import in fact follow same, and (3) unless the context clearly
         indicates otherwise, the disjunctive "or" shall include the
         conjunctive "and".

          IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be duly executed and delivered as of the date first written above.


                  [REMAINDER OF PAGE INTENTIONALLY LEFT BLANK;
                            SIGNATURE PAGES FOLLOW]


                                      -9-
<PAGE>
             [Signature Page to First Amendment to Credit Agreement
                    (Symbion, Inc.) dated January 30, 2004]


                                        BORROWER:

                                        SYMBION, INC.


                                        By: /s/ Kenneth C. Mitchell
                                            -----------------------------------
                                            Kenneth C. Mitchell,
                                            Vice President - Finance and
                                            Chief Financial Officer


                                     -10-
<PAGE>
             [Signature Page to First Amendment to Credit Agreement
                    (Symbion, Inc.) dated January 30, 2004]


                                        ADMINISTRATIVE AGENT:

                                        BANK OF AMERICA, N.A.,
                                        as Administrative Agent


                                        By: /s/ Kristine Thennes
                                           ------------------------------------
                                           Name: Kristine Thennes
                                                -------------------------------
                                           Title: Vice President
                                                 ------------------------------


                                     -11-
<PAGE>
             [Signature Page to First Amendment to Credit Agreement
                    (Symbion, Inc.) dated January 30, 2004]


                                        LENDER AND ISSUING BANK:

                                        BANK OF AMERICA, N.A.,
                                        as a Lender and as Issuing Bank


                                        By: /s/ Elizabeth L. Knox
                                           ------------------------------------
                                           Name: Elizabeth L. Knox
                                                -------------------------------
                                           Title: SVP
                                                 ------------------------------


                                     -12-
<PAGE>
             [Signature Page to First Amendment to Credit Agreement
                    (Symbion, Inc.) dated January 30, 2004]


                                        LENDER AND SYNDICATION AGENT:

                                        CREDIT SUISSE FIRST BOSTON, acting
                                        through its Cayman Islands Branch,
                                        as a Lender and as Syndication
                                        Agent


                                        By: /s/ Jay Chall
                                           ------------------------------------
                                           Name: Jay Chall
                                                -------------------------------
                                           Title: Director
                                                 ------------------------------


                                        By: /s/ Jennifer A. Pieza
                                           ------------------------------------
                                           Name: Jennifer A. Pieza
                                                -------------------------------
                                           Title: Associate
                                                 ------------------------------


                                     -13-
<PAGE>
             [Signature Page to First Amendment to Credit Agreement
                    (Symbion, Inc.) dated January 30, 2004]


                                        LENDER AND DOCUMENTATION AGENT:

                                        KEY CORPORATE CAPITAL INC.,
                                        as a Lender and as Documentation Agent


                                        By: /s/ James A. Taylor
                                           ------------------------------------
                                           Name: James A. Taylor
                                                -------------------------------
                                           Title: Vice President
                                                 ------------------------------


                                     -14-
<PAGE>
             [Signature Page to First Amendment to Credit Agreement
                    (Symbion, Inc.) dated January 30, 2004]


                                        LENDER:

                                        LASALLE BANK NATIONAL ASSOCIATION,
                                        as a Lender


                                        By: /s/ Sarah Reisher
                                           ------------------------------------
                                           Name: Sarah Reisher
                                                -------------------------------
                                           Title: First Vice President
                                                 ------------------------------


                                     -15-
<PAGE>
             [Signature Page to First Amendment to Credit Agreement
                   (Symbion, Inc.) dated January 30, 2004]


                                        LENDER:

                                        U.S. BANK, NATIONAL ASSOCIATION,
                                        as a Lender


                                        By: /s/ S.W. Choppin
                                           ------------------------------------
                                           Name: S.W. Choppin
                                                -------------------------------
                                           Title: S.V.P.
                                                 ------------------------------


                                     -16-
<PAGE>
             [Signature Page to First Amendment to Credit Agreement
                    (Symbion, Inc.) dated January 30, 2004]


                                        LENDER:

                                        FIFTH THIRD BANK,
                                        as a Lender


                                        By: /s/ Sandy Hamrick
                                           ------------------------------------
                                           Name: Sandy Hamrick
                                                -------------------------------
                                           Title: Vice President
                                                 ------------------------------


                                     -17-
<PAGE>
             [Signature Page to First Amendment to Credit Agreement
                    (Symbion, Inc.) dated January 30, 2004]


                                        LENDER:

                                        RAYMOND JAMES BANK, FSB,
                                        as a Lender


                                        By: /s/ William C. Beiler
                                           ------------------------------------
                                           Name: William C. Beiler
                                                -------------------------------
                                           Title: EVP & CCO
                                                 ------------------------------


                                     -18-