<PAGE>
                                                                     EXHIBIT 4.6


                                 AMENDMENT NO. 2
                    TO AMENDED AND RESTATED VOTING AGREEMENT

         THIS AMENDMENT NO. 2 TO AMENDED AND RESTATED VOTING AGREEMENT (the
"Amendment") is made and entered into as of April 1, 2002, by and among Symbion,
Inc., a Tennessee corporation formerly named "UniPhy Healthcare, Inc." (the
"Company"), and those persons identified on Exhibit A attached hereto
(collectively, the "Investors" and each individually, an "Investor").

                                R E C I T A L S:

         WHEREAS, the Company and certain of the Investors (the "Original
Investors") are parties to that certain Amended and Restated Voting Agreement,
dated as of June 25, 1999, as amended by Amendment No. 1 thereto, dated as of
August 11, 1999 (collectively, the "Voting Agreement");

         WHEREAS, the Company, Symbion Acquisition Sub, Inc. ("Symbion Sub") and
Physicians Surgical Care, Inc. ("PSC") are parties to that certain Agreement and
Plan of Merger, dated as of March 7, 2002 (the "Merger Agreement"), which
provides, among other things, for the merger of Symbion Sub with and into PSC
and for PSC to become a wholly owned subsidiary of the Company (the "Merger");

         WHEREAS, it is a condition of PSC's obligations under the Merger
Agreement that the Company and the Original Investors amend the Voting Agreement
to add J.H. Whitney III, L.P. ("JHW III"), J.H. Whitney IV, L.P. ("JHW IV") and
Whitney Strategic Partners III, L.P. ("WSP III" and together with JHW III and
JHW IV, the "Whitney Shareholders") as parties thereto and to provide that each
of the Whitney Shareholders and the other Investors shall vote its Investor
Shares in favor of certain designees to the Company's Board of Directors,
including certain designees of the Whitney Shareholders; and

         WHEREAS, the Company and the Investors desire to amend the Voting
Agreement as set forth in this Amendment, pursuant to Section 2.3 of the Voting
Agreement.

         NOW, THEREFORE, in consideration of the foregoing and the respective
covenants and agreements contained herein, the sufficiency of which is hereby
acknowledged, the parties hereby agree and consent to the following:

         1.       Definitions. Capitalized terms used herein without definition
shall have the same meanings ascribed to such terms in the Voting Agreement.

         2.       Effectiveness of Amendment. This Amendment shall become
effective upon the occurrence of each of the following: : (i) the effectiveness
of the Merger; (ii) the execution and delivery of this Agreement by each of the
Whitney Shareholders, adopting and accepting the terms hereof and the terms of
the Voting Agreement; and (iii) the execution and delivery of this Amendment by
the Company and the holders of at least seventy-five percent (75%) of the
Investor Shares, adopting and accepting the terms of this Amendment. This
Amendment shall be of no force or effect until the occurrence of all of the
events described in the preceding sentence.


<PAGE>

         3.       Additional Parties. Each of the Whitney Shareholders is hereby
made a party to the Voting Agreement as an Investor in accordance with the terms
and provisions of the Voting Agreement and this Amendment.

         4.       Amendment to Section 1.2 of the Voting Agreement. Section 1.2
of the Voting Agreement is hereby deleted and replaced in its entirety with the
following:

                  "1.2 Agreement to Vote. (a) Appointment of Directors. At each
         annual meeting of the shareholders of the Company, or at any meeting of
         the shareholders of the Company, at which members (each a "Director"
         and collectively, the "Directors") of the Board of Directors of the
         Company are to be elected, each Investor hereby agrees to vote or act
         with respect to such Investor's Investors Shares so as to elect one or
         more individuals nominated by certain Investors or groups of Investors
         as follows:

                  (i)      one (1) individual designated by Pacific Venture
         Group;

                  (ii)     one (1) individual designated by The Martin
         Investment Partnership or its subsidiary;

                  (iii)    one (1) individual designated by ABS Capital
         Partners, L.P.;

                  (iv)     the Chief Executive Officer of the Company;

                  (v)      the Chief Operating Officer of the Company;

                  (vi)     one (1) individual designated by Charles N. Martin,
         Jr.;

                  (vii)    one (1) individual designated jointly by Richland
         Ventures II, L.P. and Richland Ventures III, L.P.;

                  (viii)   two (2) individuals designated collectively by Arthur
         S. DeMoss Foundation, Cal Turner, Jr., First Avenue Partners, L.P.,
         HLM/CB Fund, L.P., HLM Partners VII, L.P., Piper Jaffrey, Inc. South
         Atlantic Private Equity Fund IV (QP), South Atlantic Private Equity
         Fund IV, L.P. and WW Two, L.P; and

                  (ix)     two (2) individuals designated collectively by J.H.
         Whitney III, L.P., J.H. Whitney IV, L.P. and Whitney Strategic Partners
         III, L.P.

                  (b)      Removal. If at any time any Investor or group of
         Investors, as the case may be, entitled to nominate a Director in
         accordance with Section 1.2(a) hereof notifies (such notice to be
         signed by any such Investor or by the holders of a majority of the
         Investor Shares held by such group of Investors, as the case may be)
         the other Investors of his or their, as the case may be, wish to remove
         at any time (but only for cause) a Director nominated by such Investor
         or group of Investors, as the case may be, then each Investor shall
         vote all of his, hers or its Investor Shares so as to remove such
         Director.

                  (c)      Replacement. If, at any time, a vacancy is created
         on the Board of Directors by reason of the incapacity, death, removal
         or resignation of any Director,



                                       2
<PAGE>

         the vacancy shall be filled by another individual selected in
         accordance with the provisions of Section 1.2(a) hereof. Upon receipt
         of notice of the designation of a nominee pursuant to Section 1.2(c),
         each Investor shall, as soon as practicable after the date of such
         notice, take all reasonable actions, including the voting of its
         Investor Shares, to elect the Director so designated to fill the
         vacancy."

         5.       Amendment of Section 1.6 of the Voting Agreement. Section 1.6
of the Voting Agreement is hereby deleted and replaced in its entirety with the
following:

                  "1.6     Termination. (a) Termination Event. This Amended and
         Restated Voting Agreement shall terminate in its entirety on the
         closing of an initial public offering pursuant to an effective
         registration statement under the Securities Act of 1933, as amended
         (the "Securities Act"), covering the offer and sale of the capital
         stock of the Company or any of its subsidiaries or affiliates.

                           (b) Removal of Legend. At any time after the
         termination of this Amended and Restated Voting Agreement in accordance
         with Section 1.6(a), any holder of a stock certificate legended
         pursuant to Section 1.3 may surrender such certificate to the Company
         for removal of the legend, and the Company will duly reissue a new
         certificate without the legend."

         6.       Amendment of Section 2.3 of the Voting Agreement. Section 2.3
of the Voting Agreement is hereby deleted and replaced in its entirety with the
following:

                  "2.3 Amendment. This Amended and Restated Voting Agreement may
         be amended and any term hereof may be waived only by an instrument in
         writing signed by (i) the Company, (ii) the Whitney Shareholders and
         (iii) the holders of at least seventy-five percent (75%) of the
         Investor Shares held by the other Investors."

         7.       Amendment to Section 2.4 of the Voting Agreement. Section 2.4
of the Voting Agreement is hereby deleted and replaced in its entirety with the
following:

                  "2.4 Severability. If any term or other provision of this
         Amended and Restated Voting Agreement is held to be invalid or illegal
         or otherwise incapable of being enforced by any law or public policy,
         all other terms and provisions of this Amended and Restated Voting
         Agreement shall nevertheless remain in full force and effect so long as
         the economic or legal substance of the transactions contemplated hereby
         is not affected in any manner materially adverse to any party. Upon
         such determination that any term or other provision is invalid, illegal
         or incapable of being enforced, the parties hereto shall negotiate in
         good faith to modify this Amended and Restated Voting Agreement so as
         to effect the original intent of the parties as closely as possible in
         an acceptable manner in order that the transactions contemplated hereby
         are consummated as originally contemplated to the greatest extent
         possible."

         8.       Amendment of Exhibit A. Exhibit A to the Voting Agreement is
hereby deleted and replaced in its entirety with Schedule 1 attached hereto.


                                       3
<PAGE>

         9.       No Other Changes. Upon execution and delivery of this
Amendment by the parties hereto, the Voting Agreement shall be amended in
accordance herewith and this Amendment shall form part of the Voting Agreement
for all purposes and the parties hereto shall be bound by the Voting Agreement,
as so amended. Except as expressly set forth or contemplated in this Amendment,
the terms and conditions of the Voting Agreement shall remain in place and shall
not be altered, amended or changed in any manner whatsoever, except by any
further amendment to the Voting Agreement made in accordance with the terms of
the Voting Agreement, as hereby amended.

         10.      Counterparts. This Amendment may be executed in any number of
counterparts and by the different parties hereto on separate counterparts, each
of which when executed and delivered shall be deemed an original effective for
binding the parties hereto, but all of which shall together constitute one and
the same instrument.

         11.      GOVERNING LAW. THIS AMENDMENT SHALL BE GOVERNED BY AND
CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF CALIFORNIA, WITHOUT REGARD
TO THE PRINCIPLES OF CONFLICTS OF LAW THEREOF.


                [THE REST OF THIS PAGE INTENTIONALLY LEFT BLANK]


                                       4
<PAGE>


         IN WITNESS WHEREOF, the parties hereto have executed this Amendment,
and hereby consent to the amendment and modification of the Voting Agreement
provided herein, as of the date first above written.


THE COMPANY:

SYMBION, INC.


By: /s/ Richard E. Francis, Jr.
    -------------------------------------------------
         Name: Richard E. Francis, Jr.
               --------------------------------------
         Title: President and Chief Executive Officer
                -------------------------------------


INVESTORS:

UNIPHY PREFERRED SHAREHOLDERS:

ABS Capital Partners, L.P.


By: /s/ Frederick L. Bryant
    ---------------------------------------
         Name: Frederick L. Bryant
              -----------------------------
         Title:
                ---------------------------


/s/ Clifford G. Adlerz
-------------------------------------------
Clifford G. Adlerz


-------------------------------------------
Randy W. Cook


-------------------------------------------
Paul Davis


/s/ Richard E. Francis, Jr.
-------------------------------------------
Richard E. Francis, Jr.


/s/ R. Dale Kennedy
-------------------------------------------
R. Dale Kennedy


-------------------------------------------
Tod Lambert



                                       5
<PAGE>

THE MARTIN COMPANIES, INC.


By: /s/ Charles N. Martin, Jr.
    ---------------------------------------
         Name: Charles N. Martin, Jr.
              -----------------------------
         Title:
                ---------------------------


/s/ Kenneth C. Mitchell
-------------------------------------------
Kenneth C. Mitchell


PACIFIC VENTURE GROUP, L.P.
By:      PVG Equity Partner, L.L.C.,
         its General Partner


By: /s/ Eve M. Kurtin
    ---------------------------------------
         Name:    Eve M. Kurtin
         Title:   Member


PVG ASSOCIATES, L.P.
By:      PVG Equity Partner, L.L.C.,
         its General Partner


By: /s/ Eve M. Kurtin
    ---------------------------------------
         Name:    Eve M. Kurtin
         Title:   Member


/s/ Patrick R. Rooney
-------------------------------------------
Patrick R. Rooney


/s/ Teresa F. Sparks
-------------------------------------------
Teresa F. Sparks


/s/ Gregg Stanley
-------------------------------------------
Gregg Stanley


/s/ Anthony Taparo
-------------------------------------------
Anthony Taparo



                                       6
<PAGE>


ARC KEY SHAREHOLDERS:


ARTHUR S. DEMOSS FOUNDATION


By:
    ---------------------------------------
         Name:
              -----------------------------
         Title:
                ---------------------------


/s/ Jerry M. Eyler
-------------------------------------------
Jerry M. Eyler


FIRST AVENUE PARTNERS, L.P.


By:
    ---------------------------------------
         Name:
              -----------------------------
         Title:
                ---------------------------


-------------------------------------------
William H. Freeman


-------------------------------------------
J. Michael Gould


HEALTH TECH AFFILIATES, INC.


By:
    ---------------------------------------
         Name:
              -----------------------------
         Title:
               ----------------------------


HLM/CB FUND, L.P.


By:
    ---------------------------------------
         Name:
              -----------------------------
         Title:
                ---------------------------



                                       7
<PAGE>

HLM PARTNERS VII, L.P.


By:
    ---------------------------------------
         Name:
              -----------------------------
         Title:
                ---------------------------


-------------------------------------------
W. Lawrence Hough


PIPER JAFFRAY, INC.


By:
    ---------------------------------------
         Name:
              -----------------------------
         Title:
                ---------------------------


-------------------------------------------
B. Max Lauderdale


/s/ Charles N. Martin, Jr.
-------------------------------------------
Charles N. Martin, Jr.


/s/ Charles T. Neal
-------------------------------------------
Charles T. Neal


-------------------------------------------
Thomas Patten


-------------------------------------------
Keith B. Pitts


-------------------------------------------
Gary J. Prosterman




                                       8
<PAGE>


RICHLAND VENTURES II, L.P.


By: /s/ Jack Tyrell
    ---------------------------------------
         Name: Jack Tyrell
              -----------------------------
         Title: Managing Partner
                ---------------------------


RICHLAND VENTURES III, L.P.


By: /s/ Jack Tyrell
    ---------------------------------------
         Name: Jack Tyrell
              -----------------------------
         Title: Managing Partner
                ---------------------------


-------------------------------------------
Ann R. Schaaf


SOUTH ATLANTIC PRIVATE EQUITY FUND IV (QP), LIMITED PARTNERSHIP


By: /s/ Donald W. Burton
    ----------------------------------------
         Name: Donald W. Burton
              ------------------------------
         Title: Managing Director
                ----------------------------


SOUTH ATLANTIC PRIVATE EQUITY FUND IV, L.P.


By: /s/ Donald W. Burton
    ----------------------------------------
         Name: Donald W. Burton
              ------------------------------
         Title: Managing Director
                ----------------------------


--------------------------------------------
Cal Turner, Jr.


/s/ William V.B. Webb
--------------------------------------------
William V.B. Webb



                                       9
<PAGE>

WW TWO, L.P.


By:
    ---------------------------------------
         Name:
              -----------------------------
         Title:
                ---------------------------


-------------------------------------------
James A. Webb, III


UNIPHY FOUNDERS:


-------------------------------------------
Peter Davidson


/s/ Shannon W. Fiser
-------------------------------------------
Shannon W. Fiser


THE FRANCIS IRREVOCABLE TRUST, ANN FRANCIS, TRUSTEE


By: /s/ Richard E. Francis, Jr.
    ---------------------------------------
         Name: Richard E. Francis
              -----------------------------
         Title: Executor
                ---------------------------


-------------------------------------------
Victor Giovanetti


/s/ George M. Goodwin
-------------------------------------------
George M. Goodwin


-------------------------------------------
Marlene D. Kelley


/s/ H. Edward Kleine III
-------------------------------------------
H. Edward Kleine III


/s/ Darrell Naish
-------------------------------------------
Darrell Naish


                                       10
<PAGE>

/s/ Richard Panek
-----------------------------------------------------
Richard Panek


/s/ Vickie R. Warren
-----------------------------------------------------
Vickie R. Warren


WHITNEY SHAREHOLDERS:

J.H. WHITNEY III, L.P.

By:      J.H. Whitney Equity Partners III, L.L.C.,
         its General Partner


         By:  /s/ Daniel J. O'Brien
              ---------------------------------------
                  Name:  Daniel J. O'Brien
                         ----------------------------
                  Title:  Managing Member
                          ---------------------------


J.H. WHITNEY IV, L.P.

By:      J.H. Whitney Equity Partners IV, L.L.C.,
         its General Partner


         By: /s/ Daniel J. O'Brien
            -----------------------------------------
                  Name:  Daniel J. O'Brien
                         ----------------------------
                  Title:  Managing Member
                          ---------------------------


WHITNEY STRATEGIC PARTNERS III, L.P.

By:      J.H. Whitney Equity Partners III, L.L.C.,
         its General Partner

         By:  /s/ Daniel J. O'Brien
              ---------------------------------------
                  Name: Daniel J. O'Brien
                       ------------------------------
                  Title: Managing Member
                        -----------------------------



                                       11
<PAGE>


ADDITIONAL UNIPHY PREFERRED SHAREHOLDERS:


--------------------------------------------
Bruce F. Chafin


--------------------------------------------
Ray Denson and Mary Denson, as joint tenants


--------------------------------------------
Ray Denson and Mary Denson, as Custodians
for Logan V. Denson


--------------------------------------------
Ray Denson and Mary Denson, as Custodians
for Morgan R. Denson


--------------------------------------------
Robert E. Galloway


--------------------------------------------
Stephen E. Hobbs


--------------------------------------------
Jeffrey W. Moore


--------------------------------------------
Joseph D. Moore


--------------------------------------------
Paul J. Moore


--------------------------------------------
Carol A. Murdock


--------------------------------------------
Phillip W. Roe



                                       12
<PAGE>


--------------------------------------------
Alan G. Thomas


--------------------------------------------
Daniel B. Soltman


--------------------------------------------
Ronald P. Soltman, as Custodian
for Sarah C. Soltman


--------------------------------------------
Ronald P. Soltman, as Custodian
for Joel M. Soltman



                                       13
<PAGE>



                                   SCHEDULE 1

                              SCHEDULE OF INVESTORS


UNIPHY PREFERRED SHAREHOLDERS

ABS Capital Partners, L.P.
Clifford G. Adlerz
Bruce F. Chafin
Randy W. Cook
Paul Davis
Ray Denson and Mary Denson, as joint tenants
Ray Denson and Mary Denson, as Custodians for Logan V. Denson
Ray Denson and Mary Denson, as Custodians for Morgan R. Denson
Richard E. Francis, Jr.
Robert E. Galloway
Stephen E. Hobbs
W. Lawrence Hough
R. Dale Kennedy
Tod Lambert
Kenneth C. Mitchell
Jeffrey W. Moore
Joseph D. Moore
Paul J. Moore
Carol A. Murdock
Pacific Venture Group, L.P.
Keith B. Pitts
PVG Associates, L.P.
Phillip W. Roe
Patrick R. Rooney
Teresa F. Sparks
Gregg Stanley
Anthony Taparo
The Martin Companies, Inc.
Alan G. Thomas
Daniel B. Soltman
Ronald P. Soltman, as Custodian for Sarah C. Soltman
Ronald P. Soltman, as Custodian for Joel M. Soltman
William V.B. Webb


ARC KEY SHAREHOLDERS

Arthur S. Demoss Foundation
Jerry M. Eyler
First Avenue Partners, L.P.
William H. Freeman
J. Michael Gould
Health Tech Affiliates, Inc.


                                       14
<PAGE>


HLM/CB Fund, L.P.
HLM Partners VII, L.P.
W. Lawrence Hough
Piper Jaffray, Inc.
B. Max Lauderdale
Charles N. Martin, Jr.
Charles T. Neal
Thomas Patten
Keith B. Pitts
Gary J. Prosterman
Richland Ventures II, L.P.
Richland Ventures III, L.P.
Ann R. Schaaf
South Atlantic Private Equity Fund IV (QP)
South Atlantic Private Equity Fund IV, L.P.
Cal Turner, Jr.
William V.B. Webb
WW Two, L.P.
James A. Webb, III


UNIPHY FOUNDERS

Peter Davidson
Shannon W. Fiser
The Francis Irrevocable Trust, Ann Francis, Trustee
Victor Giovanetti
George M. Goodwin
Marlene D. Kelley
H. Edward Kleine III
Darrell Naish
Richard Panek
Vickie R. Warren


WHITNEY SHAREHOLDERS

J.H. Whitney III, L.P.
J.H. Whitney IV, L.P.
Whitney Strategic Partners III, L.P.



                                       15