Mechanical complications are defined as those that occur as a direct result of technical failure from a procedure or operation. These complications include postoperative hematoma and hemoperitoneum, seroma, wound dehiscence, anastomotic leak, and those related to lines, drains, and retained foreign bodies.
Wound hematoma, a collection of blood and clot in the wound, is a common wound complication and is usually caused by inadequate hemostasis. The risk is much higher in patients who have been systemically anticoagulated and in those with preexisting coagulopathies. However, patients receiving aspirin or low-dose heparin also have a slightly higher risk of developing this complication. Vigorous coughing or marked arterial hypertension immediately after surgery may contribute to the formation of a wound hematoma.
Hematoma produces elevation and discoloration of the wound edges, discomfort, and swelling. Blood sometimes leaks between skin sutures. Neck hematoma following operation on the thyroid, parathyroid, or carotid artery are particularly dangerous, because it may expand rapidly and compromise the airway. Small hematomas may resorb, but they increase the incidence of wound infection. Treatment in most cases consists of evacuation of the clot under sterile conditions, ligation of bleeding vessels, and reclosure of the wound.
Bleeding is the most common cause of shock in the first 24 hours after abdominal surgery. Postoperative hemoperitoneum—a rapidly evolving, life-threatening complication—is usually the result of a technical problem with hemostasis, but coagulation disorders may play a role. Causes of coagulopathy, such as dilution of hemostatic factors after massive blood loss and resuscitation, mismatched transfusion, or administration of heparin, should also be considered. In these cases, bleeding tends to be more generalized, occurring in the wound, venipuncture sites, etc.
Hemoperitoneum usually becomes apparent within 24 hours after the operation. It manifests as intravascular hypovolemia: tachycardia, hypotension, decreased urine output, and peripheral vasoconstriction. If bleeding continues, abdominal girth may increase and intra-abdominal hypertension or abdominal compartment syndrome may ensue. Changes in the hematocrit are usually not obvious for 4-6 hours and are of limited diagnostic help in patients who sustain rapid blood loss.
Manifestations may be so subtle that the diagnosis is initially overlooked. Only a high index of suspicion, frequent examination of patients at risk, and systematic investigation of patients with postoperative hypotension will reliably result in early recognition. Preexisting disease and drugs taken before surgery as well as those administered during the operation may cause hypotension. The differential diagnosis of immediate postoperative circulatory collapse also includes pulmonary embolism, cardiac dysrhythmias, pneumothorax, myocardial infarction, and severe allergic reactions. Infusions to expand the intravascular volume should be started as soon as other diseases have been ruled out. If hypotension or other signs of hypovolemia persist, one usually must reoperate promptly. At operation, bleeding should be stopped, clots evacuated, and the peritoneal cavity rinsed with saline solution.
A seroma is a fluid collection in the wound other than pus or blood. Seromas often follow operations that involve elevation of skin flaps and transection of numerous lymphatic channels (eg, mastectomy, operations in the groin). Seromas delay healing and increase the risk of wound infection. Those located under skin flaps can usually be evacuated by needle aspiration if necessary. Compression dressings can then occlude lymphatic leaks and limit reaccumulation. Small seromas that recur may be treated by repeated evacuation. Seromas of the groin, which are common after vascular operations, are best left to resorb without aspiration, since the risks of introducing a needle (infection, disruption of vascular structures, etc) are greater than the risk associated with the seroma itself. If seromas persist—or if they leak through the wound—the wound should be explored in the operating room and the draining sites oversewn. Open wounds with persistent lymph leaks can be treated with wound vacuum devices.
Wound dehiscence is partial or total disruption of any or all layers of the operative wound. Rupture of all layers of the abdominal wall and extrusion of abdominal viscera is evisceration. Wound dehiscence occurs in 1%-3% of abdominal surgical procedures. Systemic and local factors contribute to the development of this complication.
Dehiscence after laparotomy is rare in patients younger than 30 years but affects about 5% of patients older than 60 years. It is more common in patients with diabetes mellitus, uremia, immunosuppression, jaundice, sepsis, hypoalbuminemia, cancer, obesity, and in those receiving corticosteroids.
The three most important local factors predisposing to wound dehiscence are inadequate closure, increased intra-abdominal pressure, and deficient wound healing. Dehiscence often results from a combination of these factors rather than from a single one. The type of incision (transverse, midline, etc) does not influence the incidence of dehiscence.
This is the single most important factor. The fascial layers give strength to a closure, and when fascia disrupts, the wound separates. Accurate approximation of anatomic layers is essential for adequate wound closure. Most wounds that dehisce do so because the sutures tear through the fascia. Prevention of this problem includes performing a neat incision, avoiding devitalization of the fascial edges by careful handling of tissues during the operation, placing and tying sutures correctly, and selecting the proper suture material. Sutures must be placed 2-3 cm from the wound edge and about 1 cm apart. Dehiscence is often the result of using too few stitches and placing them too close to the edge of the fascia. It is unusual for dehiscence to recur following reclosure, implying that adequate closure was technically possible at the initial procedure. In patients with risk factors for dehiscence, the surgeon should “do the second closure at the first operation”; that is, take extra care to prevent dehiscence. Modern synthetic suture materials (polyglycolic acid, polypropylene, and others) are clearly superior to catgut for fascial closure. In infected wounds, polypropylene sutures are more resistant to degradation than polyglycolic acid sutures and have lower rates of wound disruption. Wound complications are decreased by obliteration of dead space. Stomas and drains should be brought out through separate incisions to reduce the rate of wound infection and disruption.
2. Intra-abdominal pressure
After most intra-abdominal operations, some degree of ileus exists, which may increase pressure by causing distention of the bowel. High abdominal pressure can also occur in patients with chronic obstructive pulmonary disease who use their abdominal muscles as accessory muscles of respiration. In addition, coughing produces sudden increases in intra-abdominal pressure. Other factors contributing to increased abdominal pressure are postoperative bowel obstruction, obesity, and cirrhosis with ascites formation. Extra precautions are necessary to avoid dehiscence in such patients.
Infection is an associated factor in more than half of wounds that rupture. The presence of drains, seromas, and wound hematomas also delays healing. Normally, a “healing ridge” (a palpable thickening extending about 0.5 cm on each side of the incision) appears near the end of the first week after operation. The presence of this ridge is clinical evidence that healing is adequate, and it is invariably absent from wounds that rupture.
Although wound dehiscence may occur at any time following wound closure, it is most commonly observed between the fifth and eighth postoperative days, when the strength of the wound is at a minimum. Wound dehiscence may occasionally be the first manifestation of intra-abdominal sepsis. The earliest sign of dehiscence is often discharge of serosanguineous fluid from the wound or, in some cases, sudden evisceration. The patient may describe a popping sensation associated with severe coughing or retching.
Thoracic wounds, with the exception of sternal wounds, are much less prone to dehiscence than are abdominal wounds. When a thoracotomy closure ruptures, it is heralded by leakage of pleural fluid or air and paradoxic motion of the chest wall. Sternal dehiscence, which is almost always associated with infection, produces an unstable chest and requires early treatment. If infection is not overwhelming and there is minimal osteomyelitis of the adjacent sternum, the patient may be returned to the operating room for reclosure. Continuous mediastinal irrigation through small tubes left at the time of closure appears to reduce the failure rate. In cases of overwhelming infection, the wound is best treated by debridement and closure with a pectoralis major muscle flap, which resists further infection by increasing vascular supply to the area.
Patients with dehiscence of a laparotomy wound and evisceration should be returned to bed and the wound covered with moist towels. With the patient under general anesthesia, any exposed bowel or omentum should be rinsed with lactated Ringer solution containing antibiotics and then returned to the abdomen. After mechanical cleansing and copious irrigation of the wound, the previous sutures should be removed and the wound reclosed using additional measures to prevent recurrent dehiscence, such as full-thickness retention sutures of no. 22 wire or heavy nylon. Evisceration carries a 10% mortality rate due both to contributing factors (eg, sepsis and cancer) and to resulting local infection.
Wound dehiscence without evisceration is best managed by prompt elective reclosure of the incision. If a partial disruption is stable and the patient is a poor operative risk, treatment may be delayed and the resulting incisional hernia accepted. It is important in these patients that skin stitches, if present, not be removed before the end of the second postoperative week and that the abdomen be wrapped with a binder or corset to limit further enlargement of the fascial defect or sudden disruption of the covering skin. When partial dehiscence is discovered during treatment of a wound infection, repair should be delayed if possible until the infection has been controlled, the wound has healed, and 6-7 months have elapsed. In these cases, antibiotics specific for the organisms isolated from the previous wound infection must be given at the time of hernia repair.
Recurrence of evisceration after reclosure of disrupted wounds is rare, though incisional hernias are later found in about 20% of such patients—usually those with wound infection in addition to dehiscence.
Of special circumstance, patients with ascites are at risk of fluid leak through the wound. Left untreated, ascitic leaks increase the incidence of wound infection and, through retrograde contamination, may result in peritonitis. Prevention in susceptible patients involves closing at least one layer of the wound with a continuous suture and taking measures to avoid the accumulation of ascites postoperatively. If an ascitic leak develops, the wound should be explored and the fascial defect closed. The rest of the wound, including the skin, should also be closed.
In patients at high risk for wound dehiscence, placement of retention stitches at the initial operation should be considered. Although these do not prevent dehiscence, they may prevent evisceration and the morbidity and mortality that are associated with it.
Anastomotic leaks are reported in 1%-24% of anastomoses with higher frequencies in low pelvic anastomoses compared to more proximal ones. The morbidity and mortality for a patient with an anastomotic leak is significantly increased with a reportedly threefold increase in mortality.
Anastomotic healing follows the same principles of normal wound healing, and the risk factors for developing an anastomotic leak are identical to those that predict wound dehiscence. Systemic risk factors include age, malnutrition, vitamin deficiencies, and comorbid conditions such as diabetes, smoking, inflammatory bowel disease such as regional enteritis, previous radiation/chemotherapy and anemia. Local risk factors include tension, poor blood flow, hypotension, radiation, and contamination.
Technical considerations such as hand-sewn versus stapled anastomoses, continuous versus interrupted sutures, and single versus double-layer hand-sewn anastomoses have been extensively studied. While such topics generate much discussion and controversy, the technique chosen has less to do with anastomotic leaks than systemic and local factors. Stapled end-to-end anastomoses, however, may lead to higher rates of anastomotic strictures in long-term follow-up.
The diagnosis of an anastomotic leak can be made clinically, radiographically, and intraoperatively. Clinical signs include pain, fever, peritonitis, and drainage of purulent material, bilious succus, or fecal material. Radiographic signs include fluid and gas-containing collections tracking to an anastomosis. Intraoperative findings include gross contamination from gastrointestinal contents and evidence of anastomotic disruption.
The management of an anastomotic leak depends on several factors, including the patient’s clinical status, the time from initial operation, and the location and severity of the leak. The management strategies can range from nonoperative (observation, bowel rest, antibiotics, and percutaneous drainage of abscesses) to the operative (open drainage, proximal diversion, and revision of anastomosis).
Complications of Lines, Drains, & Retained Foreign Bodies
Complications due to central line placement and maintenance are preventable with adequate experience, preparation, and technique. Choice of site, utilization of ultrasound, and assiduous adherence to sterile technique decrease infection, as well as mechanical complications such as pneumothorax and arterial injury.
A needle or a catheter inserted into a vein and left in place will in time cause inflammation at the entry site. When this process involves the vein wall, it is called phlebitis. Factors determining the degree of inflammation are the nature of the cannula, the solution infused, bacterial infection, and venous thrombosis. Phlebitis is one of the most common causes of fever after the third postoperative day. The symptomatic triad of induration, edema, and tenderness is characteristic. Visible signs may be minimal. Prevention of phlebitis is best accomplished by observance of aseptic techniques during insertion of venous catheters, frequent change of tubing (ie, every 48-72 hours), and rotation of insertion sites (ie, every 4 days). Silastic catheters, which are the least reactive, should be used when the line must be left in for a long time. Hypertonic solutions should be infused only into veins with substantial flow, such as the subclavian, jugular, or vena cava. Venous catheters should be removed at the first sign of redness, induration, or edema. Because phlebitis is most frequent with cannulation of veins in the lower extremities, this route should be used only when upper extremity veins are unavailable. Removal of the catheter is adequate treatment.
Suppurative phlebitis may result from the presence of an infected thrombus around the indwelling catheter. Staphylococci are the most common causative organisms. Local signs of inflammation are present, and pus may be expressed from the venipuncture site. High fever and positive blood cultures are common. Treatment consists of excising the affected vein, extending the incision proximally to the first open collateral, and leaving the wound open.
Pneumothorax after placement of a central catheter into either the subclavian or internal jugular veins occurs with an incidence approaching 1%. Chances for occurrence may be minimized by proper positioning, use of ultrasound, and experience. Ultrasound, in general, has markedly decreased the complication rate of central line placement. By adequately imaging the vein prior to venipuncture, the rate of arterial injury has markedly decreased. Injury to arteries can lead to pseudoaneurysm formation, continuous bleeding, or stroke, depending upon the vessel injured, size of arteriotomy, and presence of coagulopathy. Perforation of the right atrium with cardiac tamponade can occur due to central venous lines. This complication can be avoided by checking the position of the tip of the line, which should be in the superior vena cava, not the right atrium. Complications associated with the use of the flow-directed balloon-tipped (Swan-Ganz) catheter include cardiac perforation (usually of the right atrium), intracardiac knotting of the catheter, and cardiac dysrhythmias. Pulmonary hemorrhage may result from disruption of a branch of the pulmonary artery during balloon inflation and may be fatal in patients with pulmonary hypertension. Steps in prevention include careful placement, advancement under continuous pressure monitoring, and checking the position of the tip before inflating the balloon.
Air embolism may occur during or after insertion of a venous catheter or as a result of accidental introduction of air into the line. Intravenous air lodges in the right atrium, preventing adequate filling of the right heart. This is manifested by hypotension, jugular venous distention, and tachycardia. This complication can be avoided by placing the patient in the Trendelenburg position when a central venous line is inserted. Emergency treatment consists of aspiration of the air with a syringe. If this is unsuccessful, the patient should be positioned right side up and head down, which will help dislodge the air from the right atrium and return circulatory dynamics to normal.
Ischemic necrosis of the finger
Continuous monitoring of arterial blood pressure during the operation and in the intensive care unit requires insertion of a radial or femoral arterial line. The hand receives its blood supply from the radial and ulnar arteries, and because of the anatomy of the palmar arches, patency of one of these vessels is usually enough to provide adequate blood flow through the hand. Occasionally, ischemic necrosis of the finger follows use of an indwelling catheter in the radial artery. This serious complication may be limited by evaluating the patency of the ulnar artery (Allen test) before establishing the radial line and by changing arterial line sites every 3-4 days. After an arterial catheter is withdrawn, a pressure dressing should be applied to avoid formation of an arterial pseudoaneurysm.
Postoperative drainage of the peritoneal cavity is indicated to prevent accumulation of fluid such as bile or pancreatic fluid, or to treat established abscess. Drains may be left to evacuate small amounts of blood, but drain output cannot be used to provide a reliable estimate of the rate of bleeding. The use of drains in operations not expected to have fluid leak (such as cholecystectomy, splenectomy, and colectomy) increases the rate of postoperative intra-abdominal and wound infection. Latex Penrose drains, which were used frequently in the past, should generally be avoided because of the risk of introducing infection. Large rigid drains may erode into adjacent viscera or vessels and cause fistula formation or bleeding. This risk is lessened with the use of softer Silastic drains, and removing them as early as possible. Drains should not be left in contact with intestinal anastomoses, as they may promote anastomotic leakage and fistula formation.
Studies based on hospital claims data estimate that cases of retained objects, which include sponges and instruments, occur at least once a year in those hospitals where 8000 to 18,000 major procedures are performed annually. While mortality is low, the morbidity is high due to the almost universal need for reoperation. The most common body cavity involved is the abdomen followed by the thoracic cavity. Improving communication within the operating room, formal sponge and instrument counts, and appropriate use of radiography all contribute to a decrease in this complication.