Contemporary surgical therapy is greatly helped by monitoring devices that are used during surgery and during the postoperative period. Blood pressure and pulse rate are monitored during an operation because a fall in the former and a rise in the latter give evidence of a critical loss of blood. Other items monitored are the heart contractions as indicated by electrocardiograms; tracings of brain waves recorded by electroencephalograms, which reflect changes in brain function; the oxygen level in arteries and veins; carbon dioxide partial pressure in the circulating blood; and respiratory volume and exchange. Intensive monitoring of the patient usually continues into the critical postoperative stage.
Asepsis, the freedom from contamination by pathogenic organisms, requires that all instruments and dry goods coming in contact with the surgical field be sterilized. This is accomplished by placing the materials in an autoclave, which subjects its contents to a period of steam under pressure. Chemical sterilization of some instruments is also used. The patient’s skin is sterilized by chemicals, and members of the surgical team scrub their hands and forearms with antiseptic or disinfectant soaps. Sterilized gowns, caps, and masks that filter the team’s exhaled air and sterilized gloves of disposable plastic complete the picture. Thereafter, attention to avoiding contact with nonsterilized objects is the basis of maintaining asepsis.
During an operation, hemostasis (the arresting of bleeding) is achieved by use of the hemostat, a clamp with ratchets that grasps blood vessels or tissue; after application of hemostats, suture materials are tied around the bleeding vessels. Absorbent sterile napkins called sponges, made of a variety of natural and synthetic materials, are used for drying the field. Bleeding may also be controlled by electrocautery, the use of an instrument heated with an electric current to cauterize, or burn, vessel tissue. The most commonly used instruments in surgery are still the scalpel (knife), hemostatic forceps, flexible tissue-holding forceps, wound retractors for exposure, crushing and noncrushing clamps for intestinal and vascular surgery, and the curved needle for working in depth.
The most common method of closing wounds is by sutures. There are two basic types of suture materials; absorbable ones such as catgut (which comes from sheep intestine) or synthetic substitutes; and nonabsorbable materials, such as nylon sutures, steel staples, or adhesive tissue tape. Catgut is still used extensively to tie off small blood vessels that are bleeding, and since the body absorbs it over time, no foreign materials are left in the wound to become a focus for disease organisms. Nylon stitches and steel staples are removed when sufficient healing has taken place.
There are three general techniques of wound treatment; primary intention, in which all tissues, including the skin, are closed with suture material after completion of the operation; secondary intention, in which the wound is left open and closes naturally; and third intention, in which the wound is left open for a number of days and then closed if it is found to be clean. The third technique is used in badly contaminated wounds to allow drainage and thus avoid the entrapment of microorganisms. Military surgeons use this technique on wounds contaminated by shell fragments, pieces of clothing, and dirt.
The 20th and 21st centuries witnessed several new surgical technologies to supplement the techniques of manual incision. Lasers became widely used to destroy tumours and other pigmented lesions, some of which are inaccessible by conventional surgery. They are also used to surgically weld detached retinas back in place and to coagulate blood vessels to stop them from bleeding. Stereotaxic surgery uses a three-dimensional system of coordinates obtained by X-ray photography to accurately focus high-intensity radiation, cold, heat, or chemicals on tumours located deep in the brain that could not otherwise be reached. Cryosurgery uses extreme cold to destroy warts and precancerous and cancerous skin lesions and to remove cataracts. Some traditional techniques of open surgery were replaced by the use of a thin flexible fibre-optic tube equipped with a light and a video connection; the tube, or endoscope, is inserted into various bodily passages and provides views of the interior of hollow organs or vessels. Accessories added to the endoscope allow small surgical procedures to be executed inside the body without making a major incision.
There are four major categories of surgery: (1) wound treatment, (2) extirpative surgery, (3) reconstructive surgery, and (4) transplantation surgery. The technical aspects of wound surgery, already partly discussed, centre on procuring good healing and the avoidance of infection. Extirpative surgery involves the removal of diseased tissue or organs. Cancer surgery usually falls into this category, with mastectomy (removal of the breast), cholecystectomy (removal of the gallbladder), and hysterectomy (removal of the uterus) among the most frequent procedures. Reconstructive surgery deals with the replacement of lost tissues, whether from fractures, burns, or degenerative-disease processes, and is especially prominent in the practice of plastic surgery and orthopedic surgery. Grafts from the patient or from others are frequently used to replace lost tissues. Reconstructive surgery also uses artificial devices (prostheses) to replace damaged or diseased organs or tissues. Common examples are the use of metal in reconstructing hip joints and the use of plastic valves to replace heart valves. Transplantation surgery involves the use of organs transplanted from other bodies to replace diseased organs in patients. Kidneys are the most commonly transplanted organs.