In the 20th cent., surgery has benefited from an improved understanding of the causes of shock and its treatment; knowledge of blood group typing and transfusion techniques; understanding of blood clotting and the use of anticoagulants; and the development of antibiotics to control infection and analgesics to control pain. Surgical instruments have developed along with modern technology and are now sophisticated, meticulously designed devices. Electrically powered surgical instruments are invaluable for cautery and for separating hard tissues such as bone with minimal damage. Surgical stapling instruments, first developed in the Soviet Union, can join blood vessels or other tissues in less than half the time required by hand stitching. New medical glues, surgical tapes, and even zippers now enable surgeons to close some wounds effectively without stitches. With the development of X-ray techniques and fluoroscopy and, later, CAT scans and magnetic resonance imaging (MRI), surgery gained valuable diagnostic instruments. Some operations are now being conducted inside specially adapted MRI devices, allowing the surgeon to have live images for guidance during operations. Holograms can be created using data from MRI and other diagnostic instruments and are beginning to be used in the operating room to give surgeons a three-dimensional image of the area to be operated upon.
Cryogenic, or supercooled, probe beams have been used to precisely remove tissues and abnormal growths. Ultrasound techniques, using very-high-frequency sound waves, are used to break up kidney stones and are employed in brain and inner-ear operations, which require great precision and control. They are also used to scan the pregnant uterus, a process that, unlike X-ray scanning, does not endanger the fetus. Medical lasers, which produce amplified monochromatic light waves in a very narrowly focused beam, have become useful tools in various forms of surgery, notably that of the eye, and are now commonly used to remove or "spot-weld" tissues.
The heart-lung machine made open-heart surgery possible by taking over the blood-pumping and breathing functions of these organs during operations. Hypothermia, or cold surgery, by which the body is cooled to lower the rate of metabolism, thus reducing the need for oxygen, has made long operations, especially those involving transplantation, possible. Other recent transplantation advances include procedures involving the liver, lungs, pancreas, bone marrow, and the kidney. The first human heart transplant was performed in 1967 by South African surgeon Christiaan Barnard. The usefulness of transplantation is currently limited by the fact that drugs must be used constantly to halt the body's rejection of foreign tissue.
New techniques in orthopedic surgery (see also orthopedics) have also been introduced, including the use of cementing substances to unite bones destroyed by tumor and the replacement of joints with metal or plastic devices. Plastic surgery and reconstructive surgery have made enormous strides, and microsurgery is making severed or injured limbs usable.
A trend toward less invasive surgery and shorter hospital stays began in the 1980s. By 1995 more than 56% of all surgical procedures in the United States were done on an outpatient basis, without an overnight stay in a hospital. Endoscopic surgery, using small incisions and tiny instruments attached to fiber-optic viewing devices (see endoscope), has been used in place of more traditional procedures for gall-bladder surgery, and it has been used on the fetus in the womb to correct life-threatening birth defects before birth. Angioplasty is frequently used to circumvent or postpone the need for coronary artery bypass.