Document:

<PAGE>   1
                                                                     EXHIBIT 4.3

                                 SIXTH AMENDMENT

         SIXTH AMENDMENT, dated as of June 23, 2000 (this "Sixth Amendment"), to
the Agreement and Amendment dated as of February 26, 1997, as amended by the
First Amendment, dated as of June 17, 1997, the Second Amendment, dated as of
February 3, 1998, the Third Amendment, dated as of March 26, 1998, the Fourth
Amendment, dated as of July 10, 1998 and the Fifth Amendment dated as of March
30, 1999 (as the same may be amended, supplemented or modified from time to
time, the "February 1997 Five-Year Agreement and Amendment") among HCA - THE
HEALTHCARE COMPANY (formerly known as Columbia/HCA Healthcare Corporation), a
Delaware corporation (the "Company"), the several banks and other financial
institutions from time to time parties hereto (the "Banks"), BANK OF AMERICA,
N.A., THE BANK OF NEW YORK, DEUTSCHE BANK AG, FLEET NATIONAL BANK, THE FUJI BANK
LIMITED, THE INDUSTRIAL BANK OF JAPAN, LIMITED, MORGAN GUARANTY TRUST COMPANY OF
NEW YORK, PNC BANK NATIONAL ASSOCIATION, TORONTO DOMINION (TEXAS), INC., UNION
BANK OF SWITZERLAND, NEW YORK BRANCH AND WACHOVIA BANK, N.A., as co-agents
(collectively, the "Co-Agents"), THE SAKURA BANK, LTD. NEW YORK BRANCH, THE
SUMITOMO BANK LIMITED, SUNTRUST BANK, WELLS FARGO BANK, N.A., as Lead Managers
(collectively, the "Lead Managers") and THE CHASE MANHATTAN BANK, a New York
banking corporation, as agent for the Banks hereunder ("Chase", and in such
capacity, the "Agent") and as CAF Loan Agent (in such capacity, the "CAF Loan
Agent").

                              W I T N E S S E T H :

         WHEREAS, for the convenience of the parties to the agreement and
amendment dated as of February 28, 1996 (the "February 1996 Agreement and
Amendment"), among the Company, the several banks and other financial
institutions from time to time parties thereto and Chase, as agent for the Banks
hereunder and as CAF Loan Agent, a composite conformed copy (the "Five-Year
Composite Conformed Credit Agreement") of the Credit Agreement, dated as of
February 10, 1994 as incorporated by reference into and amended by the September
1994 Agreement and Amendment, the February 1995 Agreement and Amendment and the
February 1996 Agreement and Amendment was prepared and delivered to such
parties;

         WHEREAS, the February 1997 Five-Year Agreement and Amendment adopts and
incorporates by reference all of the terms and provisions of the Five-Year
Composite Conformed Credit Agreement, subject to the amendment thereto provided
for in the February 1997 Five-Year Agreement and Amendment;

         WHEREAS, the parties hereto wish to amend certain provisions of the
February 1997 Five-Year Agreement and Amendment on the terms set forth herein;

<PAGE>   2
                                       2

         NOW, THEREFORE, in consideration of the premises and of the mutual
agreements herein contained, the parties hereto agree as follows:

         1. Definitions. Unless otherwise defined herein, terms defined in the
February 1997 Five-Year Agreement and Amendment shall be used as so defined.

         2. Amendments to the February 1997 Five-Year Agreement and Amendment in
respect of the Letter of Credit Facility. Section 3 of the February 1997
Five-Year Agreement and Amendment is hereby amended by deleting the defined term
"Consolidated Earnings Before Interest and Taxes" in its entirety and
substituting in lieu thereof the following new defined term in proper
alphabetical order:

            "'Consolidated Earnings Before Interest and Taxes': for any period
     for which the amount thereof is to be determined, Consolidated Net Income
     for such period, plus (i) all amounts deducted in computing such
     Consolidated Net Income in respect of interest expense on Indebtedness and
     income taxes and (ii) non-recurring charges incurred or made as of or for
     fiscal quarters ending on or after June 30, 2000 related to the Company's
     partial settlement with the Department of Justice not exceeding in the
     aggregate $745,000,000 on a pre-tax basis."

         3. Effective Date; Conditions Precedent. This Sixth Amendment will
become effective on June 23, 2000 (the "Effective Date") subject to the
compliance by the Company with its agreements herein contained and to the
satisfaction on or before the Effective Date of the following further
conditions:

            (a) Loan Documents. The Agent shall have received copies of this
     Sixth Amendment, executed and delivered by a duly authorized officer of the
     Company, with a counterpart for each Bank, and executed and delivered by
     the Required Banks.

            (b) Fees. The Agent shall have received, for the account of each
     Bank which executes and delivers this Amendment on or prior to 5:00 p.m.
     New York City time on June 23, 2000, an amendment fee in an amount equal to
     2.5 basis points on such Bank's Commitment as in effect prior to the
     Effective Date, payable in immediately available funds on or before the
     Effective Date.

            (c) Company Officers' Certificate. On and as of the Effective Date
     and after giving effect to this Sixth Amendment, no Default shall have
     occurred (except a Default which shall have been waived in writing or which
     shall have been cured); and the Agent shall have received a certificate
     containing a representation to these effects dated the Effective Date and
     signed by a Responsible Officer.

            (d) Second Amendment to July 1998 Agreement. That certain credit
     agreement, dated as of July 10, 1998, among the Company, the several banks
     and other financial institutions from time to time parties thereto,
     Nationsbank, N.A., The Bank of Nova Scotia, Deutsche Bank Securities, and
     The Chase Manhattan Bank, as administrative agent (the "July 1998
     Agreement"), shall have been amended in a manner corresponding to the
     amendments hereof.

<PAGE>   3
                                       3

           (e) First Amendment to March 2000 Agreement. That certain credit
     agreement, dated as of March 13, 2000, among the Company, the several banks
     and other financial institutions from time to time parties thereto, Chase
     Securities Inc., Bank of America, N.A., The Bank of Nova Scotia, Deutsche
     Bank AG New York Branch, The Bank of New York, The Industrial Bank of
     Japan, Limited, Citicorp USA, Inc., Fleet National Bank, Credit Suisse
     First Boston, Suntrust Bank, Wachovia Bank, N.A., and The Chase Manhattan
     Bank, as administrative agent (the "March 2000 Agreement"), shall have been
     amended in a manner corresponding to the amendments hereof.

         4. Legal Obligation. The Company represents and warrants to each Bank
that this Sixth Amendment constitutes the legal, valid and binding obligation of
the Company, enforceable against it in accordance with its terms, subject to the
effects of bankruptcy, insolvency, fraudulent conveyances, reorganization,
moratorium and other similar laws relating to or affecting creditors' rights
generally, general equitable principles (whether considered in a proceeding in
equity or at law) and an implied covenant of good faith and fair dealing.

         5. Continuing Effect; Application. Except as expressly amended hereby,
the February 1997 Five-Year Agreement and Amendment shall continue to be and
shall remain in full force and effect in accordance with its terms.

         6. Expenses. The Company agrees to pay or reimburse the Agent for all
of its reasonable out-of-pocket costs and expenses incurred in connection with
the development, preparation and execution of, and any amendment, supplement or
modification to, this Sixth Amendment and any other documents prepared in
connection herewith, and the consummation of the transactions contemplated
hereby and thereby, including, without limitation, the reasonable fees and
disbursements of counsel to the Agent.

         7. GOVERNING LAW. THIS SIXTH AMENDMENT AND THE RIGHTS AND OBLIGATIONS
OF THE PARTIES UNDER THIS SIXTH AMENDMENT SHALL BE GOVERNED BY, AND CONSTRUED
AND INTERPRETED IN ACCORDANCE WITH, THE LAW OF THE STATE OF NEW YORK.

         8. Counterparts. This Sixth Amendment may be executed by one or more of
the parties to this Sixth Amendment on any number of separate counterparts and
all of said counterparts taken together shall be deemed to constitute one and
the same instrument. A set of the copies of this Sixth Amendment signed by all
the parties shall be lodged with the Company and the Agent.

<PAGE>   4

         IN WITNESS WHEREOF, the parties hereto have caused this Sixth Amendment
to be duly executed and delivered by their proper and duly authorized officers
as of the day and year first above written.

                                    HCA - THE HEALTHCARE COMPANY

                                    By: /s/ DAVID G. ANDERSON
                                        ----------------------------------------
                                        Name:
                                        Title:

                                    THE CHASE MANHATTAN BANK, as Agent, as CAF
                                    Loan Agent and as a Bank

                                    By: /s/ DAWN LEE LUM
                                        ----------------------------------------
                                        Name:
                                        Title:<PAGE>   1
                                                                     EXHIBIT 4.4

                          HCA - THE HEALTHCARE COMPANY

                                       TO

                          BANK ONE TRUST COMPANY, N.A.,
                                     Trustee

                             ----------------------

                          FIRST SUPPLEMENTAL INDENTURE

                                       TO

                  INDENTURE OF COLUMBIA HEALTHCARE CORPORATION

                            Dated as of May 25, 2000

                             ----------------------

Supplementing the Indenture, dated as of December 16, 1993, by and between
Columbia Healthcare Corporation and Bank One Trust Company, N.A. (as successor
in interest to The First National Bank of Chicago).

<PAGE>   2

        THIS FIRST SUPPLEMENTAL INDENTURE (the "Supplemental Indenture"), dated
as of May 25, 2000, by and among HCA - The Healthcare Company, a corporation
duly organized and existing under the laws of the State of Delaware ("HCA"),
having its principal offices at One Park Plaza, Nashville, Tennessee 37203,
formerly known as Columbia/HCA Healthcare Corporation, and Bank One Trust
Company, N.A., a national banking association duly organized and existing under
the laws of the United States of America ("Bank One"), having its principal
corporate trust offices in the State of New York at 153 West 51st Street, New
York, New York, 10019.

        WHEREAS, Columbia Healthcare Corporation, a Delaware corporation, duly
executed and delivered to The First National Bank of Chicago, as trustee
("Trustee"), that certain Indenture, dated as of December 16, 1993 (the
"Indenture"), relating to the issuance from time to time of debentures, notes,
bonds and other evidences of indebtedness (the "Debt Securities");

        WHEREAS, Bank One is the successor in interest to the Trustee;

        WHEREAS effective as of May 25, 2000, pursuant to the terms of that
certain Certificate of Ownership and Merger (the "Merger Certificate"), dated as
of May 25, 2000, by and among HCA (then known as Columbia/HCA Healthcare
Corporation) and its wholly-owned subsidiary, HCA - The Healthcare Company, a
Delaware corporation ("Merger Subsidiary"), Merger Subsidiary was merged with
and into HCA, for the sole purpose and with the sole effect of changing HCA's
name from Columbia/HCA Healthcare Corporation to HCA - The Healthcare Company
(the "Merger");

        WHEREAS, Section 901(1) of the Indenture requires HCA to execute and
deliver a supplemental indenture to the Trustee providing for, among other
matters, the assumption by HCA of the due and punctual payment of the principal
of and interest on all the Debt Securities, according to their tenor, and the
due and punctual performance and observance of all of the covenants and
conditions of the Indenture to be performed or observed by the Company;

        WHEREAS, pursuant to Section 1001(1) of the Indenture, this Supplemental
Indenture may be executed and delivered by the Trustee and HCA (the continuing
corporation) without the consent of the Holders of the Debt Securities;

        WHEREAS, the Board of Directors of HCA has authorized the execution of
this Supplemental Indenture and its delivery to the Trustee; and

        WHEREAS, all acts and things necessary to make this Supplemental
Indenture the valid, binding and legal obligation of HCA in accordance with its
terms have been done.

        NOW, THEREFORE, in consideration of the premises, it is mutually
covenanted and agreed for the equal and proportionate benefit of all Holders of
the Debt Securities as follows. Capitalized terms used but not defined herein
shall have the meanings ascribed to such terms in the Indenture.

<PAGE>   3

                                    ARTICLE I

             ASSUMPTION OF COLUMBIA/HCA HCA HEALTHCARE CORPORATION'S
                   OBLIGATIONS BY HCA - THE HEALTHCARE COMPANY

        Section 1.1. HCA, a corporation duly organized and validly existing
under the laws of the State of Delaware, hereby expressly assumes the due and
punctual payment of the principal of and interest on all the Debt Securities,
according to their tenor, and the due and punctual performance and observance of
all of the covenants and conditions of the Indenture to be performed or observed
by the Company and shall otherwise succeed and be substituted for the Company in
the Indenture and in the Debt Securities with the same effect as if HCA had been
named therein as the Company.

        Section 1.2. HCA hereby represents and warrants that, immediately after
giving effect to the Merger, no Event of Default, and no event which, after
notice or lapse of time, or both, would become an Event of Default, has occurred
or is continuing.

                                   ARTICLE II

                                  MISCELLANEOUS

        Section 2.1. The Indenture shall be deemed to be modified and amended as
herein provided, but, except as modified and amended by this Supplemental
Indenture, the Indenture shall continue in full force and effect.

        Section 2.2. The Indenture and this Supplemental Indenture shall be
read, taken and construed as one and the same instrument.

        Section 2.3. This Supplemental Indenture shall become effective at the
effective time of the Merger upon the execution and delivery hereof by each of
the parties hereto.

        Section 2.4. Trustee makes no representations as to the validity or
sufficiency of this Supplemental Indenture, except the due and valid execution
hereof by the Trustee. Trustee's execution of this Supplemental Indenture should
not be construed to be an approval or disapproval of the advisability of the
action taken by HCA (then known as Columbia/HCA Healthcare Corporation) and
Merger Subsidiary with respect to the Merger.

        Section 2.5. This Supplemental Indenture shall be governed by and
construed in accordance with the laws of the State of New York.

        Section 2.6. This Supplemental Indenture may be executed in any number
of counterparts each of which shall be an original, but all of which together
shall be deemed to constitute but one and the same instrument.

                                        2
<PAGE>   4

        IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Indenture to be duly executed, and their respective corporate seals to be
hereunto affixed and duly attested, all as of the day and year first above
written.

                                     HCA - The Healthcare Company

                                     By: /s/ David G. Anderson
                                        ----------------------------------------
                                     Title: Vice President-Finance and Treasurer
                                            ------------------------------------

(CORPORATE SEAL]

Attest

/s/ John M. Franck II
----------------------------------------------
By: John M. Franck II
Title: Vice President and Corporate Secretary

                                        3
<PAGE>   5

                                           Bank One Trust Company, N.A.,
                                           as Trustee

                                           By: /s/ Sandra Whalen
                                              ----------------------------------
                                           Title: Authorized Signatory
                                                 -------------------------------

(CORPORATE SEAL]

Attest

/s/ Michael Pinzon
----------------------------------
By: Michael Pinzon
Title: Authorized Signatory

                                        4

<PAGE>   6

STATE OF TENNESSEE       )

COUNTY OF DAVIDSON       )

       Personally appeared before me, the undersigned, a Notary Public, David G.
Anderson, with whom I am personally acquainted, and who acknowledged that _he
executed the within instrument for the purposes therein contained, and who
further acknowledged that _he is the Vice President-Finance and Treasurer of
HCA - The Healthcare Company, a corporation, and is authorized by the
corporation to execute this instrument on behalf of the corporation.

       WITNESS my hand, at office, this 25th day of May, 2000.

                                               /s/ Susan W. Foxman
                                               ---------------------------------
                                                   Notary Public

My Commission Expires: July 26, 2003

                                        5

<PAGE>   7

STATE OF NEW YORK         )

COUNTY OF NEW YORK        )

       Personally appeared before me, the undersigned, a Notary Public, Sandra
Whalen, with whom I am personally acquainted, and who acknowledged that she
executed the within instrument for the purposes therein contained, and who
further acknowledged that she is the Authorized Signatory of Bank One Trust
Company, N.A., a national banking association, and is authorized by the
corporation to execute this instrument on behalf of the corporation.

       WITNESS my hand, at office, this 24 day of May, 2000.

                                           /s/ Mark E. Davis
                                           -------------------------------------
                                                  Notary Public

My Commission Expires:________________

                                                    MARK E. DAVIS
                                         Notary Public, State of New York
                                              Reg. No. 01DA6004466
                                           Qualified in New York County
                                        Commission Expires March 23, 2002

                                        6

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00012-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00012-of-00352.parquet"}]]