The concept of paying surgeons a global payment for all services related to a surgery started in 1992, with the implementation of the Resource Based Relative Value System (RBRVS).  This concept describes the components of the global package, and established the post op period for surgical services, which are 0, 10 or 90 days. 

The Medicare Physician Fee Schedule includes a breakdown of each surgical CPT® code into the amount of pre-op work, intraoperative work and post op work.  The pre-op work ranges from 8-12% of the global fee, the intraoperative work 70-81% and the post op work 7-20%.  Codes in a range have similar breakdowns. 

Included in the global payment is all E/M services provided the day of the surgery (unless the E/M service meets the criteria of separate and distinct, for services with 0-10 day periods--see the articles on modifier 25, or unless the E/M service was the decision for surgery, for services with a 90 day global period--see the article on modifier 57), the intraoperative work, and the related post op work for the number of days. See articles in Codapedia related to these modifiers, as well as the surgical modifiers for services after a surgery.

Here is what the Medicare Claims Processing Manual says is included in the global surgical package:

A.  Components of a Global Surgical Package
(Rev. 1, 10-01-03)
B3-15011, B3-4820-4831
Carriers apply the national definition of a global surgical package to all procedures with
the appropriate entry in Field 16 of the MFSDB.
The Medicare approved amount for these procedures includes payment for the following
services related to the surgery when furnished by the physician who performs the surgery.  
The services included in the global surgical package may be furnished in any setting, e.g.,
in hospitals, ASCs, physicians’ offices.  Visits to a patient in an intensive care or critical
care unit are also included if made by the surgeon.  However, critical care services
(99291 and 99292) are payable separately in some situations.
•    Preoperative Visits - Preoperative visits after the decision is made to operate
beginning with the day before the day of surgery for major procedures and the day
of surgery for minor procedures;
•    Intra-operative Services - Intra-operative services that are normally a usual and
necessary part of a surgical procedure;
•    Complications Following Surgery - All additional medical or surgical services
required of the surgeon during the postoperative period of the surgery because of
complications which do not require additional trips to the operating room;
•    Postoperative Visits - Follow-up visits during the postoperative period of the
surgery that are related to recovery from the surgery;
Postsurgical Pain Management - By the surgeon;
•    Supplies - Except for those identified as exclusions; and
•    Miscellaneous Services - Items such as dressing changes; local incisional care;
removal of operative pack; removal of cutaneous sutures and staples, lines, wires,
tubes, drains, casts, and splints; insertion, irrigation and removal of urinary
catheters, routine peripheral intravenous lines, nasogastric and rectal tubes; and
changes and removal of tracheostomy tubes.